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the case of discharges to the sea, consideration needs to be given to the exposure pathways arising from uses of the seawater, such as production of aquatic foods, fishing industries and recreation (paragraph 5.27 of GSG-10 [11]). In paragraph 5.30 of GSG-10 [11], it is explained that, depending on the exposure scenarios and the site characteristics, not all the possible exposure pathways may need to be included in the assessment because the contribution of an exposure pathway to the overall dose depends on the radionuclides involved, the habit data, the time spent at a location and other characteristics of the population being considered. Therefore, some exposure pathways may be excluded from the assessment on the grounds that the doses associated with them are evaluated to be non-existent or negligible. However, paragraph 5.30 in GSG-10 [11] clarifies that the decision to exclude particular exposure pathways from consideration should be justified.
In the REIA presented by TEPCO, a number of internal and external exposure pathways were initially identified as relevant for the ALPS treated water discharges to the sea. During the first mission to TEPCO, the Task Force noted that although the dominant exposure pathway is expected to be ingestion of seafood, it is good practice to demonstrate in the REIA that all plausible exposure pathways have been considered, even if the doses are expected to be very low. This is necessary to justify excluding exposure pathways that make a minor contribution to the doses. The Task Force identified the minor exposure pathways of inhalation of resuspended materials (e.g., sea-spray, beach sediments), beta doses to the skin from handling fishing nets and inadvertent ingestion of sediments, that could be considered for completeness.
Following the discussions with the Task Force, TEPCO included other minor exposure pathways in accordance with GSG-10 [11] and considered other potential exposure pathways listed in other national or international guidelines. The list of exposure pathways considered in the REIA is given in Table 3.6. TEPCO has documented its assessment of the doses from the minor exposure pathways in the February 2023 version of the REIA for completeness; a presentation and discussion of the results is given later in this Section.
TABLE 3.6. EXPOSURE PATHWAYS CONSIDERED BY TEPCO IN THE REIA (major exposure pathways in bold)
External exposure pathways
Internal exposure pathways
External exposure received from:
• Sea surface
• Hull of ship
• Immersion in water (swimming)
• Beach sediments
• Fishing nets
Ingestion of seafood (fish, molluscs and sea- weed)
Inadvertent ingestion of seawater while swim- ming
Inhalation of sea spray
Assessment of the dose to the Representative Person
Having identified the pathways by which a person can be exposed to radionuclides in the environment following the discharges to sea, the next step in the REIA is to assess the doses to the representative person. The representative person is selected to have the characteristics of individuals who are likely to be more highly exposed.
An important characteristic when assessing doses to the representative person is the assumed location of the representative person (e.g., his or her distance and direction from the point of discharge of radionuclides) as described in paragraph 5.34 of GSG-10 [11]. The location where the representative person lives can be based on an actual person or a group of persons, or on a postulated person or group of persons living at a location selected using cautious assumptions (e.g., at a point where the highest concentrations in the area can be expected).
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TEPCO stated in the REIA report that the characteristics of the representative person were set in accordance with “Public dose assessment guideline for safety review of nuclear power light water reactor”. Habit data, such as consumption rates of food for the representative person, used in the assessment were based on national statistical datasets (National Health and Nutrition Survey in Japan). Table 3.7 summarizes the characteristics of the representative person as described by TEPCO in the REIA report. TEPCO considered the habits of three age groups; adults, children and infants in the assessment of doses in the REIA.
TABLE 3.7. HABIT DATA USED IN THE REIA [17] BY TEPCO FOR THE REPRESENTATIVE PERSON
Parameter
Adult
Child
Infant
Ingestion rates [g d-1]a Fish
Invertebrate
Seaweed
Beach
Fishing
Handling fishing nets
Swimming
58(190)b 29(97) 12(39)
10(62) 5.1(31) 2(12)
11(52) 5.3(26) 2.1(10)
500
2880
1920
96
Occupancies for the representative person [hr y-1]
a Ingestion rates of seafood for the representative person are based on national statistical datasets for Japan.
b Two scenarios were considered in the assessment: one for a person who ingests seafood at the average values and the other for a person who
ingests a large amount of seafood (mean + 2σ).
For estimating doses to the representative person from all the exposure pathways considered, TEPCO used the marine dispersion model to calculate activity concentrations in sea water in a 10 km x 10 km area around the discharge point (see Fig. 3.16). These activity concentrations in seawater were used as the basis for all the doses calculated for the representative person. The Task Force discussed with TEPCO whether the average concentration used is conservative given the higher concentrations in the sea predicted using the marine dispersion model along the coast due to the sea currents both within the ‘difficult to return zone’ and just outside it. These higher concentrations in the sea were taken into consideration in the further iterations of the REIA with respect to identifying in more detail the characteristics and location of the representative person. In particular, the Task Force discussed with TEPCO that no account was being taken of members of the public using local beaches for recreational purposes. TEPCO explained that this was a conservative assumption as members of the public cannot live or undertake activities close to the coastline within the ‘difficult to return zone’ or the ‘no claim for fishing zone’; however TEPCO also recognized that whilst there are currently no inhabitants 3km north of the site, the representative person could travel to the beach. TEPCO subsequently used this location (3km north of the site) to calculate external doses in the revised versions of the REIA (see Fig. 3.16). Additionally, TEPCO recognized that individuals could also catch a small proportion of their fish and seafood consumption from local beaches at some point in the future and included a scoping calculation in the REIA to include this. The calculation indicated that the dose to an adult from ingestion of fish and seafood could increase by about 20% if 10% of their consumption was caught locally.
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Assessment point for exposure during swimming, from beach sand, from ingestion of water, and from inhalation of seawater spray
Difficult-to-Return Zones Interim storage facility site
Ukedo port
10 km
Assessment area for exposure from sea surface,
from hulls, from fishing net, and from ingestion of seafood
Point of discharge
Area where fishing is not routinely conducted*
10 km
Fig 3.16. Location of the representative person for normal operation of discharge of ALPS treated water in the REIA (taken from TEPCO [15])
Paragraph 5.36 of GSG-10 [11] explains that the individual effective dose to the representative person is the sum of the committed effective dose from intakes of radionuclides (i.e., from internal exposure by ingestion and inhalation) and the effective dose from external exposure. Doses from internal exposure are calculated using dose coefficients from intakes of radionuclides by ingestion and inhalation, which provide the committed effective dose per unit activity of intake, expressed in units of sieverts per becquerel (Sv/ Bq). Tabulated values of dose coefficients applicable for members of the public are available in GSR Part 3 [8]. Standard models exist to calculate the effective dose from external exposure, as well as compilations of dose coefficients.
The committed effective dose (calculated for the representative person) is an annual dose. This annual dose is compared with the dose constraint of 0.05 mSv per year. As discussed above, the annual committed effective dose calculated in the REIA, is the highest annual dose that could be expected over the period of the discharges. Assuming that this dose is received annually over the period of the discharges is therefore a conservative assessment.
Assessment of doses to flora and fauna and endpoints
The generic methodology for assessing exposure of flora and fauna based on the ICRP approach in GSG- 10 [11] uses representative organisms selected directly from the ICRP reference animals and plants [12; 13]. These representative organisms are selected to be those relevant for the specific major ecosystem (e.g., terrestrial, marine, freshwater) assumed to be located in the area where the exposure conditions lead to the highest doses.
The ICRP approach uses the concept of reference plants and animals [12]. The ICRP defines three species to be used as references for the protection of the marine environment. The conceptual approach is that,
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10 km by 10 km range of the station
if the criteria for those three reference species is not exceeded, then all the species can be assumed to be equally well protected, at the level of their populations (particularly for planned exposure situation). The three species were identified based on their wide global distribution and the existence of actual data on the effects of very low increments of radiation doses (increments comparable with the variation of natural radiation in different scenarios). TEPCO has calculated dose rates for the three reference marine species in ICRP, namely flat fish, crab and brown seaweed. Figure 3.17 shows the exposure pathways and the calculation undertaken to calculate dose rates (mGy per day for the 3 representative marine organisms).
Source of Radionuclides
Exposure Pathways:
Ingestion: seawater & sediment
External exposure: seawater & sediment
Activity concentrations in RAPs (flat fish, crab & brown seaweed)
Transfer in the Marine Environment
Dose Coefficients
Dose rates in RAPs
Figure 3.17. Exposure pathways and assessment of dose (mGy/day) rates to flora and fauna in the REIA
The exposure pathways considered, in line with the approach described in GSG-10 were:
• Internal exposure from radioactive materials ingested by animals or absorbed by plants
• External exposure from the surrounding seawater
• External exposure from the surrounding seabed sediments
Results of the REIA
TEPCO has presented the annual committed effective doses calculated in the REIA to the representative person for the different exposure pathways and different age groups considered. The age groups and dose coefficients used for calculating committed effective doses for adults, children, and infants were in accordance with those provided in GSR Part 3 [8].
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ADULT
Total dose = 0.008 μSv
External 8.1% Internal 91.9%
Ingestion of water 4.6% Inhalation seaspray 1.3% Ingestion seafood 94.1%
Ingestion of water 6.9% Inhalation seaspray 0.7% Ingestion seafood 92.4%
Ingestion of water 0.0% Inhalation seaspray 0.7% Ingestion seafood 99.4%
CHILD
Total dose = 0.009 μSv
External 7.1% Internal 92.9%
INFANT
Total dose = 0.008 μSv
External 8.5% Internal 91.5%
Figure 3.18: Contribution of exposure pathway to the committed effective dose for high seafood consumers as a function of age group (K4 ALPS treated water tank group)
Figure 3.18 shows the contribution of exposure pathways to the committed effective dose for high seafood consumers as a function of age group. The Figure shows that the contribution from internal exposure contributes about 90% of the total dose for all age groups and that the ingestion of seafood contributes between 92% and 99% of the internal dose. Figure 3.19 presents information for the committed effective doses calculated as a function of age and main exposure pathways based on the source term for the K4 ALPS treated water tank group. The results for the other two tank groups considered are very similar.
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Adults High
129I
14C
55F
79Se
60Co
3H
137Cs
99Tc
125Sb
155Eu
All others
Total
1.8E-05 129I
7.1E-06 14C
3.8E-06 55F
1.6E-06 3H
5.8E-07 79Se
5.0E-07 60Co
1.8E-07 240Pu
1.1E-07 239Pu
2.8E-08 241Am
2.7E-08 238Pu
1.2E-07 All others
3.2E-05 Total
2.0E-06 14C
1.6E-06 55F
8.5E-07 129I
5.0E-07 79Se
3.2E-07 3H
1.2E-07 240Pu
1.2E-07 239Pu
1.2E-07 241Am
1.1E-07 238Pu
1.1E-07 60Co
3.6E-07 All others
6.2E-06 Total
4.4E-06
2.5E-06
1.6E-06
9.5E-07
5.0E-07
3.0E-07 3.0E-07 2.8E-07 2.7E-07
2.6E-07
8.9E-07
1.2E-05
0,000040 0,000035 0,000030 0,000025 0,000020 0,000015 0,000010 0,000005 0,000000
External Internal ADULT
Total
External Internal CHILD
Total
External Internal INFANT
Figure 3.19: Committed effective dose as a function of age and exposure pathway (K4 ALPS treated water tank group)
Table 3.8 also shows that the annual committed effective dose is similar across the three ALPS treated water tank group source terms for adults. Table 3.8 shows that the relative contributions of the radionuclides to the ingestion dose varies between the three source terms but in all cases the doses are very low and more than 1000 times lower than the dose constraint of 0.05 mSv per year. Carbon-14, 129I and 55Fe are the largest contributors to the internal dose and the total dose. This is also the case for children and infants. Tritium typically contributes no more than a few percent of the total committed effective dose. The highest contribution from tritium is from the inadvertent ingestion of seawater while swimming (adults and children); it is noted that TEPCO assumes a conservative consumption rate of 0.2 l/h of sea water while swimming.
Table 3.8. Annual committed effective dose for an adult high seafood consumers as a function of radionuclide and ALPS treated water tank group
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Total
mSv per year
Age group
Seafood intake
Storage tank
Dose (mSv/y)
Storage tank
Dose (mSv/y)
Storage tank
Dose (mSv/y)
K4
J1-C
J1-G
As discussed above, the ingestion of seafood is the highest contribution to the committed effective dose for all age groups and for the three ALPS treated water source terms considered in the REIA. Figure 3.20 shows the relative contributions of radionuclides to the ingestion dose for all three age groups for a high seafood consumer. The Figure shows that the radionuclides contributing most to the ingestion dose are 129I, 14C, 55Fe and 79Se which contribute over 90% of the dose. Fe-55 and 79Se are relatively more important for children and infants due to the higher dose coefficients (Sv per Bq of intake). It is noted that TEPCO has not detected 55Fe and 79Se in the ALPS treated water and the estimated committed effective doses are based on levels of these radionuclides in the discharge being at the detection limits for the analytical technique used. It is not expected that these radionuclides will be detected in the environment and in seafood but they are included in the CRMP (see Section 3.5). However, it should be stressed that the annual committed effective ingestion dose is still very low for all age groups, and less than 0.04 μSv per year.
Total adult ingestion dose = 0.03 μSv
129I
14C
55Fe
79Se
Total Child Ingestion dose = 0.04 μSv
60Co Tritium Others
Tritium 60Co
129I
55Fe
14C
79Se
Total Infant Ingestion Dose = 0.03 μSv
Figure 3.20. Committed effective dose from ingestion for high seafood consumer as a function of age group: percentage contribution of radionuclides (K4 tank group)
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Others
Others
99Tc 137Cs
I -129
55Fe
129I
79Se
14C
60Co
Figure 3.21 shows the radionuclide contribution to the annual external dose for the representative person. The external dose is the sum over all the external exposure pathways considered in the REIA but is dominated by the exposure to occupancy on the beach (about 85% for the radionuclides contributing most to the external dose). The external dose is only calculated for an adult, as it is assumed that children only spend time on the beach when accompanied by adults and that there is no significant difference in the effective external dose received by the different age groups. Figure 3.21 shows that the two radionuclides contributing most to the effective external dose are 60Co and 137Cs.
Adult (K4 tank group) Total external dose = 0.002 μSv
60Co 60.8% 137Cs 25.5% 155Eu 4.1% 125Sb 4.1%
121I 1.5% 134Cs 1.3% 154Eu 1.0% 106Ru 1.0%
All others 0.5%
Adult (J1-G tank group) Total external dose = 0.0005 μSv
60Co 34.5% 155Eu 24.4% 137Cs 15.7% 154Eu 8.3% 241Pu 7.4% 134Cs 4.0% 125Sb 2.6% 106Ru 1.7%
All others 1.4%
Adult (J1-C tank group) Total external dose = 0.002 μSv
60Co 34.8% 155Eu 34.8% 154Eu 6.6% 241Pu 6.5% 137Cs 6.2% 106Ru 3.5% 134Cs 3.1% 125Sb 3.0%
All others 1.4%
Figure 3.21. Effective external dose as a function of radionuclide and ALPS treated water tank group (the external dose is assumed to be the same for all age groups in the REIA)
The doses to members of the public estimated in the REIA as a result of discharges of ALPS treated water are more than 1000 times lower than the dose constraint set by NRA of 0.05 mSv/y. Subsequently, using the approach of a generic methodology in conjunction with site-specific habit data is in line with the guidance in GSG-10 [11] and there is no need to refine the dose assessment with more complex models and site-specific parameter values on radiological protection grounds. However, to address the international interest in the radiological impact of the proposed discharges, in the REIA undertaken by TEPCO, a site-specific marine dispersion model and a full range of exposure pathways has already been considered.
The REIA also contains an assessment of doses to flora and fauna using the approach given in GSG-10 [11], which is in-line with the ICRP approach [12;13]. The highest dose rates to flora and fauna over the period of discharges of ALPS treated water are estimated by TEPCO to be < 1 10-6 mGy per day (0.000001 mGy per day). The calculated dose rates to the three reference organisms (flat fish, crabs and seaweed) are more than a million times lower that the lowest derived consideration reference level (DCRL) of 1 mGy per day, which is for flat fish.
