NUMO-TR-13-05

Safety of theGeological Disposal Project 2010

Safe Geological Disposal Based on Reliable Technologies

English Summary

July 2013
Nuclear Waste Management Organization of Japan（NUMO）

Ⓒ原子力発電環境整備機構: Nuclear Waste Management Organization of Japan, 2013
All parts of this work are protected by copyright. No parts of this publication may be reproduced, stored in
the retrieval system, or transmitted, in any form or by any means, without the prior permission of NUMO.
Inquiries about copying and reproduction should be addressed to:
Science and Technology Department
Nuclear Waste Management Organization of Japan
Mita NN Bldg. 1-23, Shiba 4-chome, Minato-ku, Tokyo 108-0014 JapanNUMO-TR-13-05?-**02

Safety of theGeological Disposal Project 2010
Safe Geological Disposal Based on Reliable Technologies

English Summary

July 2013
Nuclear Waste Management Organization of Japan（NUMO）

CONTENTS
1 . Introduction ...................................................................................................................................1
1.1 Background and objectives of the geological disposal project ...................................................1
1.2 Structure of the NUMO 2010 Technical Report ........................................................................2
2 . Background to the geological disposal project ...............................................................................6
2.1 Radioactive wastes destined for geological disposal..................................................................6
2.2 Specific features of the geological disposal program in Japan ...................................................7
2.3 Activities in other countries..................................................................................................... 11
3 . Strategies for ensuring safety .......................................................................................................14
3.1 Safety goals ............................................................................................................................ 14
3.2 NUMO’s policies for ensuring safety...................................................................................... 15
3.3 NUMO’s strategy for addressing particular issues relevant to the geological disposal project .23
4 . Staged project implementation..................................................................................................... 28
4.1 Basic approach ....................................................................................................................... 28
4.2 Implementation of policies (roadmaps) ...................................................................................30
4.3 Activities in each stage of the project ...................................................................................... 36
5 . Investigation and evaluation technologies for the geological environment ...................................44
5.1 Approach to investigation/evaluation of the geological environment of Japan.........................44
5.2 Approach to literature surveys and preliminary investigations................................................. 48
5.3 Literature surveys and preliminary investigations ................................................................... 51
5.4 Progress in developing the technologies supporting investigation/evaluation activities ...........56
5.5 Conclusions of chapter 5......................................................................................................... 59
6 . Technologies for design, construction, operation and closure of the repository.............................61
6.1 Basic design policy for the geological disposal project............................................................ 61
6.2 Safety functions and technical requirements for the repository................................................62
6.3 Repository design ...................................................................................................................66
6.4 Repository construction, operation and closure .......................................................................74
6.5 Design and operation technologies accounting for the variability of the geological environment79
6.6 Development of technologies that support engineered measures............................................. 83
6.7 Conclusions of chapter 6......................................................................................................... 87
7 . Technology for long-term safety assessment ................................................................................ 88
7.1 Basic strategy for safety assessment ........................................................................................88
7.2 Development of the safety assessment .................................................................................... 91
7.3 Development of technologies that support the safety assessment ............................................ 96
7.4 Conclusions of chapter 7....................................................................................................... 102
8 . Technical activities during the Literature Survey and Preliminary Investigation stages .............. 103
8.1 Site selection process from public solicitation and start of the LS to the selection of DIAs .... 104i8.2 Literature Survey stage ......................................................................................................... 107
8.3 Preliminary Investigation stage ............................................................................................. 111
8.4 Conclusions of chapter 8....................................................................................................... 116
9 . Conclusions ............................................................................................................................... 117
REFERENCES .............................................................................................................................. 119
APPENDIX ...................................................................................................................................A-1
FIGURE
Figure 2-1 HLW and TRU waste forms ............................................................................................................ 7
Figure 2-2 TRU waste groups and their characteristics ..................................................................................... 7
Figure 2-3 Three-stage site selection process .................................................................................................... 9
Figure 2-4 Examples of underground facilities for co-disposal of HLW and TRU........................................... 10
Figure 2-5 Basic engineered barrier system for the disposal of HLW .............................................................. 11
Figure 2-6 Basic engineered barrier system for the disposal of TRU waste ..................................................... 11
Figure 3-1 Overall structure of the policies for ensuring safety........................................................................ 17
Figure 3-2 Components of NUMO’s safety case and their respective roles ..................................................... 19
Figure 3-3 Relationship between disposal project, R&D milestones and fundamental R&D ........................... 21
Figure 3-4 NUMO’s stepwise closure concept................................................................................................ 26
Figure 3-5 NUMO’s concept for retrievability/reversibility and monitoring .................................................... 26
Figure 4-1 Staged implementation of the geological disposal project .............................................................. 29
Figure 4-2 Integration of the three safety measures ......................................................................................... 30
Figure 4-3 Safety roadmap ............................................................................................................................. 33
Figure 4-4 R&D roadmap .............................................................................................................................. 34
Figure 4-5 Confidence-building roadmap ....................................................................................................... 35
Figure 5-1 Flow diagram for literature surveys and preliminary investigations: An example of coordination andsharing of investigations and information................................................................................................ 49
Figure 5-2 Literature survey process flow (example based on volunteer solicitation) ...................................... 53
Figure 5-3 Staged approach during preliminary investigations (surface and borehole investigation phases) . 55
Figure 6-1 Relationship between the basic concept for ensuring safety and the different project stages ........... 63
Figure 6-2 Sequence of repository design ....................................................................................................... 68
Figure 6-3 Example of the overpack design procedure (JNC, 2000b).............................................................. 69
Figure 6-4 Design flow for buffer material (NUMO, 2011a)........................................................................... 70
Figure 6-5 Excavation of vertical shafts using the short-step method (Nakayama et al., 2008) ........................ 75ii

Figure 6-6 Schematic process for remote-controlled waste encapsulation in the overpack (carbon steel single
overpack) (NUMO, 2002) ...................................................................................................................... 76
Figure 6-7 Schematic illustration of the PEM method..................................................................................... 76
Figure 6-8 Image of the repository before submitting the closure plan ............................................................ 77
Figure 6-9 Emplacement option considering assumed underground conditions (vertical emplacement/block
emplacement) ......................................................................................................................................... 81
Figure6-10

Emplacement

optionconsidering

assumedundergroundconditions(horizontal

emplacement/in-situ construction) .......................................................................................................... 82
Figure 6-11 Emplacement option considering assumed underground conditions (horizontal emplacement/PEMtype) ....................................................................................................................................................... 82
Figure 6-12 Maximum shear strain around the tunnel (HLW repository tunnel) (NUMO, 2011d) ................... 84
Figure 6-13 TIG welding of the overpack ....................................................................................................... 85
Figure 6-14 Tests of the PEM-type EBS ......................................................................................................... 86
Figure 6-15 Example of waste retrieval technology ........................................................................................ 86
Figure 7-1 Basic procedures for safety assessment.......................................................................................... 89
Figure 7-2 Handling of uncertainties in the safety assessment ......................................................................... 91
Figure 7-3 Storyboard for the disposal of HLW (Example) ............................................................................. 94
Figure 7-4 Complementary use of performance assessment models and process models ................................ 95
Figure 7-5 Example of particle tracking analysis for one hundred thousand years (NUMO, 2011c) .............. 100
Figure 7-6 Application of sorption database (SDB) for setting Kd value ....................................................... 101
Figure 8-1 Structuring of the chapters in this report....................................................................................... 104
Figure 8-2 Sequence of activities in the LS and PI stages (for the case of formal volunteering) ..................... 106
Figure 8-3 Sequence of activities in the LS stage (for the case of volunteer application)................................ 109
Figure 8-4 Setting of PIAs and supplementary investigation areas (for the case of volunteer application)... 110
Figure 8-5 Sequence of activities in the PI stage ........................................................................................... 114

TABLE
Table 1-1 Structure of the 2010 Technical Report and the present summary report............................................ 4
Table 1-2 Organizations, legislation and regulations and reports relevant to the geological disposal project ...... 5
Table 2-1 Status of geological disposal programs in foreign countries ............................................................. 13
Table 5-1Natural phenomena to be taken into account in Japan, their potential impacts on the geologicaliii

disposal system and their treatment in the site selection process .............................................................. 46
Table 5-2 Definition of periods for forecasting natural phenomena from the viewpoint of site
investigation/evaluation .......................................................................................................................... 47
Table 6-1 Basic concept for ensuring long-term post-closure safety and safety functions ................................ 63
Table 6-2 Technical requirements for the overpack (ensuring basic barrier functions) ..................................... 64
Table 6-3 Technical requirements for the buffer (ensuring basic barrier functions) .......................................... 65
Table 6-4 Technical requirements for the backfill and plug (ensuring basic barrier functions) ......................... 65
Table 6-5 Basic safety measures for radiation protection................................................................................. 66
Table 6-6 Evaluation criteria for defining the location of the underground facilities ........................................ 72
Table 7-1 Major discussion points for constructing a safety case (OECD/NEA, 2002).................................... 96
Table 7-2 Example of potential changes in safety assessment when a new fault intersecting the repository isformed (NUMO, 2011b)......................................................................................................................... 98iv

1 . Introduction
1.1 Background and objectives of the geological disposal project
In June 2000, the Act on Final Disposal of Specified Radioactive Waste (hereafter the Final DisposalAct) came into force. The Final Disposal Act is based on the policy document issued by the Japan
Atomic Energy Commission (AEC) in 1998 entitled ”Basic Policy for the Disposal of HLW” and theSecond Progress Report on Research and Development for the Geological Disposal of HLW in
Japan (JNC, 2000a-e; hereafter H12 Report) of the Japan Nuclear Cycle Development Institute(JNC) (now the Japan Atomic Energy Agency (JAEA)); the latter compiles the achievements of
R&D conducted over more than 20 years since 1976.
Based on the Final Disposal Act, the Nuclear Waste Management Organization of Japan (NUMO)
was established in October 2000 as the implementing organization for geological disposal ofhigh-level radioactive waste (HLW). The Final Disposal Act was revised in 2007 and based on this,some types of long-lived, low heat-generating waste were also included as waste destined forgeological disposal and thus fell within the remit of NUMO. These wastes are referred to as TRU
waste for geological disposal (hereafter TRU waste).
The site selection process specified in the Final Disposal Act consists of an initial literature survey
phase and three subsequent stages: selection of Preliminary Investigation Areas (PIAs), selection of
Detailed Investigation Areas (DIAs) and selection of the repository site1. In December 2002, NUMO
issued a nationwide call for volunteer municipalities to initiate the repository siting process.
Since its establishment in 2000, NUMO has been developing the technologies required for safe
implementation of the disposal project and has carried out a range of activities aimed at improving
awareness of the project and associated public relations programs. Despite these efforts, however, noapplication has been received as yet from a volunteer municipality and no literature survey has been
initiated for a specific site. Together with the national government, the electricity utilities and otherrelevant organizations, NUMO is now making its best efforts to obtain public acceptance for starting
literature surveys.
In view of this situation, the Policy Evaluation Committee of the Japan Atomic Energy Commission
proposed in 2008 that NUMO should publish a report demonstrating the technical feasibility of safe
implementation of geological disposal. The report was to be reviewed by external, independent
academic institutions and revised and updated periodically to reflect state-of-the-art knowledge
1 In this report the following stage names are used: Literature Survey stage (LS stage) for “selection of Preliminary

Investigation Areas (PIAs)” , Preliminary Investigation stage (PI stage) for “selection of Detailed Investigation Areas(DIAs)” Detailed Investigation stage (DI stage) for “selection of the repository site”.

1

(AEC, 2008).
Against this background, NUMO issued a report in September 2011 entitled “Safety of theGeological Disposal Project 2010 - Safe geological disposal based on reliable technologies” (referredto hereafter as the NUMO 2010 Technical Report) (NUMO, 2011e). This summary report presents
the major conclusions of the report.

1.2 Structure of the NUMO 2010 Technical Report
The present report effectively has the same structure as the NUMO 2010 Technical Report, with thespecific technologies being described in chapters 2 to 8, and is divided into two main parts: project
implementation chapters that present the policies for ensuring the safe implementation of thegeological disposal project and technology chapters that present the progress made throughdevelopment of scientific knowledge and the technologies that support the safety concepts forgeological disposal since the H12 report, as well as the status of preparations for the implementationof the project (Table 1-1).
Project implementation is described in chapter 2 – ‘background to the geological disposal project’,chapter 3 – ‘strategy for ensuring safety’ and chapter 4, ‘staged project implementation’. Chapter 2
presents basic information on the geological disposal program. Chapter 3 presents the basic strategy
and component policies for ensuring the safety of geological disposal, with respect to both long-term
post-closure safety and safety during the duration of the project. The strategy is based on staged
implementation that allows the risks and uncertainties associated with a long-term undertaking
extending over approximately 100 years to be addressed. Chapter 4 presents safety, R&D andconfidence-building roadmaps that illustrate how the policies outlined in chapter 3 are realized
during staged project implementation.
The technologies developed are described in chapter 5 – ‘investigation and evaluation technologies
for the geological environment’, chapter 6 – ‘the technologies for design, construction, operation andclosure of the repository’ and chapter 7 ‘the technologies for long-term safety assessment andtechnical activities during the LS and PI stages.
The technology chapters describe the systematic development of geological disposal technologies for
ensuring long-term post-closure safety and safety during each project stage as described in the
project implementation chapters, together with specific examples. A description of the technologies
required during the LS and PI stages is also provided. In chapter 8, the procedures for safe
implementation of the project with coordination and integration of the technologies described inchapters 5, 6 and 7 are presented.

2

The discussion of the progress in R&D in the technology chapters is focused on HLW. A separate
report documents the details for TRU waste (NUMO, 2011a) and thus only key points are addressedin this report.
The Appendix documents the progress of R&D since the H12 report.
Two cases can be envisaged for initiating literature surveys (LS): voluntary application bymunicipalities or a request made by the national government to municipalities to come forward.
Unless otherwise specified, this report assumes that the literature surveys are initiated by anapplication from a municipality.
The organizations, legal and regulatory framework and reports relevant to the geological disposal
project are listed in Table 1-2.

3

Table 1-1 Structure of the 2010 Technical Report and the present summary report

Chapters
1
Project implementation

2
3
4

5

Technology

6

7

8

9

Title
Introduction
Background to thegeological disposal
project
Strategies for
ensuring safety
Staged project
implementation
Investigation andevaluation
technologies for thegeologicalenvironment
Technologies fordesign, construction,
operation and closureof the repository
Technology forlong-term safetyassessment
Technical activities
during the Literature
Survey andPreliminary
Investigation stages
Conclusions

Content
Background, objectives and overall structure of the report
Goals for ensuring safety and policies/strategies forachieving the goals
Policy 1：Staged and flexible project implementation
based on iterative confirmation of safety
Policy 2：Project implementation based on reliable
technologies
Policy 3: Technical activities for building confidence in
NUMO’s safety concept

Progress in the development of technologies for theinvestigation/evaluation of the geological environment

Progress in the development of technologies forestablishing engineering measures
Progress in the development of technologies for long-term
safety assessment

Technical activities to be conducted during the LS and PI
stagesOverall summary

4

Table 1-2 Organizations, legislation and regulations and reports relevant to the geological disposal
project

Full name

AcronymOrganizations (domestic)
Organizations (overseas)

Nuclear Waste Management Organization of Japan

NUMOJapan Atomic Energy Agency(formerly the Japan Nuclear Cycle Development Institute)

JAEA
(JNC)

Radioactive Waste Management Funding and Research Center

RWMC

Central Research Institute of Electric Power Industry

CRIEPI

National Institute of Advanced Industrial Science and Technology

AIST

National Institute of Radiological Sciences

NIRS

Federation of Electric Power Companies of Japan

FEPC

Coordination Executive for Fundamental R&D on Geological Disposal

Coordination
Executive

Atomic Energy Commission of Japan

AEC

International Atomic Energy Agency

IAEA

International Commission on Radiological Protection

ICRP

Organisation for Economic Cooperation and Development / Nuclear
OECD/NEA
Energy Agency

Laws &
regulations

Svensk Kärnbränslehantering AB (Sweden)

SKB

National Cooperative for the Disposal of Radioactive Waste (Switzerland)

Nagra

Agence Nationale pour la Gestion des Déchets Radioactifs (France)

ANDRA

Nuclear Waste Management Organization (Canada)

NWMO

Act on Final Disposal of Specified Radioactive Waste

Final Disposal Act

Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material
Nuclear Reactor Act
and Nuclear Reactors
Final Disposal Plan for Specified Waste

Final Disposal Plan

Reports

Second Progress Report on Research and Development for the Geological
H12 Report
Disposal of HLW in Japan (JNC, 2000a to e)
Second Progress Report on Research and Development
for TRU Waste Disposal in Japan (FEPC and JNC, 2005b)

5

Second TRU Report2 . Background to the geological disposal projectThis chapter aims to improve the understanding of the need for geological disposal and awareness of
NUMO’s geological disposal program by providing a brief explanation of the relevant radioactive
wastes, how the waste will be disposed of, the unique nature of the geological disposal program inJapan and activities ongoing in other countries.

2.1 Radioactive wastes destined for geological disposal
Geological disposal ensures long-term safety through a system of multiple engineered barriers
constructed in a stable geological environment (natural barrier) at a sufficient distance from thehuman environment. Based on the AEC report “Basic Policy on the Disposal of HLW” (AEC, 1998)
and JAEA’s H12 Report, the Final Disposal Act entered into force in June 2000 and specifies
systematic measures for the promotion of geological disposal of HLW. The Final Disposal Act wasrevised in 2007 to include TRU waste. A brief description of the radioactive wastes destined forgeological disposal as specified in the Final Disposal Act is provided below.
2.1.1 High-level radioactive waste (HLW)
The reprocessing of spent fuel involves dissolving the fuel with nitric acid and extracting theuranium and plutonium using an organic solvent (tributyl phosphate or TBP), leaving highly
radioactive residues containing mainly fission products and transuranic nuclides as waste (referred toas high-level radioactive liquid waste). The highly radioactive waste is mixed with glass, melted athigh temperature, poured into stainless steel canisters and cooled to form vitrified HLW (seeleft-hand side in Figure 2-1).
2.1.2 Low-level radioactive waste for geological disposal (TRU waste)
TRU waste is low-level radioactive waste generated by the operation and decommissioning of
reprocessing and MOX (mixed oxide fuel) fuel fabrication plants, containing long-lived nuclides
above specific concentrations.
NUMO is responsible for TRU waste for geological disposal. Typical TRU waste packages areshown on the right-hand side of Figure 2-1; TRU waste groups and their characteristics are presented
in Figure 2-2.

6

HLW glass

Drums

Wastepackage container

Stainless Canister

CanisterHeight ：1.3m
Diameter ：40cm
Waight ：500kg※JNFL spec.

High-level radioactive waste

TRU waste for geological disposal

Figure 2-1 HLW and TRU waste forms

Iodine adsorbent

Hull&endpieces Hull

Concentrated solution, etc.

Organic waste

Nitric acid solution waste
Mortar, etc.

Description

Silveradsorbent

Rubber gloves（incineration / compression）

Effluent
PelletIntakeAdsorbent to remove
radioactive iodine

Sectioning&
compression

Non-combustible waste

Tools

Dried pellet

Waste
package
image(e.g.)

Metal pipes

低レベル放射性廃棄物

Features• Radioactive iodine(I-129) is included• Cemented waste
form• Relatively high heatpower
• Radioactive carbon(C-14) is included• Nitrate is contained• Solidified waste with e.g.,mother or bitumen• Incineration ash or
non-combustibles• Solidified waste withcement, etc.

Group

1

2

3

4

1

Figure 2-2 TRU waste groups and their characteristics(based on the report by the Advisory Committee for Natural Resources and Energy)

2.2 Specific features of the geological disposal program in Japan
Since 2000, when NUMO was established, the circumstances surrounding the geological disposal
project have changed, including revisions made to the Final Disposal Act and the Act on theRegulation of Nuclear Source Material, Nuclear Fuel Material and Reactors (hereafter the Nuclear
7

Reactor Act). In line with these changes, the specific features of the geological disposal program inJapan are discussed in this section.
2.2.1 Three-stage site selection process and volunteer approach to siting
The site selection process consists of three stages: selection of Preliminary Investigation Areas(PIAs), selection of Detailed Investigation Areas (DIAs) and selection of the repository site, as
defined in the Final Disposal Act (Figure 2-3).
Before initiating literature surveys (LS) for the selection of PIAs, NUMO has been soliciting
volunteer municipalities nationwide as potential areas for carrying out investigations for final
repository sites since 2002 and has been involved in a range of activities aimed at encouraging
volunteer applications. This approach recognizes the importance of independent judgment by local
communities in the context of the public nature of the geological disposal project and the project
duration extending over approximately 100 years.

8All Japan
PIAs
DIAs
Repository site

Borehole investigations,etc.

Measurement andtesting in undergroundinvestigation facility
Construction of
repository

Selection of PIAs
Investigation areas:
Volunteer areas and theirsurroundings
Investigation methods:
Literature surveys
Objectives:
To confirm that there is norecord of significant
movement in geologicalformations due to natural
phenomena such as
earthquakes and to verify
their low likelihood in the
future.

Selection of DIAs
Investigation areas: PIAs
Investigation methods:
Borehole survey, geophysicalprospecting, etc.
(preliminary investigations)Objectives:
To confirm that the geologicalformations for the repository andtheir surroundings are stable
and have no obstruction to
excavating drifts, small potential
adverse impacts onunderground facilities due togroundwater flow, etc.

Selection of therepository site
Investigation areas: DIAs
Investigation methods:
Detailed surface explorations,
measurements and tests inunderground investigation
facility.
(detailed investigations)Objectives:
To confirm the suitability forrepository construction basedon the physical and chemical
properties of the geologicalenvironment.

Figure 2-3 Three-stage site selection process(NUMO, 2009b)

NUMO modified the solicitation process to include both HLW and TRU waste2 in 2008 (NUMO,
2009a-d). Applicants may choose to apply as a potential disposal site for either or both of these waste
types.
In accordance with the recommendations made in the Interim Report of the Sub-committee for the
Safety of Radioactive Waste Disposal published in November 2007 (Advisory Committe for Energy,2007), the national government was permitted to request municipalities to come forward for the
implementation of literature surveys.

2

Disposal of HLW and TRU waste at the same site is termed “co-disposal.”

92.2.2 Repository dimensions and engineered barriers
According to the Final Disposal Plan (METI, 2008), the size of the repository has been set assuming
the number of vitrified HLW containers for emplacement to be 40,000, which corresponds to theaccumulated nuclear power generation up to around 2020. The HLW containers will be emplacedwith sufficient spacing to avoid any significant impact on the disposal system from high heatgeneration, particularly during the period shortly after emplacement, although the heat generationfrom the waste will decay with time. The area of the repository is expected to be 5-6 km2, but it may
be larger depending on the geological conditions at the selected site.
For TRU waste, the repository size has been set assuming the total volume of waste packages to be
19,000 m3, considering the operation and decommissioning plans for spent fuel reprocessing plants
and other relevant facilities. Since TRU waste includes a variety of waste forms and properties withlow heat generation for the majority of the waste, it will be emplaced in large cross-section disposal
vaults, resulting in a smaller repository area of approximately 0.25 km2.
Figure 2-4 shows images of the underground facilities for co-disposal of HLW and TRU waste
constructed at coastal and inland sites.
Inlandrepository case

Coastalrepository caseSurf asef acilities

Surf asef acilities

Shaf t
Ramp

Shaft
Shaft

Ramp
Ramp

Ramp

Disposal panel(An assembly of
disposal tunnels)

Undergroundfacilities（HLW）

Undergroundf acilities（HLW）

Disposal panel(An assem bly of
disposal tunnels)

Undergroundf acilities

Undergroundf acilities

Connecting
tunnel（HLW）

Connecting
tunnel（HLW）

Connecting
tunnelFigure 2-4 Examples of underground facilities for co-disposal of HLW and TRU(NUMO, 2009a)

10

The basic configuration of the engineered barriers for geological disposal is shown in Figure 2-5 andFigure 2-6 for HLW and TRU waste respectively. For the disposal of HLW, the vitrified waste issealed in an overpack (metal container) and surrounded with a buffer consisting mainly of natural
bentonite. For the TRU waste, the engineered barriers are designed differently for each of the fourgroups depending on the characteristics of the waste. The basic configuration consists of the waste
form, buffer and backfill for Groups 1 and 2 and waste form and backfill for Groups 3 and 4 (seeFigure 2-2 for a description of the waste groups).

Waste
ガラス固化体(HLW glass)

Overpack
オーバーパック
緩衝材

BufferFigure 2-5 Basic engineered barrier system for the disposal of HLW

Backfill

Liner
Structural
supportWaste packages
encasing waste
form sWaste packages
encasing waste
forms

Liner

Buffer
Backfill(a)Group 1 & 2(b)Group 3 & 4

Figure 2-6 Basic engineered barrier system for the disposal of TRU waste

2.3 Activities in other countries
In countries with nuclear energy programs, geological disposal has also been identified as the best
option for management of high-level waste and the projects are at different stages.
As of July 2013, Finland and Sweden have both selected a repository site each. In Finland, Olkiluoto
11has been selected and the application for a construction license was submitted in December 2012. In
Sweden, a potential repository site was selected at Forsmark in June 2009 and an application for thesiting and construction of the repository was submitted in March 2011. In France, a potential
repository site has been identified in an area near Bure, where the underground rock laboratory(URL) is located. In addition to these programs, preliminary siting procedures are underway in
Switzerland, the UK and Canada.
Table 2-1shows the status of geological disposal programs in foreign countries.

12

Table 2-1 Status of geological disposal programs in foreign countries(adapted from METI, 2011)

Country
Finland

StatusIn 2000, Olkiluoto was selected as the final repository site. Construction of an underground investigation
facility began in June 2004 and the subsurface geological environment is being evaluated. The license
application for repository construction was submitted in December 2012.
Sweden
SKB has been performing a feasibility study in six municipalities since 1995 and selected three of thesein 2000 as candidates for further site investigation. After Oskarshamn and Östhammar accepted the
project, site investigations and environmental impact assessments were performed at these sites. Basedon the investigation results, SKB selected Forsmark in Östhammar as the repository site in June 2009. In
March 2011, a licensing application for repository construction was filed.
USA
The Yucca Mountain Site in Nevada was previously selected as the repository site and safetyassessments were carried out from 2008 with the aim of obtaining a construction license. However, theObama administration, which came into power in January 2009, decided to abandon the disposal plan for
the Yucca Mountain Site and applied for its revocation in March 2010. Following this, the Blue Ribbon
Commission was established in accordance with the US Federal Advisory Committee Act to discuss
how spent fuel should be dealt with. The Waste Isolation Pilot Plant (WIPP) for TRU waste started
operation in March 1999.
FranceSince 2000, ANDRA has constructed a URL at Bure and has been performing various underground tests.
Based on the 2006 Planning Act on the Sustainable Management of Radioactive Materials and Waste, anadditional investigation program has been underway since 2006 in an area of 250 km2 (including Bure)for a “reversible” repository; a license will be applied for, with the goal of starting operation in 2025.
Based on the investigation results, ANDRA narrowed the area down to 30 km2 at the end of 2009. If
the siting plan is approved via open round-table discussions, an application for a waste emplacement
license will be filed around 2014.
Switzerland Based on the Sectoral Plan for Deep Geological Repositories established in 2008, Nagra proposed threepotential candidate regions for the HLW repository site in October 2008. Following a three-stage
selection process defined in the Sectoral Plan, the final site will be decided in 2018.
UK
The UK government published a white paper on managing radioactive waste in June 2008 in order tosolicit municipalities interested in accommodating the repository. By January 2009, two cities and one
county had expressed an interest; these are currently being screened for initial siting criteria.
CanadaThe federal government decided to pursue an ”Adaptive Phased Management” strategy that starts withon-site and centralized waste storage followed by geological disposal. NWMO formulated a nine-stepsite selection process for the repository and initiated an ”Expression of Interest” phase and site selection
plan as the first step. By September 2010, four regions had expressed an interest in receiving informationfrom NWMO.
Germany
The site characterization program at Gorleben has been halted since 2000. The second Merkel
administration, however, agreed to lift the moratorium and resume investigations in October 2009.
Spain
The site selection process was interrupted in 1998 and the decision on how the waste will be disposed ofhas not yet been made. However, geological disposal is considered as a feasible option.
Belgium
An interim report on the safety and feasibility of geological disposal has been published and the R&D
program has reached its final stage. A license application for repository construction will be filed around
2020.

13

3 . Strategies for ensuring safety
This chapter describes NUMO’s strategies and policies aimed at achieving safe geological disposal(see Figure 3-1).

3.1 Safety goals
3.1.1 Context and safety goals
The ultimate goal of geological disposal is to prevent harmful effect of the radioactive waste on
humans and the environment at any time in the future after the closure of the repository, as well as on
residents and workers during each project stage before the facility is closed. NUMO’s policies are
based on the recognition that safe geological disposal requires the following goals to be achieved:− Ensuring long-term post-closure safety− Ensuring safety during project implementation.
3.1.2 Long-term post-closure safety
In order to ensure long-term safety after closure of the repository, the disposal system will be
designed based on the principles of containment3 in the deep underground and isolation4 from thehuman environment. Specifically, the waste will be emplaced in a stable underground rock formation
with a multi-barrier system consisting of natural and engineered barriers that provide the containment
and isolation functions.
The H12 report concluded that long-term post-closure safety could be assured by the following threesafety measures:(1) Selection of a geological environment suitable for disposal and confirmation of its safetyrelevant characteristics throughout the siting, construction and operational phases(selection and confirmation of suitable sites),(2) Appropriate design and construction of the repository, using engineered barriers suitable
for the selected geological environment (appropriate engineering for repository design andconstruction) and(3) Safety assessment of the post-closure performance of the geological disposal system

3 Containment is based on restricting the release of radionuclides into the groundwater by limiting the leaching rate of radionuclides fromthe waste and minimizing the transport of radioactive materials by restricting the migration of leached radionuclides (retardation).
4 Isolation involves protecting the repository from geomorphological changes such as erosion by emplacing the waste in a stable deeprock formation and reducing the likelihood of inadvertent human intrusion by making it difficult to access to the waste without special
technologies.

