Safety assessment for
the Rokkasho LLW disposal facilities

Naoyuki TAMURA
November 25, 2022

Contents2

1. Introduction (The location of JNFL and disposal sites)
2. Dose assessment for the No.3 disposal facility(1) Outline of the No.3 disposal facility(2) Regulatory requirements(3) Flow of the dose assessment in the post-institutional control period(4) Condition setting of living environment(5) Assumption of representative person(6) Assumption of exposure pathways(7) The result of dose assessment

3. Summary

Mainland of Japan

1. Introduction:
the location of JNFL
JNFL

Today, we are here!
@Kyushu Univ.

5. LLW Disposal Center3

4. Uranium Enrichment
Plant

Tokyo

3. Mixed Oxide Fuel
Plant

ObuchLake

1. Reprocessing
Plant
2. Vitrified Waste
Storage Center

Aomori Prefecture

Rokkasho-village

Pacific
Ocean

1. Introduction:
The location of LLW disposal facilities
Oippe-stream

No.2

No.1

Inoperationoperation

Futamatastream

No.3

Administrationbuilding
LLW temporary storage andinspection building

Underconstruction

Lake
Obuchi

Site area
Supervised area boundary

LLW disposal facilities
There are 3 disposal sites, No.1, No.2 and No.3.

4

No.1 & No.2
• The First 2 LLW disposal facilities havebeen in operation for 30 years.
(No.1 started operation in 1992)

30th anniversary• JNFL had disposed of more than
300,000 drums, which are generated
from the operation of NPPs.
No.3 ( New disposal facility )• Furthermore, JNFL applied for theamendment of No.3 disposal businesspermission in Aug. 2018, which got
approved in Jul. 2021 from Nuclear
Regulation Authority (NRA)

2.(1) Outline of the No.3 disposal facilityOverlooking• No.3 disposal facility consists of 8 concrete pits.
• Each concrete pit has disposal capacity 26,400 drums,
then in total 211,200 drums/8pits.
• Type of waste is solidified dry active waste, which isencapsulated in a drum of 200L.
• In addition, 3 layered-cover soil with low permeability is
to be installed to restrict the ground water flow.
Cross section(bentonite clay)

8 Concrete pits5

2.(2) Regulatory requirements for LLW

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Table: Type of radiation exposure scenario in the post-institutional control period
Type of scenario

Naturalevolution
scenario

Dose criteria

The future humanactivities

Parameters
association

Most likely
scenario

10 μSv/y( ALARA )• Realistic and plausible • Realistic value on the basis
assumptions consideringof the latest statistics andthe current lifestyles*1etc..

Most
severescenario

300 μSv/y( Dose constraints )• Conservative* values on• Conservative*
assumptions, considering
the basis of the latest
the current lifestyles*1
statistics and etc..

Human Intrusion
scenario

1,000 μSv/y( Dose limits )* To calculate so that the result of dose assessment is larger than the actual value．
*1: The current lifestyles are principally estimated on the basis of the latest statistics, investigations and literatures. Note that the trends and thesingularities in the past are considered.

2.(3) Flow of the dose assessment in thepost-institutional control period

5.Migration behavior ofradioactive nuclides
and exposure pathways

I would like to explain these details, “living environment” and “exposure pathways”.

72.(4) Condition setting of living environment

8• The radioactive nuclides would migrate from disposal area to the living environment, resulting in the radiation
exposure to the public.
• In the condition setting of living environment, Future human activities were estimated by the surroundingenvironment, such as geological and social environment.
Estimated human activities on Land Use
 Construction work Residence Ingestion of field farming products

soil
Bentonite clay

Host rockThat on Water use
 Ingestion of aquatic products Ingestion of irrigated farming products (Rice) Irrigated farming works

ObuchilakeFig. Conceptual image of dose assessment in natural evolution scenario.

2.(5) Assumption of representative person
Primary industry

Half of the workers areengaged in tertiary industry.

Thus, The inhabitant waschosen as therepresentative person in
the most likely scenario.

On the other hand, thefarmer etc., who haverelatively high ratio areadded to the R.P. in themost severe scenario.
Tertiary industry
Secondary industry

Scientific researcher
Technical service Wholesaler
Retaileretc.

Number of workers in Rokkasho-village (according to statistics in 2016)9102.(6) Assumption of exposure pathways①
Table: the assumption of exposure pathways in the most severe scenario and the most severe scenario.
• The exposure pathways are different from each type of representative person.
• Exposure pathways were estimated by considering the combination of H.A and R.P.
Representative person
Fisherman

Farmer(Rice)

Farmer(Others)

Stockbreeder

Construction
workerInhabitant

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

✔

Irrigated farming works using river water-

✔

-

---

Outside works in the disposal area

----

✔

-

Inhabitation in the disposal area

✔

✔

✔

✔

✔

✔

Ingestion of the field farming products cultivated inthe disposal area✔

✔

✔

✔

✔

✔

Scenario Humanactivities

Most likely/
Mostseverescenario

Exposure pathway

Ingestion of the aquatic products caught in Obuchinuma
Water Ingestion of the irrigated farming products
use cultivated with river water

Land
use

In the most likely scenario, dose assessment for the inhabitant was performed only.
In the most severe scenario, dose assessment for each representative person was performed

112.(6) Assumption of exposure pathways②
Table : the assumption of exposure pathways in the dose assessment in human intrusion scenario

Representative person
ScenarioHumanintrusion
scenario

Construction
Humanworkeractivities
Ingestion of the aquatic products caught in Obuchi-numa in case of low permeability of
the cover soil was lost by the large-scale construction in the disposal area
Water
Ingestion of the irrigated farming products cultivated with river water in case of lowusepermeability of the cover soil was lost by the large-scale construction in the disposalarea

Exposure pathway

Large-scale construction works in the disposal area

Land
use

To be exposed
through land use

Inhabitation on the excavated soil which accompanies the large-scale construction
Ingestion of the field farming products cultivated on the excavated soil whichaccompanies the large-scale construction

Inhabitant
✔
✔

✔

--✔

due to the land useafter excavation.
-✔

• In the human intrusion scenario, construction workers are assumed to be exposed through land use.
• In addition, it is assumed that the inhabitant would be exposed due to the land use after excavation.

2.(7) The result of dose assessment

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the result of dose assessment from No.3 disposal facility in the most likely scenario
in the post-institutional control period

10μSv/y Inhabitant : 0.088 μSv/y Maximum dose peak time : 430 ySUM

The dose*1 from No.3 disposal facility is sufficiently lower than the dose criteria*1: Pile up dose of No.1, No.2 and No.3 disposal facility:
0.46 μSv/y (the most likely scenario) and 11 μSv/y (the most severe scenario)

3. Summary• JNFL applied for the amendment of No.3 disposal businesspermission in Aug. 2018, which got approved in Jul. 2021
from Nuclear Regulation Authority (NRA)• JNFL performed the dose assessment of the No.3 disposal
facility with several representative person and the exposure
pathways, based on the latest available statistics.
• JNFL quantitatively confirmed the dose from the No.3
disposal facility would comply with the dose criteria.
(e.g. 0.088 μSv/y < 10 μSv/y (in the most likely scenario))

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