Development of the NUMO pre-selection, site-specific ... Documents... · “The NUMO pre-selection, site-specific safety case” provides the basic structure for subsequent safety

P.0

Development of the NUMO pre-selection,

site-specific safety case

24th November 2016, Vienna, Austria

International Conference on the Safety of

Radioactive Waste Management, IAEA

Nuclear Waste Management Organization of Japan (NUMO)

Tetsuo Fujiyama, Satoru Suzuki,

Akira Deguchi, Hiroyuki Umeki

P.1

In 1999, the “H12 Report” was published by JNC (now JAEA), which demonstrated the feasibility of safe geological disposal of HLW based on a generic study.

On the basis of the H12 Report, “the Final Disposal Act” for implementing geological disposal of HLW came into force and NUMO was established in 2000.

NUMO initiated the siting process by open solicitation of volunteer municipalities in 2002.

ILW (termed “TRU waste” in Japan) was also included in NUMO’s remit by amendment of the Act in 2007.

…. The Great East Japan Earthquake and the Fukushima Dai-ichi NPP accident in 2011 increased nationwide concerns about the feasibility and reliability of geological disposal in Japan

No volunteer municipality has appeared and no candidate host rock type has been specified as yet.

Evolution of geological disposal programme in Japan

P.2

“The Basic Policy”, based on the Final Disposal Act, was amended in 2015, which involves that the Government will nominate scientifically suitable areas to initiate discussions and cooperation with local municipalities, finally leading to acceptance of a site investigation, which will be carried out by NUMO.

NUMO has developed the “NUMO pre-selection, site-specific safety case”

Development of site descriptive models (SDMs) on the basis of field data obtained at URLs, provides a more advanced site-specific basis than the H12 Report.

Why make the NUMO Safety Case?

It is important at this time to present technical evidence to support the feasibility and safety of geological disposal, which will encourage stakeholder support of implementation

P.3

Staged site investigation process

Development of SDM

Outline of initial

repository concept

Outline of safety

assessment

Estimation of geological

environment

characteristics

Literature

Investigation Stage

Selection of PI areas

Planning of PI stage

Investigation

and

evaluation of

the

geological

environment

Repository

design

Safety

Assessment

Literature survey

Exclusion of unsuitable

sites

Preliminary

Investigation Stage

Preliminary design of

disposal facility

Understanding geological

environment

characteristics

Selection of DI areas

Planning of DI stage

Preliminary safety

assessment

Surface based

investigations


sites

Update of SDM

Detailed

Investigation stage

Basic design of disposal

facility

Detailed understanding of

geological environment

characteristics

Selection of the

repository site

Basic safety assessment

Surface based investigations

Investigations in the UIF

Confirmation that site is

suitable

Update of SDM

Development and review of the safety case

P.4

Development and review of the safety case

Development of SDM

Outline of initial

repository concept

Outline of safety

assessment

Estimation of geological

environment characteristics

Detailed

Investigation stagePreliminary

Investigation Stage

Literature

Investigation Stage

Selection of PI areas

Planning of PI stage

Literature survey

Basic design of disposal

facility

Detailed understanding of

geological environment characteristics

Selection of the

repository site

Basic safety assessment

Surface based investigations

Investigations in the UIF

Confirmation that site is

suitable

Preliminary design of

disposal facility

Understanding geological

environment characteristics

Selection of DI areas

Planning of DI stage

Preliminary safety

assessment

Surface based

investigations


sites


sites

Update of SDM Update of SDM

Development of SDM

Trial design of

repository

Next technical

development plan

Nationwide literature

Trial safety

assessment

At this stage

Setting of candidate

host rock type

The basic safety

case structure

Providing the basic safety case structure

P.5

PR materials(brochures)

Principles and safety of

geological disposal

Existence of suitable

geological environments

Safety in case of natural

hazards

Pre-closure safety

Retrievability of waste

General public

For geological

disposal experts

Reference R&D reports

NUMO-TR, JAEA-Research, CRIEPI-Reports,

Scientific papers etc.

Main Report350 pages

NUMO Safety

Case Report

Supporting ReportsDetailed background to support

the main report

178 documents, Total 4800 pages

Abridged report(Describing mainly key

messages of SC with simple

text, 50 pages)

Engineers & Technologists

Scientific communicators

For others

The geological

disposal community

Why geological disposal?

Basic concept of geological disposal

Basic Safety strategy

Stepwise approach

Reversibility

Transparency

・・・

Executive summary

30 pages

Documents and target audience

Presented using a web-based communication platform

P.6

1. Background and purpose

2. Safety strategy

3. Geological characterisation and synthesis ...developing geo/hydro models of potential host rock environments on the

basis of the state-of-the-art geoscientific knowledge

4. Repository design and engineering technology ...being performed on the basis of the models, providing underpinning

evidence to demonstrate the technical feasibility of geological disposal

5. Assessment of pre-closure safety

6. Assessment of post-closure long-term safety ...being performed on the basis of the models, providing underpinning

evidence to demonstrate the long-term safety of geological disposal

8. Confidence in the technical feasibility of geological disposal in

Japan

9. Conclusions

Contents of NUMO Safety Case report

7

Five rock types

P.8

1 km

Active fault Active fault

Granite

Highly fractured (weathered) domain

Sedimentary overburden

100~200 m 100~200 m

GW flow

L ≥1 km

Regional scale (50 km x 50 km)

Repository scale (5 km x 5 km)

Panel scale (800 m x 800 m x 800 m)

L ≥1 km L ≥10 m

Illustrative geological setting

Fractured media

Hard rock

Nested models for plutonic rocks

P.9




Active fault Active fault Granite Basement

Quaternary sediments (several tens of m)