14(evaluation of long-term safety).
The validity of the conclusions reached has been confirmed by AEC (AEC 2000). The three safetymeasures are consistent with the safety principles issued by the Nuclear Safety Commission (NSC
2000).
3.1.3 Safety during the project implementation
NUMO will ensure radiological and conventional industrial safety for the general public and workers
in each stage by taking appropriate safety measures, starting from site selection through totermination of the project. To ensure that the safety measures are applied appropriately, NUMO will
analyze different risks assumed during the project implementation and will reflect the results inplanning investigation/construction programs and in the formulation of the safety regulations.
Different impacts on the surrounding environment from the large-scale civil engineering work
associated with the geological disposal project, such as excavation of tunnels and temporary storageof the excavated soil/rock, will be avoided or mitigated.

3.2 NUMO’s policies for ensuring safety
3.2.1 Establishment of safety policies
In order to achieve the safety goals described above, the project needs to be implemented taking into
consideration issues relevant to geological disposal and the conditions specific to Japan.
For the long-term safety of geological disposal following repository closure, an element of
uncertainty remains due to the extremely long timescales to be considered and the heterogeneous
nature of deep geological formations. It is necessary to reduce these uncertainties as far as possible
through detailed investigations and evaluations so that safety is assured more reliably. Since it is notpossible to directly demonstrate that the facility will be safe for the extremely long time periods
involved, it is effective to use the safety case concept, where the focus is on uncertainty management,in order to establish social understanding/agreement. The safety case is a structured set of arguments
into which all the information and knowledge on safety and reliability are integrated based on
various facts, understanding and experience on safety. The safety case also plays an important role indemonstrating that geological disposal is safe. Owing to the long project timescales (typically around
100 years) between site selection and closure of the facility it is not unlikely that there will be change
in social conditions.
In order to achieve the goals of such a complex project, it is important to adopt stepwise and flexible
15

implementation of the individual task phases over the entire project duration. Through this process,the necessary confidence will be acquired in each phase to allow the project to move forward, adjust
to the changes in the social environment and strengthen the reliability of the project. Particularly
regarding the demonstration of safety, iterative assessment of safety based on the information
obtained in each stage and providing the results to the local community and the public will help toacquire more understanding for the project.
NUMO’s first policy for assuring safety is therefore defined as:
Policy 1: Staged and flexible project implementation based on iterative confirmation of safety
As noted above, safety over tens of thousands of years after the closure of the facility cannot be
assured using conventional methods.
Modeling based on state-of-the-art scientific andtechnological understanding as well as behavior prediction methods based on observed data istherefore used. In order to improve the reliability of the predictive evaluations, it is necessary toadopt highly reliable methodologies for site characterization and the associated engineering strategies.
It is crucial to use the best technology available for assessing safety and scientific/engineering
measures.
Using the best technologies possible is the responsibility of our generation in order to protect theenvironment and human health into the far future.
NUMO therefore defines its second policy for assuring safety as:
Policy 2: Project implementation based on reliable technologies
For successful implemetation of the geological disposal project, it is essential that the affected local
community/municipality and the public understand and accept the safety that has been demonstrated
through technical investigations. Confidence-building towards safety is one of the essential aspectsof the geological disposal project. In order to accomplish this, it is necessary to ensure broad
understanding by a wide range of stakeholders, which is underpinned by scientificallywell-supported evidence.
Therefore, NUMO defines its third policy for assuring safety as:
Policy 3: Technical activities for building confidence in NUMO’s safety concept
Figure 3-1 shows the relationships between NUMO’s safety goals, policies for ensuring safety andpolicy components, each of which will be discussed below in more detail.

16

Goals of ensuringsafetyImplementation of safe geological disposal

Ensuring long-term post-closure saf ety(1) Selection and conf irmation of a suitable site(2) Appropriate engineered measures f or design and construction ofa repository(3) Assessment of long-term saf ety of the repository

Compatibility

Ensuring saf ety during project
implementation(1) Ensuring radiological saf ety(2) Ensuring industrial saf ety(3) Ensuring environmental protection

Policy 1

Policy 2

Policy 3

Staged and flexible project
implementation based on iterative
confirmation of safety

Project implementation based onreliable technologies

Technical activities for building
confidence in NUMO’s safety concept

Breakdown

Breakdown

Breakdown• Formulation of a comprehensive
program covering the entire project
duration,• Iterative confirmation of long-term
post-closure safety, and• Safety measures andenvironmental preservation during
the project duration• Systematic development of• Providing information required fortechnologies• Credible quality assurance oftechnologies• Well structured NUMO organization
and a system for domestic andinternational collaboration

decision-making in each stage• Providing information relevant tosafety and technical reliability
transparently and promoting
communication on a regular basis• Securing decision-making
opportunities for future generations

Figure 3-1 Overall structure of the policies for ensuring safety

3.2.2 Policy 1: Staged and flexible project implementation based on iterative
confirmation of safety
In order to ensure long-term safety of the repository during its operation and after closure, NUMO
has formulated a comprehensive program extending over the entire duration of the geologicaldisposal project. Specifically, Policy 1can be broken down into:(1) Formulation of a comprehensive program covering the entire project duration,(2) Iterative confirmation of long-term post-closure safety, and(3) Safety measures and environmental preservation during the project duration.
Firstly, the formulation of a comprehensive program covering the entire project duration is described.
For the smooth implementation of the project, which extends over a long period of time, the program
should be established from the perspective of the entire project and implemented in a stepwise andflexible manner. This will allow continuous improvement of the arguments related to safety,
development of appropriate responses to changes in the social environment and stepwise
improvement of confidence in the project.
To formulate a program covering the entire project duration, NUMO has developed a safety roadmap.
This separates the project into 10 stages, extending from literature surveys to project termination, andspecifies project goals, safety goals, requirements for achieving the safety goals and the actions ineach stage.
For iterative confirmation of long-term post-closure safety, NUMO will continuously improve the17reliability of the safety of geological disposal by iterative confirmation at key milestones based on
close linking of the three safety measures (selection and confirmation of a suitable site, appropriate
engineering measures for design and construction of a repository and assessment of long-term safetyof the repository) and integration of the information obtained.
An approach that has been adopted in several national programs in recent years involves developing
supporting arguments for the reliability of the long-term safety of geological disposal based onalternative performance indicators and presenting results from a wider perspective.
Figure 3-2 shows the components of NUMO’s safety case and their respective roles. The safety casewill be progressively updated and refined throughout the three-stage site selection process, licensing,construction, operation and closure.
The issue of uncertainty is important in the safety case. It is important to recognize and reduce or
mitigate the effect of uncertainties in the information to be included in the safety assessment
associated with the investigation/evaluation of the geological environment as well as in the design ofthe repository.
Secondly, safety measures and environmental preservation during the project duration can be
explained as follows: During the project, both industrial and radiological safety measures will be
implemented. Their impacts on the barrier function of the geological disposal system will be
evaluated continuously to ensure that the safety goals are met both during the project andpost-closure.
During the site selection and construction stages, the emphasis will be on ensuring conventional
industrial safety because no radioactive waste is involved in these stages. The data on the geologicalenvironment required for this will be compiled through site characterization conducted during thesite investigation and construction stages.
During the stages of operation and closure of the repository, measures for ensuring radiologicalsafety will also be required in addition to those described above as radioactive waste will be present.
These stages involve handling of radioactive materials in the deep underground environment, forwhich there is no experience. Considering the unique nature of the task, the most reliable
technologies available at these stages will be utilized in the design and construction of the system.
With a view to establishing a sustainable social structure and achieving common prosperity with thelocal communities, NUMO will conduct environmental impact assessments and continue activities
aimed at preserving the environment. The actions for environmental preservation that NUMO plans
to implement are collectively termed environmental considerations here.

18

Literature
Surveystage

Detailed
investigation stage

Preliminary
Investigation
stage

Report on preliminary
repository design andpreliminary safetyassessment based on
the preliminary
investigations

Description of therepository based onliterature survey

Suppotying
document

Statutory report Basedon the detailed
investigations
Report on basic
repository design andsafety assessment basedon the detailed
investigations

Suppotying
documentNew
information

Safety review
reportSuppotying
document
Safety case2

Safety case1

Safety case

Licensing

Statutory report basedon the preliminary
investigations (PI)Siting factors
for repositorysite selection

Repository site selection

DIA selection

Statutory report basedon literature survey

Siting factors
for DIAselection

PIA selection

Siting factors
for PIAselection

Const, Oper,closure andtermination

Safety case3

Main component of safety case
Safety Strategy

Background ・Goals ・ Requirements, Strategy to establish safety case,
Methodology for safety case development

Selection of Appropriate Site and Confirmation

Appropriate Engineered Measures

Prediction and avoidance of natural phenomena ,Disposal system(Geological environment , Biosphere)

Disposal system(Surface facilities, Under ground facilities),
Safety during project implementation, Environmental issues

Reliable Long‐term Safety Assessment

Safety Argument

FEP, Scenario, Model and case, Analysis

Robustness of safety case, Uncertainty treatment

Argument on prediction andavoidance of natural
phenomena
SA process(FEPs)

Detail evidence to support safety case
Result of site investigationand site descriptive model
SA scenario

Safety during project implementation(environmental issues ,construction/operational safety)

Design and construction of
disposal facility and EBS

SA model and caseand SAparameters

SA parameters

Detail argument on safety and uncertainty
treatment

Broad concern andquestion on safety

Biosphere informationand model
SA analysis case andresults
Etc.

Present safety based onsafety case

Stakeholder
General public, Local public, Municipalities, Policy maker, regulators,
Researchers of university and research organizations etc.
Figure 3-2 Components of NUMO’s safety case and their respective roles

3.2.3 Policy 2: Project implementation based on reliable technologies

19

NUMO will use the best available technologies based on up-to-date knowledge to ensure safety with
sufficient reliability. These technologies5 have been developed and validated in other conventional
and/or nuclear industries in terms of their reliability and economic efficiency with quality assurance
to a certain level.
Although many of the technologies used in the geological disposal project have been developed inother fields, there are some that have been developed specifically for geological disposal. For these, itis necessary to perform R&D activities based on a well defined plan and the applicability of eachtechnology must be verified. Therefore, NUMO’s R&D program will follow a well defined schedule.
Furthermore, NUMO places significant emphasis on a structured training plan for its staff members
in order to create a highly reliable scheme for implementing the required activities.
Specifically, Policy 2 can be broken down into:(1) Systematic development of technologies(2) Credible quality assurance of technologies(3) Well structured NUMO organization and a system for domestic and international
collaboration
Firstly, systematic development of technologies is described. The Framework for Nuclear Energy
Policy (AEC, 2005) states that NUMO should be responsible for the development of technologies
aimed at safe implementation of geological disposal in a cost-effective and efficient manner, while
fundamental R&D organizations will be responsible for geoscientific research, improving thereliability of geological disposal technologies and improving safety assessment methodologies using
underground research laboratories and other research facilities. NUMO has been conducting R&D
within the framework of this role-sharing structure.
A “Coordination Executive” was established by the Government to outline for the fundamental R&D
organizations the technologies required by NUMO and the regulatory body to ensure that the R&D
results will address their specific needs (ANRE/JAEA, 2010). As a member of the Coordination
Executive, NUMO is able to express its needs in this respect and to evaluate and confirm the R&D
results of the fundamental R&D organizations for application in the geological disposal project(NUMO, 2010).
Figure 3-3 shows the key milestones in the geological disposal project and the relationship with thedevelopment of technologies and fundamental R&D contributing to these milestones.

5

The term “technologies” includes engineering knowledge (expertise), methodologies and tools.

20Disposal project

Present
▼

2000

2002

NUMO
established▼Open solicitation
started▼Around2020▼

Mid 2010’s▼
Selection of
DIAs▼

Selection of
PIAs
▼
LS

PI

Selection of arepository site▼
DI

Start operationlate 2030’s▼

License▼Construction,
operation andclosureNUMO’s R&D

Preparation foropen solicitation

Preparation
completed

Preparation for LS

Preparation for PI

Current
target of R&D

Demonstration
Test

Preparation for DI

Fundamental R&D

Preparation for long-term project implementation(construction, operation, closure, project, management, etc)

Needs

R&D results【 R&D in URL 】
Investigat. (surface)
H12
ReportInvestigation during
excav.ation

Investigation at
investigation facility【 R&D on repository design and geological environment 】
Generic geological environment

Specific geological environment

Figure 3-3 Relationship between disposal project, R&D milestones and fundamental R&D

NUMO will check the progress of the fundamental R&D to ensure that it is consistent with the needs
that evolve with the progress of the project. The results of the fundamental R&D will be reviewed by
NUMO in terms of technical reliability and applicability to the project and, if required, additional
studies will be conducted.
The most effective way to demonstrate the applicability of the developed technologies will be toactually apply them. Demonstration of technologies involves verifying the technologies orcomponents thereof by testing their operability under conditions simulating actual conditions. It also
includes resolving problems associated with the technologies and improving applicability andreliability.
For technologies specific to geological disposal in particular, such as remote waste emplacement
techniques, applicability and reliability will be confirmed through demonstration tests andmodifications made if necessary. Even for established technologies in other industrial areas, such as
borehole investigations and transport of waste packages, applicability will be evaluated for the
specific conditions of geological disposal and the special restrictions it imposes and reliability will be
improved through demonstration tests as appropriate.
Secondly, a description of credible quality assurance of technologies is provided below. NUMO has
21established and implemented a quality management system (QMS) for documentation (preparing
technical reports), which is the primary task in the early stages, in accordance with ISO 9001: 2000.
The QMS is applied for controlling documentation and its management with quality levels
commensurate with the significance of the information contained in the different technicaldocuments, applying consistent principles
Thirdly, the well structured NUMO organization and a system for domestic and international
collaboration is explained. NUMO will secure the human resources required for steady
implementation of the geological disposal project in Japan. As the geological disposal projectextends over approximately 100 years, it will be important to secure the human resources required tosupport the project and take account of the potential evolution of the project during the entire period.
The number of experts required is estimated to be 100 or more at peak times; they will come fromdifferent fields including geology, civil engineering and nuclear engineering. The organizational
structure of NUMO in the future has also been studied based on estimated manpower requirements
and the tasks and expertise required in each project stage.
NUMO will conduct R&D within the framework of the role-sharing structure in collaboration withdomestic organizations. This collaboration is essential as NUMO cannot claim to possess all theknowledge required; a wide spectrum of knowledge from different disciplines, where part of thetechnical knowledge is owned/managed by the relevant domestic organizations, is required for
effective implementation of the geological disposal project.
3.2.4 Policy 3: Technical activities for building confidence in NUMO’s safetyconcept
The geological disposal project involves extremely long time periods during which consideration ofsafety will be required and ethical issues solved between current and future generations. The projectwill therefore be implemented stepwise, gaining acceptance by local residents at key milestones ineach stage from site selection to decommissioning after closure of the repository.
Specifically, Policy 3 can be broken down into:(1) Providing information required for decision-making in each stage(2) Providing information relevant to safety and technical reliability transparently and promoting
communication on a regular basis(3) Securing decision-making opportunities for future generations
Regarding providing information required for decision-making in each stage, numerous decisions
will require to be made during the period from site selection to closure of the repository. For thesmooth implementation of the stepwise decision-making process, it will be necessary for the22

implementing organization to provide the information required for making these decisions to all of
the concerned parties and to provide clear explanations to facilitate understanding.
Secondly, providing information relevant to safety and technical reliability transparently andpromoting communication on a regular basis is described as follows. Achieving confidence in thesafety of geological disposal and the reliability of the technologies used is essential for effective
decision-making in each stage. NUMO will therefore provide relevant and transparent information to
the public on a regular basis. With regard to concerns or questions about the safety of geologicaldisposal raised by the local and general public, it will be important to conduct extensive analyses andstudies and to continue confidence-building activities based on the results of these studies. A system
for analyzing such aspects based on social science methodologies will be established to provide
feedback to the confidence-building activities.
Thirdly, securing decision-making opportunities for future generations ensures that certain
decision-making opportunities are reserved for future generations under the conditions prevailing at
the time, rather than the current generation attempting to determine matters 100 years into the future
based on their own assumptions.
Potentially the most important decision that will require the involvement of future generations will beon closure of the repository. The repository is designed to ensure that safety is based as far as
possible on passive measures. NUMO will take all the steps required for ensuring safety before
closure of the repository with the aim of eliminating the need for active human control.

3.3 NUMO’s strategy for addressing particular issues relevant to the geologicaldisposal project
Geological disposal involves utilization of the natural geological environment with its heterogeneityand large spatial extent, as well as a project extending over approximately 100 years that will almost
certainly be accompanied by changes in the circumstances surrounding the project. To ensure an
appropriate response to these changes, a risk management approach will be applied for project
management.
Since the ultimate goal of the geological disposal project is to ensure passive safety based on amulti-barrier system, for the closure of the repository a decision will have to be made on the timingof the shift of the safety mode from dependence on active administrative control to reliance on themulti-barrier system. The decision on shifting to the passive safety mode is equivalent to deciding toinitiate decommissioning of the repository. This will require a review of the information obtained up
to that time in the stages of site investigation, construction and operation in order to comprehensively
23

assess compliance with the requirement of passive safety. A key point for such decision-making is
how to deal with issues such as reversibility, retrievability and closure.
In this section, NUMO’s approach to the following issues will be discussed. It should be noted thatspecific measures in the areas described below have to be developed considering progress in theestablishment of a legal framework relevant to the geological disposal project in Japan andinternational trends on these issues.
••••

Risk management during the project duration
Monitoring
Reversibility and retrievability
Closure of the repository

3.3.1 Risk management during the projectIn the geological disposal project, it is required to address uncertainties associated with technologicaland societal aspects. Activities for ensuring safety involve assuming unsafe conditions and making
provisions to prevent the occurrence of these conditions or to minimize their consequences in theevent of occurrence. Many of the activities associated with assuring safety during the phases before
and after closure are common to risk management as practised in other industries: risk identification,risk analysis, risk evaluation and taking measures to prevent/minimize risk.
The aforementioned activities encompassing the risk management approach can be applied to ensure
the long-term safety of geological disposal by appropriate implementation of conventional safetymeasures. On the other hand, for safety during the project, various risks including occupational
injuries associated with investigation and construction activities, occupational radiation exposure due
to failure of waste packages during operation and closure will be identified and their likelihood andconsequences evaluated; based on this, the design of the repository and the safety assessment system
will be improved. The risk management approach based on ISO 31000 will be applied to suchactivities. How NUMO will develop a risk management system based on ISO 31000 is an important
issue to be studied in the future.
3.3.2 Monitoring
The geological disposal project employs different types of monitoring for confirming safety orprotecting the environment in each stage from site selection to repository closure. Monitoring is also
important for verifying that the project has been conducted properly. Disclosing the monitoring data
to the general public and local residents will be essential for improving confidence in the project.
Monitoring may be carried out as appropriate during the period from confirmation of repository
closure to project termination, but passive safety without reliance on active control including24

monitoring will be necessary for closure of the repository. The monitoring that will be conducted by
NUMO can be categorized into the following four types:••••

Monitoring for confirming long-term post-closure safety
Monitoring for confirming radiological safety
Monitoring for confirming industrial safety
Monitoring for confirming environmental preservation

Regarding the assurance of long-term safety after closure, due to the extremely long timescales to beconsidered it is not possible to directly confirm, with the monitoring described above, the accuracy ofthe overall scenario when assessing safety for the licensing application. Therefore, monitoring will be
used to evaluate selected individual phenomena assumed in scenarios (e.g. the saturation process inthe buffer material). Quantifying the reliability of predicted physical behavior (e.g. groundwater
variation) included in the hydrogeological model complements the reliability of the safetyassessment (Kurikami et al., 2010).
The parameters to be monitored will be determined after the site conditions have been set,considering site-specific characteristics and requirements from the viewpoint of safety assessment.
After key parameters that may affect safety have been identified, it will be determined whether or notthese are to be monitored during site investigation or their variation with time needs to be monitored.
3.3.3 Reversibility and retrievability
Reversibility means the ability to reverse one of a series of steps taken in a repository project.
Retrievability is a special case of reversibility, meaning that it is possible to recover emplaced waste
packages.
During the period before the repository closure plan is authorized, NUMO will maintainretrievability of the waste packages and, after obtaining authorization, will implement closure
according to the approved plan. Closure involves backfilling all underground spaces such as accesstunnels, shafts and ramps and installation of plugs as required (Figure 3-4).
Figure 3-5 shows an overview of NUMO’s basic policy on retrievability/reversibility and monitoring.
Monitoring required for judging whether or not to implement closure of the repository will continue
until completion of operations. When closure has been authorized, i.e. the passive safety of therepository has been established, monitoring and retrievability need not be maintained from theviewpoint of ensuring long-term post-closure safety. If closure steps have not been taken and safetymeasures are required to ensure passive safety, then monitoring for implementing safe closure should
be undertaken. In order to confirm that closure has been successfully completed, monitoring will be
continued as required.
25

Complete
operation

Completeconstruction

CompleteclosureProjecttermination

Plug
Access tunnels
Backfill

Disposal tunnels

Plug
Connection DisposalpittunnelAccess tunnels to
disposal depth,
connection tunnels
disposal tunnels

Bentonite

Waste
package

Emplacement of WPs
In disposal tunnel,
Backfill disposal tunnel,
Macharical plug

ClosureClosure of connection
and access tunnels.
plug construction if
required

Dismantling of thesurface facilities

Figure 3-4 NUMO’s stepwise closure concept

Closurepermission

Stage

Operational stage

Closureconfirmation

Projecttermination

Closure stage

Transportation andemplacement of waste
packages
Retrievability/
Reversibility

Retrievability

Closure activities

Re-do closure if required
Monitoring during theoperational stage

Monitoring during theclosure stage

Monitoring as
required

Monitoring

Figure 3-5 NUMO’s concept for retrievability/reversibility and monitoring26

3.3.4 Closure of the repository
Closure of the repository means actions taken to move from the stage where ensuring safety depends
on active administrative control during the project duration to the stage where passive long-term
safety is assured without administrative control (IAEA, 2006).
The Nuclear Reactor Act, which was revised in 2007, specifies that a closure plan application should
be prepared and submitted by the implementing organization to the national government for
authorization. The government is required to confirm long-term post-closure safety based on a final
safety review by NUMO.
Recognizing the unique features relevant to ensuring the safety of the geological disposal system,NUMO identifies the closure measures as an important milestone of the project and will start
preparing for taking appropriate actions from the current stage of the project.

27

4 . Staged project implementation
This chapter describes the implementation in practice of the policies discussed in chapter 3 using
roadmaps.
Policy 1: Staged and flexible project implementation based on iterative confirmation of safety
Policy 2: Project implementation based on reliable technologies
Policy 3: Technical activities for building confidence in NUMO’s safety concept

4.1 Basic approach
4.1.1 Staged project implementation and major milestones
NUMO has a staged project implementation program extending from initial literature surveys toproject termination as shown in Figure 4-1 (NUMO, 2009a). With the goal of ensuring passive safety,
NUMO will take the required measures during the project, with iterative confirmation of safety fromsite selection through to the post-closure stage.

28

Selection of PIAs

LS

Determination oflocation of UIF

Selection of DIAsPI

DI (surface-based)

Boreholes from theground surface

Boreholes from theground surface

Boreholes from theground surface

Boreholes from theground surface

Selection of arepository site

DI (UIF)

Safetyreview

Appliedareas

Submission of the closure
plan application

Construction

Project
authorizationSurface facility

Operation

ClosurePost-closure control

Dismantling/removal of
surface facilities

Monitoring around therepository

Surface facility

Backfill of accesstunnels

Operation
zone
Subsurface
facilities

Submission of the projecttermination application

Projecttermination

Monitoring around therepository

Construction
zone

Figure 4-1 Staged implementation of the geological disposal project(NUMO 2009a, partly revised)

4.1.2 Implementation of the geological disposal project and coordination among
different technology fields
In the geological disposal project, as noted earlier, the following three safety measures will be
implemented in a stepwise manner: selection and confirmation of suitable sites, appropriate
engineering for design and construction and evaluation of long-term safety. The three technology
fields associated with these measures (site investigation/evaluation, engineering and safetyassessment) should be coordinated and integrated to support decision-making at each stage (Figure4-2). In addition, activities supporting post-closure safety should be integrated with those required toensure safety at all stages prior to closure.

29

Site investigations
and evaluation

Site information required for
implementing theengineered measures

Needs from the safetyassessment to the site
investigations and evaluation
Needs from the perspective of
implementing engineered
measures for the site
investigation/evaluation

Site information
required for the safetyassessment

Integration
Information required for thesafety assessment of EBS
and repository

Engineered measures

Safety assessment
Needs to ensure
safetyFigure 4-2 Integration of the three safety measures

In identifying sites to be investigated in the site selection stage, justification of the selection has to be
made. Before starting the investigations in each stage, NUMO plans to establish and open to the
public so-called siting factors for the selection of investigation areas. The siting factors for theselection of PIAs have already been published. The siting factors for the selection of DIAs will be
published before initiating the DIA selection stage (preliminary investigation stage) based on
discussions on the selection of DIAs with the national goverament. Details will be discussed inchapter 8.

4.2 Implementation of policies (roadmaps)
4.2.1 Approach to the implementation of Policy 1: Staged and flexible project
implementation based on iterative confirmation of safety (safety roadmap)
The safety roadmap is divided into the stages shown below considering the entire project duration.
For each stage, milestones, requirements, activities and the resulting main documents are shown. The
ultimate goal of safe geological disposal will be achieved by reaching the milestones defined for eachstage (Figure 4-3).
-

Literature Survey stage
Preliminary Investigation stage
Detailed Investigation stage – surface-based investigations
Detailed Investigations stage – investigations in the UIF
Safety review stage
30

-Construction stage
Operational stage – during operation
Operational stage – end of operation / closure plan
Closure stage
Post-closure to project termination stage

In general, in the early stages of site investigations the emphasis is on avoiding natural phenomena
with significant impacts, such as volcanic/igneous activity and seismic/fault activity; this then shifts
to characterization of the geological environment, design and safety confirmation of the repository
and, finally, the safety review for the license application. After granting of the license, the focus will
shift to engineering activities such as construction, operation and closure of the repository.
4.2.2 Approach to the implementation of Policy 2: Project implementation based onreliable technologies (R&D roadmap)
This section summarizes how required R&D can be planned in advance based on R&D roadmaps
that compare current technology and understanding with the level required to reach the milestones
set for each project implementation stage (Figure 4-4). The technologies shown in the roadmap arethose required for achieving the goals set out in the safety roadmap, but are considered as stillrequiring further development and demonstration based on an analysis of their current technology
level.
The R&D addressed in this roadmap includes manufacturing technologies, methodologies orscientific/engineering knowledge required for integrated analysis of investigation data, design andsafety assessment, together with associated databases and research results. The R&D roadmap also
addresses how to compile research results from various organizations and integrate knowledge andtechnologies to the level of quality required at each project stage. NUMO will use this approach for
R&D management.
4.2.3 Approach to the implementation of Policy 3: Technical activities for building
confidence in NUMO’s safety concept (confidence-building roadmap)
Since geological disposal deals with issues that may be difficult to understand for many stakeholders,such as those associated with deep geological environments, extremely long timescales andradiological effects, extensive and continuous communication efforts are required in order to build
confidence in safety among stakeholders who are not experts in the field of nuclear engineering. This
report presents the activities to be addressed for building confidence in technical aspects of safety inthe form of a confidence-building roadmap (Figure 4-5).
The confidence-building roadmap is prepared in line with the three policy breakdowns described in31chapter 3: (1) providing information required for decision-making in each stage; (2) providing
information relevant to safety and technical reliability transparently and promoting communication
on a regular basis and (3) securing decision-making opportunities for future generations.