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Transboundary impacts of the ALPS treated water discharge
In paragraph 5.24 of GSG-9 [9] it is identified that if a discharge could cause significant public exposure outside the territory or other area under the jurisdiction or control of the State in which the discharge takes place, the operating organization should make an assessment of the radiological impacts of the discharges on the public and the environment in these areas.
The Task Force discussed with TEPCO that there are radionuclides in the source term that could have an impact for global circulation in the oceans (e.g., 129I, 14C, 99Tc, 3H) and that, even though doses from global dispersion and circulation in the oceans are likely to be very small, or effectively zero, doses to neighbouring countries from global circulation are of interest to the international community. Therefore, this topic should be considered and explained in the REIA. TEPCO noted that the flow of sea currents was taken into account within the model and the estimated activity concentrations of tritium in the ocean were low and, that it would be difficult, or impossible, to detect tritium from the ALPS treated water at large distances from the point of discharge.
The Task Force noted that the calculational area of simulations for the marine dispersion model is 490 km north-south and 270 km east-west and had encouraged TEPCO to use longer distance dispersion calculations to show clearly that doses to neighbouring countries are negligible. TEPCO explained that based on meteorological and oceanographic conditions over a 7-year period from 2014 to 2020, the marine dispersion model predicts very low concentrations of tritium that will be undetectable at the boundary of the simulation area (490 km north-south and 270 km east-west of the FDNPS); therefore, extending the range of the existing model boundary would not add any technical value for assessment of the radiological impact of the ALPS treated water discharges. The Task Force accepted TEPCO’s reasoning that concentrations of tritium beyond this area will be even lower and therefore there is no scientific justification for redoing the calculations for a larger area. The Task Force recommended that including estimates of activity concentrations of 14C and 129I in seawater at the boundary of the simulation area could also demonstrate that the concentrations of these radionuclides are negligible and that this would provide a useful comparison for communication with interested parties. TEPCO added this into the revised REIA in response to the Task Forces’ views. TEPCO also stated in the REIA that the yearly radioactive discharge of 14C and 129I from ALPS treated water is a very small amount, therefore its impact at global scale is negligible.
Based on the results of the marine dispersion model used by TEPCO, activity concentrations in international waters will not be influenced by the discharge of ALPS treated water into the sea and the transboundary impacts are therefore negligible. However, the baseline environmental monitoring in place around the FDNPS and in the surrounding area of the Pacific Ocean, as well as that planned by TEPCO and the Government of Japan after the start of discharges (see Section 3.5) is extremely important to ascertain any levels of radionuclides in the sea due to the discharge of ALPS treated water and to verify the findings of the REIA.
TEPCO stated in the REIA that the yearly radioactive discharge of 14C and 129I from ALPS treated water is a very small amount, therefore its impact at global scale is negligible.
TEPCO predictions of activity concentrations of tritium in the Pacific Ocean
In the REIA submitted by TEPCO, the estimated activity concentrations in the ocean based on the marine dispersion model show that:
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• Estimated tritium concentrations of sea water above 1 Bq/L is limited to an area of up to 3 km around FDNPS.
• The estimated average tritiumconcentrations for the area 10 km x 10 km for all water layers is 0.056 Bq/L and 0.12 Bq/L for the surface layer. For estimating exposures due to occupancy on the beach and from inhalation of sea spray, the underlying tritium activity concentration in water is 0.88 Bq/L.
The simulated tritium activity concentration at the eastern boundary of the simulation area is between 0.0001 and 0.0003 Bq/L. For comparison, the average H-3 concentration in the North Pacific Ocean between latitudes 30 N and 45 N is about 0.04 Bq/L1 and background activity concentrations in the sea around the FDNPS are in the range of 0.1 – 1.0 Bq/l. This means that the tritium concentration in the sea from the discharge of ALPS treated water at the boundary of Japanese territorial waters will already be lower than the background concentration of tritium in the North Pacific between latitudes 30 N and 45 N.
1. Oms, P.E., Bailly Du Bois, P., Dumas, F., Lazure, P., Morillon, M., Voiseux, C., Le Corre, C., Cossonnet, C., Solier, l., Morin, P.: Inventory and distribution of tritium in the oceans in 2016. Science of the Total Environment, Elsevier, 2019, 656, pp. 1289-1303. 10.1016/j. scitotenv.2018.11.448. hal-02336283
Assessment of doses from potential exposures
As part of the safety assessment for facilities and activities, various types of accident are postulated to identify engineered safety features and operational actions to reduce their likelihood and, if an accident does occur, to mitigate its consequences (paragraph 5.44 of GSG-10 [11]). In accordance with the recommendations provided in GSG-10 [11], a prospective assessment of potential exposures to members of the public should be performed for exposure scenarios resulting from postulated accidents identified on the basis of the safety assessment. The representative person for potential exposures needs to be identified, noting that the representative person may not be the same as that selected for normal operations, and an assessment of the dose to the representative person estimated and compared with the applicable established dose criteria.
TEPCO has included in the REIA [15] an assessment of the potential doses to a representative person from two identified accident scenarios affecting the discharge of ALPS treated water. These are:
Case 1 – Leakage from piping
In this scenario, TEPCO assumed that a leakage from a pipe occurred that caused undiluted, treated water, to flow directly into the sea. While countermeasures are in place to detect an incident of this nature within 24 hours or less, it is assumed that this scenario continued undetected over 20 days resulting in the loss of an entire tank group (10 tanks in total), or around 10,000 m3 of treated water.
Case 2 – Leakage from tanks
In this scenario, TEPCO assumed a worst-case accident where there was a catastrophic and immediate rupture of all tanks in the measurement and confirmation facility which resulted in all of the treated water being discharged directly into the sea without any further dilution. This worst-case scenario would result in all three tank groups (30 tanks in total), around 30,000 m3 of treated water, being directly discharged into the sea without dilution.
TEPCO has used a dose criterion of 5 mSv/year in line with the recommendations in GSG-10 [11].
The Task Force discussed the assumptions made by TEPCO in its initial calculation of the impact of these potential exposure scenarios. It was agreed that it is important to calculate the doses from all exposure pathways and to the three age groups considered in the REIA (adults, children and infants),
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without consideration of protective measures or mitigation measures that could be implemented if such an accident occurred. In particular, the Task Force emphasized that the REIA needs to include marine food consumption, even if it is expected that marine products in the restricted zone would in practice be banned, and all radionuclides in the potential source term need to be considered or represented in the relevant calculations.
TEPCO stated that the representative person for the potential exposure assessment is an adult fisherman who consumes a large amount of seafood; the location used for all exposure pathways is from 3 km north of the site. In addition, potential doses from internal exposure pathways for children and infants have been calculated (inhalation of sea spray, ingestion of seafood and inadvertent ingestion of water (children only)). The exposure times assumed for the adult fisherman (representative person) is given in Table 3.9.
Table 3.9. Exposure times used for the representative person for the assessment of potential exposures (taken from REIA)
Item
Case 1 (27 days)
Case 2 (8 days)
Operation hours on a ship
Swimming time Coastline stay time
210 hours
7.1 hours
37 hours
63 hours 2.1 hours
11 hours
Operation hours near fishing nets
140 hours
42 hours
Ingestion of seafood
Ingestion of persons who consume a large amount of seafood in 27 days
Ingestion of person who consume a large amount of seafood in 8 days
For potential exposures, GSG-10 [11] states that the effective dose resulting from the sum of the committed effective dose from internal exposure pathways and the effective dose from external exposure should be calculated. However, it also states that the equivalent dose to certain organs (e.g., thyroid) can be considered; the Task Force suggested that TEPCO could clarify that it had considered equivalent doses in the REIA. TEPCO explained that, although a higher concentration of radionuclides would be released in the event of an accident, the radionuclides are the same and the behaviour in the environment and exposure pathways are the same. TEPCO stated that the predicted effective doses are very low, including the highest dose from 129I (approx. 0.01 mSv for Case 2) and that the assessment of equivalent dose (e.g., to the thyroid for infants) is not needed at these very low levels of effective dose.
The range of potential committed effective doses calculated for the representative person for Case 1 (piping rupture) considering the three tank groups (K4, J1-C and J1-G) is 0.0002 - 0.0003 mSv. For Case 2 (tank damage) the range of potential committed effective doses is 0.008 - 0.01 mSv. The only significant exposure pathway for all age groups is the ingestion of seafood which contributes more than 99% of the committed effective dose. The doses for children and infants are slightly higher than those for adults but for both accident cases are less than 0.02 mSv.
Consideration of Uncertainties and Sensitivity analysis
In Chapter 8 of the REIA, various sources of uncertainties are considered and the possible impact on the results is estimated. TEPCO has considered the following items in the REIA as part of their assessment of uncertainties. Details of the uncertainty, as described by TEPCO, are given in parentheses.
• Selection of the source terms (The composition of radionuclides of ALPS treated water is unknown until secondary treatment and measurement is completed. There is uncertainty associated with the measured values).
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• Modelling of diffusion and transfer in the environment. (The meteorological and oceanographic data has annual variations. There is uncertainty associated with the diffusion simulation model).
• Migration of radionuclides from sea water to beach sediments. (The migration factor from water to beach sediments for the calculation of external dose is not element dependent, so there is uncertainty associated with the dose conversion factor).
• Transfer of radionuclides from sea water to aquatic foods. (The concentration factor for fish is uncertain, particularly for some elements, due to insufficient data).
• Selection of exposure pathways. (There are uncertainties associated with not necessarily having covered all possible exposure pathways).
• Selection of the representative person. (The area around the FDNPS is undergoing reconstruction, so habit data from before the accident have been used. As a result, there are uncertainties due to the actual habits at the current time not being known in detail. There is uncertainty associated with the sea area chosen as being representative of where seafood consumed by the representative person is caught).
In each case, details of the assessment and the calculations carried out to show the sensitivity of the results of the REIA are given. Taking account of uncertainties, the estimated doses to the representative person due to the discharges of ALPS-treated water will be far below the dose constraint.
Regulatory Review of the REIA
As described in Section 3.1, prior to approval of the Implementation Plan and the authorization of discharges, NRA reviews the Implementation Plan, including the REIA and documents its findings in the ‘Review Results Document’. The draft results of its review of the REIA are discussed with TEPCO in public meetings. The Task Force was informed at both NRA missions that during the review meetings with TEPCO, a number of topics had been discussed with TEPCO that required changes and updates to be made to the REIA and that it had been an iterative process. NRA also publishes its draft Review Results Document for 30 days of public review and comment as part of the process. An overview of the major milestones in this process is included in Annex 3.
The NRA presented to the Task Force the main points raised in the discussions with TEPCO and their requests for clarifications and further work on the REIA. The Task Force noted that the international safety standards state that the regulatory body ‘should agree that the methodology adopted is adequate for its proposed purpose’ in discussion with the applicant (GSG-9), which NRA has done.
NRA explained that it had undertaken an independent verification of TEPCO’s marine dispersion model and they presented the results to the Task Force. NRA also presented details and updates regarding its ongoing (at the time of the mission held in January 2023) review of the November 2022 version of the Implementation Plan and REIA. The Task Force specifically noted that NRA has reviewed TEPCO’s approach for calculating activity concentrations in the aquatic environment which is an important topic raised by the Task Force and other interested parties.
3.4.3 Conclusions
The IAEA has concluded that the approach taken by TEPCO and the NRA is consistent with the relevant international safety standards included under this section of the report. Further detailed findings are included below:
• A REIA has been produced and is compliant with the international safety standards. The REIA follows the assessment approach given in IAEA GSG-10 [11] for protection of the public in
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normal operations. The resulting doses are at least a factor of 1000 lower than the dose constraint
of 0.05 mSv per year.
• For the assessment of the radiological impact of accumulation of radionuclides in seabed sediments,
relatively simple models are applied in the REIA. However, the approach taken ensures that the
resulting annual doses over the period of the planned discharge are not underestimated.
• The REIA contains an assessment of doses to flora and fauna using the approach given in GSG- 10, which is in-line with the ICRP approach [12;13]. The estimated dose rates to the three marine representative animals and plants considered (flatfish, crab and seaweed) are more than 1 million
times lower than the derived consideration reference levels set by ICRP.
• In the REIA, TEPCO has included an assessment of the potential doses to a representative person from two identified scenarios resulting in the unintended discharge of ALPS treated water. Considering all ages and tank groups the resulting potential doses are more than a factor of 100
lower than the recommended criterion set by NRA of 5mSv.
• The REIA includes the sensitivity of the doses estimated to the representative person and to
reference animals and plants for relevant assumptions made by TEPCO. Taking account of uncertainties, the annual doses to the representative person (adult, children and infants) will be far below the dose constraint of 0.05 μmSv per year.
• NRA has an iterative process for reviewing the REIA with TEPCO. The review process includes opportunity for the public to comment.
3.5. Source and Environmental Monitoring
3.5.1 Background
There are two general types of monitoring that are appropriate in the context of controlling discharges and the related public exposure. As noted in GSG-9 [9], paragraph 5.75, these are:
a) Monitoring of the source, which involves measuring activity concentrations or dose rates at the discharge point.
b) Monitoring of the environment, which involves the measurement of radionuclide concentrations in environmental media (including foodstuff and drinking water) and of doses or dose rates due to sources in the environment.”
Requirement 14 of GSR Part 3 [8] on monitoring for verification of compliance states that “Registrants and licensees and employers shall conduct monitoring to verify compliance with the requirements for protection and safety.”
In addition, Paragraph 3.54 of GSG-8 [10] states that “Such monitoring should provide sufficient information to determine whether the levels of public exposures comply with the dose limits and to demonstrate that protection and safety is optimized.”
Paragraph 3.37 of GSR Part 3 [8] states: “The regulatory body shall establish requirements that monitoring and measurements be performed to verify compliance with the requirements for protection and safety. The regulatory body shall be responsible for review and approval of the monitoring and measurement programmes of registrants and licensees.”
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In accordance with paragraph 3.38 of GSR Part 3 [8], all monitoring activities are required to adhere to established criteria for quality assurance covering, inter alia, the design and implementation of the monitoring programmes, including properly maintained and calibrated equipment, sampling locations, suitably qualified and trained personnel and documented procedures.
In accordance with paragraph 3.137 of GSR Part 3 [8], the licensee is required to do the following:
• Establish and implement monitoring programmes to ensure that public exposure due to the discharges is adequately assessed and that the assessment is sufficient to verify and demonstrate compliance with the authorization;
• Maintain appropriate records of the results of the monitoring programmes;
• Report or make available to the regulatory body the results of the monitoring programme at approved
intervals;
• Report promptly to the regulatory body any levels exceeding the operational limits and conditions
relating to public exposure, including authorized limits on discharges, in accordance with reporting
criteria established by the regulatory body;
• Report promptly to the regulatory body any significant increase in dose rate or concentrations of
radionuclides in the environment that could be attributed to the discharges, in accordance with
reporting criteria established by the regulatory body;
• Establish and maintain a capability to conduct monitoring in an emergency in the event of unexpected
increases in radiation levels or in concentrations of radionuclides in the environment due to an accident
or other unusual event attributed to the discharges;
• Verify the adequacy of the assumptions made for the assessment of public exposure and the assessment
for radiological environmental impacts.
In accordance with GSG-9 [9], it is recommended to determine the requirements for monitoring, including frequency, by the assessed level of risk of radiological impact. With regard to environmental monitoring, GSG-9 [9] provides recommendations on conducting a preoperational analysis (before the discharges start) to determine the existing levels of background radiation in the environment surrounding the facility prior to the first discharge and to establish a baseline. In accordance with RS-G-1.8 [16], more frequent and detailed environmental measurements may be needed in the early stages of operation and all monitoring programmes are recommended to be subject to periodic review to ensure that measurements continue to be relevant for their purposes.