Freshwater – saline water transition

GW flow

Sea

500 m


L ≥25 m

Nested models for Neogene sedimentary rocks

Porous media with low

density of fractures

Soft rock

P.10

1000m

Quaternary sediments (several tens of m)

Thrust Freshwater – saline water transition

GW flow

Sea





Nested models for Pre-Neogene sedimentary rocks

Fractured media with

high density of fractures

Hard rock

P.11

Metal shell

Overpack Vitrified waste

Buffer

(Bentonite)

オーバーパック

緩衝材

ガラス固化体

支保工

埋め戻し材

処分孔

（処分坑道）（人工バリア）

Concrete support

Backfill

Disposal hole

Buffer

Overpack

Vitrified waste

Vertical emplacement

Backfill Concrete

support

Buffer

(Bentonite)

Waste

packages Pit

PEM

Backfill

Disposal drift

Prefabricated EBS module (PEM)

Vault waste emplacement

HLW repository TRU waste repository

(EBS)

Repository concepts to be considered in design study

P.12

予備区画

④

予備区画③

区画①

区画③

区画②

区画④

区画⑥

区画⑤

予備区画

②

予備区画

①

予備区画(TRU)

0 500m

An example of underground panel layout

Faults

(Length > 1 km)

5 k

m

Relative migration time + ‐

Unpreferable area

Short travel

time

Direction of ground water flow

Plutonic rocks model

Required scale of the facility:

Total HLW: more than 40,000

canisters of vitrified waste

Total TRU waste: more than

19,000 m3

P.13

Since safety standards for geological disposal in Japan have not, as yet, been defined, the results of the safety assessment are compared to international standards.

A risk-informed approach is introduced, based on international guidelines as well as recent national discussions on safety regulations.

Referring to the guidelines of international organisations on assessment timescales, dose calculations are carried out for up to one million years after closure.

The advanced approach and methodology for radionuclide transport modelling can be used to compare different sites and disposal concepts.

Assessment of long-term post-closure safety

P.14

Scenario

classification Definition Target dose

Likely

Scenario

This scenario is used to assess the performance

of the geological disposal system based on the

best understanding of the probable evolution, as

a reference for the optimisation of protection.

Target value: 10

μSv/y

Less-likely

scenario

This scenario is used to assess the safety of the

geological disposal system in view of

uncertainties in scientific knowledge supporting

likely scenarios.

Safety reference

value: 0.3m Sv/y

Very unlikely

scenario Possible scenarios with extremely low likelihood.

Reference value: 1～20 mSv/y

Human

intrusion

scenario

This scenario is used to check whether the

geological disposal system is robust with

assumption of human intrusion after loss of

institutional control.

Reference value；

Residents:

1～20 mSv/y

Intruder:

20～100 mSv/event

Scenario classification and target dose

P.15

EDZ t=1000mmFracture transmissivity:100

times to the original value

Cross section

of driftShotcretet=50 mm

EDZt=500mm

Backfill (Bentonite-

sand mixture)

Buffer

Deposition hole

k=1.0×10-12 m/s

Draink=1.0×10-5 m/s

k=1.0×10-5 m/s (degraded)k=1.0×10-9 m/s

3D modeling of RN transportation

100m

10

0m

EBS

Rock

Faults and fractures are represented by stochastic modelling approaches, on the basis of the site-specific dataset obtained URLs.

A 3D model is used to represent the geometry of the EBS components and geosphere to realistically evaluate transportation of RN at the near-field scale.

P.16

1E-4 1E-3 1E-2 1E-1 1E+0 1E+1 1E+2 1E+3 1E+4 1E+5

H12 Report - reference case

Likely scenario case / Plutonic rock

Uncertainties in glass dissolution rate

Bentonite alteration due to Fe-silicate minerals

Uncertainties in fracture distribution

Change of magnitude of hydraulic gradient

Uncertainties in radionuclide migration parameters (Kd, De) of rock

Concealed active fault intersects the repository

Human intrusion (exploration)

Examples of safety assessment of HLW

Maximum dose rate (μSv/y)

Likely scenario

(10 μSv/y)

Less-likely scenarios

(300 μSv/y)

Human intrusion

scenarios

Very unlikely scenarios

(1~20 mSv/y)

Plutonic rock model

P.17

Development of ‘realistic’ SDMs on the basis of key characteristics, e.g. distribution of faults, fractures and their hydraulic conductivities, in particular from studies in Japanese URLs since 2002.

A practical methodology for tailoring repository design to geological environments

Engineering feasibility of technology for retrieving waste

Pre-closure safety assessment of radiological protection during waste handling in surface facilities

The advanced approach and methodology for radionuclide transport modelling can be applied to compare different site and disposal concepts

Development of management strategy for project implementation (Quality Management, Knowledge Management, R&D, Strategy on human resources…)

Progress since H12 report

P.18

Key conclusions

“The NUMO pre-selection, site-specific safety case” provides the basic structure for subsequent safety cases that will be applied to any selected site, emphasising practical approaches and methodology which will be applicable for the conditions/constraints during an actual siting process.

The preliminary results of the design and safety assessment would underpin the feasibility and safety of geological disposal in Japan.

P.19

Finalisation of NUMO Safety Case report (for review, in Japanese)

Open to the public on a web-based communication platform

Start of domestic review by the Atomic Energy Society of Japan

January 2017

Finalisation of the NUMO Safety Case report (for review, in English) reflecting comments from domestic and international experts

Application for international review (by OECD/NEA?)

Around July 2017

Schedule for the NUMO SC report

P.20

Thank you for listening