32

Stages

Literature Survey
stage

Preliminary Investigation
stage

Selection of PIAs

Selection of DIAs

Detailed investigation stage
Surface-based
investigations

Investigations in the UIF

Safety review
stage

Construction
stage

Selection of the repository
site

Granting of a project
licenseRepository construction

ca. 20 years
Goals in each stage

Operational stageDuring operation

ca.10 years

Determining the basic
repository layout

Closure stage

End of operation/closure planca. 50 years
Operation of the repository

Post-closure to
project terminationstage

ca. 10 years

Authorization of closure
plan

Implementation of closure

Project termination

Safety goals in each stage

・Confirming that significant
・Confirm that significant
・Avoid significant impacts impacts from natural
・Iterative confirmation of ・Confirming long-term
・Avoid significant impacts
impacts from natural・Assuring long-term safety long-term safety based on safety based on updated ・Demonstrate long-termfrom natural phenomena phenomena have been・Confirming safety in thefrom natural phenomena
phenomena are avoided
・Assuring safety during
updated information
information
safety through integration
・Ensuring long-term safety avoided
closure stage(avoiding areas that are・Confirm long-term safety
implementation
・Ensuring construction
・Safety assurance during of all information
・Ensuring safety during
・Ensuring long-term safety
clearly disqualified)・Confirm safety duringsafetyoperation
implementation
・Ensuring safety during
implementation safety
implementation

・Confirmation of
long-term safety based
on updated
information
・Confirmation of safetyassurance after
closureRequirements for the goals

Compliance with legal
requirements
Compliance withenvironmental
requirements
Compliance with NUMO
working standards

Compliance withdecommissioning
authorization
standards
Compliance withstandards for projecttermination

Long-term post-closure safety

Appropriate
engineering
measuresprovided bydesign andconstruction of
repository

Characterization of thegeological environment

Compliance with the legal
requirements
Compliance with the environmental
requirements for the selection of arepository site
Compliance with the guidelines forlicensingCompliance with NUMO working
standard

Compliance with technicalstandards
Compliance with NUMO
working standard

Compliance withstandards for theauthorization of closure
planCompliance withauthorized closure plan
Compliance with NUMO
working standards

Develop site descriptive

Update the site

Update the site

descriptive model

descriptive model

descriptive model

model to be used forlicensing

Define basic layout
and preliminary design

Define basic layout

Basic design

Update the site descriptive model

Construction

Operationand basic design

Fix specifications for

ClosureclosureDetailed design

EBS

Preliminary design

Fix specifications
Demonstrate fabrication/construction

Preliminary

Qualitative assessment

Qualitative assessment for licensing

quantitative assessment

Information collection andevolution

Plan measures（surface/subsurface facilities）

Basic design

Radiological safety

Generic design

Preliminary design

Basic design

Preservation of surrounding environment

Survey boundary
conditions

Preliminary impact assessment

Impact assessment
and preservation
measures： Activities very important for ensuring safety

Compliance with technicalstandards
Compliance with NUMO
working standards

Confirm avoidance using obtained information

Develop the site

Statutory report based onliterature survey
Description of therepository based onliterature survey

Compliance with thesafety review guidelines

investigations

Generic design

Industrial safety

Main safety documents

Legends

Compliance with the legal
requirements
Compliance with repository site
selection environmental factors
Compliance with the basic
guidelines for licensing
Compliance with NUMO working
standards

Avoid based on field

Avoid based on literature
information

Subsurface facilities

Evaluation of long-term stability of thegeological system

Safety in each project stag

33

Activities in each project stage

Appropriate site
selection andconfirmation

Avoid significant impacts
from natural phenomena(active faults, volcanoes anduplift/subsidence）

Compliance with legal
requirements
Compliance with environmental
factors for selecting DIAs
Compliance with basic guidelines
for locensing
Compliance with NUMO working
standards

Construction of EBS

Fabrication/transportation

fabrication system/emplacement

Safety assessment based Safety assessment basedon the information

Supplementaryevaluationon the information obtained

Detailed design

Application

during construction

Detailed design

Supplementary study

Statutory report based on theReport on basic repository Statutory report Based on
design and safety
the detailed investigations License application
Report on preliminary repository assessment based on the Report on basic repository documents
designandsafety Environmental impact
design and preliminary safety detailed investigations
assessment based on the assessment report
Environmental Impact
assessment based on thedetailed investigations
Assessment Reportpreliminary investigations
preliminary investigations (PI)： Activities important for ensuring safety

Figure 4-3 Safety roadmap

obtained during operation

Check process

Total assessment

Safety confirmation based on thefor closure

information obtained during closure

Application/supervision

Application/supervision

Supervision

Preservation measures and supervision (additional measures)

Application document for
approval of design andGeneral license application
construction method
Closure application
Application document for facility Waste package handling
documents
inspection
license application
Application document for
Safety review report
Safety review reportpre-operational inspection
Safety review report

Closure confirmation
application

Decommissioning planauthorization
application
Safety review report
Project termination
confirmation
application

Before 2000

2000－present

Literature survey

Preliminary

stage

investigation stage

Selection of PIAs

Selection of DIAs

Stage
Feasibility

Selection &confirmation of asuitable site

Preparation for
implementation

Study on volcanoes/

R&D required

Avoid significant

active faultsfor LS

natural phenomena

R&D for surface investigations（NUMO，R&D organizations）

Technology for surface
investigations（site-specific）

34

Long-term post-closure safety

Investigations in the
UIF

Determining the basic

Selection of theGranting of arepository layout

repository site

project license

termination plan

Implementation ofclosureFocused R&D
Major activities

Evaluate geologicalconditions
Investigation of geologicalconditions in undergroundfacility

Development of
repository concept

Decide basic layout

Basic design ofrepository

Design ofundergroundinvestigation facility

Construction ofundergroundinvestigation facility

Detailed design ofrepository

Engineering
tests

Safety review

Demonstration in underground investigation facility (prediction of long-term behavior)
Development of construction technology(If necessary)

Rough assessment

Repository construction

Demonstration in underground investigation facility(emplacement of engineered barriers)

Closuretechnology

Closure (R&D in surface facility/ URL)

Safety in each projectstage over duration of
the project

operation

repository

Avoid significant natural phenomena

Prediction of long-term behavior(knowledge development in domestic/ overseas URLs and surface research facilities)

Development of safetyassessment technology
for diverse environments

Authorization of

Operation of theRepository construction

Closure stage

Generic R&D

Construction (R&D in URL)

Safety assessment
technology undertypical conditions

End of operation/closure plan

During operation

Avoid significant
natural phenomena
Evaluate geologicalconditions

Operation (R&D in surface facility/ URL)

Safetyassessment ofgeologicaldisposal system

Construction stage

Development of design technology for underground facility (engineered barriers, repository)

Study of construction
feasibility

Study onengineering
feasibility (mainly
desk study)

Surface-based
investigations

Development of investigation technologies in domestic URLs
(knowledge development)

Development ofdesign technology

Operational stage
Safety review stage

LegendTechnology forsurface investigations(additional)

Knowledge acquisition inoverseas URLs

Appropriate
engineering
measures

Detailed investigation stage

Preliminary assessment

Comprehensive assessment for safety review

Construction safety （knowledge development in URL）

Knowledge development insurface facility/ overseas URL

Operational safety (knowledge development/ expansion in domestic URL

Supplementary
assessment

Safety confirmation based on information
obtained during construction/ operation

Comprehensive
assessment forclosureRepository
construction

Operational safety (knowledge development through construction ofunderground investigation facility and investigations)Figure 4-4 R&D roadmap

Repository closure

Safety assessment technology (R&D if necessary)

Construction safety (knowledge development through construction ofunderground investigation facility and investigations)

Study on safety ofclosure operations

Demonstration(closure technology)

Closure technology (R&D if necessary)

Safety assessment technology (assessment technology for specific site/repository)

Knowledge development on
construction

Repository operation

Safety of closure operations (R&D if necessary)

Repository
operation
Safety of closure operations(demonstration)

Repository closure

Operational stage

Detailed investigation stage
StagesOpen solicitation

Goals in each stage

Start literature
surveys

Literature survery
stage

Preliminary
investigation stage

Surface-based
investigations

Investigations in the
UIF

Safety review stage

Construction stageDuring operation

ca. 20 years

Sub-policy 1
Providing information relevant to decisionmaking in each stage

・Preparation andissuing of
information
package・Open siting factors
for th e selection of
PIAs

Selection of PIAs

Selection of DIAs

・Statuto ry literature
survey report・Statutory PI report・Concepturaldesign andpreliminary
safety assessment
reports based on PI
data

・Description of
repository basedon literature data

Determining thebasic repository
layout・Basic design andsafetyassessment
report based on
DI data (interim
report)・Environmental
impact statements

ca. 50 years

ca.10 years
Selection of therepository site

Granting of a project
licenseRepository
construction

Operation of therepository

・Statutory DI report

・License application
documents

・Design /construction
authorization
application
documents，facility
verification application
documents，preoperational inspection
application・Facility verification
application
documen ts，waste
verification
application
documen ts，safety
review report・Basic design andsafety assessment
report based on DI
data

・Environmental
impact assessment
reportEnd of operation/closure plan

Authorization ofoperation terminationplan
・ Closureplan authorization
application
documents，safety
review report

Closure stage

Postclosure/terminationca. 10 years
Implementation ofclosureTermination ofoperation

・Closure confirmation
applicationd ocuments

・Termination
authorization
application documents，
safety review report，application document
for confirmation of
docommossioning
completion

Integrate all results obtained through technical activities to confirm safety (formulation of a safety case)

Disclose data relevant to avoiding significant impacts from natural phenomena (plans, results, etc.)
Literature data

35

Sub-policy 2

Providinginformation obtainedby technical activities
on a regular basis
and promoting
communication

Providing information
relevant to safety andtechnical reliability
transparently on aregular basis andpromotingcommunication

Data from
borehole/geophysicalinvestigations, etc.

Data fro m additional
borehole/geophysicalinvestigations

Disclose geological environment data obtained by site investigations (plans, results, etc.)（Before starting
literature surveys）
Prepare anddisclose documents
describing
geologicalconditions

Literature data

Data from
borehole/geophysicalinvestigations, etc.

Data from ad ditional
boreh ole/geophysicalinvestigations

Analysis of concerns, evaluationof results of activities
心配要因の分析，活動結果の分析・評価

Activities aiming at building confidence considering
concerns

Keeping literature
information

Disclose operating
conditions to the
publicDisclose construction
site to the public
Decision on
construction of
repository

Disclose data relevant toenvironmental protection
for the investigations inthe subsurface facility

Surveys of concerns about gelogical disposal project

Disclose closure
Decision on closure of
the repository

Disclose data relavant
to construction

Disclose data relevant
to op erational safety

Disclose data relevant
to safety during
closureDisclose data
relevant toenvironmental
protection during
construction

Disclose data
relevant toenvironmental
protection during
operation

Disclose data relevant
to environmental
protection during
closureReview of implemented project activities

Decision on
terminating
operation

Formulation of plan for confidence-building

Disclose domestic and international URLs to the public，show virtual repository，provide information on geological diposal in surface PR facility，
provide information on geological disposal projects in other countries，natural analogues, earthquakes/active faults/volcanoes and uplift/erosion,
activities to facilitate understanding of radiological effects.

Baselinemonitoring

Sub-policy 3
Securing decision-making opportunities for
future generations.

Data from subsurface
facility

Disclose safety program during investigation p eriod and resulting data

Disclose environmental protection program/results for surface-based
investigations
Disclose environmental protection program for the period of
subsurface facility construction and operation

Analysis of concerns
about safety ofgeological disposal
and activities aimed
at building
confidence

Disclose data that support no significant impact
from natural phenomena

Data fro m subsurface
facility

Subsurface environment monitoring

Monitoring during
construction

Monitoring during
operation

Keeping
construction
records

Keeping operation
records

Keeping site investigation records

Figure 4-5 Confidence-building roadmap

Decision on closure of
the repository

Monitoring during
closureKeeping closure
records

Decision on
terminating
operation

4.3 Activities in each stage of the project4.3.1 Site selection and safety review stage(1) Literature Survey stage
・Goal of this stage
・Safety goals
・Requirements

・Main documents：Selection of PIAs
：Avoid significant impacts from natural phenomena(avoiding areas that are clearly disqualified)：Compliance with legal requirements6
Compliance with environmental requirements
Compliance with NUMO working standards：Statutory report based on literature survey
Description of the repository based on literature survey

The goal of this stage is to select PIAs based on literature surveys of volunteer areas. In order toensure safety, areas that have any significant impact from natural phenomena will be avoided. The
requirements for achieving the goal include “Compliance with statutory requirements”, “Compliancewith environmental requirements for PIA selection” and “Compliance with NUMO working
standards” (include siting factors for PIA selection (NUMO, 2009b)).
Overall evaluation and relative comparison will be carried out using favorable factors which areincluded in the siting factors for PIA selection, as required.
Initially, prior confirmation of geological conditions will be carried out to decide whether or not a
volunteer site will be suitable as a literature survey area. As already published (NUMO, 2009b), priorconfirmation of geological conditions is based on evaluations of seismic and volcanic activity
throughout Japan. Only after a volunteer site fulfills the siting factors will the literature survey start.
Information will initially be collected from databases, relevant institutions and other available
sources. Documents will relate to natural phenomena and geological conditions of the target area(s).
The collected information will be structured and managed using a geoenvironment data management
system.
Based on the evaluation factors for qualification - namely impacts from natural phenomena such as
seismicity/active faulting, volcanism/igneous activity, uplift and erosion - areas with significant
impacts from natural phenomena will be excluded. Finally, based on an evaluation of unconsolidated
Quaternary sediments and mineral resources, PIAs will be selected and a statutory report based on
6

The siting factors for selection of PIAs consist of factors relating to legal requirements (evaluation factors for qualification (EFQ)) andfavorable factors (FF) that are not part of legal requirements. The EFQ include earthquake and fault activity, igneous activity, upliftand erosion, unconsolidated Quaternary sediments and mineral resources.

36

literature survey will be produced.
In parallel, a regional site descriptive model (SDM) will be produced and, depending on thegeological conditions of the area, an outline design of the repository will be developed. Based on this,a preliminary assessment will be made of the long-term post-closure safety of the repository. Fromthese outline safety assessments, a general layout of the surface and subsurface facilities will be
developed and documented in a report describing the the outline repository. This will then bereflected in the planning of the subsequent stage.
At the same time, safety will be examined in terms of industrial (operational) safety, radiologicalsafety measures and preservation of the surrounding environment. For industrial safety, a risk
assessment will be carried out for the construction and operational phases, looking at potential risks
from natural phenomena and the seismic resistance of the underground structures. Radiologicalsafety measures will be evaluated both for workers and the general public for the period when waste
packages are being transported to the surface facility and handling of the waste packages in thesurface facility. Surveys will be carried out concerning preservation and protection of thesurrounding environment. The results for project safety will be documented in a report entitled ‘A
Description of the repository based on the literature survey.’(2) Preliminary Investigation stage
・Goal of this stage：Selection of DIAs
・Safety goals：Avoid significant impacts from natural phenomena
Ensuring long-term safety
Ensuring safety during implementation
・Requirements：Compliance with legal requirements
Compliance with environmental factors for selecting DIAs
Compliance with basic guidelines for licensing
Compliance with NUMO working standards
・Main documents：Statutory report based on the preliminary investigations (PI)
Report on preliminary repository design and preliminary
safety assessment based on the preliminary investigations
The goal of this stage is to select areas for detailed investigation. Safety goals in this stage include“Avoiding significant impacts from natual phenomena”, “Ensuring long-term safety “and “Ensuringsafety during implementation”. The requirements for reaching the overall target are compliance withthe evaluation factors for qualification, compliance with environmental requirements for DIAs,
compliance with the guidelines for the safety review and compliance with NUMO working
standards. Taking these safety goals and requirements into account, NUMO will carry out thefollowing activities in order to achieve the goal of this stage.

37

As part of the preliminary investigations, surface explorations, geophysical surveys and borehole
investigations will be carried out in order to obtain regional-scale geological data. From this, it will
be shown that areas with significant impacts from active faults, volcanism, uplift and erosion can be
avoided. The geological data will also be used to update the site descriptive model produced in theprevious stage and a more detailed model will be prepared on a scale that is sufficient for the DIA.
Additionally, the basic layout of the surface and underground facilities will be developed from the
updated site descriptive model and preliminary assessments will be made of long-term safety and thefeasibility of constructing the engineered barrier system (EBS). A reference repository design will
also be developed taking into account the specific geological environmental conditions, safety andsocio-economic aspects.
Safety will be examined in terms of industrial safety, radiological safety measures and preservationof the surrounding environment, as in the previous stage. In this stage, a more detailed evaluation
will be possible using the information on the site obtained from surface explorations, geophysicalsurveys, trench surveys and borehole investigations. Attention will be paid to the surrounding
environment as well as worker safety when carrying out the surveys.
Based on the above activities, DIAs will be selected and a report documenting the surveys carriedout in the detailed investigation areas will be produced according to the Final Disposal Act. Also, anevaluation of the repository design and long-term safety will be documented in a report on repository
design based on the preliminary investigations and preliminary safety assessments.
(3) Detailed Investigation stage
It is expected that the detailed investigation stage will be divided into two stages in practice: (i)surface-based investigations and (ii) investigations in the underground investigation facility (UIF).
（i） Surface-based investigations
・Goal of this stage：Determining the basic repository layout
・Safety goals：Confirming that significant impacts from natural phenomena
have been avoided
Ensuring long-term safety
Ensuring safety during imprimentation
・Requirements：Compliance with legal requirements
Compliance with repository site selection environmental
factors
Compliance with the basic guidelines for licensing
Compliance with NUMO working standards
・Main documents：Report on basic repository design and safety assessment
based on the detailed investigations
Environmental Impact Assessment Report
38

The goal of this stage is to determine the basic repository layout. The orientation and configurationof the repository layout will depend on the information obtained on the geological environment.
The goals for demonstrating safety in this stage include confirming that significant impacts fromnatural phenomena can be avoided, ensuring long-term safety and ensuring safety during
imprimentation. The requirements for achieving these goals are compliance with the evaluation
factors for qualification, compliance with repository site selection environmental factors, compliancewith the safety review guidelines and compliance with NUMO working standards. In order toachieve the project milestone while maintaining the goals and requirements above, the following
activities will be carried out.
The surface-based investigations will involve confirming the geological information obtained fromthe preliminary investigations in the previous stage, with special focus on obtaining information on
the underground environment in the vicinity of the candidate repository site. The site descriptivemodel will again be updated using new datasets for the geological environment and, based on therevised site descriptive model, the design of the EBS and the repository panel layout will be modified.
Next, the basic layout of the repository will be determined taking into account assessments oflong-term safety and transport and emplacement of the waste packages and EBS materials. These
results will be documented in an interim report on the description of the repository design based on
detailed investigation data and preliminary safety assessments.
Additionally, a preliminary environmental impact assessment starting from construction of theunderground facility will be carried out and appropriate measures for preserving the environment
will be taken. These results will be documented in an environmental impact statement (EIS) report.
（ii） Investigations in the UIF・Goal of this stage
・Safety goals

・Requirements

・Main documents：Selection of the repository site
：Confirm that significant impacts from natural phenomena are
avoidedConfirm long-term safety
Confirm safety during implementation：Compliance with legal requirements
Compliance with the environmental requirements for theselection of a repository site
Compliance with the guidelines for licensing
Compliance with NUMO working standards：Statutory report based on the detailed investigations
Report on basic repository design and safety assessment
based on the detailed investigations (interim report)
39

The goal of this stage is to select a site for construction of the repository. In this stage, the goals for
ensuring safety are: confirming that significant impacts from natural phenomena are avoided,
confirming long-term safety and confirming safety during implementation. The requirements forreaching these goals are compliance with evaluation factors for qualification, compliance with theenvironmental requirements for the selection of a repository site, compliance with the guidelines forlicensing and compliance with NUMO working standards.
In this stage, the suitability of the host rock will be evaluated through tunnel excavation andinvestigation of the target rock formation at repository depth, including performing in-situ
experiments. Additionally, demonstration experiments will be carried out in the UIF to develop thenecessary technologies for repository construction and operation.
(4) Safety review stage
・Goal of this stage
・Safety goals
・Requirements
・Main documents：Granting of a project license：Assuring long-term safety
Assuring safety during implementation：Compliance with the safety review guidelines：License application documents
Environmental impact assessment report

In this stage, a project license application will be submitted to the government and an
environmental impact assessment report will be produced, describing environmental preservation
measures and findings from preliminary assessements of impacts on the surrounding environment
due to construction and operation of the repository. In parallel, supplementary investigations andevaluations will be carried out as needed for preparation of the application documents for
authorization of the design and construction methods.
4.3.2 Construction stage through project termination stage(1) Construction stage
・Goal of this stage
・Safety goals

・Requirements
・Main documents：Repository construction：Iterative confirmation of long-term safety based on updated
information
Ensuring construction safety：Compliance with technical standards
Compliance with NUMO working standards：Application document for approval of design and40

construction method
Application document for facility inspection
Application document for pre-operational inspection
Safety review report
After obtaining a license from the government, preparatory work will be initiated for repository
construction. A construction license application will be submitted and, after authorization,
construction of the surface facility, including the waste package reception and storage facilities, will
start in parallel with construction of the underground facilities. Construction of the surface andunderground facilities will proceed in accordance with the license application and the repository
design presented in the application documents for authorization of the design and construction
methods and following appropriate quality control procedures. After construction, the government
will carry out a pre-operational inspection to confirm that the facility has been constructed as
designed.
During construction, the safety of the repository will be verified by carrying out further safetyassessments using new geological information and a range of monitoring data. The results will thenbe published in a safety review report.
If necessary, the locations of the disposal tunnels and emplacement positions of the waste packages
will be modified within the framework of the Final Disposal Act to improve safety based on theactual geological findings obtained during repository construction.
(2) Operational stage (during operation)
・Goal of this stage：Operation of the repository
・Safety goals：Confirming long-term safety based on updated information
Safety assurance during operation
・Requirements：Compliance with technical standards
Compliance with NUMO working standards
・Main documents：General license application
Waste package handling license application
Safety review report
This stage will involve activities such as encapsulation of the vitrified waste into the overpack in
the waste reception facility, followed by transport and emplacement of the waste packages in theunderground facility. As well as confirming compliance with the different standards and guidelines,
the government will carry out inspections of the waste reception facility to ensure that all safety andradiological protection regulations are being strictly adhered to. Repository safety will be
re-confirmed using additional data and scientific knowledge obtained through monitoring and theresults will be documented as safety review reports that will be published on a regular basis.
41

The results of long-term EBS experiments carried out after the DI stage and tests demonstrating thetechnical feasibility of repository closure will also be published.
As the next stage approaches, overall repository safety will be assessed based on the results of thedemonstration experiments and the iterative safety confirmations carried out in each stage and theclosure plan for the repository will be produced.
(3) Operational stage (end of operation/ closure plan)・Goal of this stage：Authorization of closure plan・Safety goals：Demonstrate long-term safety through integration of all
information
・Requirements：Compliance with standards for the authorization of closure
plan・Main documents：Closure application documents
Safety review report
In this stage, repository operation will be completed and the safety case will be revised by carryingout safety assessments based on all the information obtained from the site selection stage to the endof repository operation. Based on this, safety will be confirmed and a safety report will be publishedin order to obtain acceptance for repository closure.
Under the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Nuclear
Reactors (hereafter the Nuclear Reactor Regulation Act) and related regulations, in order to close therepository NUMO will have to prepare a closure plan and obtain authorization from the Ministry of
Economy, Trade and Industry (METI) by submitting a formal closure application. Before the closure
plan is authorized, NUMO will maintain the option to retrieve waste packages.
(4) Closure stage
・Goal of this stage
・Safety goals
・Requirements
・Main documents：Implementation of closure：Confirming safety in the closure stage：Compliance with authorized closure plan
Compliance with NUMO working standards：Closure confirmation application

In this stage, in order to fulfil the quality standards according to the regulations based on the
Nuclear Reactor Reguation Act, the repository will be closed by backfilling the connecting andaccess tunnels, etc. When repository closure has been completed, a closure confirmation application
including details relating to topography, geology and groundwater conditions prior to and after
closure will be submitted to METI. Once the repository is closed, authorization also has to be granted
42

by METI, stating that the condition of the repository complies with the standards prescribed in the
Final Disposal Act. NUMO must also submit all repository records to METI for permanentarchiving.
(5) Post-closure to project termination stage
・Goal of this stage：Project termination
・Safety goals：Confirmation of long-term safety based on updated
information
Confirmation of safety assurance after closure
・Requirements：Compliance with decommissioning authorization standards
Compliance with standards for project termination
・Main documents：Decommissioning plan authorization application
Safety review report
Project termination confirmation application
In this stage, as the project moves towards termination, an overall assessment of long-term safety
will be carried out and the safety case revised. Based on this, a safety review report will be publishedand a decommissioning plan authorization application will be submitted. Based on the authorized
decommissioning plan, decommissioning of the surface facility will be implemented in line with therequired quality controls. When decommissioning is complete, a project termination confirmation
application will be submitted to the government. Once project termination is officially authorized by
the government, the disposal project is no longer covered by the terms of the nuclear legislation.
After repository closure, NUMO will be responsible for managing the area covering the repository
footprint until NUMO is disbanded (within the framework of the Final Disposal Act, a new law willbe established for this).
Also, depending on the Final Disposal Act, if NUMO deems it necessary to protect the area above
the repository footprint and surrounding areas, on receiving an application from NUMO thegovernment can designate these areas as protected areas. Within the protected areas, any type of
excavation would be forbidden without the authorization of METI. At present, it is planned that aseparate law will be enacted for handling the repository after NUMO has been disbanded, when it isexpected that the responsibility for managing and assuring repository safety will lie with the national
government.

43

5 . Investigation and evaluation technologies for thegeological environment
This chapter describes how the technologies required for selection and confirmation of suitable sites one of the three policies that support long-term post-closure safety - have been developed steadily,
focusing on literature survey stage and preliminary investigation stage. In addition, NUMO’sapproach to the investigation/evaluation of the geological environment is outlined and the progress in
the required technologies over the the past ten years is then described.

5.1 Approach to investigation/evaluation of the geological environment of JapanDue to the fact that the islands of Japan are located in a tectonically active zone, potential impacts
due to disruptive natural phenomena such as volcanic/igneous activity, seismic/fault activity anduplift/erosion need to be evaluated (Table 5-1). In this context, sites where significant impacts offuture natural phenomena could be avoided will be selected in the first step. The long-term evolutionof the geological environment at the potential repository sites will then be forecasted, with the site forrepository construction being selected from the perspectives of designing and constructing arepository and ensuring its long-term post-closure safety.
5.1.1 Forecast of natural phenomena in the future
There is a consensus in Japan that forecast of natural phenomena up to approximately one hundred
thousand years into the future is justifiable based on geological records of stability over the past
several hundreds of thousands of years (e.g. AEC 1997; JNC 2000b; JSCE 2001; NUMO 2004b).
Based on this, NUMO has formulated a basic concept for predicting natural phenomena in the future
as follows.
The forecast of future natural phenomena will be conducted by extrapolation, taking into account thevolume and accuracy of information and geotectonic history that differ by area and by phenomenon,
with clear statement of the assumptions made. The periods for forecasting natural phenomena fromthe view poin of site investigation/evaluation are defined as follows depending on the uncertainties
associated with the forecast:
Period A: period when forecast by extrapolation is justified, with reliable geomorphological/
geological data for a sufficiently longer period in the past than the timescale of forecast;
Period B: period when forecast is justified using certain assumptions but with larger uncertainties;
44Period C: period for which forecast by extrapolation or any other method is difficult to justify (Table
5-2).
In the safety assessment, scenarios will be developed with a reasonable understanding of degree of
uncertainties for these periods.

45

Table 5-1Natural phenomena to be taken into account in Japan, their potential impacts on thegeological disposal system and their treatment in the site selection process
Naturalphenomena

Volcanic/igne
ous activity

Potential impacts on thegeological disposal systemand surface facility▪ Direct destruction of therepository by intrusion/
eruption of magma▪ Increaseinrock
temperature due to heat
convection or alteration insurrounding rocks.
▪ Convection of hot waterandassociatedenhancement of nuclide
migration.
▪ Change in groundwaterflow and groundwaterchemistrydue
tointroductionofhotwater/volcanic gas into thegroundwater.
▪ Change in topography andassociatedgroundwaterflow conditions due tolarge-scale eruption ofmagma or pyroclastic flow.
▪ Destruction or loss of safetyfunctions of the surface
facility due to ash fall,volcanic
mudfloworpyroclastic flow.
▪ Destruction of subsurface
facilities due to seismic
ground motion▪ Change in groundwaterlevel and groundwaterpressure due to change incrustal strain before andafter an earthquake

Earthquake/fault
activity▪ Direct
destructionofrepository and/ or waste
packages due to movement/
fracturing of rocks▪ Mechanical perturbations
due to fracturing and/orrock displacement▪ Changeinhydraulicproperties in surroundingrocks due to generation ofsmall fault and joints.
▪ Destruction or loss of safetyfunctions of subsurface
facilities due to seismic
ground motion

Potential consequences

Treatment in the site selection process▪ Release of radionuclides to theground surface▪ Impacts such as a significant
decrease in geological disposal
system performance.

▪ Groundwater flow conditions
could vary depending on thescale of the topographic change
due to volcanic activity.

▪ Could endanger safety functionsof the surface facility during
operation.

▪ Only small ground motions
have been observed at relevant
depths. Significant groundmotion is thus unlikely.
▪ Recovery in several weeks toseveral months has beenmeasured. Permanent effects on
groundwater flow are thus
unlikely.
▪ A newly formed fracture zone
may become a preferential
pathway for migration ofradionuclides from subsurface
facilities to the ground surface.

▪ Avoid areas with evidence of Quaternary
volcanism based on the literature or field
investigations and those where such activity
can be anticipated within relevant time
periods based on trends of past volcanic
activity.

▪ Assuming the scale and location of thechange in topography based on literature
information and site measurements to beconsidered as one of the factors of long-term
evolution.
▪ Evaluate volcanic events, their scale, arrival
time at the site and impacts on the surface
facility based on literature information andsite measurements and develop a method foravoidance or countermeasures depending on
their level.
(Guidelines or standards as defined for thedesign of reactor facilities have not yet beendeveloped.)▪ Evaluate and confirm that seismic design
can withstand credible ground motions,using literature information and sitemeasurements▪ Evaluate
suchoccurrences
andconsequences
basedonliterature
information and site measurements.
▪ Avoid areas where active faulting is evident
based on literature information and field
investigations.

▪ The level of impacts would not
be so large as to have significant
impacts on the disposal facility,
but will only open the fractures,causing changes in the rockconditions.

▪ Evaluate the extent where strain, small faults
or joints are formed around the fault andcharacterize them based on literature
information and site measurements as partof characterization of the geologicalenvironment.

▪ Could endanger safety functionsof the surface facility during
operation.

▪ Evaluate and confirm that seismic design
can withstand credible ground motions,using literature information and sitemeasurements.

▪ Significant impacts may becaused such as shifting of theunderground facility to anoxidizing environment andUplift/erosion
increase in groundwater flowrate and flux if extent of
uplift/erosion is significant
compared to the disposal depth.
(Adapted from e.g. JSCE, 2001, 2006; NUMO, 2004b etc)
▪ Approach of repository to
the ground surface andassociated changes ingroundwater flow andchemistry46▪ Areas with significant uplift are assumed tohave associated high erosion and should be
avoided.

Table 5-2 Definition of periods for forecasting natural phenomena from the viewpoint of site investigation/evaluation
Periods for forecastinggeological evolution

futurePeriod A

Period B

Period C

Forecast by extrapolation is justified with sufficient Forecast by extrapolation is justified, but associated with Forecast by extrapolation is not justifiable.
information from the past.
larger uncertainties.