The regulatory body places requirements on the operator for the frequency for reporting of results and the form and required content of the reports. Paragraph 5.76 of GSG-9 [9] states that “The requirements for source monitoring and environmental monitoring should be specified in the authorization for discharges by the regulatory body. The necessity for and frequency of monitoring should be determined by the assessed level of risk of radiological impact.” The regulatory body is also responsible for review and approval of monitoring programmes, for ensuring their proper implementation and for recording and making available the results. The regulatory body also needs to periodically perform an independent review of the licensees’ or registrants’ source (and environmental) monitoring programmes and make provision for independent monitoring.
Paragraph 5.74 of GSG-9 [9] states that “The operating organization should make available, on request, results from source monitoring. This request may be incorporated within the operational limits and conditions of the authorization or specified in other regulatory documents.”
Paragraphs 5.84–5.85 of GSG-9 [9] provide recommendations for independent monitoring to the regulatory body. Paragraph 5.85 states that;
“The purpose of such independent monitoring may be one or more of the following:
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a) To verify the quality of the results provided by the operating organization; b) To verify the assessment of doses to the representative person”
Paragraph 5.6 of RS-G-1.8 [16] states that ‘One of the main goals of the monitoring programme is to check the assumptions and validate the results of the safety assessment. Thus, the monitoring programme should pay particular attention to the critical [exposure] pathways and critical radionuclides.”
3.5.2 Review and Assessment
Source monitoring
TEPCO’s approach for source monitoring is based on sampling and laboratory measurements of activity concentrations in the sample (‘batch discharges’) and subsequent confirmation that the results demonstrate compliance with the authorized discharge limits. This is in line with Safety Guide RS-G-1.8 para 5.18 [16] which states: “In the case of batch discharges, the material for discharge is adequately characterized by the volume of the batch and the radionuclide composition of a sample taken at the reservoir from the homogenized batch prior to discharge”.
Discharge methodology
TEPCO has provided details of its discharge methodology, the discharge facility that it has constructed at FDNPS and its source monitoring plan in its Implementation Plan and the REIA contained therein. Prior to a given discharge occurring, ALPS treated water will be transferred from individual tanks at the FDNPS site into the measurement and confirmation facilities. The measurement and confirmation facility is shown within the context of the broader ALPS processing, storage and discharge facilitates in Figure 3.20. The measurement and confirmation facilities are comprised of three groups of tanks, with each tank group containing 10 interconnected tanks. If needed the water will be first treated again using a secondary ALPS treatment, before being transferred to the measurement and confirmation facilities.
Circulation and agitation will be applied in each tank group to ensure homogeneity of the ALPS treated water prior to collecting representative samples and performing confirmatory measurements to ensure that the sum of ratios of the legally required activity concentrations of radionuclides other than tritium is less than one (see Section 3.3). The total volume of ALPS treated water contained in a single tank group can be regarded as a ‘batch’ (according to RS-G-1.8 para 5.18). The total radionuclide content of all batches discharged per annum defines the source which is compared to authorized limits on discharges (in Bq per year).
The proposed methodology for measurement and confirmation that each batch of ALPS treated water complies with the regulatory concentration limits prior to discharge can be summarized (for each group of 10 tanks in the measurement and confirmation facility) as follows:
1. An empty tank group in the measurement and confirmation facility is filled.
2. Homogeneity is achieved through agitation (intra-tank) and circulation (inter-tank) [20].
3. A single sample is taken for confirmatory analyses for all 30 radionuclides in the ALPS source term.
4. If the data indicates compliance with the discharge authorization, valves are opened to allow the ALPS
treated water to be transferred for dilution and discharge.
Samples collected from the measurement and confirmation facility are the focus of the IAEA’s corroboration of source monitoring.
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Sr removed Water, etc.
Storage water transfer pump
Sum of ratios of the concentration of each radionuclide other tan tritium to the regulatory standard of each is less than one
ALPS treated water dilution/discharge facility
ALPS treated Water,
etc.
Sample tank of ALPS or ALPS treated water storage tank
ALPS
Sum of ratios of the concentration of each radionuclide other thank tritium to the regulatory standard of each is more than one
ALPS treated Water
Measurement/confirmation facility
Secondary treatment facility
Figure 3.20. ALPS processing, storage and discharge facilities
Dilution Facility
Seawater pip header
Sampling and analysis
Measurement/ confirmation tanks
150m3/day or more
Transfer Facility
Emergency isolation valve
Tritium concentration after dilution less than1,500 Bq/L
Waste
K4 area tank group: 35 tanks
Transfer pump
Seawater transfer pump
Unit 5 intake channel
The water is mixed and diluted
with seawater taken from the sea and transformed to the discharge vertical shaft
Discharge vertical shaft (upper-stream storage)
Transfer pump for ALPS treated water
Discharge facility
Discharge Outlet tunnels
Discharge vertical saft (down-stream storage)
K4- A10
K4- A1
K4- A2
K4- A3
K4- A4
K4- A5
Group A (10 TANKS)
K4- A9
K4- A8
K4- A7
K4- A6
K4- B10
K4- B1
K4- B2
K4- B3
K4- B4
K4- B5
K4- B9
K4- B8
K4- B7
K4- B6
K4- D10
K4- C1
K4- C2
K4- C3
K4- C4
K4- C5
Group C (10 tanks)
K4- D9
K4- D8
K4- D7
K4- D6
K4- E1
K4- E2
K4- E3
K4- E4
K4- E5
(5 tanks)
Group B (10 tanks)
Charge tribasic sodium phosphate
Circulation line sampling point (B)
Temporary circulation pump (B)
K4-B2
K4-B2
K4-B6
K4-B3
K4-B7
K4-B4
K4-B8
K4-B5
K4-B9
Temporary circulation pump (B)
Circulation line sampling point (B)
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K4-B10
Agitator
Agitation demonstration test: Performed in November 2021
Circulation and agitation demonstration test: Performed in February 2022
Figure 3.21. Infrastructure used by TEPCO to ensure homogeneity of ALPS treated water in the measurement and confirmation facility
Homogeneity and representative sampling
To ensure that samples taken from each batch are representative, achieving homogeneity in the measurement and confirmation tanks is fundamental. TEPCO has carried out an experiment to demonstrate how it intends to achieve homogeneity through agitation (intra-tank) and circulation (inter-tank).
The experiment was based on the addition of a known concentration of a stable, easy to measure tracer – tribasic sodium phosphate – into the tank group contents (see Figure 3.21). Circulation and agitation was then performed. Samples of the phosphate tracer were taken beforehand, while circulation and agitation was in progress and after 144 hours (6 days) had passed when there was indication that sufficient homogeneity within the tank group contents had been achieved. Analysis of the latter samples, 30 in total taken at three locations – upper (10m), middle (5m) and lower (1m) – from each of the 10 individual tanks demonstrated a relative standard deviation in phosphate concentrations of 10.5%. There was also consistency, within measurement uncertainty, between the known volume of phosphate added and that determined following dilution in the tank group contents from these measurements.
TEPCO also analysed the 30 samples for activity concentrations of tritium and other radionuclides that could be detected (60Co, 90Sr, 129I, 137Cs) and compared them to results from before the homogeneity test [19]. The relative standard deviation for tritium was 1.9%, reduced from 8.1%. The degree of heterogeneity in activity concentrations measured at each point in each individual tank was also demonstrated to be lower for the other radionuclides, with the exception of 60Co which effectively remained the same. The relative standard deviations for these radionuclides following circulation and agitation ranged from 4.5% to 14.9%.
On the basis of this experiment, TEPCO concluded that an adequate degree of homogeneity that would allow for representative samples to be taken had been achieved. Equivalent equipment for circulation and agitation has been incorporated into its operational plan for managing the discharges.
To ensure the ongoing effectiveness of this process, the maintenance of this equipment is included in the general maintenance plan for the measurement and confirmation facilities that TEPCO has developed. TEPCO shared this maintenance plan with the IAEA and has submitted it to the NRA for approval as part of the NRA’s inspection programme.
Measurement and confirmation
The radionuclides to be measured and confirmed as being below regulatory limits prior to discharge of each batch of ALPS treated water are those identified in the source term (see Section 3.3).
The detection limit of each method is informed by the regulatory limit for discharge of each respective radionuclide – TEPCO’s target for detection limits is <1% of the respective regulatory limit. The results of the first ILC for corroboration of source monitoring [1] showed that they have achieved this detection limit for all 30 radionuclides in the ALPS treated water source term (see Table 3.10).
A lot of radionuclide-specific measurement data exist – over many years since 2011, from different points in the processing stream, covering a broad range of radionuclides. These include long-lived, high-yield fission and neutron activation products, and isotopes of uranium and transuranics, including isotopes of Np, Pu, Am, and Cm.
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TABLE 3.10. COMPARISON OF TEPCO’S DETECTION LIMITS WITH RESPECTIVE JAPANESE REGULATORY LIMITS FOR DISCHARGE (Table 9 [1])
Regulatory limit (RL) (Bq/L)
Detection limit (DL) (Bq/L)
DL relative to RL (%)
3H 60000
14C 2000
54Mn 1000
55Fe 2000
60Co 200
63Ni 6000
79Se 200
90Sr 30
99Tc 1000
106Ru 100
125Sb 800
129I 9
134Cs 60
137Cs 90
144Ce 200
147Pm 3000
151Sm 8000
154Eu 400
155Eu 3000
234U 20
238U 20
237Np 9
238Pu 4
239Pu 4
240Pu 4
241Pu 200
241Am 5
244Cm 7
210 0.35
1.6 0.080
0.047 0.0047
19 0.94
0.028 0.014
8.1 0.13
0.85 0.43
0.069 0.23
0.43 0.043
0.42 0.41
0.10 0.013
0.026 0.29
0.057 0.10
0.036 0.040
0.59 0.30
0.32 0.011
0.012 0.00015
0.072 0.018
0.19 0.0063
0.031 0.15
0.031 0.15
0.031 0.34
0.031 0.76
0.031 0.76
0.031 0.76
0.84 0.42
0.031 0.61
0.031 0.44
TEPCO has put significant effort into characterizing the source term and, because this is already more than sufficiently conservative, the IAEA supports using the list of radionuclides identified as a basis for source monitoring. IAEA does not recommend monitoring for additional radionuclides, especially those identified in early iterations of the methodology. These include short-lived radionuclides. Monitoring for these radionuclides that could not possibly be present in the water more than 12 years after cold shutdown could result in confusion.
TEPCO has established a quality management system (QMS) for the analysis of radionuclides (for both source and environmental monitoring). The NRA inspects this and other laboratory and quality manuals before the start of operation, and as necessary once the discharges are in option. The aspects of TEPCO’s QMS subject to inspection include procurement, analytical method development, human resources and training, maintenance and calibration of instruments, and document management and record keeping. Each of these has been linked to relevant clauses of ISO 9001 [20] and ISO/IEC 17025 [21] as evaluation criteria that are utilised during NRA’s inspections.
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TEPCO’s sampling and analytical methods for both source and environmental monitoring related to ALPS treated water have also been reviewed by the IAEA. This involved both desktop and onsite components (a technical review of TEPCO’s laboratories at FDNPS was conducted March 2023), in which a representative example of relevant technical records at TEPCO’s FDNPS laboratories were assessed.
ALPS treated water has been characterized for alpha emitters as per the source term. Reported activity concentrations are often <1/100th of the regulatory limit. To ensure effective use of resources and optimization of analysis time whilst remaining fit for purpose, the utilization of a gross alpha screening method is justified. A pre-defined action limit is set, and if it is exceeded, a structured response plan is in place.
When discharges are operational, daily monitoring of tritium in samples of diluted ALPS treated water collected from the discharge piping after dilution will also be undertaken by TEPCO to ensure that there is compliance with the discharge limit of 1,500 Bq/L for tritium. This sampling point will be closest to the discharge point and, being diluted, the samples will be identical to the ALPS treated water actually released into the environment.
Independent monitoring by NRA
GSG-9 requires that independent monitoring should be undertaken by the regulatory body or on behalf of the regulatory body by another organization that is independent of the operating organization.
The NRA has undertaken a verification of TEPCO’s source monitoring. It contracted a Technical Support Organization (TSO) laboratory (JAEA, Nuclear Safety Research Centre) to analyse a sample of ALPS treated water taken prior to the start of discharges for a subset of radionuclides: tritium, 14C, 36Cl, 55Fe, 60Co, 79Se, 90Sr, 99Tc, 106Ru, 125Sb, 129I, 134Cs, 137Cs. The sample was taken at the same time as those used for the IAEA’s 1st ILC for corroboration of source monitoring [1] ;TEPCO reported identical results for both exercises. For radionuclides for which activity concentrations above detection limits were reported by both TEPCO and JAEA, the results were compared against TEPCO’s results using scores [22]. All such results (tritium, 14C, 60Co, 90Sr, 99Tc, 129I, 137Cs) were found to be in agreement, although JAEA were required to re-analyse the sample for 14C.
Additionally, NRA requires that certain radionuclides are analysed for their presence in ALPS treated water (separate from the analytical comparison with TEPCO results) as an additional level of independent assessment. The analytical results prepared for NRA include the identification of any discrepancies and their potential cause. NRA explained the process for responding to discrepancies between the independent monitoring and TEPCO measurements and that the information required for a root cause analysis (e.g., quality assurance and control processes, analytical method/instrumentation used) should be defined in advance.
Samples collected from the K4-B tank group were the focus of the IAEA’s first Interlaboratory Comparison (ILC) for corroboration of source monitoring [1] and Section 4. The results of this ILC confirmed the appropriateness of TEPCO’s analytical methods and sample collection procedures, including the techniques used to ensure homogeneity and thus to obtain representative samples.
Environmental monitoring
Monitoring of the marine environment involves the measurement of radionuclide concentrations in environmental media (including seawater, sediments, seafood and flora and fauna). The objectives
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of environmental monitoring are to verify the results of source monitoring and the adequacy of the assumptions made for the assessment of public exposure and the assessment of radiological environmental impacts. Additional reasons for environmental monitoring are to detect any unpredicted changes in activity concentrations and to evaluate long term trends; to provide data to enable the assessment of actual or prospective doses to the reference person; and to provide information to the public.
Environmental monitoring is conducted off-site. The activity concentrations detected in environmental monitoring are normally lower than those estimated by conservative models, and, consequently, retrospective dose calculations are often based on source monitoring data and appropriate modelling.
The Government of Japan’s Comprehensive Radiation Monitoring Plan (CRMP) [7] is a coordinated initiative undertaken by government agencies aimed at monitoring and managing radiation levels throughout the country. It is coordinated jointly by the Ministry of Environment and NRA. It was developed in April 2011 in response to the accident at FDNPS and has been reviewed and revised as necessary each year since [7]. The objectives of the CRMP include:
Monitor Radiation Levels: The CRMP has established a comprehensive monitoring system to continuously measure radiation levels in environmental media, including air, soil, water, and food.
Assess Health Risks and Plan and Evaluate Interventions: The collected data are analyzed to assess the potential health risks associated with radiation exposure. This includes evaluating the impact on individuals, communities, and the environment, and identifying any areas or populations that may require specific attention or intervention such as decontamination or re-evaluation of evacuation zones.
Ensure Transparency and Communication: The CRMP emphasizes effective communication of e results of monitoring to the public. By providing accurate and accessible information, the plan aims to enhance public awareness, understanding, and confidence in radiation monitoring efforts.
Environmental Protection: The CRMP focuses on safeguarding the environment, including marine ecosystems, from the potential impacts of radiation. It includes monitoring and assessing the transfer of radioactivity between different environmental compartments, for example seawater, marine sediments and biota such as fish, shellfish and seaweed.
The marine monitoring component of the CRMP defines sampling locations, frequency of sampling, detection limits and responsibilities of the organizations involved. Monitoring comprises sampling and analysis of seawater to different depths, sediment and marine biota (fish, shellfish and seaweed) and is separated into zones at varying distances from the FDNPS site which are: the sea area close to FDNPS; the coastal area; the off-shore area; and the outer sea area. The aim of this plan includes ensuring a comprehensive overview of the radiological situation in the marine environment and providing an adequate basis for assessments of radiation exposures from marine pathways.
