NRA presentation
C-2-1 Assessment for Representative Person
and Reference Animals and Plants
OGINO Haruyuki
Nuclear Regulation Authority JAPAN
IAEA Regulatory Review Mission on ALPS Treated Water Handling
23 March 2022
1. NRA’s Views on Assessment for Representative Person and
Reference Animals and Plants
2. TEPCO’s Responses and Points to be Further Clarified
Contents12
• NRA reviews the TEPCO’s radiological environmental
impact assessment
– whether the assessment methodology is in line with the relevant IAEA
Safety Standards;
– whether the assessed impact to humans is sufficiently small. For this
review, NRA has set the criteria of 50 μSv/y for the Representative
Person, which is practically regarded as the dose constraint; and
– whether the assessed impact to the flora and fauna is smaller than the
lowest value of the Derived Consideration Reference Levels for the
Reference Animals and Plants.
1. NRA’s Views on Assessment for Representative Person and
Reference Animals and Plants3i. Uncertainties
TEPCO should explain uncertainties involved in the Radiological Impact Assessment
and identify which uncertainties could affect the assessment or make it conservative.
ii. Transfer Model
TEPCO should explain the concept of selection, including the comprehensiveness
and the reasoning of excluding some from the assessment.
iii. Exposure Pathways
TEPCO should explain the concept of selection, including its comprehensiveness
and the reasoning of excluding some from the assessment.
iv. Parameters
For the applied input values not from the reference documents such as the IAEA
Guides, TEPCO should explain the basis and appropriateness thereof, taking into
account the associated uncertainties in the assessment.
1. NRA’s Views on Assessment for Representative Person and
Reference Animals and Plants4v. Dose Coefficients for Tritium
TEPCO should explain the consideration on the existing ratio of tritiated water (HTO)
and organically bound tritium (OBT) and provide its reference documents.
vi. Potential Exposure
TEPCO should explain the concept of the assessment which does not follow the flow
shown in Fig. 3 of GSG-10, including the basis for selection of the scenario.
vii. Seawater Intake
TEPCO should explain the impact of radioactive materials contained in the intake
seawater on dose assessment.
1. NRA’s Views on Assessment for Representative Person and
Reference Animals and Plants
• Dispersion model is covered by the presentation C-2-2.
• Potential exposure is covered by the presentation C-2-3.52. TEPCO’s Responses and Points to be Further Clarified
i. Uncertainties
• TEPCO examined the magnitude of uncertainties for each item
listed below in the REIA report.
Selection of source term, dispersion and transfer model in the
environment, exposure pathways, setting of representative
person, and dose assessment
• TEPCO explained that the assumed uncertainty falls within the
range of conservatism mainly associated with the source term and
the seafood intake setting.
Points to be further clarified
• To be based on more realistic assumptions and then consider
uncertainties, rather than building up excessive conservatism.
• This is the general comment that the NRA is seeking at the review
meetings for the entire REIA report.6ii. Transfer ModelsAndii. Exposure Pathways
• Based on GSG-10, TEPCO explained how the transfer models and
exposure pathways were selected in the REIA report.
• To confirm the validity of the exclusion of some in the selection, an
additional evaluation was conducted in accordance with TECDOC-1759*.
• TEPCO confirmed that the initially selected models and pathways were
sufficiently dominant and valid.
• However, internal exposure due to inadvertent ingestion of seawater
during swimming will be added in the revised report.
• TEPCO revised the settings of representative person in light of the
prevailing circumstances surrounding the site.
Points to be further clarified
• None – waiting for detailed documentation
2. TEPCO’s Responses and Points to be Further Clarified
* IAEA TECDOC-1759, Determining the Suitability of Materials for Disposal of Sea under the London Convention
1972 and London Protocol 1996: A Radiological Assessment Procedure (2015).7iv. Parameters
• TEPCO provided the source of the citation and the reason for using
parameters that are not in the IAEA or other references
Points to be further clarified
• None – waiting for detailed documentation
2. TEPCO’s Responses and Points to be Further Clarified8v. Dose Coefficients for Tritium
• TEPCO presented that OBT was not detected in the results of previous
environmental sampling in the surrounding area.
• As a reference, a dose assessment was conducted for the case where a
certain percentage of Tritium in the on-site storage tanks existed as OBT,
and it was confirmed that the results were not significantly affected.
Points to be further clarified
• None – waiting for detailed documentation
2. TEPCO’s Responses and Points to be Further Clarified9vi. Potential Exposure
• TEPCO reorganized the exposure pathways for potential exposure
• New exposure pathways listed below were added
• External and internal exposure during underwater work, external
exposure from ship hulls, beaches, and fishing nets, and internal
exposure from ingestion of marine products
• Dose assessment results increased from 10-5 to 10-1 order of magnitude.
However, they were still below the dose criterion of 5 mSv.
2. TEPCO’s Responses and Points to be Further Clarified
• Potential exposure is covered by the presentation C-2-3.
vii. Seawater Intake
• Seawater for dilution of ALPS process water is planned to be taken from seawater
outside the port (on the north side of the water discharge outlets of Units 5 and 6) to the
intake of Unit 5, after a dike is constructed between the port and the intake of Unit 5.
• TEPCO evaluated the radiation effects of radioactive materials contained in the
seawater in two cases: one in which seawater from outside the port was taken from
the north side of the Unit 5 and 6 intakes, and the other in which seawater from inside
the port (north side within port) was taken directly from inside the port.
( Source: TEPCO, the 9th Review Meeting, 15 February 2022 )
2. TEPCO’s Responses and Points to be Further Clarified
vii. Seawater Intake
• TEPCO confirmed that in all cases, the impact of radioactive materials in seawater on
the representative person is well below 50 μSv/year.
( Source: TEPCO, the 9th Review Meeting, 15 February 2022 )
Points to be further clarified
2. TEPCO’s Responses and Points to be Further Clarified
• None – waiting for detailed documentation