▪ Forecast will be possible with reliable data (e.g. trends ▪ Forecast will be based on data (e.g. trends of evolution, ▪ Uncertainties in the forecast will be large because changesof evolution, mechanisms and driving forces) for a mechanisms and driving force) covering a shorter time in the trend of tectonic evolution cannot be ruled out or no
sufficiently longer period in the past than the timescale period in the past than the timescale of the forecast.
trend in the past can be identified.
Approach to the forecast of future of the forecast.
▪ Several theories explaining trends in tectonic evolution ▪ Phenomena that could occur after the evolution need to be▪ Although there may be several theories explaining need to be postulated due to insufficient data and assumed.
geological evolution
trends in tectonic evolution, their differences are knowledge or their variability. This will increase
considered to be small.
uncertainties.
Relative degree
Type
Uncertainties in
the forecast
Noteparameter
setting

Small
Uncertainties associated with data

MediumUncertainties associated with conceptualization and data Uncertainties associated with conceptualization▪ Take into consideration intrinsic variability of ▪ Take into consideration both uncertainties by ▪ Interpretation of the trend of tectonic evolution involves
for phenomena and observation errors during the postulating several theories explaining trends in tectonic large uncertainties.
investigation.
evolution and intrinsic variability of phenomena and ▪ Phenomena that could occur after the evolution should beobservation errors during the investigation.
assumed based on the information in other areas undersimilar conditions, and appropriate parameters should thenbe set.

47

Volcanic/e.g. Distribution of volcanoes and evolution and fluctuation of location of the volcanic front
igneous activity
Exampleof Earthquake/
uncertainties to be fault activity
taken into accountUplift/erosionLargee.g. Spatial distribution, activity, range of deformed zone, branching/extension of faults
e.g. Error in the estimation of uplift/erosion rate

e.g. Generation of new conduits
e.g. Reactivation of geological faults, generation of faults

e.g. In addition to error estimation of uplift/erosion rate, e.g. Trends in uplift/erosion and rapid change in the modechanges in modes of motionof motion.

5.1.2 Consideration of a wide range of geological environment in Japan
Geological environment in Japan can generally be represented by combinations of crystalline rocks(hard fractured media) or sedimentary rocks (soft porous media) and fresh or saline groundwater interms of transport of groundwater and solutes. Investigation/evaluation technologies for coastal
regions where fresh and saline water come into contact are partly different from those for inland
settings. These investigation/evaluation technologies have been developed mainly by fundamental
R&D organizations. NUMO will utilize the evaluation results described in later in section 5.4.2 toinvestigate and evaluate the geological environment suitable for the repository site.

5.2 Approach to literature surveys and preliminary investigations
5.2.1 Stepwise investigation and evaluation
The geological environment extending over several square kilometers for a potential repository has awide range of characteristics. The long-term safety assessment covering a period of several tens of
thousands of years or longer after repository closure will also inevitably contain spatial and temporal
uncertainties. In order to efficiently evaluate the geological environment with its inherent
uncertainties, including its long-term stability, it will therefore be important to demonstrate stepwise
the ability of the geological disposal system to ensure safety (Figure 5-1). This is done using anapproach in which investigation/evaluation results are checked against safety goals in each step;elements with higher uncertainty and key significance for each milestone are identified andprioritized in terms of data acquisition in subsequent stages. To this end, information fromcharacterization of specific sites will be integrated into site descriptive models (SDM) and its
reliability will be confirmed and uncertainty factors will be identified. Furthermore, based on the
results from evaluation and investigation of the geological environment, uncertainty factors with highpriority will be identified and reflected in the investigation plan in the next step. Stepwise evaluationand investigation is effective for incorporating new scientific/technical findings and know-how into
the investigations in each step and for optimizing the evaluation/investigation plans.

48

Overall investigation/evaluation flow diagram
Evaluation (interpretation/integration – selection of investigation areas)
Plan /investigation

Impacts of natural phenomena

Geological environment information

Repository
design/safetyassessment

Literature survey plan
Geology/geological structure
Groundwater flow, geochemistry,rock properties (physical,
mechanical, thermal), others(mass transport, features
relevant to design and operation)

Distribution and activities of Quaternary
volcanoes/active faults, trends in
uplift/subsidence/erosion

Literature surveys

Geological structure evolution
processes

Literature surveys

Site descriptive modelLong-term evolution ofgeological environment
conditions

Volcanic/igneous activity,
earthquake/fault activity anduplift/erosion in the future

Exclude fromPIA

・Develop genericrepository concepts
・Generic safetyassessment

Evaluation basedon siting factors

Not acceptable

Acceptable

Selection of PIAs

Preliminary investigations(surface based investigation phase)PI planGeological structure development
process
Site descriptive model

Develop borehole
investigation plan for
PIAs

Preliminary investigations(borehole investigation phase)

Geology/geological structure
Groundwater flow, geochemistry, rockproperties (physical, mechanical,
thermal), others (mass transport,
features relevant to design andoperation)

Distribution and activities of Quaternary
volcanoes/active faults, trends in
uplift/subsidence/erosion

PI (surface-based
investigations)

PI (Borehole
investigations)

Volcanic/igneous activity,
earthquake/fault activity anduplift/erosion in the futureLong-term evolution of geologicalenvironment conditions

Presence of Quaternary volcanoes/active
faults, distribution, age and sedimentation
environment of sediments near groundsurfaceGeology/geological structure
Groundwater flow, geochemistry,rock properties (physical,
mechanical, thermal), others (masstransport, features relevant to designand operation)

・Confirmation/update ofgeneric repository
concepts
・Confirmation/update ofgeneric safetyassessment

Geological structuredevelopment process
Site descriptive modelLong-term evolution of geologicalenvironment conditions

Volcanic/igneous activity,
earthquake/fault activity anduplift/erosion in the future

Exclude from
DIA

Not acceptable

・Develop reference
repository concepts
・Preliminary safetyassessment

Evaluation basedon siting factors

Acceptable

Selection of DIAs

DI plan: Plan:Investigation:Analysis/evaluation: Decision-making (Note: Basis for the final decisions will include other investigations and evaluations)Figure 5-1 Flow diagram for literature surveys and preliminary investigations: An example ofcoordination and sharing of investigations and information
The steps from the acquisition of common information to selection of each investigation site in the highly variable geologicalenvironment in Japan are presented. In order to perform site investigations and evaluations efficiently,
geological/geostructural investigations will be optimally planned and information will be shared.

495.2.2 Uncertainties in investigaton and evaluation
Uncertainties in the data and in conceptualization are associated with investigation and evaluation of
the geological environment. Uncertainties in the data are contained in data obtained through various
measurements as well as datasets into which data from multiple sources are integrated (e.g. dataset
for the SDM) and result from different factors such as measurement errors and measurement
accuracy (spatial resolution, frequency). Uncertainties in conceptualization result from
temporal/spatial data interpretation and cannot be avoided in predicting future natural events andunderstanding ongoing processes at the site.

Data obtained in the literature survey stage relate to the near-surface environment and information
about the deep underground environment is limited. This leads to a large element of uncertainty in
the SDM at this stage. For example, only the surface distribution and dip are known for faults; theirshape and distribution deeper underground will have to be estimated and extrapolated frommeasurements made at the surface, which will contain inherent uncertainties. In addition, in the
preliminary investigation stage the SDM will have to be constructed based on an insufficient amountof information in order to model the geostructure, geological environment and other phenomena. In
such a case, the level of understanding of the geological environment based on the available
information, information on the type and degree of uncertainty in the interpretation and forecast will
have to be reported to the facility design and safety assessment groups. Furthermore, throughengineering strategies and safety assessment based on the dataset, important structural/environmental
features that might affect the feasibility of the disposal facility and post-closure safety assurance willbe identified. The results will be reflected in the investigation plan for the next step and theuncertainties will be reduced.
5.2.3 Applicability of investigation and evaluation technologies
In order to assure safety with sufficient reliability, NUMO will implement the project usingstate-of-the-art technologies based on the latest findings. When applying such technologies,
optimization of the project, including economic aspects, will be considered. For the investigation andevaluation of the geological environment, technologies that have been verified in various fields suchas natural science, resource exploration, civil engineering and nuclear facility construction as well as
technologies developed by NUMO and fundamental R&D organizations will be used.
Regarding the investigation and evaluation technologies for natural phenomena, NUMO iscompiling existing research examples and evaluating the results with respect to applicability to thegeological disposal project. For example, NUMO has been hosting an International Tectonics
Meeting (ITM; Chapman et al., 2009a) in recent years. As part of this project, natural processes suchas volcanic/igneous activity, seismicity and faulting as well as uplift/erosion have been evaluated and50

it was concluded that the existing investigation/evaluation technologies are basically applicable to thegeological disposal project in Japan.
In addition, for investigation and evaluation of the characteristics of the geological environment,
through collaborative research with CRIEPI (Kondo et al., 2011) NUMO is currently examining theapplicability of different technologies such as drilling as well as systematic investigation methods(which integrate multiple methods).
The process of confirmation of the investigation and evaluation technologies described above is oneof the key elements of building a safety case and will be continued further.

5.3

Literature surveys and preliminary investigations

5.3.1 Literature surveys
According to the Final Disposal Act, literature surveys (LS) are conducted to exclude clearly
unsuitable areas where significant natural phenomena cannot be avoided and to select areas forpreliminary investigations by further avoiding locations where constructing the repository would be
difficult and where human intrusion, such as mining activities, is highly likely. Information is to becollected on topography, geology, geological structure, groundwater flow and chemistry, rockcharacteristics (mechanical and thermal) and solute transport. Using the information, a preliminary
evaluation of the underground facility and the EBS, as well as a preliminary safety assessment(sensitivity analysis), will be performed. Based on the evaluation results, information to be obtainedwith high priority to reduce uncertainties for future safety assessments will be identified and reflectedin the planning of the next investigation step. Literature surveys will be performed as follows (Figure
5-2).
(1)

Planning of literature surveys

The area to be covered by the literature surveys will be determined and an LS plan prepared,
including the list of literature to be collected. Information to be compiled will be used to evaluate theappropriateness of the volunteer region, i.e. not only the volunteer municipality but also thesurrounding areas. The content will be categorized into information that is legally required andadditional information necessary to evaluate the siting factors for selecting the PIAs. The former
includes earthquake and fault activity, volcanic/igneous activity, uplift/erosion, unconsolidated
Quaternary sediments and occurrence of mineral resources. The latter includes rock formation
properties, groundwater properties, difficulty of investigation/evaluation, natural disasters,
acquisition of land and transportation routing.

51

(2)

Collection and management of literature information

Collection of literature information will be performed by three methods: database search, visiting
relevant organizations/authorities and collecting information from the public. All collected
information will be managed in the data management system developed by NUMO in order toensure transparency and traceability of the information on the preliminary investigation area
selection process.
(3)

Analysis and evaluation of the literature information (geosynthesis)

In the geosynthesis, information on topography, geology, structure, volcanic/igneous activity,
earthquake/fault activity and uplift/erosion, mineral resources, properties and characteristics of rockand groundwater, meteorology/surface hydrology and natural disasters will be compiled. If necessary,data from remote sensing and geodetic and geophysical surveys will also be analyzed. The siting
factors for selecting the PIAs will then be evaluated. In addition, a SDM for geology/structure,groundwater flow and chemistry and rock properties will be constructed and the characteristics of thegeological environment will be evaluated.

52

ITAC･DTAC

Nuclear Waste Management Organization of Japan (NUMO)

Pre-confirmation of geologic conditio ns
Release on NUMO web site

Municipalit y

PublicGovernment

Application

NUMO-GIS

Notification of decision

Notificatio n

Literature survey plan

Explanation

Licenseapplication

Application to amend program

Approval
Inclu sion of LS plan
Integrated geolo gicalin vestig atio n
Analysis/
evalu atio n

Evaluatio n ofliterature list to
be collected

Literature info
analysis
Collected data
analysis

Literature
information
Geoenvironment data
management system

Airborne photos Literature info
selection/
Satellite images
summary
GPS data

G eoenv. Model Seismic dataG eology
Survey data
G W flow
G W chemistry Meteorologic data
Rock mechanics Geophysical data
T hermal conditions
Boring data・ ・・Hot springs

Interimevaluatio n ofliterature list

Working group for evaluation of LS outcomes

Finalevaluatio n ofliterature list

Collected
data

Literature collection

GW
Modeling
GW flow・・ ・
GW chemistry
Rock mechanics
・・・
Evaluation
Geoenv.
characteristics
Long-term stability
Environmental impact
Land usage
Infrastructure・ ・・

Repository preliminary
evaluation
Impact on environment(preliminary)

Literature
management(registeration/search/display functions)

DatabasesearchAdvertising to
Visit relevant public fororganizations literature/in formation

Listing literature Listing relevant 1st call fororganizations literature to
publicLiterature/
document
collection

Literature info
management(registration, search,display functions)

Literature/
document
solicitation

Receiving
literature/
documents

Literature/
document
collection
2nd call for
literature to
publicDataset management(registration, search,display functions)

Receiving
literature/
documents

Preliminary
explanatio n

Literature to
be collected
Disclo sure
Provideinformation
Provideinformation

Preliminary
explanation

Interimliterature list
Disclo sure
Provid e
information
Provideinformatio nManagement of resultsfrom modeling/evaluatn management(registration, search,display functions)Final
literature
list

Preliminary
explanatio n

Disclosure

Summary of lit erature analysis, evaluation(geological environment, long term stability,
repository concept, environmental impact)

Selection of PIAs
Appropriateness based on siting factors

Evaluation based on additional factors(relative evaluation)

Appropriatenessof the sele cted
PIAs

LS results and PIA selection(tentative) reporting/abstract

Official
sitin g report

Reply to inquiries

Submission
Sending ofreportDisclosure,explanation
Inquiries
Sending ofreportSelection of PIAs taking inquiries
into accountRelease on NUMO web site

Application

Application for amendment in
implementation plan

Amendment of final
disposal plan

Approval
Approval on
implementation planamendment

Completio n of PIA selection

Figure 5-2 Literature survey process flow (example based on volunteer solicitation)

53

5.3.2 Preliminary investigations
Preliminary investigations are conducted to select DIAs with the prospect of ensuring safety during
the project duration as well as long-term post-closure safety. This is done based on investigations
from the ground surface, including geophysical surveys and borehole investigations. Applying theevaluation factors for qualification, the selection will be based on confirmation that significant
impacts from natural phenomena can be avoided in the area, that there are no difficulties in terms of
excavating tunnels and that there would be no adverse impacts of rock temperature or groundwaterflow on the repository. In order to achieve this, evaluation of the results based on literature
information will be confirmed by directly acquiring site information. The SDM from the previous
step will then be updated and the long-term evolution of the site geological environment will be
evaluated. Based on this, the preliminary design of the underground facility and the EBS will be
prepared and a preliminary safety assessment performed. In the preliminary design, based on the
SDM and associated datasets, the location and layout of the underground facility and operationalsafety will be examined. In the preliminary safety assessment, groundwater modeling, geochemical
modeling,mechanicalmodeling,
radionuclidetransport
modeling
andthermo-hydro-mechanical-chemical coupled modeling will be performed. Safety assurance during
the operational phase, work efficiency and economic aspects of the project will also be considered
and all the results will be evaluated comprehensively. Finally, sites which are more appropriate will
be selected for detailed investigations. Information with high priority in terms of reducing
uncertainties in the safety assessment will be identified and reflected in the next detailed
investigation planning stage. The preliminary investigations will be performed as follows:(1) Planning preliminary investigations
The preliminary investigation plan is prepared, including the objectives, the investigation area,
methods, target results, schedule and implementation framework. The area to be investigated consistsof the “preliminary investigation area (PIA)” and “surrounding areas for supplementary
investigations”. The preliminary investigation area will be selected from the area including thevolunteered site that meets the siting factors for selecting the PIAs. If necessary, areas for
supplementary investigations will be selected in order to further investigate the effects of naturalprocesses, such as volcanic/igneous activity, earthquake/fault activity and uplift/erosion, on thegeological environment in the PIA.
(2) Implementation of preliminary investigations
In order to acquire the information necessary for evaluating the PIA and surrounding areas,
preliminary investigations will be basically performed in two different phases: surface exploration
and borehole investigations (Figure 5-3). During the surface investigation phase, surface mappingand geophysical surveys (airborne, ground, off-shore) will be performed and the literature survey
54

evaluation results will be confirmed and improved. Based on these results, the outline of thegeological environment will be interpreted and a plan for the subsequent borehole investigation
phase will be developed. In the drilling phase, the focus will be on investigations using deep
boreholes. These will include core logging, borehole imaging, geophysical logging, hydraulic tests,
laboratory tests using core samples and groundwater chemical analyses. Through these investigations,information on the deep underground that was not obtained through the surface investigations, suchas geology/geostructure, groundwater (including non-volcanic hydrothermal water) flow andchemical characteristics, rock mass properties (mechanical, thermal) and solute transport, will beobtained.

LS areas

Active faults
identified by the LS

MarineQuaternary
volcanoes identified
by the LS
15km radiusfrom theQuaternary
volcanoes **NUMO(2009b)

Literature Surverys

Preliminary investigations(Surface investigation phase)

Preliminary investigations(Borehole investigation phase)

Figure 5-3 Staged approach during preliminary investigations(surface and borehole investigation phases)(3) Evaluation of preliminary investigations
In the preliminary investigations, it will be evaluated whether or not a PIA is suitable as a detailed
investigation area (DIA) based on the siting factors for selecting DIAs to be established in the near
future. Regarding natural events, potential impacts of Quaternary volcanic/igneous activity andactive faults that were not sufficiently investigated in the literature surveys and volcanic/fault activity
identified in the literature surveys will be evaluated. Uplift and erosion identified in the literature
surveys will be confirmed and the effects on the safety of the geological disposal system will be
evaluated. Regarding the geological environment characteristics, information necessary forrepository design and safety assessment, such as fracture distribution, groundwater chemistry,
permeability, physical/mechanical properties, thermal properties and groundwater pressure
distribution and chemistry, will be obtained. In each investigation phase, the concept of thegeological environment developed based on the literature survey will be re-evaluated and reflected in
the updated SDM. The long-term evolution of the geological environment will also be evaluatedbased on the investigation of the effects of natural events. Based on the above, a preliminary designfor the underground facility and the EBS as well as a preliminary safety assessment will be
conducted.

55

5.4 Progress in developing the technologies supporting investigation/evaluation
activities
Regarding the technologies for evaluating the effects of natural phenomena and the geologicalenvironment in the literature surveys and preliminary investigations, the status and open issues at thetime of the completion of the H12 report, as well as progress since then, are being summarized. The
technologies developed since the H12 report are compiled in Table A.5-1 through Table A.5-8 in
Appendix. The evaluation and application of the technologies that NUMO considers to be ofparticular importance are described below.

5.4.1 Investigation and evaluation technologies related to the effects of natural
phenomena(1) Investigation and evaluation technologies for volcanic/igneous activity
Prior to the completion of the H12 report, and following the progress in dating of volcanic activity, anationwide distribution of Quaternary volcanoes in Japan (Committee for the Catalogue of
Quaternary Volcanoes in Japan 1999) was compiled. It was shown that there is a heterogeneous
distribution of Quaternary volcanoes in active regions and that changes in volcanic activity over thelast 100,000 years can be attributed to expansion/contraction of the active areas. In addition, methods
for evaluating the temperature gradient of volcanoes and their impact on groundwater are also welldeveloped in the geothermal field. For example, a nationwide geothermal gradient distribution has
already been prepared and the thermal impact and duration of such effects around volcanoes andmagma chambers have already been studied.
In the H12 report, it was recommended to further investigate the likelihood of new volcano
formation on the backarc side and in the monogenetic volcanic fields of south-west Japan and toevaluate high temperature anomalies in non-volcanic regions.
With regard to progress since the H12 report, with the advances in deep geological analysis
techniques such as seismic tomography, the reliability of evaluation methods has improved to theextent that it is possible to evaluate the generation of new volcanoes and movement of magma and toevaluate deep heat sources (e.g. Kondo, 2009; Umeda, 2009, Table A.5-3 in Appendix). In addition, amethod for evaluating deep geothermal waters based on geochemical methods has been developed,
leading to identification of thermal waters originating from sources other than magma (e.g. Umeda etal., 2009). As an alternative approach to these deterministic methods, probalilistic methods for
estimating new volcano formation were developed based on the probabilistic methods applied inother countries. Their applicability in evaluating regional areas and monogenetic volcanic fields in
56

Japanhave been confirmed (Chapman et al., 2009b; Martin et al., 2004). Based on the above
developments, data on the distribution of Quaternary volcanoes and records of past volcanic activity
could be obtained and future activity be forecasted using current technologies.
(2) Investigation and evaluation technologies for earthquake/fault activity
Prior to the completion of the H12 report, methods for investigating the distribution of major active
faults and characteristics of groundwater around active faults had been developed by combining
interpretation of aerial photographs, geophysical surveys, surface mapping and trench investigations.
This led to the production of a 1:2,000,000 map of active faults in Japan (Nakata and Imaizumi,2002). It was also demonstrated that major earthquake/fault activity has shown similar temporal
recurrences over the last 100,000 years, although the spatial distribution is not uniform in that active
fault type and activity vary depending on region.
In the H12 report, evaluation of the effects of fault activity and detection methods for faults that do
not have clear surface expression were listed as future open issues for further investigation.
Since the H12 report, investigation of earthquakes that have caused damage in inland areas where
active faults have not been identified at the surface raised issues such as the relationship between
earthquake source faults and active faults, identification of concealed active faults and immaturefaults, and the adequacy of existing active fault maps. Methods that have been employed to addressthese issues, such as evaluation of active faults not associated with clear displacement at the surface,have used a combination of GPS, geomorphology, structural geology, geophysics, and geochemistry(Aoyagi and Abe, 2009; Umeda et al., 2010, Table A.5-4 in Appendix). For the evaluation of zones
influenced by faults, an evaluation method that compares the results of numerical analyses based onmodeling of fault-related folding (folding with subsurface fault movement) and sandbox experimentswith field observations has been developed (e.g. Ueda, 2011). As an alternative to the above
deterministic approach, a method for probabilistic evaluation of future fault activity was developed
based on strain rates obtained from several measurement methods such as GPS, earthquake andsurface deformation and its applicability to regional areas in Japan has been confirmed (Chapman
et al., 2009b). Based on the above developments, data on the distribution of Quaternary volcanoes
and records of past volcanic activity could be obtained and future activity predicted using current
technologies.
(3) Investigation/evaluation technologies for uplift and erosion
Prior to the completion of the H12 report, methods for evaluating past uplift and erosion had beendeveloped based on river terrace deposits, etc. Nationwide uplift/subsidence rates were compiled(Koike and Machida, 2001) and erosion rates in each region were evaluated both in terms of planar
and linear erosion. Regarding planar erosion, a nationwide map was developed (Fujiwara et al.,57

1999) based on the fact that planar erosion is closely related to surface topography. The rate andextent of linear erosion is investigated from major rivers.
The H12 report recommended that improvements should be made in the methods used to evaluate
the reliability of inland uplift and erosion rates and that sea-level change should be taken into accountwhen evaluating the future evolution of surface topography.

Since the H12 report, methods for determining site-specific uplift/subsidence and erosion
depths/erosion rates, and for estimating past climate/sea-level changes have been improved (Table
A.5-5 in Appendix). With the improved technologies for correlating and dating fluvial terrace
deposits, the reliability of estimates of uplift in inland areas over the past hundred thousand years has
been improved (e.g. Hataya et al., 2009). Forecast methods and simulation techniques for futuregeomorphological changes have also been developed based on erosion history and climate/sea-levelchanges in the past, allowing information to be provided for long-term groundwater flow analysis(e.g. Sanga and Yasue 2008). Based on the above developments, uplift/subsidence, erosion
depth/erosion rate and climate/sea-level change can be estimated and future activity predicted using
current technologies.
5.4.2 Investigation/evaluation technologies relevant to the characteristics of thegeological environment
Prior to the completion of the H12 report, development of tools and methodologies for investigating
groundwater flow and solute transport and validation of fundamental tools such as for geophysicalsurveys had been carried out.
It is the goal of R&D since the H12 report to accumulate sufficient knowledge on the deep
geological environment under various conditions and to systematize investigation/evaluation
methods for the geological environment.
Based on the above, existing investigaton/evaluation methods for specific targets, e.g.
geology/structure, groundwater flow and chemistry, solute transport, issues related to construction
and safety and monitoring, have been improved/updated (Table A.5-5 in Appendix).
From the viewpoint of geological disposal, the geological environment in Japan can be divided
roughly into crystalline rocks (hard fractured media) and sedimentary rocks (soft porous media),
combined with fresh and saline groundwater environments. In addition, near the coastline where
freshwater and saline water meet, different technologies and concepts are needed forinvestigation/evaluation.

58

In JAEA’s program, the geological environments in crystalline rock-freshwater and sedimentaryrock-saline water have been studied in two URLs (Saegusa et al., 2007; Ota et al., 2007). These
programs are examples of systematic investigation/evaluation, in which a series of tasks ranging
from data acquisition to model development during the first investigation phase from the surface
were conducted iteratively to improve understanding of the geological environment and to reduce
uncertainties. With regard to coastal areas, technologies for characterization of active faults based onliterature data, geophysical surveys from the surface and the sea floor, identification of thesaline/freshwater interface geometry, surveying groundwater discharge at the sea floor andinvestigations using controlled drilling technology have been developed. This will allow continuous
investigation/evaluation straddling the inland and off-shore areas (e.g. AIST, 2010). Other than R&D
in the geological disposal field, similar underground exploration is being conducted in fields such as
resource exploration, active fault investigations and some test methods in civil engineering projects.
Findings from these developments will also be incorporated into the geological disposal project.
NUMO has also conducted demonstration studies at CRIEPI’s Yokosuka site as part of a
NUMO-CRIEPI collaborative project with the objective of confirming the investigation/evaluation
technologies developed by fundamental R&D organizations and developing an investigation
management strategy (Kondo et al., 2011). Through stepwise data acquisition via literature surveys,
geophysical surveys and borehole investigations, interpretation of data and updating of the site
descriptive model, systematic investigation/evaluation technologies to be used in the preliminary
investigation phase have been developed. The effectiveness of the methodologies for appropriate andrational decision-making on schedule, quality controls and safety management were confirmed byconducting a series of tasks from planning of investigation programs through evaluation of theresults.

5.5 Conclusions of chapter 5
The H12 report indicated that geological environments that meet the requirements for safe geologicaldisposal are widely distributed in Japan and that whether or not such requirements are met can be
judged using investigation/evaluation technologies available at the time. Since the completion of theH12 report, NUMO has been synthesizing the technologies developed to investigate/evaluate theimpacts of natural phenomena and geological environment characteristics for use in the selection of
PIAs and DIAs. In parallel, NUMO and fundamental R&D organizations have collected data on thegeological environment and have improved and refined various methodologies that may be required
for site characterization. As a result of the efforts described above, NUMO is prepared for carryingout the literature surveys and preliminary investigations as well as evaluations for site selection when
there are applications or acceptance of governmental nomination from a municipality. Furthermore,
new scientific findings and advances in investigation/evaluation technologies will continuously be59incorporated in order to improve the reliability of investigation/evaluation technologies for thegeological disposal project.

60

6 . Technologies for design, construction, operation andclosure of the repository
This chapter describes the technologies required for implementing the policy on appropriate
engineering for design and construction of the repository.
Since the completion of the H12 report, the understanding of the long-term behavior of, andinteraction among the engineered barriers has improved and technologies for transporting andemplacing the engineered barriers have made significant progress. Based on this, NUMO hassystematically formulated technical requirements for the design of the repository and demonstrated
combinations of waste package emplacement methods and operating technologies suitable for arange of geological environments.

6.1 Basic design policy for the geological disposal project
6.1.1 Staged design implementation
Information on the geological environment of potential sites will be accumulated progressively
throughout the three-stage site selection process. NUMO will iterate the design of the surface andsubsurface facilities that make up the repository in line with accumulated understanding anddevelopment of technologies towards more detailed and refined design.
The ultimate goal of geological disposal is to ensure long-term post-closure safety and the design ofthe subsurface facilities, including the engineered barriers, therefore requires consideration of factorsthat can cause changes in barrier performance associated with the long project timescales.
Therefore, R&D on engineered barrier materials such as bentonite-based materials, cement-basedmaterials and metallic materials will be carried out in cooperation with fundamental R&D
organizations and up-to-date knowledge on the engineered barriers will also be accumulated within
and outside Japan. In addition, development of technologies for achieving safe and effective
operating systems will continue and progress will be reflected in the selection of construction,
operation and closure technologies.
Based on the stepwise improvement of the information on the geological environment outlined
above, advancement of technologies and validation of these in the underground investigation facility(UIF) during the DI phase, design specifications appropriate for the site conditions will be
determined and the reliability and practicality of the design will be improved.
616.1.2 Handling uncertainties in the design
Uncertainties associated with information obtained through geological investigations will exist
because of the spatial extent and heterogeneity of the host rocks where the repository is to beconstructed. In structural design, large tolerances are generally allowed in the design specification forcomponents with uncertainties, which will also be applicable in the design of the repository.
Uncertainties associated with the geological environment will be accommodated by selecting asuitable area of potential host rock to locate the underground facility, considering areas that may be
unfavorable for emplacing waste packages. The size of the repository footprint may change
depending on the host rock properties, but the accuracy of the size estimation should increase withtime because more reliable data on the mechanical and thermal properties of the host rock will beavailable.
For ensuring long-term post-closure safety, consideration will have to be given to factors that could
compromise safety from a long-term perspective in the design of the underground facility and theengineered barriers. The performance of the engineered barriers will evolve with time anduncertainties will increase. Factors that could cause changes in the engineered barrier performanceand lead to increased uncertainty will be taken into account in the design to assure basic performance
when the engineered barriers are constructed using current technologies, based on the results of thesafety assessment and long-term behavior analysis.