With a view to assisting the Government of Japan in its objective of making the marine monitoring component of the CRMP comprehensive, credible and transparent, the IAEA, through its Marine Environment Laboratories, is helping to ensure the high quality of data and to prove the comparability of the results. A project ‘Marine Monitoring: Confidence Building and Data Quality Assurance’ was initiated in 2014 as a follow-up activity to recommendations made on marine radioactivity monitoring in a report issued by the IAEA in 2013 which reviewed Japan’s efforts to plan and implement the decommissioning of the FDNPS. The project has been extended several times since. So far, 10 sampling missions and interlaboratory comparisons (ILCs) and 7 proficiency tests (PTs) have been completed and the project is ongoing.
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To date the results of the ILCs, published as IAEA reports, for example [26; 27], have concluded that Japan’s sample collection procedures follow the appropriate methodological standards required to obtain representative samples and that Japanese laboratories involved in the analyses of radionuclides in marine samples for the CRMP demonstrate a high level of accuracy and competence. These results are backed up up by the conclusions of the PTs. More information on this work is available through a dedicated website6.
The IAEA is also corroborating the results of environmental monitoring undertaken specifically to address the discharges of ALPS treated water (see Part 4.2 and this Section).
The locations at which samples are collected for analysis in interlaboratory comparisons for the near shore sea area, coastal sea area and offshore sea area [28].
Revision of Japan’s Comprehensive Radiation Monitoring Plan
Japan’s Comprehensive Radiation Monitoring Plan (CRMP) has, since March 2022, been revised to address ALPS treated water discharges. An expert group (nominated by the Government of Japan) provided guidance on the enhancement of the CRMP to address the ALPS treated water discharges and will continue to be utilized to provide advice on details of the environmental monitoring taking place around FDNPS. An overview of the interaction of the expert group with the MOE (coordinator of marine monitoring within the CRMP), the NRA and TEPCO as a data provider is schematized in Figure 3.22. The expert group has considered the parameters set regarding location and frequency of environmental sampling and will also be involved in reviewing the monitoring data. The coordination of the organisations contributing to the CRMP and the expert group is presented in Figure 3.22.
NRA TEPCO
Regulation
Data
Advice and confirmation
Figure 3.22: The interaction of the expert group with the MOE (coordinator of marine monitoring within the CRMP), the NRA and TEPCO
The revised plan includes monitoring of tritium in seawater at an increased frequency plus the identified “seven major radionuclides” in seawater quarterly. Monitoring of organically bound tritium (OBT), free- water tritium (FWT) and 14C in fish and 129I in seaweed has also been undertaken.
As already stated in Section 3.4, the radionuclides contributing most to ingestion doses - over 90% of the total – are 129I, 14C, 55Fe and 79Se. These radionuclides are included in the CRMP: 125I is measured in seaweed (as a bioindicator); 14C (in fish); and 55Fe and 79Se in seawater once a year.
6 https://www.iaea.org/about/organizational-structure/department-of-nuclear-sciences-and-applications/division-of-iaea-marine-environment-laboratories/ marine-monitoring-confidence-building-and-data-quality-assurance)
Expert meeting
MOE
FUKUSHIMA Pref.
FAJ
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Baseline monitoring
Baseline monitoring has started and is in line with GSG-9 recommendations on conducting a preoperational analysis (before the discharges start) to determine the existing levels of background radiation in the environment surrounding the facility prior to the first discharge and to establish a baseline. It is also in accordance with the possible need for more frequent and detailed environmental measurements suggested by RS-G-1.8 [16], which may be needed in the early stages of operation. The monitoring programmes should be reviewed periodically to ensure that it continues to be relevant for its purposes.
The baseline monitoring, along with measurements made in the vicinity of Japan and the wider Asia Pacific region is important to establish ‘background’ levels of radionuclides in the oceans and marine biota and seafood. The activity concentrations in the marine environment estimated in the REIA are very low compared to the available measured values in the region [24]. It is expected that the results from the monitoring undertaken by TEPCO and within the CRMP will not be statistically distinguishable from the ‘background’ values, at distances of a few km from the FDNPS. Therefore, any measurable concentrations of tritium, or other radionuclides in the Asia Pacific region (or beyond) should not automatically be attributed to the discharged water from the FDNPS.
Independent monitoring by NRA
GSG-9 also requires that independent monitoring should be undertaken by the regulatory body or on behalf of the regulatory body by another organization that is independent of the operating organization. The NRA has provided details on how the results of TEPCO’s monitoring will be assessed and compared against those from the organizations independent of TEPCO under the CRMP [7]. NRA’s requirements on TEPCO for identifying and resolving discrepancies between TEPCO’s monitoring results and those from independent monitoring (CRMP) have also been described. This involves statistical analysis of the time-series of measurement results for each radionuclide from each sampling location by NRA. Any discrepancies will be evaluated against the results from neighbouring sampling locations.
Further information on the IAEA’s independent corroboration of environmental monitoring can be found in Part IV of this report.
Link of monitoring programme to REIA
The Task Force discussed with TEPCO and NRA the importance of using the environmental monitoring programme to help verify the impact of discharges on environmental concentrations and doses that have been calculated in the REIA; this is one of the roles of environmental monitoring described in the international Safety Standards.
The importance of linking reviews of the environmental monitoring programme to the results of the REIA is vitally important and was also discussed. This will ensure that environmental monitoring is focussed on the most important radionuclides and exposure pathways contributing to the doses to the public.
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3.5.3 Conclusions
The IAEA has concluded that the activities and approach taken by TEPCO and NRA are consistent with the relevant international safety standards included under this section of the report. Further detailed findings are included below:
• The IAEA acknowledges that clearly defined plans for source monitoring covering sampling and analysis at the measurement and confirmation facility is in place. Additionally plans for sampling of water after dilution are also noted.
• TEPCO has put significant effort into characterizing the source term and, because this is already sufficiently conservative, the IAEA supports using the list of radionuclides identified as a basis for source monitoring.
• IAEA has found TEPCO’s methodology to achieve homogeneity and thus representative samples to be appropriate.
• Quality criteria for both source and environmental monitoring have been clearly defined by the NRA and observed to have been met by TEPCO.
• Arrangements for independent monitoring by the NRA, for source monitoring, were found to adhere to the requirements of the international safety standards.
• A clearly defined plan for enhanced environmental monitoring by TEPCO and the Government of Japan to address the discharges of ALPS treated water is in place.
• The activity concentrations in the marine environment estimated in the REIA are very low compared to the available measured values in the region and these will not be distinguishable from the ‘background’ values, at distances of a few kilometres from the FDNPS.
• Due to the unique nature of Japan’s CRMP, government agencies (such as NRA) and TEPCO conduct monitoring independently but according to a common plan. Arrangements for checking data for consistency and the identification and investigation of discrepancies are in place.
3.6. Involvement of Interested Parties
3.6.1 Background
In accordance with GSR Part 3 [8], the government or the regulatory body are required to provide information to, and engage in consultation with, parties affected by its decisions and, as appropriate, the public and other interested parties.
In the IAEA international safety standards, the term interested parties is used in a broad sense to mean a person or group having an interest in the activities and performance of an organization. In the context of radioactive discharges to the environment, ‘interested parties’ typically include individuals or organizations representing members of the public; industry; government agencies or departments whose responsibilities cover public health, nuclear energy and the environment; scientific bodies; the news media; environmental groups; and groups in the population with particular habits that might be affected significantly by the discharges, such as local producers and indigenous peoples living in the vicinity of the facility or activity under consideration.
GSR Part 3 [8] states:
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“3.124. When a source within a practice could cause public exposure outside the territory or other area under the jurisdiction or control of the State in which the source is located, the government or the regulatory body: ...
(c) Shall arrange with the affected State the means for the exchange of information and consultations, as appropriate.”
Paragraph 5.99 of GSG-9 [9] states: “Because the regulatory control of radioactive discharges takes into account both operational and societal aspects, such as radioactive waste management in the facility and the optimization of the level of protection of the public, there are a number of different interested parties whose views should be considered, as appropriate. A process resulting in the granting of an authorization for discharges is likely to necessitate an exchange of information between the regulatory body, the applicant, and other interested parties. Some interested parties may be located in other States, especially in neighbouring States.”
Paragraph 5.101 of GSG-9 [9] further notes that:
“In some cases, there may be specific requirements for the exchange of information with interested parties before the authorization for discharges has been finalized. One means of doing this is through the establishment of a group reflecting local public concerns for liaison with both the operating organization and the regulatory body. Among other things, the results of the prospective radiological environmental impact assessment should be a focal point of the discussions.”
Any exchange of information relating to the control of discharges may form part of other decision making processes. Such exchange of information should include consideration of societal aspects, for example public concern over the risks associated with radiation exposure, and consideration of the doses to the public that might result from discharges during operation.
3.6.2 Review and Assessment
Throughout the safety review, the Task Force carefully considered how the Government of Japan, and TEPCO, involved interested parties in their activities and planning for the discharge of ALPS treated water. In general, the Task Force used the issuance of the Basic Policy by the Government of Japan as the starting point for consideration of this topic, but when available, the Task Force appreciated additional more historical data provided by METI, TEPCO, or NRA that would help to provide useful background information.
METI provided an overview of the primary means through which METI, MOFA, and TEPCO engage with interested parties. These include briefing sessions for diplomatic missions in Tokyo (more than a hundred such sessions had been held since 2011), bilateral interactions through various forms of communication with other Governments or authorities, including those of neighbouring countries and regions, conduct of site tours, presentations at technical conferences, public reports that detail the progress of the site decommissioning and presentation of environmental monitoring results, publishing information in international periodicals to ensure the public is made aware of developments.
METI noted that the Government of Japan has been engaging with the public on the issue of handling ALPS treated water for many years; however, the past two to three years have seen many opportunities to share relevant updates and developments with interested parties. METI also noted that some outreach to
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neighbouring countries has been conducted in the native language of those countries to facilitate a better understanding and exchange of views.
METI further highlighted that owing to intense communication efforts over the past 10 years, the public is reasonably familiar with safety concepts and how these relate to the decommissioning of the Fukushima Daiichi Nuclear Power Station. However, more nuanced concepts such as risk reduction and optimization of decommissioning, which are also relevant to the handling of ALPS treated water, are still not widely understood by the general public.
The Task Force noted that the involvement of interested parties can improve the understanding of the characteristics of the representative person and the acceptability of resulting estimated dose with site- specific habit data provided by relevant interested parties, and that involvement of interested parties is seen as an important input to the optimization process. The Task Force also noted that the long-term nature of the proposed discharge could present unique or different communication needs and TEPCO could consider elaborating a plan to describe the involvement of the interested parties throughout the duration of the project. In particular, the Task Force stressed the importance of maintaining awareness of changes in the local area (e.g., use of the land) and population habits as that could have a direct impact to the assumptions in the REIA and the definition of the representative person.
The Task Force also highlighted the critical role of a regulatory body in ensuring interested parties are involved and their views considered as part of the authorization process. Throughout the review, the NRA provided periodic updates of their progress and how the involvement of interested parties was factored in. This primarily considers two different approaches: 1) public comment periods for key regulatory documents and milestones, and 2) outreach and engagement activities conducted specifically by the regulatory body for interested parties in local, national, and international settings.
The NRA provided an overview of the actions undertaken for public communication and involvement of interested parties. The NRA highlighted that their main message to the public on ALPS Treated Water Discharge is: “ALPS treated water discharge does not have substantial adversary effects to health and the environment as far as satisfying the regulatory requirements and it is necessary to progress the decommissioning of the FDNPS.”
After TEPCO submitted amendments to their implementation plan to facilitate the discharge of ALPS treated water at FDNPS, the NRA and TEPCO have been participating in regular review meetings to discuss TEPCO’s plan. These review meetings are open to the public, both for in-person attendance and via web-streaming. All materials, including the minutes of the meetings, are posted on the NRA website, and are also made available in English. The NRA explained that they intend to publish the draft result of their review, solicit public comments and reflect such comments to the draft as appropriate. More specifically, the draft results will be posted on the Government website in Japanese, and the English version will also be provided for reference. The period for receiving comments from the public is generally set at one month. For the first review of the revised Implementation Plan, as an example, the NRA noted that the review results were available for 30 days and after this period closed they report 1,233 received comments. As part of its second mission to NRA, the Task Force requested further information about how the public comments are handled. NRA noted that they are first reviewed for technical relevance to the topic at hand (i.e., discharge of ALPS treated water) then further organized into key topics and duplicate comments/ questions are condensed. The NRA issued its regulatory approval of the revised Implementation Plan on 10 May 2023 only after fully considering the feedback received.
The NRA highlighted to the Task Force their communication framework at the national level that consists of the following components:
• Local government meetings held in prefectures around Fukushima; 96
• Explanations provided to political parties and interested groups after the adoption of the Basic Policy;
• National diet7 sessions where the status of NRA’s review and future schedules have been raised;
• Regular press conferences for the provision of updated information to the public;
• NRA’s website where NRA posts the materials and minutes of the review meetings.
At the international level, the NRA has held meetings with other countries and organizations and explained the up-to-date status around the ALPS treated water discharge. The NRA has provided and indicated their willingness to continue to provide information to neighbouring states as appropriate, including through the framework for cooperation among regulatory bodies, and the NRA response to questions submitted by other countries.
The Task Force commented positively on the efforts undertaken by the NRA and noted that the NRA is following a comprehensive approach in their communication with interested parties. In future engagements the Task Force noted the importance of:
• Using appropriate language and presentation means when communicating with the public.
• Clarifying the difference in risks associated with ALPS treated water discharge from those
associated with overall decommissioning of the site.
• Ensuring that the actions undertaken by the NRA are presented in an open and transparent manner
and can be reviewed by interested parties in the future.
3.6.3 Conclusions
The IAEA has concluded that the activities and approach taken by TEPCO and NRA are consistent with the relevant international safety standards included under this section of the report. Further detailed findings are included below:
• The approaches for engagement with local, national and international interested parties will differ, however the need to address the views of interested parties over the entire length of the proposed discharge will remain an important factor for sustainability.
• The identification of interested parties by the Government of Japan, and TEPCO, was conducted in such a way to ensure that a wide range of interested parties have been included in the associated outreach and communication efforts.
• The Government of Japan, TEPCO, and NRA have provided information to and engaged in consultations with the parties that are affected by the planned discharge of ALPS treated water. This includes both international, and domestic, interested parties.
• The involvement of interested parties in the domestic regulatory authorization process managed by NRA has been clearly demonstrated.
• TEPCO and METI have conducted significant outreach activities to ensure transparency.
7 The National Diet is Japan’s bicameral legislature and it is the highest organ of State power.
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3.7. Occupational Radiation Protection
3.7.1 Background
Control, monitoring, assessment and recording of occupational exposure are essential for proper management of radiation protection of workers in any workplace. GSR Part 3 [8] sets requirements applicable to the regulatory body as well as to registrants or licensees. These requirements include the establishment of dose limits for workers, optimization of protection and safety of workers, including dose constraints applied to occupational exposure control in planned exposure situations through a licensing process.
Occupational radiation protection has a strong operational emphasis and GSR Part 3 also sets requirements for establishing and maintaining organizational, procedural and technical arrangements for the designation of controlled areas and supervised areas, for local rules and for monitoring of the workplace, in a radiation protection programme with necessary guidance provided by GSG-7 [23].
Paragraph 5.3 of GSG -7 states that:
“Contamination of areas can arise from facilities and activities that are subject to regulatory control in terms of the requirements for planned exposure situations, as a result of authorized activities such as discharges, the management of radioactive waste and decommissioning. An exposure situation resulting from such contamination is controlled as part of the overall practice and is, therefore, a planned exposure situation and not an existing exposure situation.”
The responsibilities of the regulatory body specific to occupational exposure in planned exposure situations are laid out in Requirement 19 and paras 3.69–3.73 of GSR Part 3 [8]. The regulatory body is required to establish and enforce requirements to ensure that protection and safety is optimized and is required to enforce compliance with the applicable dose limits. Further, the regulatory body is responsible for the establishment and enforcement of requirements for the monitoring, recording and control of occupational exposures in planned exposure situations in accordance with the requirement 25 of GSR Part 3 [8], and for the review of monitoring programmes of registrants and licensees.
Requirement 21 of GSR Part 3 [8] states that: “Employers, registrants and licensees shall be responsible for the protection of workers against occupational exposure. Employers, registrants and licensees shall ensure that protection and safety is optimized and that the dose limits for occupational exposure are not exceeded.”
In planned exposure situations, employers, registrants and licensees are responsible for ensuring that appropriate radiation protection programmes are established and implemented in accordance with the requirement 24 of GSR Part 3 [8], including organization of radiation protection (management), radiation dose and medical surveillance of occupationally exposed workers (radiation work categories & surveillance), area and zoning based on radiation exposure conditions / pathways, work permit, training, procedures and control arrangements.
Requirement 22 of GSR Part 3 [8] states that: “Workers shall fulfil their obligations and carry out their duties for protection and safety.” This requirement reflects that workers can by their own actions contribute to the protection and safety of themselves and others at work. For contractors providing specialized services (in the case of ALPS, entire operation is conducted by contractors), legislative arrangements are required for employers to ensure that workers of contractors, including subcontractors, are provided
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with the necessary information on radiological characteristics of the workplace and the management of facilities should ensure that contractors carry out work with competent personnel.
In accordance with the GSR Part 3 [8] and GSG-7 [23], special attention should be given to the establishment and maintenance of a national dose registry as a central point for the collection and maintenance of dose records. The storage of information at the national dose registry should be designed to allow workers, during and after their working life, to retrieve information on the doses they received while being occupationally exposed.
Coordination of different authorities with responsibilities for safety within the regulatory framework including safety of workers is required by GSR Part 1 (Rev.1) and arrangements for protection of workers is considered in the process of applying graded approach to review and assessment of the facility or activity [14, 8].
Radiation protection of workers is only one element in ensuring the overall health and safety of workers and should be established and implemented in close cooperation with those responsible for other areas of health and safety such as industrial hygiene, industrial safety and fire safety (para 3.50 of GSG-7 [23]).
3.7.2 IAEA Review and Assessment
Arrangements under the Radiation Protection Programme
The Nuclear Regulation Authority (NRA) and the Ministry of Health, Labor and Welfare (MHLW) are the primary governmental authorities responsible for the implementation of the legislative requirements concerning occupational exposure through “the Reactor Regulation Act” (which includes provisions for the establishment of controlled areas, measuring and recording of air dose rates of controlled areas, measures to control exposure of radiation workers and special education) and “the Industrial Safety and Health Act” (which includes provisions for medical examinations and delivering exposure records to the designated institution), respectively. The NRA described their role during the March 2022 mission in the establishment of dose limits for occupational exposure, and also in the approval of an operational safety programme (including arrangements for monitoring and recording of occupational exposures). The NRA explained that optimization of the radiation protection of workers at Fukushima Daiichi Nuclear Power Station (FDNPS) is conducted using dose limits and concentration limits for radioactive materials in the air inhaled by workers with limits prescribed by the NRA.
The Tokyo Electric Power Company (TEPCO) explained during the first mission that the entire site is designated as a controlled area and arrangements are in place for individual and workplace monitoring of occupational exposure according to “the Radiation Controlled Area Measuring Guide” and “the Guide for Management of Setting, Releasing and Changing of Controlled Areas and Managed Areas”.
Radiation Protection Programme (RPP)
Registrants and licensees are responsible for protection and safety. These responsibilities include the performance of an appropriate safety assessment and the establishment and maintenance of a system of protection and safety to protect workers against exposure.
The RPP for occupational exposure, which is a combination of good design, high quality construction and proper operation, primarily includes, as appropriate (Paragraph 3.60 of GSG-7):
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a) The maintenance of organizational, procedural and technical arrangements for the designation of controlled areas and supervised areas, for local rules and for monitoring of the workplace;
b) The assessment and recording of occupational exposure;
c) Workers’ health surveillance;
d) Provision of adequate information, instruction and training.
References: [8; 24]
Assessment and Recording of Occupational Exposure and Workers’ Health
Surveillance
Specific to ALPS treated water discharge facility, occupational exposures are associated with the construction, operation and maintenance of systems required for the discharge. TEPCO explained in the November 2022 mission that all workers entering the management area of FDNPS (the entire site is considered a controlled area) are required to use personal protective equipment (PPE) and individual passive /active dosimeters provided by authorized technical service providers operated under a quality management system, regardless of the magnitude of the exposure. Additionally, all workers are monitored periodically by in-vivo radiobioassay for internal exposure due to 137Cs, using a whole body counter with plastic scintillation detectors. Nasal cavity sampling and monitoring for 90Sr is conducted at FDNPS, and a software called “Monitoring to Dose Calculation” (MONDAL) is used for internal dose assessment.
TEPCO provided information on the individual monitoring programme for exposures from intakes of radionuclides which is conducted for identified workers who are exposed over recording levels due to contamination as well as those who use respiratory protective equipment. TEPCO explained that occupational exposure data for workers, including contractors, is gathered, stored, and maintained by TEPCO and submitted to a central database. Also, a programme for workers’ health surveillance is conducted in the FDNPS, consisting of medical checks every 6 months with necessary record keeping arrangements based on the “Health Monitoring Manual” and the “Long-term Healthcare Manual”.
TEPCO provided information explaining that the requirement for dose assessment and optimization applies only where the doses of workers are likely to exceed certain levels and therefore only a small proportion of the workforce would need to be assessed. TEPCO will carry out further workplace and individual monitoring programmes, as appropriate, for dose assessment purposes and for providing warning of changing exposure conditions. TEPCO explained that for all work conducted in the facility, there are radiation control plans in place, submitted by the responsible organization (including contractors) and validated by TEPCO. Meetings to discuss the control of exposure in work plans (so-called ‘ALARA’ meetings) are organized in advance at the planning stage.
In addition, TEPCO explained that internal doses due to tritium are low. Tritium is measured as HTO in water and then its concentration in the air is estimated. TEPCO added that all workers wear appropriate personal protective equipment although exposure due to inhalation is not expected.
The NRA provided detailed information during the January 2023 mission about the basis for regulatory oversight with regard to monitoring requirements (e.g., implementation of investigation levels and recording levels) through the implementation of the NRA Ordinance for FDNPS, and NRA Notification for FDNPS. Regarding occupational exposure record keeping, the NRA explained that the Radiation Effects Association (Radiation Dose Registry Center, RADREC) is the registry institution of dose records of radiation workers (i.e., nuclear workers, radioisotope workers, and decontamination workers) as stipulated in the NRA Ordinance for FDNPS.
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Monitoring and recording of occupational exposure
The personal (individual) monitoring of workers for occupationally exposed workers and the recording of the radiation doses received by workers for proper occupational exposure control are important aspects of any Radiation Protection Programme.
Paragraph 3.105 of GSR Part 3 states that: “Records of occupational exposure shall include:
a) Information on the general nature of the work in which the worker was subject to occupational exposure;
b) Information on dose assessments, exposures and intakes at or above the relevant recording levels specified by the regulatory body and the data upon which the dose assessments were based;
c) When a worker is or has been exposed while in the employ of more than one employer, information on the dates of employment with each employer and on the doses, exposures and intakes in each such employment;
d) Records of any assessments made of doses, exposures and intakes due to actions taken in an emergency or due to accidents or other incidents, which shall be distinguished from assessments of doses, exposures and intakes due to normal conditions of work which shall include references to reports of any relevant investigations.”
GSG-7 provides guidance for the collection, analysis, and dissemination of occupational radiation exposure information in the form of national dose registry as a central point for the collection and maintenance of dose records.
Optimization of occupational exposure
The NRA explained that optimization of the radiation protection of workers at FDNPS is conducted using dose limits and concentration limits for radioactive materials in the air inhaled. Some Task Force members highlighted that there is no single way to implement optimization of occupational exposure and added that the approach followed by the NRA is well documented.
TEPCO benefits from the implementation of optimization of protection and the use of dose constraints for the radiation protection of workers in addition to their own long-term operational experience. TEPCO effectively utilizes safety measures such as target values, daily dose follow-ups, and work permits related to workplace characteristics (including ALPS treated water discharge facility).
Optimization of protection and safety
For occupational exposure, optimization of protection and safety should be considered at all stages in the lifetime of equipment and installations, in relation to both exposures from normal operations and potential exposures. Optimization is an obligation of means, and not an obligation of results in the sense that the result of optimization depends on processes, procedures, and judgements and is not a given value of dose or exposure. The result of optimization depends on processes, procedures, and judgements and is not represented by a given value for exposure.
Paragraph 1.23 of GSR Part 3 [8] states that: “... For occupational exposure, the dose constraint is a tool to be established and used in the optimization of protection and safety by the person or organization responsible for a facility or an activity.... After exposures have occurred, the dose constraint may be used as a benchmark for assessing the suitability of the optimized strategy for protection and safety...that has been implemented and for
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making adjustments as necessary. The setting of the dose constraint needs to be considered in conjunction with other health and safety provisions and the technology available.”
3.7.3 Conclusions
The IAEA has concluded that the activities and approach taken by NRA and TEPCO are consistent with the relevant international safety standards included under this section of the report. Further detailed findings are included below:
• Relevant regulatory arrangements in Japan for occupational radiation protection are consistent with the relevant international safety standards. The IAEA confirms that NRA’s approach to enforce the occupational exposure control, monitoring, assessment and recording is sufficient.
• TEPCO has a reliable and sustainable radiation protection programme. The IAEA observed clear evidence of self-regulation by TEPCO for an advanced design and implementation of occupational exposure control measures and monitoring arrangements related to the operation of ALPS treated water discharge facility.
• Occupationally exposed workers working at FDNPS including workers involved in activities associated with the planned discharges of ALPS treated water, regardless of whether they are contractors or staff, are under the same occupational radiation protection regime.
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PART 4
MONITORING, ANALYSIS, AND CORROBORATION
4.1. Overview of Corroboration Activities
The IAEA’s safety review of the handling of ALPS treated water at FDNPS includes the following three components: the assessment of protection and safety; the review of regulatory activities and processes; and independent sampling, data corroboration, and analysis activities. The third component is included in the overall safety review to provide confidence in the accuracy of data provided by TEPCO and the Japanese authorities. Additionally, these corroboration activities provide another layer of assurance that TEPCO and the Government of Japan are adhering to relevant international safety standards. The IAEA’s corroboration will not be exhaustive but rather is intended to allow interested parties to infer the accuracy of all the available data by validating the key data provided by the laboratories in Japan responsible for producing and publishing analytical results from the ALPS treated water discharge process. The IAEA’s corroboration activities will complement the broader monitoring and verification regime that is the responsibility of the Government of Japan who maintains the overall responsibility for the safety of its nuclear facilities and activities. The IAEA’s involvement is a critical element for demonstrating the accuracy and validity of data being reported by Japanese authorities related to the discharge of ALPS treated water, and therefore building confidence in the overall IAEA safety review.
Currently, the IAEA’s independent sampling, data corroboration, and analysis activities include three major components:
• Sampling, analysis and interlaboratory comparison for ALPS treated water from the FDNPS.
• Sampling, analysis and interlaboratory comparison for environmental samples (e.g., seawater,
fish) from the surrounding environment of FDNPS.
• Assessment of the capabilities of dosimetry service providers involved in the monitoring of internal and external radiation exposure of workers at FDNPS.
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Corroboration of Source and Environmental Monitoring
The IAEA corroboration of source and environmental monitoring related to discharges of ALPS treated water from FDNPS is comprised of three distinct elements (see also Figure 4.1):
• Review of sampling and analytical methods for source and environmental monitoring related to ALPS treated water at FDNPS used by TEPCO and relevant Japanese authorities8.
• Corroboration of source monitoring undertaken by TEPCO, including a comprehensive radiological characterization of ALPS treated water samples.
• Corroboration of environmental monitoring undertaken by TEPCO and relevant Japanese authorities.
1. Review of sampling and analytical methods
+
Corroboration of radiological data
2. Corroboration of source monitoring
Figure 4.1: A schematic overview of the elements of the corroboration being undertaken by the IAEA laboratories and the links between these elements.
Corroboration of individual monitoring
The corroboration of source and environmental monitoring will be based on interlaboratory comparisons
Review of analytical methods
(ILCs). ILCs, along with proficiency tests (PTs), are standard methods for laboratories to assess the quality of their measurement results in comparison with those of other participating laboratories, and to identify
Corroboration of Corroboration of
any potential improvements. PTs involve the evaluation of performance against pre-established criteria
external exposure internal exposure
whereas ILCs involve the organization, performance and evaluation of measurements on the same or
monitoring capabilities monitoring capabilities
similar items by two or more laboratories in accordance with predetermined conditions.
For the corroboration of source monitoring, samples of ALPS treated water that is considered by TEPCO to be ready for dilution and discharge – pending final confirmation by analyses – are being collected from tanks at FDNPS. For the corroboration of environmental monitoring, samples of seawater, sediment and marine biota are being collected from locations on the east coast of Japan around FDNPS. Sample collection and pre-treatment activities undertaken by TEPCO, and relevant Japanese authorities will be facilitated and observed by the IAEA. The homogeneity of all samples will be ensured. These samples will be split, and sub-samples will be provided to the laboratories participating in the ILCs for the analysis of the activity concentrations of a range of relevant radionuclides.
Corroboration of Occupational Radiation Protection
An individual monitoring programme is designed to assess radiation doses to workers arising from exposure due to external sources of radiation and from exposure due to intakes of radionuclides. The IAEA’s corroboration for occupational radiation protection capabilities is comprised of three distinct elements (see also Figure 4.2):
8 TEPCO has sole responsibility for source monitoring at FDNPS. All environmental monitoring related to the nuclear accident at FDNPS is conducted according to the Comprehensive Radiation Monitoring Plan (CRMP) . TEPCO and other relevant Japanese authorities have responsibilities under the CRMP. In practice, sampling and analysis are often carried out by contracted laboratories. Within this report it is assumed that TEPCO and the other relevant Japanese authorities as defined in the CRMP have responsibility for reporting the results of the monitoring for which they are responsible. However, the participants in the ILCs could be the laboratories that have contracts in place to undertake analyses.
3. Corroboration of environmental monitoring
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1. Review of sampling and analytical methods
1. Corroboration of relevant Japan+ese indiv3i.dCuoarlrobmoorantiotonroinfg services (IMS) capabilities for 2. Corroboration of
monitoring and assessing external exposure; environmental
source monitoring
Corroboration
2. Corroboration of relevant Japanese IMS capabilities for monitoring and assessing internal
exposure; and
3. Review of analytical methods in external and internal dosimetry used by the relevant Japanese
IMS.
monitoring
of radiological data
Corroboration of individual monitoring
Review of analytical methods
Corroboration of external exposure monitoring capabilities
Corroboration of internal exposure monitoring capabilities
Figure 4.2. Schematic overview of the corroboration of individual monitoring.
First, the IAEA will corroborate the capabilities of IMS used by TEPCO for the assessment of occupational exposure of workers from external sources of radiation. An interlaboratory comparison (ILC) will be the principle means of accomplishing this corroboration, which will focus on TEPCO’s monitoring programme for assessing the occupational exposure of workers involved in handling ALPS-treated water. Personal dosimetry systems with integrated passive detectors will be provided by and evaluated at the IAEA Radiation Safety Technical Services Laboratory (RSTSL) and relevant Japanese IMS. Irradiation of dosimeters will be carried out in two phases for whole-body and extremity dosimeters, respectively, at primary or secondary standards dosimetry laboratories. The IAEA will also conduct a review of analytical methods relevant to external dosimetry used by the relevant Japanese IMS. The results of this review will contribute to ensuring the validity of the data generated as part of the above-mentioned ILC.