6.2 Safety functions and technical requirements for the repository
The technical requirements for long-term post-closure safety have been considered based on thedevelopment of international criteria (IAEA, 2006, 2011) and advances in technologies since theH12 report. Specifically, based on the principles for ensuring safety, i.e. isolation and post-closure
confinement, technical requirements are systematically defined for each repository component suchthat these components will achieve their safety functions. With the progress ofinvestigation/evaluation of the geological environment, the technical requirements for each
investigation area will be clarified and reflected in the design.
Figure 6-1 shows the relationship between the basic concept for ensuring radiological safety and thedifferent project stages. During the period from reception of the waste packages to closure of therepository, the focus will be on safety in each prior project stage and the principal safety measures
will therefore consist of confinement during operation and radiation shielding, as well as control ofradiation exposure. During the period after closure, the focus will shift to isolation and containment.
These measures will be applied to both HLW and TRU waste. The relationship between isolationand containment after closure of the repository and the safety functions is shown in Table 6-1.
62

Period requiring safety measures

Operational safety measures(Radiological safety)

Post closure period

Confinement during operation(Waste package, facility)

Radiation shielding(Radiation shield)

Radiation exposure control(Controlled area, radiation control, monitoring)

Long-term post-closure
safetySafety measures

Reception of WP - Closure

Isolation(Avoid disruptive natural phenomena,
restriction of human access)Post-closure containment(Limiting leaching, migration, formationof migration pathways)

Figure 6-1 Relationship between the basic concept for ensuring safety and the different project stages
Table 6-1 Basic concept for ensuring long-term post-closure safety and safety functions

Containment

Isolation

Basic
concept

Safety functions

Description of the safety functions

Protection fromlong-term geologicalevolution

Emplace waste packages deep underground, isolated from thehuman environment to protect them from topographic changes
such as erosion.

Limiting human
intrusion

Make the access to the waste packages difficult without
special technologies in order to reduce the likelihood of
inadvertent human intrusion.

Reducing leaching ofradionuclides

Reduce the nuclide release rate to the groundwater by
restricting the leaching rate of radionuclides from thewaste.

Retardation of nuclide
migration

Reduce radioactive material migration rate byretardation of nuclide migration.

Engineered measures that ensure isolation and containment after closure complement those that
reduce subsequent radiological impacts on the human environment; this is the basis of themulti-barrier system. With regard to the relationship between the safety functions for the repository
and the multi-barrier system components, the natural barrier will be responsible for the functions“protection against long-term geological evolution” and “restriction of human intrusion”, the waste
package and overpack for the safety function “restriction of leaching of radionuclides” and the buffer,
backfill, plug and natural barrier for the safety function “retardation of nuclide migration”.
63Three types of technical requirements will be set: those for securing basic barrier performance, thosefor maintaining long-term barrier integrity and those for ensuring engineering feasibility. The basic
barrier performance relates directly to the safety functions and is essential for ensuring safety. The
long-term integrity of the barriers refers to the situation where basic barrier performance can be
maintained even if the barrier properties have been subjected to change during the long post-closure
period. The technical requirements will be set in such a way that the barrier performance required
for ensuring safety will not fail due to changes in material properties such as alteration due to heatgeneration from the waste packages. Ensuring engineering feasibility means that the production,
manufacture and cost of the engineered barriers will not be unrealistic. The technical requirements
for maintaining the long-term integrity of the engineered barriers and ensuring engineering feasibility
will be subordinate to the requirement of basic barrier performance. The technical requirements forbasic barrier performance specified in accordance with the concept described above are shown in
Table 6-2 through Table 6-4.
Table 6-2 Technical requirements for the overpack (ensuring basic barrier functions)

Description of thetechnical
requirements
Safety functions
should not be
Corrosion
endangered due toresistancecorrosion for a
Preventing
defined period
contact with
Maintain structural
Restriction
groundwater
integrity against
Structuralof leaching
during the
integrity
mechanical loadingof
period when theafter emplacement
radionuclides heat generation
Achieve mechanicalrate isCorrosion
strength andsignificant
resistance of thecorrosion resistanceweld andof the weld
structuralcomparable to those
integrityof the base metal
Safety functions

Technical
requirements

64

Design items
Overpack design(material,configuration andthickness)
Overpack design(material,configuration andthickness)
Overpack design(material, lid
structure, welding
method and welding
conditions)Table 6-3 Technical requirements for the buffer (ensuring basic barrier functions)

Safety functions
Restriction of
migration by
advection
Retardation
Prevention andof nuclide
restriction of colloid
migration
migration
Retardation of
nuclide migration
by sorption

Technical
requirements
Lowpermeability

Description of thetechnical requirements
Restrict groundwaterflow (advection) in thebuffer to restrict the
migration ofradionuclides

Design items
Buffer design(material,configuration,
thickness)

Colloidfiltration

Restrict colloidal
migration ofradionuclides

Buffer design(material,configuration,
thickness)

Sorption
capability

Retard migration ofradioactive materials
leached from the glassby sorption

Buffer design(material)

Table 6-4 Technical requirements for the backfill and plug (ensuring basic barrier functions)

Safety functions

Retardationof nuclide
migration

Preventing theaccess tunnel
and rocks
around thetunnel fromfunctioning as apreferential
migration path

Technical
requirements

Description of
the technicalrequirements

Design items

Restriction offormation of
migration paths
along the tunnel

Restrict formationof preferential
groundwater flow
paths along thetunnelBackfill design(material design),
sealing plug design(material, layout),mechanical plug design(material, layout)

The concept for radiological safety measures is described below. Safety measures based on theradiation protection concept for the repository are: containment of radionuclides during operation,
radiation shielding and radiation exposure control. They are shown in Table 6-5 together with theassociated measures. The concept of safety measures against abnormal events is described below.
Abnormal events are those which could cause deviation from normal operating conditions in thesurface or subsurface facilities. Examples include dropping, falling or collision of waste packages inthe surface or subsurface facilities. An accident is an event which causes radioactive materials to bereleased from the facility under extended abnormal conditions. To be extended to an accident
triggered by abnormal events, such as earthquake, fire, tsunami and loss of power, a combination ofseveral events will be required, such as dropping the waste package, failure of the waste package anddispersal of released radioactive materials.
65

In the case of an abnormal event, measures to prevent the spread of the contamination by, forexample, installing a ventilation system with a decontamination function such as filters will be
required to prevent dispersal of radioactive materials. If the situation should extend to accident
conditions, actions to mitigate the consequences, e.g. decontamination, should be taken.
Table 6-5 Basic safety measures for radiation protection

Concept

Confinement
duringoperation

Radiation
Shielding
Radiation
exposurecontrol

Safety measures

Description

Prevention of releaseof radioactive
materials from thewaste packages

Prevent leakage of radioactive materials from waste
packages during operation

Prevention ofexcessive release ofradioactive materials
from the facilities tothe environment

Prevent excessive release of radioactive materials
from handling facilities during operation (onreception of waste packages)

Shielding of radiation

Reduce air dose rate by shielding radiation from thewaste package

Setting radiation
controlled areas

Limit access to radiation controlled areas

Monitoring/radiation
exposure control

Control radiation exposure to workers and monitor
radiation controlled areas and areas around the site

6.3 Repository design
6.3.1 Design procedures
The repository design, including the specifications of the surface and underground facilities and the
EBS in order to ensure safety during each phase of the geological disposal project, is clarified
depending on the progress of site investigation and evaluation.

The basic approach and procedure for designing the EBS, the underground facility and the surface
facility are outlined in Figure 6-2. The repository will be designed with sufficient safety and to satisfy
corresponding technical requirements.
Firstly, the characteristics of the geological environment such as the thermal environment, the66mechanical and hydrological regimes, the geochemical environment and the extent of the host rock
will be evaluated. Based on the results, the maximum tunnel depth determined largely by mechanicalstability around the tunnels and the waste thermal characteristics, regions with longer radionuclidetransport times and pathways and repository dimensions determined by the volume of waste will beconsidered and the depth and location of the underground facility will be specified.
Based on the characteristics of the host rock at the repository location, the overpack and buffermaterial components of the EBS will be designed and the specifications of the EBS such as thematerial, shape and thickness of the overpack and buffer will be determined.
An access route will then be considered and the tunnel cross-sections and waste emplacement
specifications in the disposal tunnels will be determined. Once tunnel dimensions sufficient foraccommodating the waste and the EBS have been determined, the support measures necessary for
maintaining these dimensions will be calculated based on evaluation results of tunnel mechanicalstability. Heat generation from the waste will then be quantified and waste package spacing
determined such that no significant temperature increase in the EBS will occur.
Based on the tunnel cross-sections and waste emplacement density, repository panel dimensions andconfigurations, main/connecting tunnel layouts and the number of access tunnels and their locations
will be determined and the layout of the entire underground facility will be specified. The tunnel
backfilling and plug specifications and their positions will then be designed.
Regarding the surface facility, a potential site will be selected based on natural and social
environmental conditions and transport infrastructure. The entrance location will then be decided
based on the position of the underground facility. Radiation controlled areas and transport ofconstruction materials and machinery will be considered in deciding on the configuration of otherrequired facilities.
After confirming that the safety performance of the geological disposal system is sufficient, all of theabove will form the repository concept. NUMO will further improve the accuracy and reliability ofthese procedures through iterative updating of information, technologies and know-how in each stepof the project.
The above description of the design flow process is relatively one-way. The actual design will be
carried out with more flexibility by feeding back the results for the EBS, underground facilities,
surface facilities and investigation and evaluation results into decisions for adjusting parameters andre-designing repository components.

67

Repository design
Waste characteristics
Defining requirements for repository and design features

Chapter 5
Geological environment data ofpotential host rock

Engineered barriers

Subsurface facilities

Surface facilities

Selection of locationsof subsurface facilities

Selection of locations of surface

Therm al, m echanical,hydrological, chem ical environment
Volum e of host rock,schedule cost,→Depth & area※

Design of
overpack

Design of buffer

Access method

Locationof portal

Material, shape, thickness
Zoning of facilities

Specifications fortunnels & waste

Site preparation
plan/facility design

Tunnel cross-section (support)
Waste emplacement density(in terval)

Layout of subsurface
facilities
Disp osal panel (size, number, layout)
Main, connecting, access tunnels(n umber, layout)

Feed back to the design
as required.

Design of backfill
and plug

Selection of technologies for construction,
operation and closure
Chapter 7
Long-term repository safety assessment

Environment impact

Repository
concept* For TRU waste f or geological disposal

Design of buffer

Design of backfill

Figure 6-2 Sequence of repository design686.3.2 Design of the engineered barriers
The engineered barriers for the HLW repository consist of the vitrified waste, the overpack and thebuffer material, while those for TRU waste consist of backfilling and buffer materials. In thissection, the design procedure for the engineered barriers based on the technical requirements is
described. The production of the vitrified waste is excluded as this is done during reprocessing.
(1) Design of the overpack
The safety function of the overpack is to prevent radionuclide leaching; in particular, the overpack
must not be in contact with groundwater during the high heat generation period. Considering thevitrified waste and its thermal properties, this period is expected to be the first 1,000 years after
emplacement. The technical requirements for the overpack to ensure fundamental performance andthe behavior of the intact base material as well as welded sections should show sufficient resistanceto corrosion and structural strength to withstand loading. Based on this, the design of the overpack
involves determining its material, shape and thickness. Carbon steel is currently considered as thebest candidate material due to its good workability. An example of the design procedure for a carbon
steel overpack with a lifetime of 1,000 years is shown in Figure 6-3.

Design period: 1000 yrs
Material: carbon steel
Shape: cylindrical
Overpack thickness

Corrosion resistance
Determination of corrosion
tolerance(a)Radiation shielding
Determination of thickness(c) sothat no local corrosion will occur
due to radiation

Pressure resistance
Determination of
thickness(b)Max value(b or c)Overpack thickness;
a+MAX (b or c)

Figure 6-3 Example of the overpack design procedure (JNC, 2000b)

Since the NUMO 2010 report, the technologies for evaluating the corrosion behavior of carbon steel
have been further developed and the conservativeness of the above design example and its feasibility69were confirmed. For example, the results from a carbon steel corrosion test in a radiation field withan intensity that is expected in the repository showed that there was a negligible effect on theproperties of the carbon steel. Therefore, it is possible to reduce the overpack thickness by
re-evaluating such effects.
(2) Design of the buffer material
The safety function of the buffer material is to prevent radionuclide transport, in particular advective
transport, and colloid migration and to retard radionuclide migration via sorption. For these safetyfunctions, the technical requirements for assuring fundamental buffer performance are low
permeability, colloid filtration and sorption capacity. Figure 6-4 shows a design flow for the buffermaterial. In order for the technical requirements for assuring fundamental barrier performance,
maintaining long-term stability and engineering feasibility to be satisfied, a range of buffer material
specifications is considered. The final buffer material specifications, shape and dimensions will be
determined taking into account quality control procedures and economic aspects depending on thebuffer fabrication, transportation and emplacement methods. Once the buffer material specifications
have been determined, the long-term stability of the material will be evaluated. If long-term stability
is found to be insufficient, the design specifications will be modified by, e.g., increasing the buffer
thickness or dry density.

START
Define safety functions

Define technical-requirements

Fequirements needed for defining specifications
Fequirements necessary for long-term safety evaluation

Feedback

Buffer specification range

Fundamental barrier functions,constructability

Design of material specification, shape,
dimensions

QM, economical aspects

Improvement needed

Evaluate long-term stability

END
Figure 6-4 Design flow for buffer material (NUMO, 2011a)

Since the NUMO 2010 report, more data on buffer material fundamental characteristics and on
scientific understanding of long-term stability have been obtained. For example, the reduction in
swelling pressure due to salinity is now better understood and such information can be used to70

evaluate self-sealing. Concrete supports and grouts are expected to be used for the construction of theunderground facilities. Therefore, experimental investigations and development of modelingmethods for the interaction between cement-based and bentonite-based materials are being advanced.
The results will be reflected in future evaluation of long-term buffer stability.

6.3.3 Design of the underground facilities
The design of the underground facilities will be performed in the order 1) selecting the location of theunderground facilities, 2) tunnel specifications and waste emplacement configuration, 3)
underground facility layout and 4) backfill and plug design.
(1) Location of the underground facilities
Table 6-6 shows examples of the criteria to be evaluated in determining the location of theundeground facilities. These criteria include the extent of the host rock and other aspects such asschedule and economic feasibility, in addition to geoenvironmental characteristics such as thermal,
hydraulic, mechanical and chemical properties.
From the viewpoint of the thermal environment, since the rock temperature increases with depth, themaximum depth of the repository location will be determined considering the working environment
and thermal restrictions on the engineered barriers. From a mechanical viewpoint, tunnel diameter at
a depth of 300 m or more (one of the evaluation factors for qualification) will be determined by the
relationship between rock strength and ground pressure applied to the tunnel. The general trend is forground pressure to increase with depth, leading to mechanical instability of the tunnels. The
maximum depth where mechanical stability can be maintained should therefore be determined.
Considering the hydrogeological regime, groundwater flow characteristics in the host rock andgroundwater flow paths and flow rates in potential disposal areas and depths will be evaluated andmore promising areas from the viewpoint of radioactive material transport, e.g. areas that have longer
groundwater migration paths and slower groundwater flow rates, are selected based on mechanicaland thermal feasibility.

71

Table 6-6 Evaluation criteria for defining the location of the underground facilities

Factors to be evaluated[Thermal environment]
Low post-closure temperature of therepository[Mechanical field]
Ensuring mechanical stability oftunnels
Post-closure mechanical field in andaround the repository appropriate toensuring stability of engineered
barriers[Hydraulic field]
Low post-closure groundwater flux
and velocity in and around therepository[Chemical environment]
Chemical environment in and aroundthe repository that keeps the solubilityof nuclides low and is appropriate forbarrier material stability[Extent of rock body]
Sufficiently large area (volume) that
permits layout of the repository andconfiguration that allows effective
arrangement of disposal panels[Schedule, economics, etc.]
Good prospect for keeping schedules
and efficient construction processes

Evaluation indicators(example)
Waste emplacement area
based on thermal output of thewaste packages and rockproperties and evolution of
the repository temperature
with time

Information required for theevaluation
Layout of waste packages andevolution of temperature calculatedusing models incorporating thermal
output of waste packages and rockproperties

Spacing of disposal tunnels
and specification of tunnel
support based on rockproperties

Rock property model, initiallithostatic load, lateral pressure, rockmechanical properties , competence
factor, etc.

Groundwater migration path
length, groundwater travel
time, etc.

Hydrogeological model, long-term
evolution of the geologicalenvironment, hydraulic gradient,geothermal gradient, groundwaterchemistry, hydraulic conductivity,
effective porosity, groundwater flow
direction, etc.

Long-term behavior ofengineered barriers based on
groundwater chemistry

Groundwater chemistry model,
redox potential, pH, groundwaterchemistry, rock mineralogy, etc.

Repository-scale, number andconfiguration of disposal
panelsSite descriptive model, spatial
extent of host rock, distribution of
fault/fracture zones, etc.

Construction and operation
schedules, rough estimate ofconstruction costs, etc.

Length of access tunnels, disposal
concept, disposal tunnel
cross-section(2) Tunnel and waste emplacement specifications
When determining tunnel specifications, the cross-sectional dimensions and the tunnel shape andsupport are the main items. For HLW emplacement, determining the waste package spacing (waste
emplacement density) is the major item from the viewpoint of the thermal environment.
The tunnel specifications will be determined based on the space required for emplacing the buffer
and the waste and constraints associated with the facilities for buffer and waste transport andemplacement (i.e. minimum dimensions needed to accommodate such facilities). The shape of thetunnel cross-section has to ensure sufficient mechanical stability (small deformation), goodworkability and economic advantages (as small as possible, while maintaining the required volume).
72

The tunnel support measures will be evaluated based on the results of the mechanical stability
assessment of the tunnel cross-section. The pitch between the emplacement tunnels and the waste
packages is determined from the viewpoint of mechanical effects and thermal effects due to the heatfrom the waste, given the temperature constraint in the EBS after backfilling. In particular, the waste
emplacement density will be set in such a way that the buffer material will not be altered by the risein temperature due to the heat from the waste. The temperature evolution with time in the near-field
after the waste is emplaced will thus be evaluated numerically and the emplacement tunnel andwaste package spacing will be determined such that the maximum temperature in the buffer material
will not exceed a predetermined threshold value.
For TRU wastes disposal, the tunnel specification design approach will be the same as that for the
HLW. Tunnels with a higher waste emplacement density are economically preferable. TRU wastes
generate less heat than the HLW and a larger number of waste packages can thus be emplaced in alarge cross-section tunnel (NUMO 2011a). Tunnels with a large cross-section are typically excavatedin steps to ensure mechanical stability and safety. The mechanical stability of the tunnels is evaluated
via numerical simulations incorporating the actual excavation steps.
(3) Underground facility layout
For the underground facility layout, the size and number of disposal panels and the orientation of thetunnel groups are determined. The main tunnels and access shaft/ramp connecting with the surface
facility are then determined. For the orientation/configuration of the tunnel groups, in addition toassuring safety during the construction, operation and closure phases and smooth transport ofmaterials, geoenvironmental characteristics such as the direction of principal stresses andgroundwater flow in the rock mass will be considered.
Orienting the tunnels in the direction of the maximum principal stress within the horizontal plane is
the most efficient way to reduce rock deformation and ensure stability. By aligning the short side of
the underground facility perpendicular to the groundwater flow, the amount of groundwater seeping
into the facility is minimized. This is efficient from the viewpoint of radionuclide transport. The
longest tunnel will be determined based on the fracture conditions in the rock mass that can affect themechanical and hydraulic fields.
(4) Design of backfill and plugs
The backfill material and sealing plugs are expected to prevent radionuclide transport due toadvective groundwater flow after closure. The mechanical plug is expected to reduce swelling thatwould result in a decrease in buffer density. In particular, the remaining voids in the tunnels arebackfilled and the excavation damaged zones (EDZ) are separated with sealing plugs as needed.
Mechanical plugs are installed at the end of the emplacement tunnels to prevent buffer movement73and buffer erosion. The design will be evaluated not in terms of individual elements such as backfill
or plug, but as an isolation system into which all the elements are integrated.
6.3.4 Design of the surface facility
The design procedure for the surface facility consists of 1) zoning for the surface facility, 2) access tothe underground facility, 3) zoning for other facilities and 4) construction plan for the surface facility.
Zoning of the surface facility will be performed considering natural environmental conditions in thevolunteer area, the risk of natural disasters such as landslides or tsunami and the socio-economic
environment, such as adjacent land use. The depth and location of the underground facility andaccess routing from the surface to the underground facility, i.e. vertical shaft, ramp or a combinationof these, will be determined. The waste treatment facility, operational materials facility, otherfacilities for construction/closure and the site management facility will be located such that each canfunction with optimum efficiency. For the construction plan for the surface facility, measures will betaken to reduce the spreading of excavated soil due to wind and rain. Each component of the surface
facility will be designed to meet the requirements specifically set for that facility.

6.4 Repository construction, operation and closure
6.4.1 Repository construction
Repository construction starts with preparing the land, building roads, providing the infrastructure forpower and water as well as site management facilities. Following installation of a ventilation system
and a drainage water processing plant, construction of the underground facility will start. For
constructing the surface facilities, existing technologies used for conventional industrial or nuclear
facilities can be used, paying sufficient attention to protecting the surrounding environment.

Construction of the underfround facility is done in such a way as to ensure safety and a safe working
environment at all times, including emergency evacuation routes and ventilation shafts/tunnels. The
construction methods will be determined based on the rock mass conditions and other factors. For
excavating vertical shafts, ramp and horizontal tunnels, the most appropriate methods will beselected from those used in similar geotechnical projects, taking into account the geoenvironmental
conditions, safety and working efficiency as well as reduction of the EDZ around the tunnels. For
example, at the Mizunami and Horonobe URLs (Nakayama et al., 2008, Figure 6-5), the short-stepmethod is employed for excavation of the vertical shafts.

74

NUMO has analyzed the issues to be resolved for implementing the construction process(approximately ten years from the start of construction to the start of repository operation) and theoperation schedule (approximately 1000 canisters of vitrified HLW will be disposed of per year). For
example, excavation of disposal vaults and disposal of the excavated rock will be a critical factor thatcan significantly influence the project schedule and, to this end, effective construction technologies
have been developed.

Excavation
methodSupportmethodVentilation/West shaft : mechanical

Drilling rig

Short-step method

excavation East shaft : blasting
Vent duct

Scaffold

Lining concrete

Small shovel

Small shovel

Excavation screw
Hoisting machine

Scaffold

Excavation machine anddebris loader

Inside ventilation shaft (incl. bottom)

Excavation machine and debris loader (ventilation

Schematic image of drilling rig

Shaft: connection with 140m horizontal tunnel)

Figure 6-5 Excavation of vertical shafts using the short-step method (Nakayama et al., 2008)

6.4.2 Repository operation
Repository operation consists of receiving, encapsulating and inspecting the vitrified high-level
waste in the surface facility, transport to the underground facilities and emplacement in the disposal
tunnels.
The vitrified waste (in transport containers) will be transported to the HLW reception/ encapsulation/
inspection facility using a special vehicle. The waste will be inspected for any potential damage tothe container and the vitrified waste caused during transporation before encapsulation in the
overpack. Vitrified waste that passes the inspection will be transported to the underground facilities
after 1) encapsulation in the overpack, 2) welding of the overpack lid and 3) inspection of the welded
section. Figure 6-6 illustrates the waste production process based on welding of the overpack andinspection of the welded section using ultrasonic damage detection.

75

Containmentof vitrified glass
ガラス固化体収納

Welding of overpack lid
オーバーパック上蓋溶接

Inspectionof welded part
溶接部検査

Figure 6-6 Schematic process for remote-controlled waste encapsulation in the overpack (carbon steel
single overpack) (NUMO, 2002)

NUMO has investigated methods for improving the reliability of the quality of the engineered
barriers and reducing underground work (transport and emplacement). As part of this, thePrefabricated Engineered barrier system Module (PEM) method was selected as a promisingtechnique together with conventional in-situ construction and emplacement methods. In the PEM
case, the engineered barriers are prefabricated as an integrated module and then transported andemplaced underground. A schematic illustration of the PEM method is shown in Figure 6-7.
Metal cell (PEM container)
Bentonite
Metal overpack
Vitrified waste

Figure 6-7 Schematic illustration of the PEM method

The most obvious advantages of the PEM method are improved quality and efficient transportbecause the module is assembled at the surface. On the other hand, considering its heavy weight(total of about 35 tons, including waste package, buffer and steel shell), R&D has been conducted byfundamental R&D organizations on horizontal transport/emplacement techniques in the tunnel with
its spatial constraints and backfilling the gap between the PEM container and the disposal tunnel.

766.4.3 Repository closure
When closing the repository, the access and connecting tunnels as well as any boreholes will bebackfilled to isolate the underground facilities from the surface facilities. On completion of theoperational phase, the surface facilities will be dismantled and removed as soon as they are no longer
required. Backfilling of the tunnels and plugging the entrance will be defined as the “closure plan”
and closure processes will be initiated after the plan has been approved by the Ministry of theEnvironment, Trade and Industry (METI). Figure 6-8 shows an image of the repository before
submitting the closure plan. The brown parts are those that have already been backfilled during theoperational phase and the white parts are those to be backfilled during the closure phase. As noted inchapter 3, R&D will continue until the closure plan is approved.

Closure of the horizontal tunnels will be done using in-situ methods such as emplacing bentonite
blocks, compacting the backfill material or shotcreting. For vertical shafts, it will be more efficient torepeat cycles of backfilling and compacting from the bottom. More flexibility will be needed in thecompacting methods when backfilling in ramp.

Access tunnel

Backfilled
Backfilled
Backfilled

Backfilled

Backfilled
Connecting
tunnelBrown : Backfilled tunnel
White : Open tunnel

Backfilled

Figure 6-8 Image of the repository before submitting the closure plan

6.4.4 Approach for operational safety
During the operational phase, radioactive waste will be transported to the repository and thefundamental safety strategy for avoiding exposure to radiation will be confinement during operation,
radiation shielding and radiation exposure control. These are the same as the strategies adopted forother nuclear facilities. Efforts will be made to design and construct reliable facilities, develop
77technologies and assure safety considering the unique aspects of deep geological disposal ofradioactive waste, with a view to minimizing dose to the public and to workers.
For example, as part of radiation exposure control, radiation controlled areas will be set up within therepository according to the Nuclear Reactor Act. In the access tunnels and other undergroundtransport routes that are outside the radiation controlled areas, the HLW will be contained in ashielding container and transported using special vehicles with a view to achieving confinement
during operation and radiation shielding. In addition, tasks in the surface facilities such as
encapsulation of the vitrified waste in overpacks and then the shielding container, removal of thewaste packages from the shielding containers and emplacement underground will be done remotely
in radiation controlled areas.

NUMO selected various abnormal events, considered their effects and developed countermeasures
based on multiple safety measures consisting of the following steps: (a) identifying abnormal events,(b) taking measures to prevent these (abnormal event prevention measures), (c) identifying abnormal
events that could occur even if such measures are taken, (d) preparing automatic response systems in
the case of an abnormal event, (e) providing multiple lines of preventive measures in the case of
non-activation of such systems (prevention of propagation of abnormal events) and (f) taking
mitigation measures in the case of release of radioactive materials outside the facility (mitigation
measures).

6.4.5 Analysis of the compatibility of pre-closure safety and long-term post-closure
safetyOperational safety measures that will not endanger long-term post-closure safety have been studied
by considering factors that could influence them.
Activities during the construction, operation and closure stages could alter the deep undergroundenvironment conditions to varying degrees. For the safe implementation of work procedures,materials other than those for the engineered barriers (mainly man-made materials) need to be
introduced underground. Specifically, tunnel support will be required to ensure mechanical stability(steel or cement-based materials) and grouting using cement-based materials may be required torestrict seepage during tunnel excavation. Many of these materials will be left in the subsurface
facilities or surrounding rock.
Construction, operation and closure could have two types of effect on the functions expected for thenatural and engineered barriers in terms of ensuring post-closure safety: changes in deep geologicalenvironment conditions and the presence of materials other than engineered barrier materials.
78

The effects on long-term post-closure safety will be determined based on research results on theinteraction between materials other than engineered barriers materials and groundwater, rock and theengineered barriers.
If it is considered that there will be impacts on long-term post closure safety and that these will besignificant, materials that can be removed from the repository will be removed. Materials that will
not have a significant impact on the barrier functions but may be left in large quantities and thus havean impact that cannot be ignored fundamentally consist of cement-based and organic materials.
Low-pH cement has been developed as an alternative and its applicability in construction of therepository has been tested. For other materials that may have adverse impacts but cannot be removed
or substituted, or whose effects are not clear, their impact should be analyzed before establishing an
operating plan to ensure that appropriate safety measures can be implemented to avoid
compromising long-term post-closure safety.

6.5 Design and operation technologies accounting for the variability of thegeological environment
6.5.1 Design considerations specific to coastal areas
NUMO has developed technologies for repository design, construction, operation and closure
considering the range of geological environments in Japan.
Given that Japan is surrounded by sea, design features and considerations were listed from theviewpoint of groundwater flow regime and groundwater chemistry in coastal areas in addition toinland areas which were the focus of the H12 report. Specifically, an approach was developed for
determining the location of the underground facility, taking into account the change in groundwaterflow patterns associated with changing sea-level.
The long-term characteristics of the geological environment in coastal areas will depend on the shiftof the saline/freshwater interface associated with periodic sea-level change. Therefore, forradionuclide migration, the effects of periodic changes in groundwater flow rate, discharge points
and groundwater salinity (solubility and distribution coefficients of radioactive materials) on
migration should be evaluated.
The swelling properties of bentonite, which is one of the key components of the buffer/backfill
materials, are affected by salinity. For regions with saline water offshore from the freshwater/saline
water interface, it is necessary to determine specifications for the buffer/backfill materials (i.e.
79materials, composition) considering the effect of saline water on the bentonite properties. Since theH12 report, new findings have been made on the effect of salinity on the EBS material characteristics.
Based on these findings, the specifications of the buffer/backfill materials will be evaluated andchanges in groundwater chemistry, such as salinity changes, may lead to different buffer/backfill
material specifications being selected.
Another important issue in coastal regions is the design of the access tunnels. In particular, whenplacing the underground facilities beneath the seabed, the surface facilities cannot be positioned
directly above. Consequently, the access tunnels will be longer compared to surface facilities that lie
directly above the underground facilities. As the length of the access tunnels increases, construction
will take longer and ventilation and drainage systems will need higher capacities. For access tunnels
longer than 10 km, it will be necessary either to increase the number of tunnels or increase thecross-section.