Second, the IAEA will corroborate the capabilities of IMS used by TEPCO for the assessment of occupational exposure of workers due to intake of radionuclides. An ILC will be the principle means of accomplishing this corroboration for in-vitro and in-vivo radiobioassay and will focus on TEPCO’s capabilities to detect radionuclide activities in urine reference samples and in phantoms emulating the human body. In the first phase, urine reference samples will be prepared by accredited laboratories and distributed for comparative analysis at the IAEA RSTSL and relevant Japanese IMS. In a second phase, a solid, leak-proof sliced bottle mannequin absorption (BOMAB) phantom containing exempt laminated planar radionuclide sources inserted between layers of polyethylene will be measured at body counters in Fukushima Daiichi and at IAEA Headquarters in a round-robin test. The IAEA will also conduct a review of analytical methods relevant to internal dosimetry used by the relevant Japanese IMS. The results of this review will contribute to ensuring the validity of the data generated as part of the above-mentioned ILC.
Participating Laboratories
The IAEA will involve several of its own laboratories and third-party laboratories as part of these corroboration activities. A list of the relevant IAEA laboratories is included below:
• IAEA Marine Environment Laboratories, Radiometric Laboratory (RML), Monaco.
The Radiometrics Laboratory (RML) in Monaco fosters expertise in marine radioactivity measurement, monitoring and assessment and in the application of radiotracers for marine pollution, climate change and oceanographic studies. RML operates specialised radiochemistry
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laboratories and an underground counting facility for the analysis of low levels of radionuclides in marine and atmospheric samples and environmental forensics applications. The laboratory maintains an open access marine radioactivity data portal (MARIS [24]) and assists Member States to prepare for nuclear and radiological incidents or emergencies that could impact the marine environment. By supporting data quality in Member States for analyses of radionuclides in seawater, sediment and marine biota, including through production of reference materials according to an accredited quality system and PTs and ILCs, RML contributes to the credibility of monitoring and research results.
• IAEA Terrestrial Environmental Radiochemistry Laboratory (TERC), Seibersdorf, Austria.
The Terrestrial Environmental Radiochemistry (TERC) laboratory in Seibersdorf (Austria) assists Member States in assuring the quality of performed analytical work by supporting respective laboratories active in the fields of environmental radioactivity, stable isotope and trace element analysis. TERC provides technical support to Member State laboratories by providing suitable certified reference materials for calibration and quality control, by organising PTs to facilitate checks of analytical quality, by providing thoroughly tested and published analytical methods, and by training laboratories in their setup and operation.
• IAEA Isotope Hydrology Laboratory (IHL), Vienna, Austria.
The Isotope Hydrology Laboratory (IHL) in Vienna provides analytical services, training, and expert technical advice to Member States to develop their own analytical facilities and to help ensure the quality of isotope measurements conducted in their laboratories. The IHL houses state-of-the-art analytical equipment for the collection and measurement of stable and radiogenic isotopes and noble gases from water and hydrological samples and provides analytical support to the IAEA’s Water Resource Programme’s global hydrology monitoring networks, including the global network of isotopes in precipitation (GNIP), and the global network of isotopes in rivers (GNIR). Isotopic data produced by the IHL are included in the GNIP and GNIR databases, and are made available cost-free to Member States via the internet.
• IAEA Radiation Safety Technical Services Laboratory (RSTSL), Vienna, Austria.
The Radiation Safety Technical Services Laboratory (RSTSL) provides radiation protection services, including individual monitoring of workers (e.g., IAEA staff) for occupational exposure due to external and internal sources of radiation. Since 2006, RSTSL holds accreditation to ISO/ IEC 17025 [21], demonstrating the technical competence and the impartiality of the laboratory in providing valid results.
Under the coordination of the participating IAEA laboratories, selected third-party laboratories, members of the network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA) with demonstrable competence in the methods required, are also conducting analyses of samples as participants in the ILCs. ALMERA is a network comprising 190 member laboratories globally that is coordinated jointly by RML and TERC. It provides a platform for maintaining and developing capability on the determination of radionuclides in air, water, soil, sediment and vegetation that can be used for both routine and environmental emergency monitoring in the IAEA Member States.
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4.2. Update on Corroboration of Source Monitoring
For the first ILC under the IAEA’s ALPS safety review, the ALPS treated water samples were taken in March 2022 from the K4-B tank group at FDNPS. The water contained in the K4-B tank group is expected to be the first batch of ALPS treated water that will be discharged, only once TEPCO receives all regulatory approvals from NRA. The focus of the analysis efforts for this ILC were on the radionuclides in the source term which are included in the radiological environmental impact assessment conducted by TEPCO. Participating laboratories were also encouraged to analyse for additional radionuclides beyond the source term.
Analyses were undertaken by TEPCO and by the following three participating IAEA Nuclear Sciences and Applications Laboratories:
• IAEA Marine Environment Laboratories, Radiometrics Laboratory (RML), Monaco;
• Terrestrial Environmental Radiochemistry Laboratory (TERC), Seibersdorf, Austria;
• Isotope Hydrology Laboratory (IHL), Vienna, Austria.
Additionally, under the coordination of the participating IAEA laboratories, selected third-party laboratories, members of the network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA) with demonstrable competence in the methods required, also conducted analyses of samples as participants in the ILCs.
The laboratories participating in this ILC were:
• Spiez Laboratory (LS – Labor Spiez), Switzerland
• Institut de Radioprotection et de Sûreté Nucléaire (IRSN), France
• Los Alamos National Laboratory (LANL), United States of America
• Korea Institute of Nuclear Safety (KINS), Republic of Korea
The results of the analyses undertaken at each laboratory were reported to the IAEA. For results that could be intercompared (i.e., for radionuclides for which activity concentrations above detection limits were reported by at least two laboratories) a statistical evaluation to assess agreement was carried out by the IAEA. The method used for the statistical evaluation was based on techniques currently used by the International Bureau of Weights and Measures’ (BIPM) Consultative Committee for Ionizing Radiation, Section II: Measurement of Radionuclides, CCRI(II) and, thus, adhered to best international practice.
For other radionuclides, the detection limits reported by participating laboratories were compared to evaluate whether the analytical methods used by TEPCO were broadly equivalent and thus appropriate and fit for purpose.
On 31 May 2023 the IAEA published a detailed report including the results from this ILC [1]. The results are presented in tables and charts in this report. Reference is made to the relevant regulatory limit for discharge to sea for each radionuclide as appropriate. The key findings of this ILC are:
• TEPCO has demonstrated a high level of accuracy in their measurements and technical competence.
• TEPCO’s sample collection procedures follow the appropriate methodological standards required to
obtain representative samples.
• The selected analytical methods utilized by TEPCO for different radionuclides were appropriate and
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fit for purpose.
• Neither the IAEA, nor the participating third-party laboratories, detected any additional radionuclides
(i.e., radionuclides beyond what is included in the source term) at significant levels.
In the report, the IAEA notes that these findings provide confidence in TEPCO’s capability for undertaking accurate and precise measurements related to the discharge of ALPS treated water. Furthermore, based on the observations of the IAEA, TEPCO has demonstrated that they have a sustainable and robust analytical system in place to support the ongoing technical needs at FDNPS during the discharge of ALPS treated water.
In October 2022, the IAEA witnessed the collection of two additional batches of samples of ALPS treated water. These samples are being used in the second and third ILCs to support the corroboration of source monitoring.
The samples were collected from the G4S-B10 and the G4S-C8 tanks. In contrast to the samples collected for the first ILC for the corroboration of source monitoring, these are standard tanks for storage of ALPS treated water and not interconnected or subject to circulation and agitation. To ensure inter-sample homogeneity in each case, ALPS treated water was first transferred to a 300 L plastic tank, then to a second 300 L plastic tank and, finally, back to the first 300 L plastic tank. Sample containers (3 L) were then filled and prepared for shipping to each participating laboratory. The sample volume was smaller for the second and third ILCs as robustness testing will not be carried out for these samples, having already been completed for the earlier samples.
As well as TEPCO and the IAEA laboratories, the ALMERA laboratory Korea Institute of Nuclear Safety (KINS) will participate in these ILCs. The IAEA’s samples were received by TERC in November 2022. KINS also received its samples in in November 2022. A report including the analysis of these samples is expected to be published later in 2023.
4.3. Update on Corroboration of Environmental Monitoring
In November 2022 the IAEA participated in a sampling mission in Japan to collect environmental samples (e.g., seawater, marine sediment, fish, seaweed) for the first ILC to corroborate environmental monitoring related to discharges of ALPS treated water. These samples were collected jointly with experts from Japan according to methods mirroring existing sampling practices utilized by the IAEA for ILCs organized within the project NA3/38 (Marine Monitoring: Confidence Building and Data Quality Assurance) over the past nine years.
Participating laboratories have been instructed to submit results according to a similar protocol to that used for the first ILC for the corroboration of source monitoring. Following the evaluation of all submitted data, the results of the ILC will be made available by the IAEA in the second half of 2023. The results of future monitoring of environmental samples will be compared against this baseline to assess any measurable impacts from the future discharges of ALPS treated water.
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4.4. Update on Corroboration of Occupational Radiation Protection
The results from the first ILC for occupational radiation protection will be available later in 2023. This first ILC will focus on external dosimetry for whole-body exposure, whereas future ILCs for occupational radiation protection will focus on external dosimetry for extremity exposure and internal monitoring for radionuclide intakes. ILCs for occupational radiation protection will be conducted between the IAEA’s Radiation Safety Technical Services Laboratory and the individual monitoring services used by TEPCO for FDNPS workers.
In the first half of 2023, the IAEA initiated the corroboration for external dosimetry. The IAEA has issued a contract to a secondary standards dosimetry laboratory to have dosimeters irradiated under reference conditions in support of the corroboration of external dosimetry. The irradiated dosimeters will then be returned to relevant Japanese IMS and the IAEA’s RSTSL for analysis.
After the relevant Japanese IMS and RSTSL have completed their analysis in the second half of 2023, the IAEA will collect and analyse the results. The IAEA will collect the results from all participating laboratories and conduct a screening to ensure that all laboratories have submitted a complete assessment package with all necessary documentation. The IAEA will draft a report highlighting the results, which will be published by the end of 2023.
Furthermore, in the second half of 2023, the IAEA will initiate the steps to conduct the corroboration for in-vitro and in-vivo internal monitoring. The IAEA will identify vendors for the urine samples spiked with certified reference materials and will ship the urine samples for in-vitro and a reference phantom for in- vivo bioassay to TEPCO as part of the ILC. RSTSL will also conduct analyses of the spiked urine samples and the phantom throughout 2024.
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PART 5
FUTURE ACTIVITIES
As noted previously, this comprehensive report is a synthesis of nearly two years of work by the IAEA Task Force and includes explanations and insights over a broad range of topics that are important to understanding the overall safety of this process. The purpose of this comprehensive report is to present the IAEA’s final conclusions and findings of the technical review to assess whether the planned operation to discharge the ALPS treated water into the Pacific Ocean over the coming decades is consistent with relevant international safety standards. However, once any discharges begin, many of the technical topics reviewed and assessed by the Task Force will need to be revisited at various times to assess the consistency of activities during the operation of the ALPS treated water discharges with relevant international safety standards
So far, the focus of the IAEA’s review has been on ensuring consistency with with requirements in the international safety standards that apply during the pre-operational phase of the planned discharge of ALPS treated water (i.e., prior to beginning the water discharges). However, in the coming months the Task Force will shift its focus to requirements for the operator or the regulatory body that can only be assessed during operations. Additionally, the Task Force has noted that many of these technical topics that are being assessed before operations begin, should also be reviewed periodically in the future to ensure continued consistency with the relevant international safety standards.
Regarding future activities, after the publication of this report, the IAEA will continue implementing its safety review using the overall three elements highlighted below.
Components of IAEA’s Review
Assessment of Protection and Safety
Regulatory Activities and Process
Independent Sampling, Data Corroboration and Analysis
• Review TEPCO’s implementation plan and supporting documentation.
• Focus on technical considerations such as source characterization, safety related aspects of the approach, occupational radiation exposure, radiological environmental impact assessment.
• Review NRA actions and processes relevant to the project
• Focus on safety objectives, regulatory requirements, regulatory assessment, regulatory inspections.
• Independent sampling and analysis to corroborate data from Japan. • Perform analysis of source term and environmental samples.
• Corroborate monitoring results for occupational exposure.
Figure 5.1 Components of the IAEA review
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Additionally, the IAEA has established a presence at the FDNPS with the establishment of an IAEA site office. IAEA experts will maintain a constant presence on site for a number of weeks before and after the planned discharges of ALPS treated water. Outside of this timeframe, the IAEA experts will be on site for major activities and will conducting monitoring as needed.
5.1. Review Missions
For the first two elements, namely the assessment of protection and safety, and regulatory activities and processes, the IAEA will utilize a similar model of conducting periodic review missions to Japan using the Task Force model with technical experts from the IAEA Secretariat and independent external experts. However, unlike in the past, future review missions will be combined given the strong connection between technical and regulatory topics. These future review missions will be guided by the main technical considerations that are highlighted in Part 3 of this report. Below is a list of example topics that will be reviewed by the Task Force in due course, after the discharges of ALPS treated water have begun.
Regulatory Control and Authorization
• NRA’s approach to encourage optimization of protection and safety during future reviews of the authorization.
• NRA’s approach to reviewing and potentially revising discharge limits in response to TEPCO’s ongoing optimisation of protection and safety.
• NRA’s approach to identify “unusual values” and refine action limits based on incoming environmental monitoring data and other operational experience.
Safety Related Aspects of Systems and Processes for Controlling Discharges
• The implementation of maintenance plans for the various equipment and structures that make up the ALPS discharge process.
• Operational or environmental changes that would require a reassessment of the safety and potentially the change of any engineered aspects of the process.
• Identification and review of any abnormal occurrences and the subsequent actions taken by TEPCO and their interactions with NRA consistent with domestic regulatory requirements.
Characterization of the Source
• TEPCO’s and NRA’s review of the source term as 1) the decommissioning process at FDNPS continues and as the radionuclide content and other properties of contaminated water potentially change and 2) the operational ALPS technology at FDNPS potentially evolves.
• TEPCO’s consideration of changes to the source characterization as the size of the ALPS-related monitoring database – both source and environmental – grows. This will be helpful in ensuring
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there is a strong connection between the characterization of the source and environmental monitoring programmes.
Radiological Environmental Impact Assessment
• Checking whether TEPCO and NRA have undertaken a periodic review of REIA.
• Reviewing TEPCO’s approach to updating the REIA if information changes, including the source term, habits of the population over time and results of the environmental monitoring indicate that the REIA results need revising.
• The Task Force will review the implementation of the process put in place by the NRA to periodically review the authorization of the discharges of ALPS treated water (see Section 3.1) in the future.
Source and Environmental Monitoring
• How future results from source and environmental monitoring published by TEPCO, and by independent organizations under the CRMP, are being used to verify and demonstrate compliance with the discharge authorization and requirements for the control of public exposures.
• How environmental monitoring results are being used to verify the assumptions made for the assessment of public exposure and radiological environmental impacts
• Observation of the process utilized by the Government of Japan, NRA, and TEPCO to respond to any potential abnormal results from monitoring programmes.
Involvement of Interested Parties
• The involvement of interested parties in further regulatory steps related to the ALPS treated water discharges.
• The involvement of interested parties in potential future changes to key aspects of the discharge such as the discharge limits or design for the discharge.
• Periodic updates on the Action Plan for the Continuous Implementation of the Basic Policy on Handling of ALPS Treated Water as it relates to the involvement of interested parties.
• How interested parties are involved over time to ensure that up-to-date habit data is considered as part of future reviews of the REIA and monitoring programmes.
• Information exchange and communication, as needed, with the Governments of neighbouring countries throughout the entire time when discharges of ALPS treated water are occurring.
Occupational Radiation Protection
• Reviewing when TEPCO reassesses ALPS treated water discharge facility on a periodic basis while taking into account the evolution of the radiological conditions (including occupational
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exposure data for external and internal exposures of TEPCO workers & contractors including sub-contractors) in the relevant areas and during normal operation in the future.
5.2. IAEA’s Independent Sampling, Data Corroboration, and Analysis
The activities related to the corroboration of source monitoring, the corroboration of environmental monitoring, and the corroboration of occupational radiation protection; these will continue as described in Part IV above and in previous reports.
Corroboration of Source and Environmental Monitoring
The IAEA corroboration of source and environmental monitoring related to discharges of ALPS treated water from FDNPS is comprised of three distinct elements:
• Review of sampling and analytical methods for source and environmental monitoring related to ALPS treated water at FDNPS used by TEPCO and relevant Japanese authorities.
• Corroboration of source monitoring undertaken by TEPCO, including a comprehensive radiological characterization of ALPS treated water samples.
• Corroboration of environmental monitoring undertaken by TEPCO and relevant Japanese authorities.
On May 2023, the IAEA published a report [1] detailing the results of the first interlaboratory comparison conducted for the determination of radionuclides in samples of ALPS treated water. These findings provide confidence in TEPCO’s capability for undertaking accurate and precise measurements related to the discharge of ALPS treated water. Furthermore, based on the observations of the IAEA, TEPCO has demonstrated that it has a sustainable and robust analytical system in place to support the ongoing technical needs at FDNPS during the discharge of ALPS treated water.
Additional sampling for the corroboration of source and environmental monitoring will occur throughout the year and on different frequencies depending on operational considerations. Future ILCs are planned for the corroboration of source monitoring in 2024, and future ILCs are planned for the corroboration of environmental monitoring later in 2023 after the discharges of ALPS treated water have begun. The ILCs will involve third party laboratories and the IAEA is currently considering additional third-party laboratories to include in these future ILCs.
Corroboration of Occupational Radiation Protection
An individual monitoring programme is designed to assess radiation doses to workers arising from exposure due to external sources of radiation and from exposure due to intakes of radionuclides. The IAEA’s corroboration for occupational radiation protection capabilities is comprised of three distinct elements:
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1. Corroboration of relevant Japanese individual monitoring services (IMS) capabilities for monitoring and assessing external exposure;
2. Corroboration of relevant Japanese IMS capabilities for monitoring and assessing internal exposure; and
3. Review of analytical methods in external and internal dosimetry used by the relevant Japanese IMS.
In the first half of 2023, the IAEA initiated the corroboration for external dosimetry. The IAEA has issued a contract to a secondary standards dosimetry laboratory to have dosimeters irradiated under reference conditions in support of the corroboration of external dosimetry. The irradiated dosimeters will then be returned to relevant Japanese IMS and the IAEA’s RSTSL for analysis. After the relevant Japanese IMS and RSTSL have completed their analysis in the second half of 2023, the IAEA will collect and analyse the results. The IAEA will collect the results from all participating laboratories and conduct a screening to ensure that all laboratories have submitted a complete assessment package with all necessary documentation. The IAEA will draft a report highlighting the results, which will be published by the end of 2023.
Furthermore, in the second half of 2023, the IAEA will initiate the steps to conduct the corroboration for in-vitro and in-vivo internal monitoring. The IAEA will identify vendors for the urine samples spiked with certified reference materials and will ship the urine samples for in-vitro and a reference phantom for in- vivo bioassay to TEPCO as part of the ILC. RSTSL will also conduct analyses of the spiked urine samples and the phantom throughout 2024.
5.3. Real Time Monitoring
The IAEA has also chosen to display data provided by TEPCO on a real-time or near real-time basis share the status of the ALPS discharge facilities for members of the public. Many of the data points included in this real time monitoring approach are key operational parameters or controls in place and therefore provide the IAEA with insights as to the ongoing reliability of the ALPS discharge facilities; this will be combined with the insights and observations gained through other Task Force activities anticipated to occur in 2023 and beyond.
The data from TEPCO will be displayed graphically on the IAEA’s website along with a short explanation to help the reader understand the different data points. Examples of data the IAEA plans to display include:
• ALPS treated water flow rates
• Seawater flow rates for dilution
• Online radiation monitors installed in multiple locations as screening measures
• Concentration of tritium after dilution
Additionally, over time, the IAEA will display the results of its independent corroboration of source and environmental monitoring, as well as the results of its corroboration of the capabilities of relevant Japanese individual monitoring services for occupational radiation protection on this website to enhance the availability of relevant data for interested parties.
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5.4. IAEA Continuous Presence at the FDNPS
The IAEA, consistent with its commitment to being involved before, during, and after the ALPS treated water discharges, has a continuous presence at the FDNPS from summer 2023. The IAEA has a dedicated office at the FDNPS.
The main aspects to consider in that presence are to:
• Observe the safety aspects related to the TEPCO’s Implementation Plan
• Witness the water sampling activities and the process for dispatching samples to the IAEA corroboration and third parties laboratories.
• Observe preparatory activities taken by TEPCO leading up to the start of water discharges.
• Periodically meet with NRA and observe their regulatory inspections, the activities related to the discharges of ALPS treated water and their findings.
• Routinely visit the main technical equipment and structures associated with the ALPS water discharges.
• Liaise with TEPCO if any abnormalities, deviations or changes occur during the implementation and coordinate between FDNPS and IAEA HQ.
• To coordinate future Task Force meetings at the FDNPS, as required.
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4. INTERNATIONAL ATOMIC ENERGY AGENCY. IAEA Follow-up Review of Progress Made on Management of ALPS Treated Water and the Report of the Subcommittee on Handling of ALPS treated water at TEPCO’s Fukushima Daiichi Nuclear Power Station: Review Report April 2020. https://www.iaea.org/sites/default/files/20/04/review-report-020420.pdf
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11. INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONS ENVIRONMENT PRO- GRAMME, Prospective Radiological Environmental Impact Assessment for Facilities and Activi- ties, IAEA Safety Standards Series No. GSG-10, IAEA, Vienna (2018).
12. INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Environmental Pro- tection - the Concept and Use of Reference Animals and Plants. ICRP Publication 108. Ann. ICRP 38 (4-6) (2008).
13. INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Protection of the Envi- ronment under Different Exposure Situations. ICRP Publication 124. Ann. ICRP 43(1) (2014).
14. INTERNATIONAL ATOMIC ENERGY AGENCY, Governmental, Legal and Regulatory Frame- work for Safety, IAEA Safety Standards No. GSR Part 1 (Rev. 1), IAEA, Vienna (2016).
15. TEPCO. Implementation Plan for Fukushima Daiichi Nuclear Power Station as Specified Nuclear Facility February 20 2023, Application Documents for Approval to Amend the Implementation Plan for Fukushima Daiichi Nuclear Power Station Specified Nuclear Facility
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16. INTERNATIONAL ATOMIC ENERGY AGENCY, Environmental and Source Monitoring for Pur- poses of Radiation Protection, IAEA Safety Standards Series No. RS-G-1.8, IAEA, Vienna (2005).
17. INTERNATIONAL COMMISSION ON RADIOLOGICAL, Age-dependent Doses to Members of the Public from Intake of Radionuclides - Part 1. ICRP Publication 56. Ann. ICRP 20 (2) (1990).
18. INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Radiation weighting for Reference Animals and Plants. ICRP Publication 148. Ann. ICRP 50(2) (2021).
19. TEPCO. Reference material – FDNPS measurement/verification tank (K4 tank group) circulation/ agitation demonstration test results, 11 July, 2022 Fukushima Daiichi Nuclear Power Station Mea- surement/verification tank (K4 tank group) circulation/agitation demonstration test results (tepco. co.jp)
20. INTERNATIONAL ORGANISATION FOR STANDARDISATION. Quality Management Systems - Requirements, ISO 9001:2015, Geneva, 2015.
21. INTERNATIONAL ORGANISATION FOR STANDARDISATION. General requirements for the competence of testing and calibration laboratories, ISO/IEC 17025:2017, Geneva, 2018.
22. INTERNATIONAL ORGANISATION FOR STANDARDISATION. Statistical methods for use in proficiency testing by interlaboratory comparisons, ISO 13528: 2022, Geneva, 2022.
23. INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR OFFICE, Oc- cupational Radiation Protection, IAEA Safety Standards Series No. GSG-7, IAEA, Vienna (2018).
24. INTERNATIONAL ATOMIC ENERGY AGENCY. Marine Radioactivity Information System (MARIS). IAEA, Vienna, https://maris.iaea.org/home
25. INTERNATIONAL ATOMIC ENERGY AGENCY, Generic Models for Use in Assessing the Impact of Discharges of Radioactive Substances to the Environment, IAEA Safety Report Series No. 19, IAEA, Vienna (2001).
26. INTERNATIONAL ATOMIC ENERGY AGENCY, Interlaboratory Comparisons 2017–2020: De- termination of Radionuclides in Sea Water, Sediment and Fish, IAEA Analytical Quality in Nuclear Applications Series No. 67, IAEA, Vienna (2022)
27. INTERNATIONAL ATOMIC ENERGY AGENCY, Interlaboratory Comparisons 2014–2016: De- termination of Radionuclides in Sea Water, Sediment and Fish, IAEA Analytical Quality in Nuclear Applications Series No. 59, IAEA, Vienna (2019)
28. INTERNATIONAL ATOMIC ENERGY AGENCY, IAEA Review of Safety Related Aspects of Handling ALPS-Treated Water at TEPCO’s Fukushima Daiichi Nuclear Power Station, Report 3: Status of IAEA’s Independent Sampling, Data Corroboration, and Analysis, IAEA, Vienna, 2022.
29. INTERNATIONAL ATOMIC ENERGY AGENCY, Sediment Distribution Coefficients and Con- centration Factors for Biota in the Marine Environment, IAEA Technical Report Series No. 422, IAEA, Vienna, 2004.
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LIST OF CONTRIBUTORS
Caruso, G. Freeman, E. Nikolaki, M. Clark, A.
Brown, J.
Telleria, D.
Okyar, B.
Cruz Suarez, R. Hajek, M. Melhem, S. Proehl, G. Abraham-Ponti, C. Bartocci, J. Blinova, O. Camin, F.
Cook, M.
Copia, L.
Deneke, M. Descroix-Comanducci, F. Dioszeghy, A.
Fujak, M. Groening, M. Horsky, M. Kim, S.-B., Levy, I. Matsumoto, T. McGinnity, P. Miller, J. Murphy, N. Nadalut, B. Osvath, I. Patterson, S. Pham, M. K. Pommé, S.
Rovan, L.
Seel, P.J.
Seslak, B. Sobiech-Matura, K. Tucakovic, I. Ulanowski, A.
International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency European Commission Joint Research Centre, Geel, Belgium
International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency International Atomic Energy Agency
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Independent External Experts
Gonzalez, A. Tinker, R. Gregoire, M-C. Liu, S. Lachaume, J-L. Kim, H-S. Gauvis, C. Shinkarev, S. Nettleton, J. Boyd, M. Nguyen Q. H.
Argentina*
Australia*
Canada*
China*
France*
Korea, Republic of* Marshal Islands*
Russian Federation* United Kingdom*
United States of America* Viet Nam*
*All independent experts serve in their individual capacity
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ANNEX 1
Summary of IAEA Review Missions and Published Technical Reports
The IAEA has carried out five review missions to Japan since the beginning of the IAEA’s safety review in 2021. Members of the IAEA Task Force participated in these missions and each mission focused on interactions with particular Japanese authorities or TEPCO. After each of the first four review missions, the IAEA has published a technical report that reflects the discussions between the Task Force and Japa- nese authorities or TEPCO, as indicated, and which documents the observations and findings made by the Task Force.
• 13-19 February 2022: Review Mission to TEPCO and METI o 29 April 2022: Report 1 published.
• 21-25 March 2022: Review Mission to NRA o 16 June 2022: Report 2 published.
• 14-18 November 2022: Review Mission to TEPCO and METI o 5 April 2023: Report 4 is published.
• 16-20 January 2023: Review Mission to NRA o 4 May 2023: Report 5 published
• 29 May – 12 June 2023: Comprehensive Review Mission
o No report was issued after the comprehensive review mission.
In addition, the IAEA has published a report on the status of the IAEA’s independent sampling, data cor- roboration and analysis, as well as a report on the first interlaboratory comparison on the determination of radionuclides in ALPS treated water.
• 29 December 2022: Report 3 on the Status of IAEA’s Independent Sampling, Data Corroboration, and Analysis is published.
• 31 May 2023: Report on the First Interlaboratory Comparison on the Determination of Radionu- clides in ALPS Treated Water is published.
Copies of these reports can be downloaded from that IAEA webpage dedicated to the IAEA’s ALPS safety review:
https://www.iaea.org/topics/response/fukushima-daiichi-nuclear-accident/fukushima-daiichi-alps-treat- ed-water-discharge/reports
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ANNEX 2
Summary of relevant international safety standards used in the IAEA safety review
1. [SF-1] EUROPEAN ATOMIC ENERGY COMMUNITY, FOOD AND AGRICULTURE ORGA- NIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR ORGANIZATION, INTERNATIONAL MARITIME ORGANI- ZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZA- TION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANI- ZATION, Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, IAEA, Vienna (2006).
2. [GSG-9] INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONS ENVIRON- MENT PROGRAMME, Regulatory Control of Radioactive Discharges to the Environment, IAEA Safety Standards Series No. GSG-9, IAEA, Vienna (2018).
3. [GSG-10] INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONS ENVIRON- MENT PROGRAMME, Prospective Radiological Environmental Impact Assessment for Facili- ties and Activities, IAEA Safety Standards Series No. GSG-10, IAEA, Vienna (2018).
4. [GSR Part 1] INTERNATIONAL ATOMIC ENERGY AGENCY, Governmental, Legal and Reg- ulatory Framework for Safety, IAEA Safety Standards No. GSR Part 1 (Rev. 1), IAEA, Vienna (2016).
5. [GSR Part 2] INTERNATIONAL ATOMIC ENERGY AGENCY
6. [GSR Part 3] EUROPEAN COMMISSION, FOOD AND AGRICULTURE ORGANIZATION
OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNA- TIONAL LABOUR ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMER- ICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, IAEA Safety Standards Series No. GSR Part 3, IAEA, Vi- enna (2014).
7. [RS-G-1.8] INTERNATIONAL ATOMIC ENERGY AGENCY, Environmental and Source Monitoring for Purposes of Radiation Protection, IAEA Safety Standards Series No. RS-G-1.8, IAEA, Vienna 2005
8. [GSG-7] INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR OF- FICE, Occupational Radiation Protection, IAEA Safety Standards Series No. GSG-7, IAEA, Vi- enna (2018).
9. INTERNATIONAL ATOMIC ENERGY AGENCY, Generic Models for Use in Assessing the Impact of Discharges of Radioactive Substances to the Environment, IAEA Safety Report Series No. 19, IAEA, Vienna (2001).
10. [GSG-8] INTERNATIONAL ATOMIC ENERGY AGENCY, UNITED NATIONS ENVIRON- MENT PROGRAMME, Radiation Protection of the Public and the Environment, IAEA Safety Standards Series No. GSG-8, IAEA, Vienna (2018).
11. [IAEA Safety Glossary] INTERNATIONAL ATOMIC ENERGY AGENCY, IAEA Nuclear Safety and Security Glossary, 2022 Interim Edition, IAEA, Vienna, (2022).