6.5.2 Repository concepts/technologies that that take into account the variability of
the geological environment
Based on state-of-the-art technologies, NUMO has developed a range of options for waste package
emplacement concepts and operating techniques that can be adapted assuming a range of operating
environments. The emplacement concepts and operating techniques are defined here as a
combination of waste package emplacement method, emplacement tunnel dimensions and operating
technologies. The emplacement concept can be divided into vertical emplacement and horizontal
emplacement.
For these emplacement concepts, considering the conditions assumed in the undergroundenvironment (groundwater seepage, high humidity, locally weak mechanical rock strength),techniques considered to be promising were selected for both vertical and horizontal emplacement
options taking into account the level of technology development and the prospect of improving
working efficiency: vertical emplacement/block emplacement, horizontal emplacement/spraying,horizontal emplacement/PEM. Images of these three emplacement concepts are shown in Figure 6-9,
Figure 6-10 and Figure 6-11.

80Water conducting feature
Basic type without seepage

Locations withsignificant seepage
discarded

Measures to prevent
contact with water forsmall seepage
Measures against
seepage

Drainage trench
Vacuum pump

Drainage trench
Vacuum pump

Disposal pit discarded

Drainage trench

Vacuum pump

Steel liner

Cover hole
Reduction of seepage

Drain pit
Drainage

Drain pit
Prevention of contact

Figure 6-9 Emplacement option considering assumed underground conditions (verticalemplacement/block emplacement)

81

Spacer

Overpack

Blast concrete
Steel bed
Cross section ofhorizontal emplacement(H12 report)
Invert = buffer bed

Buffer (Spraying type)

Bottom buffer (Block type)

Invert = gutter = spraying
machine runway

Figure 6-10 Emplacement option considering assumed underground conditions (horizontal
emplacement/in-situ construction)

PEM handlingmachineSpace backfillingmachineFigure 6-11 Emplacement option considering assumed underground conditions (horizontal
emplacement/PEM type)The above options are compared below based on design features that were applied as evaluation
factors in the development of repository concepts (NUMO, 2004a), particularly for technicalfeasibility. Although the comparison is only qualitative because the repository site has not yet been
selected, the features of the three proposed disposal concepts and technical options based on thedesign objectives have been analyzed. Engineering feasibility was evaluated from the viewpoint ofschedule, workability, efficiency and adaptability to the underground environment. The weighting of
the criteria and evaluation indicators will depend on the volume/quality of geological environment
data and the level of technology development at the time. With the progress of site selection,
narrowing-down of the repository concept/technology options will be carried out based on acomprehensive comparison of these features.

82

6.6 Development of technologies that support engineered measures
Since the H12 report, the understanding of the phenomena relevant to the long-term behavior of, andinteraction among, the engineered barriers has progressed and technologies for transporting andemplacing the engineered barriers have developed significantly. Focusing on the results of R&D, thecurrent status of the following technologies is described.

¾ Technologies for evaluating basic properties and long-term behavior of the engineered
barriers- Long-term behavior of the vitrified waste- Long-term behavior of the overpack- Interaction between buffer properties and long-term behavior¾ Evaluation of seismic resistance of the geological disposal facility¾ Construction/operation technologies- Applicability of low-pH cement- Remote welding of overpack and inspection- Buffer production, transportation and emplacement technologies¾ Retrieval of wastes

6.6.1 Technologies for evaluating basic properties and long-term behavior of theengineered barriers
The engineered barriers will be designed such that their integrity will be maintained over a long
period of time based on an understanding of the phenomena expected in the near-field. In this context,
the fundamental R&D organizations have studied overpack corrosion and the effects of radiation on
the overpack, the properties of the buffer material under saline conditions and the interaction between
the buffer material and cement or iron. These results have been compiled as fundamental data to bereflected in the design and safety assessment.

In the H12 report, the dissolution rate of glass was found to decrease with time. From the viewpointof conservative numerical evaluation, however, the rate of dissolution of radioactive substances fromthe vitrified waste was assumed to be constant over time. In order to advance the understanding ofglass dissolution and further improve the models, dependence of dissolution on pH is being
investigated (Inagaki et al., 2009, 2010).

83

Table A.6-1 in Appendix summarizes the current status of scientific understanding of corrosion
behavior of the overpack base metal and weld. Basic properties, long-term behavior and interaction
with buffer materials, including behavior under saline conditions and interactions between buffer andcement or iron, are summarized in Table A.6-2and Table A.6-3 in Appendix.

6.6.2 Seismic resistance of the geological disposal facility
The repository is unique in that it will be constructed deep underground, has large tunnel
cross-sections and is interconnected with large-scale connecting tunnels; its safety must also be
assured even after the facility is closed. In Japan, where seismic activity is very high, the safety of the
facility in the event of an earthquake is extremely important.
Therefore, NUMO evaluated the seismic resistance of the repository tunnels during the operational
phase using a rock mass model that is similar to that used in the 2010 report. More specifically, thestress field when the tunnel is excavated was obtained using a two-dimensional FEM analysis.
Assuming that the stress field is that under normal conditions, incremental stress induced by the
hypothetical earthquake was computed using a dynamic FEM simulation (horizontal and verticalmovements considered simultaneously). By adding these two results, the seismic resistance (safety)
was evaluated. Figure 6-12 shows an example of the simulation results. It was confirmed that the
maximum shear strain during normal and earthquake conditions was about the same and that theeffects of an earthquake on the repository tunnels would be insignificant.

20% of tunnel diameter

20% of tunnel diameter

0.1

0.1
0.01340.0134

γ0

0.010

0.010

0.005

0.005
0.004

0.004

(γmax)max=0.0202

γ0(γmax)max=0.0204

0.003

0.003

0.002

0.002

0.001

0.001

0

0

Ultimate shear strain：γ0=0.0134

Ultimate shear strain：γ0=0.0134(normal)(earthquake)
Figure 6-12 Maximum shear strain around the tunnel (HLW repository tunnel) (NUMO, 2011d)

84

6.6.3 Construction and operation technologies
In the repository, it is expected that cement-based materials will be widely used to ensure sufficient
structural strength. However, it is suspected that the dissolution of the cement will lead to generationof highly alkaline components, resulting in a reduction of the swelling capacity of the buffer material
or alteration of the rock mass (natural barrier). In order to avoid/reduce such effects, low-pH cement
was developed as an alternative material and its characteristics are being investigated (Iriya and
Mihara, 2003). To verify the applicability of the low pH cement under practical conditions, sometests, including shotcreting tests, were performed. The results confirmed reasonable workability as
well as strength (Nakayama et al., 2009).
Welding tests on the overpack have been conducted for electron beam welding (typical high energy
welding technique with a high rating in the H12 report) and TIG welding (Tangsten Inert Gas
Welding) (Figure 6-13) and MAG welding (Metal Active Gas Welding) techniques (representativearc welding techniques) using full-scale lid structures. Welding technologies have been evaluated interms of technical aspects such as applicability to the overpack (including lid structure) and welding
conditions（RWMC, 2009a）

Close
up

(a): Vertical(b): Horizontal

Figure 6-13 TIG welding of the overpack(a) From RWMC (2009a), (b) From RWMC (2003)

For operating technologies and the buffer transport/emplacement technology, fabrication of blocks,
in-situ compaction, pellet backfilling, shotcreting and PEM are being developed. Each of these has
been tested in 1:1 scale validation tests and confirmed to have reasonable workability as well as
sufficient density.
The PEM test includes fabrication of a full-scale PEM, determination of the difference in the tunnel
floor level that the air bearing tramsportation can clear during horizontal transfer and a PEM lifting
test with an air jack (Figure 6-14) (RWMC, 2009b).

85

ウェイト

荷重支持装置走行面(a) Full-scale PEM container(b) Air bearing tramsportation test(c) Lifting up & down of PEM
using an air jackFigure 6-14 Tests of the PEM-type EBS(from RWMC (2009b) for (a) and (c) and RWMC (2004) for (b))

As part of fundamental R&D, gap filling tests have also been conducted using pelletized buffers
for a simulated full-scale disposal tunnel (horizontal emplacement type) (RWMC, 2008). Parameters
include shape and dimensions of the pellets, the effect of using a mixture of pellets with different
sizes, gap filling density and pellet feed rate. Based on a quantitative evaluation, the feasibility andapplication conditions of the technique for filling gaps with pelletized buffer using pressurized air
were established.
A bentonite spraying method using a supersonic nozzle was demonstrated as being able to achievea suitable dry density, even using bentonite only (RWMC, 2010). It was confirmed that buffer with ahomogeneous density distribution could be constructed with the spraying method.
Regarding waste retrievability, retrieval methods before and after backfilling of the repository tunnels
are being developed. One possible method is shown in Figure 6-15. This is based on the overcoring
technology typically used for cutting rocks and concrete.
Vehicle for removal of constraint from
buffer around overpack

Overcorer

Towing vehicle ofretrieval system

Waste package

Figure 6-15 Example of waste retrieval technology

866.7 Conclusions of chapter 6
As described above, technologies for repository design and operating technologies applicable to avariety of geological environments have been developed considering the long-term behavior of theengineered barriers.
Since the H12 report, there has been a significant improvement in the safety and reliability of thetechnologies for repository design and engineering technologies such as construction andtransportation and emplacement of the engineered barriers.

In close collaboration with fundamental R&D organizations, NUMO will continue its efforts towards
reliable implementation of the engineered measures for long-term post-closure safety and measuresfor ensuring safety in each project stage.

87

7 . Technology for long-term safety assessment
This chapter describes the technologies required for evaluating long-term safety which is one of
NUMO’s three policies for assuring safety.
In the H12 report and the second TRU report, a basic methodology was demonstrated for evaluating
the long-term safety of geological disposal under generic geological environment conditions. Since
the H12 report, NUMO has developed a program of staged safety evaluation of the geologicaldisposal system for each of the site selection stages. In parallel with this, NUMO and fundamental
R&D organizations have been improving the individual technologies aimed at evaluating the safetyof the disposal system for a range of geological environments and more practical design options. The
progress in evaluating the safety of the geological disposal system is described below.

7.1 Basic strategy for safety assessment
7.1.1 Procedures for safety assessment
An important and unique difference between the safety assessment of the geological disposal systemand that for conventional engineering systems is that the former involves extremely long time
periods compared to other nuclear facilities such as nuclear reactors; it also has to consider aheterogeneous and huge natural spatial environment, i.e. geology. This means that is not possible toapply the approach used in conventional engineering, i.e. optimization and demonstration throughthe process of constructing actual objects, checking their behavior and feeding back the results to thedesign (OECD/NEA, 1983).

88Consept for ensuring safety

Safety assessment

Scenario development

Sharing of Knowledge
via storyboard

Condition setting

Investigation /evaluation ofgeological environment
Design of a repository

Site descriptive model Long‐
term evolution of geologicalenvironment features

R&Ds

Scenario development/grouping
Identification of
uncertainty factors andevaluation of their effects

Selection of models
Setting datasets
Safety analysis
Comparison with criteria

Repository design
Construction/operation/
closure program

Provide information forformulation programs
and optimization
Evaluate reliability of the safety
asseement

No
Reduce uncertainties by R&D

No
Is the reliability at the stage satisfactory?

Yes

Reduction of uncertainties by investigation/Mitigation of effectsof the uncertainties by design

Safety assessment strategy

Integration of knowledge(as safety cases)
Communication with stakeholders

Figure 7-1 Basic procedures for safety assessment

In projects run by international organizations, there is a consensus that a reference methodology has
been established to a satisfactory level (OECD/NEA, 1991b, 1997) through discussion based on
research and experience in different countries (e.g. OECD/NEA, 1991a and 1991b). The genericapproach involves scenario development, selection of models, defining datasets, safety analysis andcomparison of the analysis results with relevant safety criteria. As described in section 3.2, the safetyassessment is generally incorporated into the framework of the safety case that demonstrates
long-term safety from multiple aspects, including investigation/evaluation of the geologicalenvironment, repository design, uncertainties and their treatment and use of alternative safety
indicators. Based on the above, basic procedures for evaluating long-term safety were established(Figure 7-1). Although the fundamental procedures are common to each stage, the focal points will
differ in different stages depending on the major actions to be carried out and the availability of
information.
During the literature survey stage, the availability of geographical, geomorphological, geostructuraland geoenvironmental information is generally limited. There is therefore a relatively large degree of
uncertainty associated with the performance assessment of the host rock as the natural barrier. ,whichleads to a rather conservative EBS design. Therefore, the focus of the safety assessment at this stage
is not to systematically evaluate whether or not the geological disposal system has the required safety
performance, but to identify important factors that can affect the safety assessment in the later stages
89and effectively reduce the uncertainties.
In the preliminary investigation stage, in addition to the information obtained through the literature
survey, information on geoenvironmental characteristics as well as findings on long-term stability of
the rock mass will be enhanced through surface investigations, geophysical investigations andborehole investigations. The selection of the host rock and the preliminary design of the undergroundfacilities and the EBS will be performed based on these findings. Therefore, the safety assessment
will mainly focus on confirming the appropriateness of the repository design, comparing possible
options, developing the safety case and planning the detailed investigations.
During the detailed investigation stage, more tunnel-scale findings will be obtained throughinvestigations in the underground investigation facility. Based on the repository design developed in
the previous stage, specifications for the underground facility and the EBS will be determined and aplan for construction/operation/closure will be prepared. The safety assessment in this stage will
mainly focus on a generic assessment of safety based on reconsideration of the prerequisites relating
to the geological environment and repository design, confirmation of safety for the license
application, preparation of the license application and updating of the safety case.
7.1.2 Approach to dealing with uncertainties
As discussed in section 3.2.2, handling of uncertainties is an important issue in the safety case. The
uncertainties will be reduced as far as possible by performing stepwise geologicalinvestigations/evaluations, with more detail being incorporated as the project proceeds. The
repository is then designed conservatively by considering the remaining uncertainties, such that theeffects of the uncertainties will be further reduced. Although uncertainties cannot be eliminatedcompletely, in the safety assessment they will be addressed through an iterative process ofidentifying uncertainties, classification of their effects/importance, reduction of their effects andreflection in the safety assessment (Figure 7-2). During the iterative process, not all potential
uncertainties and their combinations are considered, but effectively only those that are essential forthe safety assessment as follows:
・ Combinations of uncertainties that are too conservative for investigation and evaluation of thegeological environment and repository design will not be considered. For optimizing therepository design and demonstrating its performance, impractical assumptions, such as acertain safety performance being lost, may need to be considered.
・ For uncertainties that can significantly affect safety based on expert judgement or sensitivity
analyses, if their effects cannot be eliminated they will be handled in such a way that areasonable level of conservativeness will be added to the design.
・ Comprehensiveness (effects of one event are included/emcompassed in those due to anotherevent) will be considered.
90

Investigation/evaluation ofgeological condition
Repository design
R&D

Treatment of uncertainties in safetyassessment in the current stage
Identifying uncertainties

Findings

Prioritization
Feedback

Reduce impact of uncertainties

Planning for the
next stage

Include in safety assessment
Issues and solutions

Figure 7-2 Handling of uncertainties in the safety assessment

7.2 Development of the safety assessment
7.2.1 Construction of scenarios
Scenarios for safety assessment provide the framework for model development and parameter
determination by describing the future evolution of the geological disposal system, allowing asystematic evaluation of disposal system safety. Scenarios will also need to be developed dependingon the uncertainties associated with predicting the distant future. When developing scenarios, thefeatures of the geological disposal system, events that can affect the features and processes in the
future evolution of the system, collectively referred to as FEPs, have been the main focus. Recent
trends are based on the safety functions rather than conventional FEP-based scenario development(e.g. ONDRAF/NIRAS, 2001; Nagra, 2002; ANDRA, 2005; SKB, 2006; Ebashi et al., 2010). Thisapproach emphasizes what features of the geological disposal system contribute to the safetyfunctions and how the safety functions will be affected by the future evolution of the system. It
allows the scope of the key phenomena to be defined and is thus expected to lead to a much clearer
definition of the scenario development process and effective development of scenarios. Therefore,
NUMO will develop scenarios using both FEP-based and safety function-based approaches. In
predicting the future evolution of the geological disposal system, storyboards (Figure 7-3) will be
used as a tool for knowledge-sharing across different disciplines. Because the future evolution of the91

system will involve different phenomena that will evolve in different ways, it will be difficult toclearly understand and represent all of them accurately. Therefore, the phenomena to be included in
the scenarios have to be selected based on international FEP lists and existing FEP lists and from theviewpoint of conservativeness in the safety assessment.
7.2.2 Model selection
Models to be used in the safety assessment will be selected based on additional
information/understanding of the features of the geological disposal system and the objectives of thesafety assessment, both of which evolve as the project stages progress.It should be recognized thatdetailed modeling of the complex behavior of the actual geological disposal system will be difficult
due to the variability of relevant phenomena, the heterogeneous geological environment and lengthof the assessment duration. Therefore, two types of models will be used complementarily: system
performance assessment models that are simplified and focused on safety functions andphenomenological analysis models used for realistic evaluation of individual phenomena and barriercomponents (Figure 7-4). The simplification in the system performance assessment models will betested to the extent possible using phenomenological models, while key uncertainties will be coveredby conservatism, supported by system understanding (NUMO, 2004a).
Therefore, options, for safety assessment models need to be shown and the influence of the model
selection on the safety assessment must be understood considering the degree of process
understanding for modeling, and the level of conservativeness and simplification.
7.2.3 Dataset selection
Information on a specific site will be limited in the early stages of the project. Therefore, datasets will
be prepared by selecting data similar to those for the potential target site. With the progress of theinvestigation/evaluation of the geological environment, newly obtained site-specific data (e.g.
sorption data using rock samples and groundwater sampled at the site of interest) will be reflected in
the datasets. Furthermore credibility of the dataset will be increased by comparison with existing
database. Different uncertainties associated with datasets and the interpretation of data will becovered by appropriate values or ranges of values that assure appropriate conservatism.
7.2.4 Safety analysis
The safety analysis uses scenarios, models and datasets. It will be mainly deterministic, with a single
value being explicitly assigned to a parameter, complemented using statistical methods asappropriate. Safety indicators will be radiological dose and other performance or supplementary
indicators. Regarding uncertainties, variations will be considered for the scenarios, models anddatasets to check the compliance of the safety assessment results for different analysis cases with the92safety criteria. The effects of the uncertainties will be evaluated and a comparison of different design
options will also be conducted and reflected in the formulation of the investigation program andoptimization of the repository design for the subsequent stages.

93Assumed conditions● 処分場深度● 岩種：第三紀堆積岩（泥岩）● 動水勾配● 透水係数● 有効間隙率● 隆起速度● 地温勾配● 気温● 降雨量● 河川流出高● 処分場立地周囲：淡水域，還元雰囲気

酸化域

還元域
淡水域

Initial surface condition

還元域
塩水域

還元域
淡水域

Condition during glaciation

Initial condition at repository

海水準変動

還元域
塩水域

● 岩種：第三紀堆積岩● 動水勾配● 透水係数● 有効間隙率● 隆起速度● 地温勾配
● 海水準
● 気温
● 降雨量
● 河川流出高● 凍土厚さ
● 処分場立地周囲：淡水域，還元雰囲気

時間枠
Beforeonstruction/operation/backfill
EBS 定置中

掘削中

Transition to full re-saturation

Overpack confinement period

Radionuclide release/start of migration – start of climate change

Period during which natural event prediction is possible

埋戻し中Disposal concept
・陸地処分・ガラス固化体4 万本・堆積岩・処分場（平面配置）
・廃棄体竪置き方式

核種のプリュームの拡大

EBS scale

地下水

Conditions at depth・ 初期応力・ 間隙水圧・ 地温

表土層【Overpack containment】

プラグ

地表面

地表面

【EBS confinement】【EBS confinement】

94

地下水の再冠水

repository scale

Scal

低透水層

地表面

地表面

高透水ゾーン（ガスの滞留）埋戻し

埋戻し【Repository scale confinement】【Repository scale confinement】
支保工の劣化プラグ

支保工

核種のブリューム

支保工

支保工

Conditions at depth・ 初期応力・ 間隙水圧・ 地温・ 塩水の存在（古海水など）

Natural barrier scale
Surfacehydrology

Comments【Overpack containment】

地表面

地表面
排水

高透水層

Other natural events【Overpack containment】

・ ガラス固化体の溶解進展→核種の浸出→ベントナイト中の拡・ 掘削→掘削影響領域（EDZ）の発生→間隙の増大， ・ 廃棄体の発熱→ベントナイト温度上昇 ・ 地下水のオーバーパック接触
・ 地下水とガラス固化体の接触
応力緩和→透水性の増加
・ 再冠水→間隙水圧の回復→ベントナイ →腐食→ガス発生→ベントナイト中の移行 →ガラス固化体の溶解→核種の浸出→ベントナイト中の拡散移行（収着）→EDZ
散移行（収着）→EDZ／埋戻し中への移行拡大（拡散・希釈・・ 覆工背面での排水→不飽和領域の発生
トの膨潤→腐食膨張→ベントナイト変形／埋戻し中への移行（拡散・希釈・収着）
収着）
・ オーバーパックからの発熱→ベントナイトの温度上昇
・ 岩盤のクリープ変形→岩盤応力の回復 →腐食生成物→ベントナイトの変質
・ オーバーパックの腐食進展→腐食膨張／腐食生成物→ベントナイトとガラス固化 ・ オーバーパックの腐食進展→腐食膨張／腐食生成物→ベン・ ベントナイトへの再冠水→膨潤圧発生
・ 支保工の劣化→高 pH プリュームの発・ ・ 岩盤クリープ変形→岩盤応力の回復
トナイトとガラス固化体の変質・変形の進展→安全機能への体の変質・変形→安全機能への影響
・ 岩盤のクリープ変形→岩盤応力の回復
生→間隙増加→透水性増大
・ 支保工の劣化→高 pH プリュームの発生 ・ 支保の劣化→高透水領域の発生／高 pH プリュームの発生→岩盤／ベント
影響・ 埋め戻し部への再冠水→EDZ 不飽和領域の回復→間隙増加→透水性増大・ 高 pH プリュームによる岩盤／ベントナイトの変質の進展→
ナイトの変質による安全機能への影響
安全機能への影響

・ 建設・操業中の排水→アクセス坑道，処分坑道周辺・ ・ オーバーパック発熱→処分場周辺の温 ・ 地下水は処分場内の高透水ゾーンを優 ・ 核種の人工バリアからの放出（地下水流動の方向とEDZに沿って卓越経路の移行 ・ 核種の人工バリアからの継続した放出の間隙水圧の減少，地表近辺の地下水面の低下
度上昇→熱対流の発生
先的に移動
可能性）
・ オーバーパックの発熱→処分場全域での温度上昇
・ 再冠水→処分場周辺の間隙水圧の回 ・ 熱の影響の低減
・ コンクリート支保工の劣化→坑道に沿っての地下水流動の卓越ルートの形成
・ 埋戻し→再冠水→間隙水圧の回復
復・ コンクリート支保工の劣化→地下水流動 ・ 高pH 環境の形成
・ 埋戻し→処分場周辺応力場の回復
・ 支保工の劣化→坑道周辺の高透水領の卓越経路が EDZ に沿って発生する可・ プラグ設置→地表への地下水経路の遮断
域の発生→坑道に沿っての地下水流動能性（ガスの移行経路）
・ 支保工の劣化→高pHプリュームの発生 ・ 高pH 環境の形成
滞水層（酸化水）

地下水（還元水）

・ 地下水移行が基本プロセス
・ 隆起・侵食速度
・ 淡水，還元環境

滞水層（酸化水）

地下水（還元水）滞水層（酸化水）【 Confinement/isolation by
the natural barrier】

地下水（還元水）滞水層（ 酸化水）

塩水環境【Confinement/isolation by the natural barrier】
流出点の変化（海から河川に）

地下水+核種地下水+
地下水+核種・ 処分場の建設・操業→処分場周辺の地下水流動場の ・ 閉鎖後→処分場周辺の地下水流動場 ・ 処分場スケールでの地下水流動場の擾 ・ 初期の地下水流動系の維持→移流・分散・拡散での核種移行・ 気候変動→海水準変動→地下水流動場の変化→流出点の変変化→天然バリア性能への影響（回復プロセスの予測）の回復
乱の回復
・ 気候変動の始まり→海水準変動→地下水変動→地下水流動系の変化（有意な化（海から河川に）・ 広域では初期の地下水流動状態（処分場スケールでの ・ 広域では初期の地下水流動状態（処分
変化なし？）
・ 高透水ゾーンに沿う核種移行速度の増大
地下水流動場の擾乱）・ 天然バリア中の核種収着場スケールでの地下水流動場の擾乱）

現状での海水産物の消費状況が・ 初期状態の継続
基本となる

・ 初期状態の継続

・ 初期状態の継続

・ 地下水の流出点→海底堆積物での収着→海水による希釈→現状の生態系維持・ 氷河期の到来→生物圏の変化（海から河川に）→凍土の発生→地表水系の変化→生態系の変化

火山・活断層・泥火山・マスムー 火山・活断層・泥火山・マスムーブメントによる著しい影響 火山・活断層・泥火山・マスムーブメントに 火山・活断層・泥火山・マスムーブメントによ 火山・活断層・泥火山・マスムーブメントによる著しい影響はサイト選定と工学的対策 火山・活断層・泥火山・マスムーブメントによる著しい影響はサイト選
ブメントによる著しい影響はサイ はサイト選定と工学的対策で回避よる著しい影響はサイト選定と工学的対策 る著しい影響はサイト選定と工学的対策で で回避
定と工学的対策で回避ト選定と工学的対策で回避
で回避
回避・ 処分深度に古海水の存在の ・ 安全機能への残置物の影響度［セメント材料による高ア ・ 再冠水のプロセスと環境回復の程度
・ オーバーパックの腐食膨張と生成物の安 ・ 高アルカリ，腐食生成物，ガス，微生物によるベントナイトの変質プロセスと安全機 ・ 気候変動に伴う地表水文系と地形の変化予測
能への影響
・ 凍土発生の深さと分布確認
ルカリ影響］
・ 処分場スケールでの不飽和領域の残存
全機能への影響・ 生物圏の設定
・ 建設・操業による天然バリアへの影響（領域と程度）の影響
・ EDZ と支保劣化に伴う卓越流路の形成 ・ 生物圏の設定
・ 海底の堆積物と食物チェーン
・ EDZ に沿った卓越流路の形成可能性（プラグなどの対策の効果）

EDZ：Excavated Disturbed Zone（掘削影響領域），EBS：Engineered Barrier System（人工バリアシステム），高 pH プリューム：岩盤中に形成される高アルカリ性の地下水領域

Figure 7-3 Storyboard for the disposal of HLW (Example)

Performance Assessment Models

Safety of a total system

Important uncertainty ina total system

Support validity(fulfillment of safety functions)

Process Models

Specify uncertainties to be
reduced

System understanding

Set of a disposal system

Site characterization · Repository design

Figure 7-4 Complementary use of performance assessment models and process models(from Ishiguro et al., 2007, partly modified)

7.2.5 Evaluation of safety assessment reliability and integration of findings
On completion of the safety analysis, the long-term reliability will be evaluated, e.g. based onalternative indicators other than dose as proposed by the OECD/NEA (2002) (Table 7-1). Whensufficient long-term reliability has been confirmed for each stage, the results of the safety analysis,
open issues for the next step and solutions will be integrated into the safety case. If the long-term
reliability is insufficient, on the other hand, issues where a further reduction of uncertainty isnecessary have to be clarified and reliability will be improved through information feedback to thegeological environment investigations, repository design and the R&D program.

95

Table 7-1 Major discussion points for constructing a safety case (OECD/NEA, 2002)

Category

Arguments

Confidence in the・Intrinsic robustness of the multi-barrier system

proposed disposal system

・“What if?” scenarios and calculations

・Comparisons with familiar examples and natural analogues

Confidence in the data

・

Quality of the research programme and site investigations

and knowledge of the・

Quality assurance procedures

disposal system・Data from a variety of sources and methods of acquisition・

Use of formal data tracking techniques

Confidence in the・

Logical, clear, systematic assessment approachassessment approach・Assessment conducted within an auditable framework

・

Building understanding through an iterative approach・Independent peer review of approach

Confidence in the IPA・Explaining why results are intuitivemodels・Consideration of alternative conceptual models and modelingapproaches – simple and complex

・

Testing of models against experiments and observations of
nature・Model comparison exercises・Comparisons with natural analogues

・Independent evidence such as paleohydrogeological information

Confidence in the safety

・

Clear statements and justifications of assumptions

case and the IPA analyses

・Demonstrate that assumptions are representative or conservative・

Sensitivity studies

・

Clear strategy for managing and handling uncertainty

・Multiple safety indicators

・

Multiple lines of reasoning

Confidence via feedback

・Support for any disposal concept design changes

to design and site・

Overall quality and safety of the disposal systemcharacterisation

7.3 Development of technologies that support the safety assessment
Since 2000, NUMO and fundamental R&D organizations have been leading R&D programs
necessary to implement the project and allow the following:(1) Handling of the variability of the geological environment and its long-term evolution(2) Analysis of different design options(3) Incorporation of updated knowledge into the safety assessment and96

(4) Evaluation of significant impacts from natural phenomena.
The progress of R&D on safety assessment technologies by NUMO and fundamental R&D
organizations since the H12 report is summarized in the Table A.7-1through Table A.7-4 in Appendix.
Major technologies relevant to the above four points are discussed below.
7.3.1 Scenario development technologies
The geological environment will be affected over long periods of time by uplift/erosion and changes
in climate and sea-level. In coastal areas, consideration will have to be given to the effects of saline
water and the long-term evolution of the saline/freshwater interface. NUMO has developed a method
for identifying the conditions of the geological disposal system to allow the effects of saline waterand long-term evolution of the saline/freshwater interface to be handled realistically (NUMO,
2011b).
Knowledge relevant to geological disposal will be accumulated in a stepwise manner through R&D
and other research and it will be important for NUMO to incorporate it into the safety assessment tomeet defined milestones. The near-field environment has the important barrier function of restricting
nuclide migration. The performance of the near-field is less dependent on the site-specific geologicalenvironment than the natural barrier. Development of technologies relevant to the near-field cantherefore be carried out now before a specific site has been selected to provide a starting-point forincorporating the features of specific sites. NUMO has therefore developed a scenario development
methodology for the long-term evolution of the near-field, based on knowledge on long-term
evolution of the geological disposal system, focusing on its safety functions (NUMO, 2011b).
The FEP information that will form the basis for the scenario development has been compiled as a
FEP database by the fundamental R&D organizations (Kanzaki et al., 2009). For TRU waste, the
FEP information used in the second TRU report has been compiled as a comprehensive FEP list
(FEPC/JNC, 2005a).
Significant impacts from natural phenomena should, in principle, be avoided by selecting a suitablesite. However, due to the extremely long timescales involved, the uncertainties associated with thetime and frequency of their occurrence need to be taken into account. NUMO and the fundamental
R&D organizations are developing scenarios for the impacts from earthquakes and faults (Table 7-2),
as well as methods for evaluating their effects (NUMO, 2011b; Miyahara et al., 2008).
Based on these results, fundamental technologies and information databases for scenario
development were improved.