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ANNEX 3
List of updates and amendments to TEPCO’s Implementation Plan and NRA Regulatory Review Milestones
1. List of updates and amendments to TEPCO’s Implementation Plan, including the REIA
• November 2021
o https://www.tepco.co.jp/en/hd/newsroom/press/archives/2021/20211117_01.html
• December 2021
o https://www.tepco.co.jp/en/hd/newsroom/press/archives/2021/20211221_02.html
• April 2022
o https://www.tepco.co.jp/en/hd/newsroom/press/archives/2022/20220428_03.html
• May 2022
o https://www.tepco.co.jp/en/hd/newsroom/press/archives/2022/20220513_01.html
• July 2022
o https://www.tepco.co.jp/en/hd/newsroom/press/archives/2022/20220715_01.html
• November 2022
o https://www.tepco.co.jp/en/hd/newsroom/press/archives/2022/20221114_01.html
• February 2023
o (14th) https://www.tepco.co.jp/en/hd/newsroom/press/archives/2023/20230214_01.html o (20th) https://www.tepco.co.jp/en/hd/newsroom/press/archives/2023/20230220_01.html
• April 2023
o https://www.tepco.co.jp/en/hd/newsroom/press/archives/2023/20230424_02.html
2. NRA Regulatory Review Milestones
• 24 December 2021
o Public review meeting between NRA and TEPCO
• 11 December 2021
o Public review meeting between NRA and TEPCO
• 20 December 2021
o Public review meeting between NRA and TEPCO
• 27 December 2021
o Public review meeting between NRA and TEPCO
• 1 January 2022
o Public review meeting between NRA and TEPCO
• 7 January 2022
o Public review meeting between NRA and TEPCO
• 15 January 2022
o Public review meeting between NRA and TEPCO
• 25 January 2022
o Public review meeting between NRA and TEPCO
• 1 February 2022
o Public review meeting between NRA and TEPCO
• 10 February 2022
o Public review meeting between NRA and TEPCO
• 18 February 2022
o Public review meeting between NRA and TEPCO
• 11 March 2022
o Public review meeting between NRA and TEPCO
• 15 April 2022
o Public review meeting between NRA and TEPCO
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• 19 May – 17 June 2022
o NRA establishes a public comment period for first regulatory review results
• 22 July 2022
o First regulatory review results approved by NRA Commission
• 21 November 2022
o Public review meeting between NRA and TEPCO
• 7 December 2022
o Public review meeting between NRA and TEPCO
• 21 December 2022
o Public review meeting between NRA and TEPCO
• 27 December 2022
o Public review meeting between NRA and TEPCO
• 17 February 2023
o Public review meeting between NRA and TEPCO
• 23 February – 24 March 2023
o NRA establishes a public comment period for second regulatory review results
• 10 May 2023
o Second regulatory review results approved by NRA Commission
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ANNEX 4
#Japan legal and regulatory provisions applied to the FDNPS
1. Act on the Regulation of Nuclear Source Material, Nuclear Fuel Materials Reactors “Reactor Regu- lation Act”
The document is related to the requirements for licensing of nuclear facilities in order to prevent accident re- sulting from i) nuclear fuel material, ii) material contaminated by nuclear fuel material, iii) reactors, and iv) to protect specified nuclear fuel material, and v) if necessary, to designate facilities that require special measures for the operational safety or physical protection of the specified nuclear fuel.
The following topics are explicitly included:
• The requirement for the preparation of an implementation plan for nuclear facilities including measures operational safety or physical protection of the specified nuclear fuel.
• If a facility is no longer classified as a nuclear facility, the obligation to submit an implementation plan expires.
• It has to be announced officially i) if a facility is classified a nuclear facility or ii) revoked the classifica- tion as nuclear facility.
• A licensee of the nuclear facility shall create an implementation plan to get the permission for operation.
• The modification of an approved implementation plan requires the approval of the regulatory body.
• If deemed necessary by the regulatory body, the regulatory body may request an amendment of the im-
plementation plan.
• Any licensee of the nuclear facility shall implement measures for operational safety and physical protec-
tion of nuclear fuel material in compliance with the implementation plan.
• The licensee of a nuclear facility shall undergo an inspection conducted by the regulatory body for check
compliance with the implementation plan.
2. Cabinet order on special provisions of the Act on the Regulation of Nuclear Source Material Nuclear Fuel and Reactors about the Nuclear Reactors at TEPCO’s Fukushima Daiichi Nuclear Reactors
The documents summarizes the application of specific paragraphs of the “Act on the Regulation of Nuclear Source Material Nuclear Fuel and Reactors” to include also the works for decommissioning of the Fukushima Daiichi Nuclear Power Station.
3. NRA Ordinance for Operational Safety and Protection of Specified Nuclear Fuel Materials of the Nu- clear Reactors at TEPCO’s Fukushima Daiichi NPS
Ordinance of the Nuclear Regulation Authority No. 2 on April, 12, 2013
The document deals with aspects on operational safety and the safe handling of fuel materials. It has 42 articles, the articles 6-8, 11, 21, 23, 30, 32, 34-41 have no content.
Article 16 is the most important article regarding the discharge of ALPS treated water. It includes the possible measures to reduce radionuclide concentrations before the discharge (e.g.: filtering, evaporation, adsorption by the ion-exchange resins, storage, dilution with large volumes of water). The radionuclide concentrations shall comply with the concentration limit specified by the Nuclear Regulation Authority.
5. Notification to Establish Requirements for Operational Safety and Physical Protection of Specified Nuclear Fuel Materials of the Nuclear Reactors at TEPCO’s Fukushima Daiichi NPS
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Notification No. 3 of the Nuclear Regulatory Authority on April 12, 2013
The document deals with requirements for operational safety and the safe handling of fuel materials. It has 13 articles, the articles 11 and 12 have no content.
The document provides regulatory criteria for:
• Surface density limits
• Dose Limits for Radiation Workers
• Dose Limits for Radiation Workers during Emergency Work
• Concentration Limits Radionuclides in Air at Workplaces
• Concentration Limits for Radionuclides to be discharged to the atmosphere and to water bodies.
• General guidance on calculation of doses for Workers
• Limits of radioactivity concentrations that do not require encapsulation in containers
Article 1 Article 2 Article3
Article 4 Article 5 Article 6 Article 7 Article 8 Article 9 Article 10 Article 13
Article 13-2
Article 13-3 Article 13-4 Article 13-5 Article 13-6 Article 13-7 Article 13-8
Article 14
Record of Dose Equivalent Rate, etc
Designation of a nuclear facility
Standards to be Endeavoured to Observe in the Case of Storage by Electromagnetic Methods
Surface Density Limit
Dose Limits for Radiation Workers
Concentration Limit for Radiation Workers
Dose Limit for Radiation Workers Pertaining to Emergency Work
Concentration Limit Outside the Surrounding Monitoring Area, etc
Calculation of Dose, etc. Pertaining to External Radiation
Criteria Pertaining to Person Responsible for Operation
Limit of Radioactivity Concentration of Substances Contaminated by Nuclear Fuel Materials Not Required to Be Encapsulated in Containers
Application Form for Approval of Measures Concerning Transport of Substances Significantly Difficult to be Encapsulated in Containers
Dose Equivalent Rate for Load and Transport Equipment
Hazardous Materials
Sign
Application Form for Approval of Special Measures
Dose Equivalent Rate Pertaining to Load Subject to Special Measures
Calculation of Dose Equivalent Rate Pertaining to Transport of Nuclear Fuel Material, etc. at Factory or Place of Activity
Authority of Officials Who Conduct Inspections
6. Notification to Establish Dose Limits in Accordance with the Provisions of the NRA Ordinance on Activities of Refining Nuclear Source or Nuclear Fuel Materials, etc.
Notification No. 8 of the Nuclear Regulatory Authority on August 31, 2015
This document is referred in the “Notification to Establish Requirements for Operational Safety and Physi- cal Protection of Specified Nuclear Fuel Materials of the Nuclear Reactors at TEPCO’s Fukushima Daiichi NPS” (Notification No. 3 of the Nuclear Regulatory Authority on April 12, 2013).
Dose limits
The document defines a dose limits for the public for effective dose of 1 mSv/a; if approved by the Nuclear Regulation Authority, the effective dose limit may be 5 mSv/a. Limits for the equivalent dose for skin and lens of the eye are 50 mSv/a and 15 mSv/a respectively.
126
These limits are applied in the following rules and regulations:
• Rules for Smelting
• Rules for Test Reactor
• Rules for Nuclear Raw Material Use
• Rules for Nuclear Fuel Material Use
• Rules for Processing
• Rules for Reprocessing
• Rules for Commercial Reactor
• Rules for Research and Development Reactor
• Rules for Category 1 Radioactive Waste Disposal
• Rules for Category 2 Radioactive Waste Disposal
• Rules for Radioactive Waste Management
• Rules for Storage
• Rules for Storage Contract
• Regulations on Technical Standards for Design and Construction Methods of Processing Facility
• Regulations on Technical Standards for Design and Construction Methods for Specified Waste
Disposal Facility or Specified Management Facility
• Regulations on Technical Standards for Performance of Processing Facility
• Regulations on Technical Standards for Performance of Reprocessing Facility
• Regulations on Technical Standards for Commercial Power Reactors and their Affiliated Facilities
• Regulations on Technical Standards for Performance of Specified Waste Disposal Facility or
Specified Management Facility
• Regulations on Technical Standards for Design and Construction Methods of Spent Fuel Storage
Facility
• Regulations on Technical Standards for Performance of Spent Fuel Storage Facility
• Regulations on Technical Standards for Nuclear Power Reactor under Research and Development
Stage and its Affiliated Facilities
Limits for average radionuclide concentrations
The document provides for all radioisotopes relevant for exposure on workplaces and for discharges of radionuclides to the environment the following quantities:
1. Dose coefficients for effective dose for inhalation [mSv/Bq]
2. Dose coefficients for effective dose for ingestion [mSv/Bq]
3. Limits for radionuclide concentration in air at working places [Bq/cm3]
4. Limit for radionuclide concentrations in air to be discharged from nuclear facilities to the atmo-
sphere [Bq/cm3]
5. Limit for radionuclide concentrations in water to be discharged from nuclear facilities to water
bodies [Bq/cm3]
For many isotopes, the values are given for various chemical forms. Guidance is provided how to evaluate compliance with limits. These values for maximal radionuclide concentrations are used in the following rules and regulations:
6. Rules for Test Reactor
7. Rules for Nuclear Fuel Material Use
8. Rules for Processing
9. Rules for Nuclear Raw Material Use
10. Rules for Commercial Reactor
11. Rules for Category 1 Radioactive Waste Disposal
12. Rules for Category 2 Radioactive Waste Disposal
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13. Rules for Radioactive Waste Management
14. Rules for Storage
15. Regulations on Technical Standards for Design and Construction Methods of Reactors, etc. used
for Research Reactor
16. Regulations on Technical Standards for Performance of Reactors, etc. Used for Research
17. Regulations on Technical Standards for Design and Construction Methods of Processing Facility 18. Regulations on Technical Standards for Performance of Reprocessing Facility
19. Regulations on Technical Standards for Commercial Power Reactors and Their Affiliated Facili-
ties
20. Regulations on Technical Standards for Design and Construction Methods for Specified Waste
Disposal Facility or Specified Management Facility,
21. Regulations on Technical Standards for Performance of Specified Waste Disposal Facility or
Specified Management Facility
22. Regulations on Technical Standards for Design and Construction Methods of Spent Fuel Storage
Facility
23. Regulations on Technical Standards for Performance of Spent Fuel Storage Facility,
24. Rules for Research and Development Reactor
25. Regulations on Technical Standards for Nuclear Power Reactor under Research and Development
Stage and Its Affiliated Facilities
6. Items required for Measures which should be taken at Tokyo Electric Power Co., Inc.’s Fukushi-
ma Daiichi Nuclear Power Station in line with the Designation as the Specified Nuclear Facility
Decision of NRA Commission, 7 November 2012
The document summarizes the work areas to be considered during decommissioning of the damaged FDNPP. The following aspects should be taken into account and the following measures should be taken during the decommissioning work:
• Measures to be Taken with regard to the Overall Process and Risk Assessment
• Items concerning Measures to be taken for Design and Equipment
— Monitoring of reactors
— Removal of residual heat
— Monitoring of primary containment atmosphere
— Maintenance of an inert atmosphere
— Fuel removal and, appropriate storage and management of removed fuel
— Ensuring power source
— Design considerations for loss of power
— Treatment, storage, and management of radioactive solid waste
— Treatment, storage, and management of radioactive liquid waste
— Radiation protection, etc. in the area surrounding the site by restricting release of radioactive
materials, etc.
— Management, etc. of workers’ exposure dose — Emergency measures
— Design considerations
• Measures for security of the specified nuclear facility
• Measures for physical protection of specified nuclear fuel materials
• Measures for retrieval of fuel debris and reactor decommissioning
• Considerations for developing the implementation plan
• Efforts to facilitate the understanding of the implementation plan
• Review procedure for the implementation plan
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ANNEX 5
Tritium in the environment
Tritium is a radioactive hydrogen isotope with one proton and two neurons, it is the heaviest isotope of hydrogen. The physical half-life of tritium is 12.3 years. Tritium is a low-energy-beta-emitter, the mean beta-energy is only 5.7 keV.
Tritium is produced by natural and artificial processes. Naturally, tritium is generated mainly in the upper layers of the atmosphere as a result of reactions of cosmic radiation with nitrogen and oxygen. Tritium is produced in nuclear facilities, especially in nuclear power plants and reprocessing plants. For the period 1998 to 2002, in UNSCEAR [1], the average annual release of tritium from nuclear facilities was estimated to be 12 PBq and 16 PBq to the at- mosphere and the aquatic environment, respectively. From nuclear installations, tritium is released predominantly as tritiated water (HTO) or elemental hydrogen, which reacts quickly with oxygen to form HTO, which then enters the global hydrological cycle.
Furthermore, anthropogenic tritium was generated during atmospheric test of nuclear weapons. According to UN- SCEAR [2], during 504 atmospheric tests conducted in the period from 1945 to 1980, about 200000 PBq of tritium were released. Approximately, 95% of all tritium releases from atmospheric tests occurred in the period from 1952 to 1962.
Data on tritium concentrations in oceans were compiled and analysed by Oms et al. [3]. From these data, average tri- tium concentrations for the upper 500 m of the oceans were estimated for 21 compartments of the Atlantic Ocean, In- dian Ocean, and Pacific Ocean. Because atmospheric nuclear weapons tests were conducted primarily in the northern hemisphere, the values are higher north of the equator than south of the equator. The tritium concentrations — decay corrected for January 1, 2016 — are in the range of 0.006-0.12 Bq/L. Standard deviations for tritium concentrations vary for the different oceanic compartments, with a range of about 15-90% of the mean. In the North Pacific, tritium concentrations are reported in the range of 0.027-0.057 Bq/L, and a mean tritium concentration of 0.057±0.015 Bq/L is reported for the area between latitudes 30 N to 45 N.
In marine waters, most tritium is bound in the water as HTO. However, because tritium atoms are interchangeable with normal hydrogen atoms, some of the tritium ingested by marine organisms can be incorporated into organic compounds such as carbohydrates, fats, proteins, and other organic compounds; this tritium fraction is referred to as organically bound tritium (OBT) [1]. A tritium atom in OBT that is bound to a carbon atom is essentially fixed until the compound is metabolized (i.e., the tritium is not exchangeable). Tritium bound to oxygen, sulphur, nitrogen, or phosphorus atoms is considered readily exchangeable with hydrogen in water, so tritium in such bindings is not considered as OBT.
In the human body, the turnover of tritium bound to HTO is much faster than that of OBT tritium. This is also re- flected in the dose coefficients for HTO and OBT1. In the ICRP model [4] for estimating dose coefficients for uptake of tritium, it is assumed that 97% of HTO taken up into the blood is distributed in body water and 3% of HTO is converted to OBT. The biological half-life of tritium in humans is 10 and 40 days for HTO and OBT, respectively. The dose coefficients for ingestion for all age groups considered in ICRP are about a factor of 3 higher for OBT compared to HTO [4].
1 The ‘dose coefficient’ is the committed effective dose from an intake of a radionuclide (ingestion or inhalation) for a unit intake of radioactivity. The unit is Sv/Bq. Dose coefficients are given for different age groups in [4]
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INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA
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