97

Table 7-2 Example of potential changes in safety assessment when a new fault intersecting the repository is formed (NUMO, 2011b)
Immediate effects after new fault formation
廃棄体の破壊・緩衝材のせん断
Failureof waste/shearing of buffer
Temperature rise
温度上昇
Dissolution/release of radionuclide
核種の溶解・散逸

Gradual transition after new fault formation
Re-activation
再活動
Steady flow
定常流れ
(upward)（上昇流の場合）

Fault displacement
断層変位

Steady flow
定常流れ
(downward)（下降流の場合）
Oxygen diffusion in buffer

酸素の緩衝材への拡散
Reduction due to ferrous
minerals
鉄鉱物等による還元などによる還元

Thermal water
熱水対流
convection

ダメージゾーン

プロセスゾーン
Fracture formation
割れ目の形成微小亀裂の形成
Increase in permeability
透水性上昇

岩石のせん断Pathway
formation
fromrock shearing
卓越流路形成Fault
角礫breccia

Dam aged zone
ダメージゾーン
Rock-groundwater
interaction
岩石－地下水反応
Alterationof fault
角礫の変質
breccia

Fine-grained
細粒破砕物
cataclasite

Expansion of

ダメージゾーン
プロセスゾーン
dam aged zoneの拡大
Alteration of cataclasite
細粒破砕物の変質
Fault gauge form ation
断層ガウジの生成
Perm eability reduction
透水性低下

98

T: Temp. rise to > 300 due to fault friction‐induced T: Temp. rise during re-activation
heat several minutes
H: Hot water convection due to heat generation
H: Hot water convection and degradation of buffer sealing M: Repeated shear in buffer
Waste intersected by fault
Scenario 1
due to heat generation
C: Radionuclides completely released
M: Failure of waste, shear in buffer(Rise of reducing
C: Dissolution of radionuclides and release through EBS
deep groundwater)
T: Slight temp. rise (short-term)
T: Other waste
H: Transitional flow due to porewater pressure changes
H: Flow increase due to increase in permeability in deformation area
M: Seismic motion
M: Seismic motion
C: C: Radionuclide migration under reducing condition
T: Temp. rise to > 300 due to fault friction‐induced T: Temp. rise during re-activation
heat several minutes
H: Hot water convection due to heat generation
H: Hot water convection and degradation of buffer sealing M: Repeated shear in buffer
Scenario 2
Waste intersected by fault
due to heat generation
C: Radionuclides completely released
M: Failure of waste, shear in buffer(Entrapment of
C: Dissolution of radionuclides and release through EBS
oxidizing surface
water)
T: Slight temp. rise (short-term)
T: H: Transitional flow due to porewater pressure changes
H: Flow increase due to increase in permeability in wide deformation area
Other waste
M: Seismic motion
M: Seismic motion
C: C: Oxidation of groundwater, reduction due to iron minerals in buffer
T: Thermal effects, H: Hydraulic effects, M: Mechanical effects, C: Chemical effects

7.3.2 Development of modeling technologies
Features in coastal areas include changes in groundwater chemistry, flow direction and flow rate dueto the shift of the saline/freshwater interface around the repository, as well as changes in thegeosphere-biosphere interface (GBI, locations at ground surface which can be reached by radioactive
substances) and environmental conditions with time. This necessitates nuclide migration analyses
considering the specific features of coastal areas in addition to analysis of preferential flow paths inheterogeneous host rock. With the aim of developing a method for realistically incorporating thefeatures of coastal areas, a modeling methodology was developed to evaluate nuclide migration in
the natural barrier and biosphere, considering the evolution of groundwater flow and groundwaterchemistry (NUMO, 2011c).
In the staged geological disposal project, multiple design options (e.g. panel/tunnel arrangement andwaste package emplacement method) will be developed in order to respond to different uncertainties
and constraints. Narrowing down the design option will require evaluation of differences among theoptions from different viewpoints such as safety and economic efficiency. In identifying differencesamong the design options from the safety assessment point of view, a quantitative differentiation isdifficult when a one-dimensional model is used because the 3D configuration of the engineered
barriers and subsurface facilities and the heterogeneity of the surrounding rock are conservatively
simplified. Therefore, 3D modeling tools were developed to allow more realistic analysis (Wakasugi
et al., 2008; NUMO, 2011c). Among the developed tools, the solute transport model was applied to
two types of rock heterogeneities (Figure 7-5). The colors in Figure 7-5 indicate the particle velocity
at the time step shown. For type 1, the particles show random movement within the buffer andbackfill materials via diffusion. For type 2, on the other hand, the drift intersects with a highly
permeable fault at the midpoint; particle movement is thus locally enhanced along the fault. This typeof information is important when determining the configuration of the emplacement drifts. These
results have contributed to updating and expanding the technology bases to respond to the safetyassessment needs, expanding technical options in the selection of safety assessment models.

99

Hard rock: Type 1

Hard rock: Type 2

Log scale of the velocity
ofparticles (m/s)
粒子の速度(m/s)の対数 －15.00～－7.00

Log scale of the velocity
ofparticles (m/s)
粒子の速度(m/s)の対数 －13.00～－8.50

Figure 7-5 Example of particle tracking analysis for one hundred thousand years (NUMO, 2011c)(Hard rock 1: Low permeability and random distribution of factures with low frequency; Hard rock 2:
Highly permeable factures as well as permeable faults)

7.3.3 Development of datasets
Preparing appropriate datasets is important for building confidence in the long-term safetyassessment. Since the H12 report, the fundamental R&D organizations have published databases andresearch data on parameters relevant to nuclide migration analysis as follows:
・ Thermodynamic database (JAEA-TDB): Modified thermodynamic database on radioactive
elements and geochemical elements compiled in a format that can be used for different
geochemical codes (e.g. PHREEQC) (Kitamura et al., 2010)
・ Sorption database (JAEA-SDB): Data on distribution coefficients for bentonite and rockcompiled from domestic and international literature. It is equipped with functions of data
retrieval that match assigned conditions and conducting regression analysis for a data group(Tachi et al., 2009).
・ Diffusion database (JAEA-DDB): Data on effective diffusion coefficients for different rocks
found in Japan compiled from the literature (Tochigi & Tachi, 2009, 2010).
・ Glass dissolution database (GlassDB): Data on glass composition, test methods, solution
chemistry, co-emplaced material and constituents, alteration products, testing conditions, test
results, etc. compiled from the literature (Hayashi et al., 2005).
・ Environmental migration data: Collection of parameters on the mobility of nuclides in rice
fields and soil (Kd) and the fractions of nuclides that are transferred to agricultural products(TF) (NIRS 2008, 2009, 2010).

100

Figure 7-6 Application of sorption database (SDB) for setting Kd value (from Tachi et al., 2009)

Sorption and diffusion databases are derived systematically, taking into account the assessment ofdata of differing quality in terms of experimental conditions, traceability and the reliability (Ochs etal., 2008). Guidelines consisting of multiple decision criteria were established for evaluating
reliability.
Studies were also conducted on how to define parameters using the developed databases. Since theH12 report, in order to improve the reliability of parameter settings, a method for correcting the datafor different environmental conditions has also been developed. For example, after extracting data on
distribution coefficients with a certain level of reliability, data are corrected based on the difference
between the experimental conditions when the data were obtained and the geological environment
conditions assumed in the safety assessment. Such a correction method has been validated forsorption behavior of Cs in sedimentary rocks; Cs is one of the major radionuclides for safetyassessment. It was shown that, based on a correction considering illite content and Na ions, theresults were roughly consistent with the experiments (Ochs et al., 2008).
For TRU waste, sorption distribution coefficients are defined for different alteration zones in the
cement-based materials for a range of pH values (Mihara & Sasaki 2005). With regard to the effectof nitrate on backfill and buffer materials, the second TRU report defined sorption distribution
coefficients for relevant nuclides, considering the nitrate reduction process by mineral and microbial
influence on the nitrate transformation scheme. It is appropriate to consider such effects as thosedescribed in the report (NUMO, 2011a).
Based on these results, fundamental information for preparing datasets for analyzing radionuclidetransport was improved.
1017.4 Conclusions of chapter 7This chapter described the basic strategy for stepwise assessment of the long-term safety of thegeological disposal system at an actual site. It also presented the different technologies that NUMO
and fundamental R&D organizations have developed aimed at realistic evaluation of a range of
geological environments and design options from the perspective of long-term safety since the H12report. Based on these activities, the reliability of the technologies that support the long-term safetyassessment has been improved further in terms of response to the variability and long-term evolutionof the geological environment, to different design options and incorporation of updated knowledge.
In close coordination with R&D ongoing in fundamental R&D organizations, NUMO will continue
its effort to improve the reliability of the long-term safety assessment technologies.

102

8 . Technical activities during the Literature Survey andPreliminary Investigation stages
This chapter summarizes the descriptions provided in the previous chapters. The procedures for the
Literature Survey (LS) stage and the Preliminary Investigation (PI) stage, as well as themethodologies required in these stages, will be described.
Figure 8-1 shows how the chapters in this report are structured.
Two cases are expected for initiating the LS stage: a volunteer application from a municipality or arequest made by the national government to municipalities to come forward. Although the two cases
may be different before initiating the LS, the technical procedures thereafter will be the same. This
report assumes an application made by a municipality, if not specifically mentioned otherwise.

103

Chapters 2 Background to the geologicaldisposal project
Chapters 3

Safety measures

Strategies for ensuring safety
Project
Implementation

Policies and policy
breakdowns for project
impementation

Selection andconfirmation of asuitable site

Appropriate engineered
measures for design andconstruction ofa repository

Assessment oflong term safetyof the repository

Chapters 4 Staged project implementation

Technical outlook of the project
implementation

Chapters 5

Chapters 6

Chapters 7

Investigation andevaluation technologies
for the geologicalenvironment

Technologies for design,
construction, operationand closure of therepository

Technology for long‐term
safety assessment

Technology

Development of the technologies
for safe geological disposal

Chapters 8 Technical activities during the Literature Survey andPreliminary Investigation stages

Site selection procedure by interaction of threesafety measures

Figure 8-1 Structuring of the chapters in this report

8.1 Site selection process from public solicitation and start of the LS to theselection of DIAs
The key milestones during the project are the three steps for site selection (LS stage, PI stage and DI
stage) and the subsequent project licensing. The sequence of project activities and technical activities
in the stages from public solicitation to the PI stage are shown in Figure 8-2.
When an application is received, NUMO will check the geological conditions before initiating a104

literature survey to confirm that:・ No active faults documented in the literature based on a nationwide investigation using
interpretation of aerial photographs for inland areas and marine acoustic exploration formarine areas are present and・ No area within 15 km of the center of a Quaternary volcano is included, considering thepotential extent of magma activity tens of thousands of years in the future.
The results of the advance check will be sent to the mayor of the applying municipality. A literature
survey will not be conducted for areas that do not meet the above confirmation points.
After explainng the LS plan to the relevant municipality, the LS will be initiated to check whether or
not the area satisfies the basic criteria for selecting PIAs. If the criteria are not met, the area will not
be considered as a PIA. If they are met, statutory reports compiling the investigation results will be
published in each site selection stage and submitted to the mayors of the applicant municipalities andthe relevant prefectural governor for inspection. Briefing sessions will also be held and NUMO will
respond to comments or questions submitted on these occasions. Based on these procedures, NUMO
will select investigation areas for the subsequent stage and submit an application for the modified
implementation plan to METI. METI will collect opinions from the prefectural governor and mayorsof the municipalities. Respecting their opinions, and consulting with the Japan Atomic Energy
Commission (AEC) and the Nuclear Safety Commission (NSC), METI will determine the revisionof the final disposal program; this will be finalized in a cabinet meeting. The modification of theimplementation plan will be authorized via the process mentioned above and the first stage of the site
selection process will be completed. In parallel with this, NUMO will prepare a plan for the next
preliminary investigation (PI) stage.
In the PI stage, DIAs will be selected following a similar procedure and an application for themodified implementation plan will be submitted to METI. METI will collect opinions from theprefectural governor and mayors of the municipalities. Again respecting their opinions, andconsulting with AEC and NSC, METI will determine the revision of the final disposal program
which will then be finalized in a cabinet meeting. The modification of the implementation plan will
be authorized via the process mentioned above and the site selection process will be completed. In
parallel with this, NUMO will prepare a plan for the next DI stage.
The processes in the DI stage will be similar.

105

Local Residents, Prefectural
Governors and Mayors

Minister of Economy, Trade andIndustry

NUMO
Decision making etc.

Technical activities

Siting factors for PIA selection

Open Solicitation

Applications
Application from Mayors

ReciptFrom application
to start of
Literature
Survey(LS)Prior Confirmation of geologicalcondition
Notification to Mayors

No Literature
surveyNo

Compliance

Yes
Application ofchanges toannual plan

Planning of LS

Approval
Explanation of Investigation Plan

Staｒt LS
Report on investigation status, if necessary

Implementation of LS

Siting Factors for the selection of PIAs

Notification to Mayors

No

Not PIAs

Literature
Survey(LS)stageCompliance

Yes

Send to Prefectural Governors and Mayors
Public announcement/inspection
Hold Briefing

PIAs selection report
Selection of PIAs
(Selection that gives
consideration to opinions
of local residents, etc.)

Opinion report

Send opinion outline and NUMO's view

Opinions ofGovernors andMayorsApplication ofchanges to
Implementation
Plan

Revision of Final Disposal Plan
(Cabinet decision)・Respect opinion of Governors/
Mayors・Opinions of Atomic Energy
Commission
・Opinions of Nuclear Safety
Commission

Siting factors for the selection of DIAs

Approval of changes toimplementation

Complete
Selection

Planning of PI

Explanation of Investigation Plan

Staｒt PI

Report on investigation status, if necessary

Implementation of PI

Siting factors for the selection of DIAs
Notification to MayorNo

Not DIAs
Send to Prefectural Governors and Mayors
Public announcement/inspection
Hold Briefing

Preliminary
Investigation(PI)stage

Compliance

Yes
DIAs selection report
Selection of DIAs
(Selection that gives
consideration to opinions
of local residents, etc.)

Opinion report

Send opinion outline and NUMO's view

Revision of Final Disposal Plan

Opinions ofGovernors andMayors(Cabinet decision)・Respect opinion of Governors/
Mayors・Opinions of Atomic Energy
Commission
・Opinions of Nuclear Safety
Commission

Approval of changes toimplementation

Detailed
Investigation(DI)stage

Application ofchanges to
Implementation
Siting factors for the selection of DI

Complete
Selection

Planning of DI

Continued

Continued

Licenseapplication

Safety review stage

Figure 8-2 Sequence of activities in the LS and PI stages(for the case of formal volunteering)106

8.2 Literature Survey stage
8.2.1 Activities in the Literature Survey stage
In the LS stage, the goal is to select PIAs and achieve the goals relevant to safety assurance, such as
avoiding significant impacts from natural phenomena (avoiding clearly unsuitable areas: see section
4.3).
In this stage, the area for which the LS will be performed will be determined. If necessary, additional
investigation areas around the PIA will be selected to acquire data on volcanic/igneous activity,
seismic/fault activity and uplift/erosion in order to evaluate the effects of these natural events andgeoenvironmental characteristics on the PIA.
Based on an LS manual, literature and documents are compiled systematically to manage theinformation on the geological environment and other relevant information. Information to becollected includes that relevant to the impacts of natural phenomena, geological environment
characteristics, the natural environment and the social environment.
Determining the impacts of natural phenomena involves investigating volcanic/igneous activity,
uplift/erosion, unconsolidated Quaternary sediments and mineral resources.
With regard to the site descriptive models, conceptual models of the geology/geological structure
will be developed first based on geological structure development history and then conceptualmodels of the geological environment characteristics, including hydrology, groundwater chemistry
and rock mechanical properties, will be developed. Based on the conceptual models, the site
descriptive model will be developed to quantitatively represent and visualize information onhydrology, groundwater chemistry, rock properties (physical, mechanical and thermal) and masstransport properties.
The evaluation of the long-term evolution of the geological environment characteristics involves
analyzing how current geology will evolve within the developed site descriptive model. This will use
the results of the investigation/evaluation of impacts from natural phenomena, interpretation of thegeological structure development history and assessment of changes in the hydrogeologicalenvironment using a paleogeological approach.
Based on the evaluation of the long-term evolution of the geological environment characteristics andthe impacts of natural events, information on the potential PIAs is compared to the siting factors forthe selection of PIAs and any areas that clearly do not meet these criteria will be excluded. The
results will be compiled as a statutory report on site selection.
During the preliminary review of the repository concept, the applicability of the design of the107

engineered barriers and the repository as a whole will be assessed based on the site descriptive model.
In addition, in order to reflect this in the PI program and design studies in the subsequent stage, theengineering feasibility, economic efficiency and construction schedule for the project will also becomprehensively evaluated to identify investigation parameters and design issues for the subsequent
stage.
In the preliminary review of safety, based on the limited volume of information on the geologicalenvironment obtained during the LS, the performance of the host rock as a natural barrier will be
evaluated based on a preliminary safety assessment of the design, emphasizing the conservativenessof the engineered barriers.
The preliminary development of repository concepts will be compiled in the form of an overview of
the repository based on literature information, based on the preliminary review of the repository andpreliminary review of safety.
The statutory report on the LS and the description of the repository based on LS will be made public
and will be available for inspection in the affected areas; briefing sessions will also be held in therelevant prefectures. Comments on the report will be compiled and NUMO will respond to these.
Figure 8-3 shows the flow of the processes in the LS stage.

108

Activities during Literature Survey (LS) stage
Decision making etc.

Investigation and evaluation of geological environment

Open Solicitation

Siting factors for PIA selection of the PIAs

Repository Design

Safety Assessment

Recipt ofApplication

Preparation of
Literature
SurveyPrior Confirmation of geological conditionNo

No Literature
surveyCompliance

Yes
Application ofchanges toannual plan

Planning of LS

Staｒt LS

Implementation of LS(Collection of literature information)

Evaluation Impacts ofnaturel phenomena

Site descriptive model

Long‐term evaluationof geological evolution
Provisional study on
Repository

Literature Survey

Qualitative study on
safetySend，Publicannouncement/inspec
tion
Hold Briefing

Check compliance with the siting
factors for the selection of PIAs

Provisional Repository

PIAs selection report

Prescription of Repository based on Literature
Information

Selection of PIAs
(Selection that gives
consideration toopinions of local
residents, etc.)

Application ofchanges to
Implementation Plan

Selection
Siting factors for the selection of DIAs

Requirements for Geologicalinvestigationas and evaluations

Preparation of thenext stage

Requirements for Repository
designRequirements for Safety
Assessment

Planning of PI

Safety important documentation

Decision

Work flow

Main activities

Technical work

Feedback

Figure 8-3 Sequence of activities in the LS stage (for the case of volunteer application)

109

In the PIA (bounded by the dotted/dashed line in Figure 8-4), investigation and evaluation of thegeoenvironmental characteristics will be the main tasks. In the supplementary investigation area(bounded by the dotted line), impacts due to natural events, particularly volcanic/igneous activity,
seismic/fault activity and uplift/erosion, and evolution of the regional geological structure will be
investigated. Figure 8-4 shows the schematic setting of a PIA and the supplementary investigation
areas.
Literature
Survey area

Area within 15km
radius of the centerof a Quaternary
volcano that falls
under the NEF

Volunteer area

Geomorphic surface
where uplift canbe
quantifed(A case that is notincluded in the PIA.)

Zone affected bythermaland hydrothermal
activity identified
by specificliterature surveys

PIA(including
volunteer area )Supplementary
investigation area
Active fault that falls
under the NEF

Active fault identified by
specific literature surveys

Figure 8-4 Setting of PIAs and supplementary investigation areas(for the case of volunteer application) (from NUMO, 2004b)

・ PIAs will be selected via the process discussed below: Areas where active faults or igneous
activity as defined in the evaluation factors for qualification (see below) are found will be
excluded from potential PIAs.
・ Potential PIAs may be larger than the volunteer area, depending on the relative location ofactive faults or igneous activity zones, but the area not included in the volunteer area will be
subjected only to preliminary investigation. NUMO will not select anywhere outside the PIA
as a repository site
・ The area around PIAs may be investigated for more detailed characterization of the PIAs.
8.2.2 Siting factors for the selection of PIAs
The siting factors for the selection of PIAs are factors to be evaluated in selecting PIAs based on the
Final Disposal Act considering the guideline “Environmental Factors to be Evaluated in Selecting
Preliminary Investigation Areas for the Disposal of HLW” (NSC, 2002).
The siting factors for the selection of PIAs consist of evaluation factors for qualification (EFQ) andfavorable factors (FF).
EFQ define the conditions of areas to be excluded as PIAs. The suitability of areas that apply as PIAs
will be evaluated in terms of factors related to earthquake/fault activity, uplift/erosion,
unconsolidated Quaternary sediments and mineral resources, based on the LS for each applicant area
and their surrounding areas.
110Specifically, the evaluation factors for qualification for this stage are:・ No record of significant tectonic movement due to natural phenomena such as earthquakes
・ Low likelihood of significant movement due to natural phenomena such as earthquakes far
into the future
・ No record of unconsolidated Quaternary sediments in the potential repository area (to be
specified by ministerial ordinance of METI)・ No record of valuable mineral resources in the potential repository area (to be specified byministerial ordinance of METI)
Favorable factors were also defined for areas not excluded from selection as PIAs based on the EFQ,
in accordance with the requirement that NUMO should also consider the economic and operational
efficiency of the project on the premise that safety has been assured (MITI, 2000). Areas wherecompliance with the EFQ is confirmed will be compared with each other in terms of factors related
to (1) properties and characteristics of the geology, (2) groundwater characteristics, (3)investigation/evaluation of the geological environment, (4) potential natural hazards during
construction and operation, (5) land acquisition and (6) transportation.

8.3 Preliminary Investigation stage
8.3.1 Activities in the Preliminary Investigation stage
For the PI stage, the goal is to select DIAs and meet the goals relevant to assuring safety, such as
avoiding significant impacts from natural phenomena, the prospect of ensuring long-term safety andthe prospect of ensuring safety during the project duration (avoiding clearly unsuitable areas: seesection 4.3).
The PIs are conducted in two phases: surface investigations and borehole investigations.
The implementation of surface investigations includes confirmation of LS results at the sites toroughly understand the geological environment of the PIAs and investigation of topography andgeology from the surface by reconnaissance and trench surveys and geophysical exploration (aerial,
ground surface and marine) to obtain information for planning of the borehole investigation phase.
Based on the findings from the surface investigations, investigation/evaluation of the impacts ofnatural events including volcanic/igneous activity, seismic/fault activity and uplift/erosion will be
performed. According to rock type, lithofacies, stratigraphy, distribution of fractures, fracture
conditions and weathering/alteration level and geostructural elements (rock body, strata, faults and so111on) will be categorized, the results from the LS will be evaluated and the geostructural model will be
updated. Using the updated model, the geoenvironmental model, including hydrogeological structure,groundwater chemistry and rock mass characteristics, will be updated. The updated
geoenvironmental model will provide an understanding of the evolution of the geological structure.
Forecast of geoenvironmental evolution based on a paleogeological approach will be used toevaluate the long-term evolution of geoenvironmental conditions.
In the borehole investigation phase, data on the deep underground not available from the surface
investigations will be acquired. Based on data from the surface and borehole investigations,volcanic/igneous activity, earthquake/fault activity and uplift/erosion will be investigated andevaluated.
Geological and structural elements (rock bodies, strata and structural discontinuities such as faults)
are classified and characterized based on information such as rock types, rock facies, stratigraphy,
fracture distribution, deformation, degrees of weathering and alteration obtained from the surface andborehole investigations. These are compared with of the information from the Literature Survey
stage to update the geological model. The hydrogeological model, hydrochemical model and rockmechanical model are also revised based on the updated geological model and the results ofhydrological, hydrochemical and rock mechanical investigations.
The evaluation of the long-term evolution of the geological environment characteristics involves
analyzing how current geology will evolve within the updated site descriptive model. This will use
extended results of the investigation/evaluation of impacts from natural phenomena, interpretation of
the geological structure development history and assessment of changes in the hydrogeologicalenvironment using a paleogeological approach.
In the confirmation of suitability referring to the siting factors for the selection of DIAs to be
described later, it will be checked whether or not unsuitable areas are included in the potential DIAs
based on data obtained by the PI. The results will be compiled as the statutory report on PIs.
The selection of potential host rocks involves evaluating suitability based on site descriptive models
and data on long-term evolution of the geological environment. Suitability as a host rock will be
evaluated in terms of thermal environment, mechanical regime, hydrological regime, chemical
environment, size of the rock mass, schedule, economic efficiency, etc. Potential host rocks for therepository site in the subsequent stage will be selected from those determined as being suitable.
Based on the site descriptive model and the characteristics of the host rock, the conceptual design ofthe repository will be performed. This involves defining the location of the underground facility(depth and area), designing the engineered barriers (e.g. materials and structure), defining thespecifications of tunnels (e.g. vault diameter, support and tunnel spacing) and defining the basic
112

layout of the underground facility (e.g. configuration, number and layout of the disposal panels andaccess method), as well as designing the surface facility. Regarding the disposal concept, technicaloptions will be narrowed down based on the geological environment, the feasibility of theconstruction schedule and economic aspects.
Based on the site descriptive model and conceptual design of the repository, the preliminary safetyassessment involves assessing cases based on scenarios, models and datasets to be developed
separately.
The development of a reference repository concept involves compiling the results of the conceptual
design of the repository and the preliminary safety assessment and integrating them into a repository
concept; this is supported by a report on conceptual design and preliminary safety assessment basedon the PI.
As in the case of selection of PIAs, a statutory report based on PI and a report on preliminary
repository design and preliminary safety assessment based on the PI will be made public, opened forinspection in affected areas and briefing sessions held in the relevant prefectures. Comments on thereport will be compiled and NUMO will respond to them.
Figure 8-5 shows the sequence of activities in the PI stage.

113

Activities during Preliminary Investigation (PI) stage
Decision making etc.

Repository Design

Investigation and evaluation of geological environment

Safety Assessment

Staｒt PI
Implementation of PI (Surface based )Surface based
investigaton
phase

Evaluation of Impactsof naturel phenomena

Construction of Sitedescriptive model

Long‐term evaluation ofgeological environment
conditions

Requirements for
Repository design

Requirements for Safety
Assessment

Planning of Borehole investigaton phase during PI

Implementation of PI(Borehole investigaton etc.)

Impacts of naturel
phenomena の評価

Site descriptive model

Long‐term evaluationof geologicalenvironment
conditions

Selection of potential host rock

Preliminary Repository Design

Borehole
investigaton
phase

Preliminary Safety Assessment

Siting factors for the selection of DIAs
Establishment of Reference repository concept

Send，Publicannouncement/inspe
ction
Hold Briefing

Report on repository concept and safety assessment based on PI
information

Report on selection of DIAs

Selection of DIAs
(Selection that gives
consideration toopinions of local
residents, etc.)

Application ofchanges to

Selection(Approv
al of changes)

Siting Factors for the selection of DI

Preparation of
the next stage

Requirements for Geologicalinvestigationas and evaluations

Requirements forrepository design

Planning of DI

Safety important documentation

Decision

Work flow

Main activities

Technical work

Feedback

Figure 8-5 Sequence of activities in the PI stage

114

Requirements for Safety
Assessment

8.3.2 Siting factors for the selection of DIAs
In selecting DIAs, on the premise of ensuring safety during the project duration, the emphasis in theevaluation will be on compliance with the evaluation factors for qualification as specified in the Final
Disposal Act. Since the selection of DIAs is the intermediate stage in the siting process, siting factors
for the selection of DIAs should be established considering not only the evaluation factors for
qualification for this stage, but also requirements for the subsequent repository site selection stage as
specified in the Final Disposal Act.
Evaluation factors for qualification for this stage are:・ No significant tectonic activity due to natural phenomena such as earthquakes has occurred in
the geology of concern for a long period of time・ There are no difficulties in terms of excavation in the geology of interest
・ Any active fault, fracture zone or groundwater flow found in the geology of interest isunlikely to have adverse impacts on tunnels or other subsurface facilities
・ Other requirements as specified in a ministerial ordinance of METI
Tectonic activity, including earthquake/fault activity, volcanic/igneous activity and uplift/erosion will
be evaluated. Regarding difficulties in tunnel excavation, the requirements for judging feasibility will
be evaluated from the perspective of ensuring safety during each project stage.
If there are highly permeable zones (water flowpaths) such as large-scale fracture zones, shallow or
deep groundwater could reach the repository location via these flowpaths, with the result thatgroundwater flow characteristics, geochemistry and thermal properties could have a significant
impact on the barrier functions of the underground facility. Therefore, compliance with theevaluation factors for qualification for DIAs will be evaluated from the point of view of impacts ofgroundwater flow on the underground facility.
Detailed investigations, including construction of the underground investigation facility, require alarge investment of time and money. From the implementer’s point of view, it is therefore necessary
to ensure that the DIA selection process is not only safe but also feasible in terms of project
implementation. Regarding the characteristics of the DIAs from various viewpoints such as
post-closure safety, feasibility of construction and safety assurance during operation, reduction ofadverse impacts on the environment, acquisition of the land, securing of financial aspects andschedule, factors that are not required by the law (geoenvironmental characteristics, naturalenvironment, and social environment) will be evaluated. This allows confirmation of compliancewith the requirements and an assessment of the feasibility of geological disposal.
The siting factors for the selection of DIAs will be specified and published before starting the DIA
115

selection stage, taking into account discussions in committees within AEC.

8.4 Conclusions of chapter 8This chapter describes the LS stage and the PI stage stages as shown below, indicating that
preparations for implementing these stages have been achieved from a technical viewpoint:・ The goals and activities for implementing LS and PI have been clarified
・ Fundamental implementation procedures for selecting PIAs and DIAs have been prepared bycoordinating investigation/evaluation technologies for the geological environment,
technologies for design, construction, operation and closure of the repository andtechnologies for long-term safety assessment
・ The applicability of the technologies presented in chapters 5 through 7 has been checked inaccordance with the implementation procedure in each stage.

116

9 . Conclusions
Important issues in implementing the geological disposal project are to ensure both long-term safety
after closure of the repository as well as safety during the project duration. NUMO therefore
established two goals, namely ensuring long-term post-closure safety and ensuring safety during the
project implementation.
The activity of the waste inventory will decay with time, but its potential effect on the environment
will remain for a very long period of time. It therefore has to be confirmed that there will be noharmful effect on future generations during tens of thousands of years following completion of the
project. This will require detailed investigations during site selection, to ensure that a stablegeological environment is selected and to confirm that the radioactive materials are safely confinedand isolated using a multi-barrier system consisting of engineered and natural barriers. In
implementing the project, both safety during the project implementation and long-term post-closure
safety will be checked iteratively in each of the construction, operational and closure stages.
Implementation of the geological disposal project will extend over approximately 100 years. Such along project duration requires provisions to allow modification of the project plan as appropriate inorder to reflect advances in technologies and social changes.
NUMO will implement the project in accordance with three policies for ensuring safety: Policy 1:
Staged and flexible project implementation based on iterative confirmation of safety; Policy 2:
Project implementation based on reliable technologies and Policy 3: Technical activities for building
confidence in NUMO’s safety concept. NUMO has established specific measures for implementing
each policy; these are described in the roadmaps for appropriate implementation in each stage of the
project.
With regard to the technologies that support safe geological disposal, it is important to use the best
available technologies at the time in each stage. NUMO has been systematically developing
technologies in collaboration with fundamental R&D organizations since its establishment in 2000,
so that these will be available when required. NUMO will continue to develop technologies aimed atachieving safe geological disposal, as well as improving the economy and efficiency of
implementation and integrating the results of both NUMO and fundamental R&D organizations toestablish systematic technologies required for the project.
The NUMO 2010 Technical Report and this report describe the up-to-date results of R&D on
technologies that support safe geological disposal carried out with the support of organizations suchas the Japan Atomic Energy Agency (JAEA), the Radioactive Waste Management Funding andResearch Center (RWMC), the National Institute of Advanced Industrial Science and Technology
117

(AIST), the Central Research Institute of Electric Power Industry (CRIEPI), the National Institute ofRadiological Science (NIRS), the Federation of Electric Power Companies of Japan (FEPC) andJapan Nuclear Fuel Limited (JNFL).
The H12 report demonstrated that the technical basis for the safe implementation of the geologicaldisposal project has been established. On this basis, technologies for the implementation of the
project have made steady progress in the following areas since NUMO’s establishment:(1) Technologies that allow more realistic investigation /design /safety assessment(2) Practical technologies for systematic site selection(3) Technologies that allow response to a range of geological environments during
investigation /design /safety assessment
The progress of these technologies has contributed to improving the technical reliability of theimplementation of the project and specific technologies for the LS stage and subsequent PI stage
have been prepared. Technologies for implementing the repository site selection stage andsubsequent stages have also been developed. In close cooperation with the fundamental R&D
organizations, NUMO will continue its efforts in this area, focusing on site-specific issues andtechnologies required in the stages after the PI stage, with the aim of further improving reliability.
The key content of the NUMO 2010 Technical Report is summarized in this report. In preparing thisreport, constructive comments and input were provided by many experts and organizations, including
NUMO’s Technical Advisory Committee and fundamental R&D organizations. The report was also
reviewed by third parties such as the Atomic Energy Society of Japan and experts from othercountries. This report was finalized to reflect the review comments.

118

REFERENCES
ANDRA (2005): Dossier 2005 Argile.
Advisory Committee for Natural Resources and Energy (2006): Radioactive Waste Subcommittee
report, Subcommittee on Radioactive Waste, Advisory Committee for Natural Resources andEnergy. (in Japanese)
Advisory Committee for Natural Resources and Energy (2007): Interim Report on the Enhancementof the Activities to Promote the Final Disposal, Subcommittee on Radioactive Waste,
Advisory Committee for Natural Resources and Energy. (in Japanese)
AEC (Atomic Energy Commission of Japan) (1997): Guideline on Research and Development
Related to Geological Disposal of High-level Radioactive Waste in Japan, Advisorycommittee on Nuclear Fuel Cycle Backend Policy. (in Japanese)
AEC (Atomic Energy Commission of Japan) (1998): Basic Concept of High-Level Radioactive
Waste Disposal, Special Committee on Disposal of High-Level Radioactive Waste (Special
Committee) of the Atomic Energy Commission of Japan. (in Japanese)
AEC (Atomic Energy Commission of Japan) (2005): Framework for Nuclear Energy Policy, AEC
decision on 11 Oct. 2005 (2005). (in Japanese)
AEC (Atomic Energy Commission of Japan) (2000) : Review of the H12: Project to Establish the
Scientific and Technical Basis for HLW Disposal in Japan, Advisory Committee on Nuclear
Fuel Cycle Backend Policy, Atomic Energy Commission of Japan, 11th Oct. 2000. (inJapanese)
AEC (Atomic Energy Commission of Japan) (2008): Evaluation of the Basic Concept ofApproaches to the Treatment and Disposal of Radioactive Waste, Specified in the
Framework for Nuclear Policy, Policy Evaluation Committee of the Japan Atomic Energy
Commission. (in Japanese)
AIST (National Institute of Advanced Industrial Science and Technology) (2010): Development ofTechnologies for Characterizing Saline/fresh Groundwater Interface and Faults at Coastal
Areas, FY 2011 report on the national research project on geological disposal. (in Japanese)
ANRE (Agency for Natural Resources and Energy), JAEA (Japan Atomic Energy Agency) (2010):
Fundamental R&D Program for the Geological Disposal of HLW and TRU. (in Japanese)
Aoyagi, Y. and Abe, S. (2009): Discovery of Source Fault in the region without no obvious active
fault - Geophysical Survey in the Source Area of the 1984 Western Nagano Prefecture
Earthquake -, CRIEPI Civil Engineering Research Laboratory Rep.No.N09038. (in Japanese)
Chapman, N., Apted, M., Beavan, J., Berryman, K., Cloos, M., Connor, C., Connor, L.,Ellis, S.,
Jaquet, O., Kiyosugi, K., Litchfield, N., Mahony, S., Smith, W., Sparks, S., Stirling, M.,
Villamor, P., Wallace, L., Goto, J., Miwa, T., Tsuchi, H. and Kitayama, K. (2009a) :Development of Methodologies for the Identification of Volcanic and Tectonic Hazards toPotential HLW Repository Sites in Japan,-Summary Report -, NUMO-TR-09-03.
Chapman, N., Apted, M., Beavan, J., Berryman, K., Cloos, M., Connor, C., Connor, L., Jaquet, O.,
Litchfield, N., Mahony, S., Smith, W., Sparks, S., Stirling, M. and Wallace, L. (2009b) :Development of Methodologies for the Identification of Volcanic and Tectonic Hazards toPotential HLW Repository Sites in Japan,-The Tohoku Case Study-, NUMO-TR-08-03.

119Commettee for Geosphere Stability Research (2011)： Geological Leaflet 4, Japanese Island-arc andGeosphere Stability, The Geological Society of Japan. (in Japanese)
Committee for the Catalogue of Quaternary Volcanoes in Japan (1999): Catalogue of Quaternary
Volcanoes in Japan, v 1.0 (CD-ROM), Volcanol. Soc. Japan. (in Japanese)
Ebashi, T., Ishiguro, K., Wakasugi, K., Kawamura, H., Gaus, I., Vomvoris, S., Martin, A. J. andSmith, P. (2010): Trends in Scenario Development Methodologies and Integration in
NUMO’s Approach, Proceedings of the 13th International Conference on Environmental
Remediation and Radioactive Waste Management (ICEM2010), ICEM2010-40124.
FEPC (The Federation of Electric Power Companies and Japan Nuclear Fuel Cycle Development
Institute), JNC (Japan Nuclear Cycle Development Institute) (2005a): Technical Report on
Disposal Technologies for TRU waste (Supporting Document) FEP dictionary. (in Japanese)
FEPC (The Federation of Electric Power Companies and Japan Nuclear Fuel Cycle Development
Institute), JNC (Japan Nuclear Cycle Development Institute) (2005b): Second Progress
Report on Research and Development for TRU Waste Disposal in Japan - Repository Design,
Safety Assessment and Means of Implementation in the Generic Phase, JNC TY1400
2005-013, FEPC TRU-TR2-2005-02. (in Japanese)
Fujiwara, O., Sanga, T. and Ohmori, H. (1999): Regional Distribution of Erosion Rates Over theJapanese Islands, JNC Technical Review, No.5, pp.85-93. (in Japanese)
Hataya, R., Yanagida, M. and Sato, M. (2009): Study on characterisation of Quaternary Tectonic
Movement by Uplift Estimation Using Fluvial Terraces, Stability and Buffering Capacity of
the Geosphere for Long-term Isolation of Radioactive Waste: Application to Crystalline
Rock, Workshop Proceedings, Manchester, United Kingdom, 13-15 November 2007,
OECD/NEA No.6362, pp.217-225.
Hayashi, M., Satake K., Yoshikawa, H., Yui, M. (2005): Development of Glass Dissolution
Database, JNC TN8400 2005-008. (in Japanese)
IAEA (2006): Geological Disposal of Radioactive Waste, Safety Requirements, IAEA Safety
Standard Series No. WS-R-4, International Atomic Energy Agency.
IAEA (2011): Disposal of Radioactive Waste, SSR-5, International Atomic Energy Agency.
Inagaki, Y., Mitsui, S., Makigaki, H., Idemitsu, K., Arima, T., Banba, T. and Noshita, K. (2009):
Measurement of HLW Glass Dissolution/Alteration Kinetics by Using Micro-Reactor
Flow-through Test method, Scientific Basis for Nuclear Waste Management XXXIII, MRS.
Inagaki, Y., Makigaki, H., Mitsui, S., Idemitsu, K., Arima, T. and Noshita, K. (2010): Initial
Dissolution rate of P0798 Simulated HLW Glass as a Function of pH and Temperature
Measured by Using Micro-Reactor Flow-through Test, American Ceramic Society, Glassand Optical Material Division.
Iriya K. and Mihara M. (2003): Development of low-pH concrete with high pozzolan containment,
Concrete Research and Technology Vol.25, No.1, pp.185-190. (in Japanese)
Ishiguro, K., Ueda, H., Wakasugi, K., Sakabe, Y., Kitayama, K., Umeki, H. and Takase, H. (2007):EBS Modelling for the Development of Repository Concepts Tailored to Siting
Environments, Engineered Barrier Systems (EBS ) in the safety case: The role of modeling,
Workshop proceedings La Coruna, 24-26 August 2005, OECD/NEA.
JNC (Japan Nuclear Cycle Development Institute) (2000a): H12: Project to Establish the Scientificand Technical Basis for High-Level Radioactive Waste Disposal in Japan: Second Progress120

Report on Research and Development for the Geological Disposal of HLW in Japan, Project
Overview Report, JNC TN1410 2000-001.
JNC (Japan Nuclear Cycle Development Institute) (2000b): H12: Project to Establish the Scientificand Technical Basis for High-Level Radioactive Waste Disposal in Japan: Second Progress
Report on Research and Development for the Geological Disposal of High-Level
Radioactive Waste in Japan, Supporting Report 1 Geological Environment in Japan, JNC
TN1410 2000-002.
JNC (Japan Nuclear Cycle Development Institute) (2000c): H12: Project to Establish the Scientificand Technical Basis for High-Level Radioactive Waste Disposal in Japan: Second Progress
Report on Research and Development for the Geological Disposal of High-Level
Radioactive Waste in Japan, Supporting Report 2, Repository Design and Engineering
Technologies, JNC TN1410 2000-003.
JNC (Japan Nuclear Cycle Development Institute) (2000d): H12: Project to Establish the Scientificand Technical Basis for High-Level Radioactive Waste Disposal in Japan: Second Progress
Report on Research and Development for the Geological Disposal of High-Level
Radioactive Waste in Japan, Supporting Report 3, Safety Assessment of the Geological
Disposal System, JNC TN1410 2000-004.
JNC (Japan Nuclear Cycle Development Institute) (2000e): H12: Project to Establish the Scientificand Technical Basis for High-Level Radioactive Waste Disposal in Japan: Second Progress
Report on Research and Development for the Geological Disposal of High-Level
Radioactive Waste in Japan, Supplementary Report: Background of Geological Disposal.,JNC TN1410 2000-005.
JSCE (Japan Society of Civil Engineers) (2001): Geological Factors to be Considered in the
Selection of Preliminary Investigation Areas for HLW Disposal., Sub-committee of theUnderground Environment, Civil Engineering Committee of the Nuclear Facilities, Japan
Society of Civil Engineers .(in Japanese)
JSCE (Japan Society of Civil Engineers) (2006): Geological Factors to be Considered in the
Selection of Detailed Investigation Areas for HLW Disposal., Sub-committee of theUnderground Environment, Civil Engineering Committee of the Nuclear Facilities, Japan
Society of Civil Engineers .(in Japanese)
Kanzaki, Y., Takeda, S., Kimura, H. (2009): FEP database for Scenario Construction on
Groundwater Migration in Safety Assessment for a Geological Disposal of High-Level
Radioactive Waste (Contract research), JAEA-Data/Code 2009-011. (in Japanese)
Koike, K. and Machida, H. (eds.) (2001): Atlas of Quaternary Marine Terraces in Japanese Islands(CD-ROM and attached mapps), University of Tokyo Press. (in Japanese)
Kitamura, A., Fujiwara, K., Doi, R., Yoshida, Y., Mihara, M., Terashima, M. and Yui, M. (2010):
JAEA Thermodynamic Database for Performance Assessment of Geological Disposal of
High-level Radioactive and TRU Wastes, JAEA-Data/Code 2009-024.
Kondo, H. (2009): Regional-scale volcanology in support of site-specific investigations, Volcanic
and Tectonic Hazard Assessment for Nuclear Facilities, edited by Connor, C., Chapman, N,
Connor, L., Cambridge University Press, pp.307-325.
Kondo, H., Kiho, K., Goto, K., Hasegawa, T., Hamada, T., Oyama, T., Suzuki, K., Goto. K.,
Suenaga, H., Nakata, K., Tanaka, S., Nagaoka, T., Kubota, K., Tsuchi, H., Miwa, T.,
Muramoto, T., Kawano, K. and Ito, H. (2011): Verification study on Technology for
Preliminary Investigation -Applicability and Isses of Methods for Borehole Drilling and121

Tests in Considerations of Geological Environment-, CRIEPI Civil Engineering ResearchLaboratory Rep.No.N15. (in Japanese)
Kurikami, H., Takahashi, Y., Yoshizawa, Y., Miwa T., Akamura, S., Kawano, K. (2010): Study on
Monitoring and Primary Baseline for Geological Disposal of Radioactive Waste,
NUMO-TR-10-01. (in Japanese)
Martin, A., Umeda, K., Conner, C., Weller, J., Zhao, D. and Takahashi, M. (2004): Modeling
Long-term Volcanic Hazards Through Bayesian inference: An Example from the Tohoku
Volcanic Arc Japan, J. Geophys. Res., Vol.109, B10208, 20p, doi:10.1029/2004JB003201.
METI (Ministry of Economy, Trade and Industry) (2008): Plan of the Final Disposal of Specified
Radioactive Waste, Cabinet approval on 14 March 2008. (in Japanese)
METI (Ministry of Economy, Trade and Industry) (2011): Introduction of Overseas Geological
Disposal Programs. (in Japanese)
Mihara, M. and Sasaki, R. (2005)：Radionuclide Migration Datasets (RAMDA) on Cement,
Bentonite and Rock for the TRU Waste Repository in Japan, JNC-TN8400 2005-027.
MITI (Ministry of International Trade and Industry) (2000): Basic Policy for Final Disposal ofSpecified Radioactive Waste, Cabinet Approval on 29 September 2000. (in Japanese)
Miyahara, K., Inagaki, M., Kawamura, M. and Ebina, T. (2008): "What-if?" Calculations to Illustrate
Fault-Movement Effects on a HLW Repository, Proceedings of International High-Level
Radioactive Waste Management Conference, Las Vegas, Nevada, September 7-11, 2008,
pp.593-599.
Nagra (2002): Project Opalinus Clay: Safety Report, Nagra Technical Report 02-05, Nagra,
Wettingen, Switzerland.
Nakata, T. and Imaizumi, T. (eds.) (2002): 1:2,000,000 Active Fault Map of Japan, Sheet Map
Attachment to Digital Active Fault Map of Japan, University of Tokyo Press. (in Japanese)
Nakayama, M., Kobayashi, Y., Noguchi, A., Miura, N., Noda, M., Iriya, K., Hitomi, T. (2009):
Study on Application of Low Alkaline Cement in Horonobe Underground ResearchLaboratory Project (III) (Contract Research), Japan Atomic Energy Agency, JAEA-Research
2009-036. (in Japanese)
Nakayama, M., Sanada, H., Yamaguchi, T., Sugita, Y. (2008): Horonobe Underground ReseachLaboratory Project - Investigation Program for the 2008 Fiscal Year, JAEA-Research
2008-063
NIRS (National Institute of Radiological Sciences) (2008): Advanced researches on radionuclidetransfer parameters in the biosphere, H19 Fund for basic technical research surveys onradioactive waste management, Funded by METI. (in Japanese)
NIRS (National Institute of Radiological Sciences) (2009): Advanced researches on radionuclidetransfer parameters in the biosphere, H20 Fund for basic technical research surveys onradioactive waste management, Funded by METI. (in Japanese)
NIRS (National Institute of Radiological Sciences) (2010): Advanced researches on radionuclidetransfer parameters in the biosphere, H21 Fund for basic technical research surveys onradioactive waste management, Funded by METI. (in Japanese)
NSC (Nuclear Safety Commission of Japan) (2000): Basic Concept of Safety Regulation on
High-Level Radioactive Waste Disposal (First Report). (in Japanese)122

NSC (Nuclear Safety Commission of Japan) (2002): Environmental Requirements to be Consideredat the Selection of the Preliminary Investigation Areas for High-Level Radioactive Waste
Disposal. (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2002): Information Package for Open
Solititation of Volunteering for Areas to Explore the Feasibility of Constructing a Final
Repository for High-level Radioactive Waste - Repository concept (Supporting document
No.2). (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2004a): Technology and Safety ofGeological Disposal of High-level Radioactive Wastes, NUMO-TR-04-01. (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2004b): Scientific Background andPractical Application of NUMO's Siting Factors for the Selection of Preliminary
Investigation Areas, NUMO-TR-04-02. (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2009a): Information Package forOpen Solititation of Volunteering for Areas to Explore the Feasibility of Constructing a Final
Repository for High-level Radioactive Waste - Applicants Outline of the Repository Site
(Supporting Document No.1). (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2009b): Information Package forOpen Solititation of Volunteering for Areas to Explore the Feasibility of Constructing a Final
Repository for High-level Radioactive Waste - Siting Factors for the Selection of Preliminary
Investigation Areas (Supporting Document No.2). (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2009c): Information Package forOpen Solititation of Volunteering for Areas to Explore the Feasibility of Constructing a Final
Repository for High-level Radioactive Waste - Outreach Scheme (Supporting Document
No.3). (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2009d): Information Package forOpen Solititation of Volunteering for Areas to Explore the Feasibility of Constructing a Final
Repository for High-level Radioactive Waste - Open Solicitation for Candidate Sites for Safe
Disposal of High-level Radioactive Waste. (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2010): R&D Needs for Geological
Disposal Project - for the Selection of Detailed Investigation Areas -, NUMO-TR-10-02. (inJapanese)
NUMO (Nuclear Waste Management Organization of Japan) (2011a): Disposal Technologies andSafety of LLW for Geological Disposal, NUMO-TR-10-03. (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2011b): Development of Safety
Assessment Methodologies for Geological Disposal Project (I): Improvement of Scenario
Development Methodologies, NUMO-TR-10-09. (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2011c): Development of Safety
Assessment Methodologies for Geological Disposal Project ( Ⅱ ): Improvement ofRadionuclides Migration Analysis Model, NUMO-TR-10-10. (in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2011d): Earthquake Resistance
Evaluation of Geological Disposal Facility, NUMO-TR-10-13.(in Japanese)
NUMO (Nuclear Waste Management Organization of Japan) (2011e): Safety of the Geological
Disposal Project 2010 - Safe Geological Disposal Based on Reliable Technologies,
NUMO-TR-11-01. (in Japanese)123

Ochs, M., Kunze, S., Saito, Y., Kitamura, A., Tachi, Y. and Yui, M. (2008): Application of theSorption Database to Kd -Setting for Horonobe Rocks, JAEA-Research 2008-017.
OECD/NEA (1983): Long-Term Management of High-Level Radioactive Waste; The Meaning of a
Demonstration, OECD/Nuclear Energy Agency.
OECD/NEA (1991a): Can Long-term Safety be Evaluated? A Collective Opinion of the Radioactive
Waste Management Committee, OECD/Nuclear Energy Agency, and the International
Radioactive Waste Committee, IAEA endorsed by the Experts for the Community Plan of
Action in the Field of Radioactive Waste Management, CEC, OECD/Nuclear Energy
Agency.
OECD/NEA (1991b): Review of Safety Assessment Methods, Disposal of Radioactive Waste, A
Report of the Performance Assessment Advisory Group of the Radioactive Waste
Management Committee, OECD/Nuclear Energy Agency.
OECD/NEA (1997): Lessons learnt from Ten Performance Assessment Studies, OECD/Nuclear
Energy Agency.
OECD/NEA (2002): Establishing and Communicating Confidence in Safety Case of Deep Geologic
Disposal: Approaches and Arguments, OECD/Nuclear Energy Agency.
ONDRAF/NIRAS (2001): Technical Overview of SAFIR-2: Safety Assessment and Feasibility
Interim Report 2, ONDRAF/NIRAS Report NIROND 2001-05E, Belgium.
Ota, K., Abe, H., Yamaguchi, T., Kunimaru, T., Ishii, E., Kurikami, H., Tomura, G., Shimano, K.,
Hama, K., Matsui, H., Niizato, T., Takahashi, K., Niunoya, S., Ohara, H., Asamori, K.,
Morioka, H., Funaki, H., Shigeta, N., Fukushima, T. (2007): Honobe Underground ResearchLaboratory Project Synthesis of Phase I Investigations 2001-2005 Volume "Geoscientific
Research", JAEA-Research 2007-044
RWMC (Radioactive Waste Management and Funding and Research Center) (2003): Study on
Remote Operation Technology in a HLW Repository - Volume 1/2 funded by METI. (inJapanese)
RWMC (Radioactive Waste Management and Funding and Research Center) (2004): Study on
Remote Operation Technology in a HLW Repository - Volume 2/2 funded by METI. (inJapanese)
RWMC (Radioactive Waste Management and Funding and Research Center) (2008): Developmentof Advanced Technology for Engineering Components of HLW Disposal - Volume (2/2)
funded by METI. (in Japanese)
RWMC (Radioactive Waste Management and Funding and Research Center) (2009a): Developmentof Advanced Technology for Engineering Components of HLW Disposal - Volume (1/2)
funded by METI. (in Japanese)
RWMC (Radioactive Waste Management and Funding and Research Center) (2009b): Developmentof Advanced Technology for Engineering Components of HLW Disposal - Volume (2/2)
funded by METI. (in Japanese)
RWMC (Radioactive Waste Management and Funding and Research Center) (2010): Developmentof Advanced Technology for Engineering Components of HLW Disposal - Volume (2/2)
funded by METI. (in Japanese)
Saegusa, H., Seno, Y., Nakama, S., Tsuruta, T., Iwatsuki, T., Amano, K., Takeuchi, R., Matsuoka, T.,
Onoe, H., Mizuno, T., Ohayama, T., Hama, K., Sato, T., Kuji, M., Kuroda, H., Semba, T.,124

Uchida, M., Sugihara, K., Sakamaki, M.(2007): Final Report on the Surface-based
Investigation (Phase I) at the Mizunami Underground Laboratory Project, Japan Atomic
Energy Agency, JAEA-Research 2007-043.
Sanga., T. and Yasue. K. (2008): Simulation of the Longitudinal River Profile, Trensactions,Japanese Geomorphological Union, Vol.29, No.1, pp.27-49. (in Japanese)
SKB (2006): Long-term safety for KBS-3 repositories at Forsmark and Laxemar - a First Evaluation,
Main Report of the SR-CAN project, SKB Technical Report TR-06-09, SKB, Stockholm,
Sweden.
Tachi, Y., Tochigi, Y., Suyama, T., Saito, Y., Ochs, M., Yui, M. (2009): Development of theSorption and Diffusion Database System for Safety Assessment of Geological Disposal,
JAEA-Data/Code 2008-034. (in Japanese)
Tochigi, Y. and Tachi, Y. (2009): Development of Diffusion Database of Buffer Materials andRocks , JAEA-Data/Code 2008-035. (in Japanese)
Tochigi, Y. and Tachi, Y. (2010): Development of Diffusion Database of Buffer Materials andRocks; Expansion and Application Method of Foreign Buffer Materials, JAEA-Data/Code
2009-029. (in Japanese)
Ueta, K. (2011): Kinematic Evolution of Fold and Thrust Belts: Insites from Experimental Modeling,
CRIEPI Civil Engineering Research Laboratory Rep.No.N10049. (in Japanese)
Umeda, K. (2009): An Integrated Approach for Detecting Latent Magmatic Activity BeneathNon-volcanic Regions: An Example from the Crystalline Iide Mountains Northeast Japan, In
Stability and Buffering Capacity of the Geosphere for Long-term Isolation of Radioactive
Waste: Application to Crystalline Rock, Workshop Proceedings, Manchester, United
KIngdom, 13-15 November 2007, OECD/NEA No.6362, pp.289-301.
Umeda, K., Ninomiya, J. and Negi, Y. (2009): Heat Source for an Amagmatic Hydrothermal System,
Noto Peninsula, Central Japan,J. Geophys. Res., Vol.114, .B01202, doi:10.1029/
2008JB005812.
Umeda, K., Yasue, K and Asamori, K. (2010): Current status and perspective of faulting studies forhigh level radioactive waste disposal, Monthly Chikyu, Vol.32, No.1, pp.52-63. (in Japanese)
Wakasugi, K., Ishiguro, K., Kitayama, K., Takase, H., Noguchi, T., Shizawa, A. and Hane, K.(2008):
Development of Performance Assessment Methodologies to Evaluate Differences Among
Repository Design Options, 2008 East Asia Forum on Radioactive Waste Management Conference,
20-23 October 2008, Tokyo, Japan.

125

APPENDIX
Table A.5-1 Summary of investigation/evaluation technologies for volcanic/igneous activity (1/2)
Relevant stage
Evaluation items

Database

A- 1

Volcanic evolution

Description

LS PI

Nationwide databases include Quaternary volcanoes in Japan, a new version of the tephra atlas, a borehole temperature○
database,, a hot springs chemistry database and hydrothermal deposit atlas of JapanFor eject samples from Quaternary volcanoes for which it is difficult to apply the radioactive dating technique, different
methods were developed such as the RIPL method that identifies tephra-origin subvisible materials or tephra ashfall horizons,
techniques using chemical compositions of trace elements, chemical composition of major components of the glass inclusion
in volcanic ash origin quartz and refraction index of the plagioclase phenocryst.

○

Intrusion and eruptionof magma

A volcano generation forecast method was developed for the North-east Japan Arc based on relationships among volcanoes
and topography/tectonic structure, distribution of low velocity seismic waves and plate movement. With regard to caldera and○ ○Generation of new volcanoes
large-scale pyroclastic flow, a correlation between caldera formation and tectonics was identified, which led to the proposal ofa working hypothesis for the evaluation of caldera-forming eruptions.
Migration of magma fromexisting volcanoes

Deep heat source

Deep geological structure○: Most relevant stage

A method for evaluating horizontal magma migration has been proposed. It uses the results of studies of migration of craters○ ○that reveal a relationship between the chemical composition of magma and direction of conduit distribution.
A method was developed for evaluating underground magma conditions and thermal effects of the magma based on
evaluation of deep heat sources in areas where no volcanoes are distributed in the back arc of North-east Japan by combining
seismic velocity structure from seismic tomography, distribution of microseismicity, resistivity structure by the MT method ○ ○and geochemical data (3He/4He). In the Noto Peninsula, in order to identify the heat source of non-volcanic hot springs, isotope
analysis of noble gases in the hot spring gas and 3D resistivity structural analyses were conducted.
New technologies for evaluating intrusion/eruption of magma were developed, such as the double difference tomography andseismic wave analysis techniques using the receiver function or following wave, which contributed to improving the accuracy ○ ○of the evaluation of the presence of magma in the deep underground and the ascending process of the magma.

DITable A.5-2 Summary of investigation/evaluation technologies for volcanic/igneous activity (2/2)
Relevant stage

A- 2

Geothermal activity

Evaluation items

Description

LS PI

DI

As a basis for evaluation, thermal/hydrothermal abnormal areas were identified by overlapping geological and geophysicaldata and areas with high temperature zones were categorized. Based on this categorization, methods were developed such as
Comprehensive
the geothermal distribution evaluation method using the geothermal simulator, a thermal anomaly○ ○ ○thermal/geothermal evaluation identification/characterization method and an alteration zone analysis method. An analysis technique for groundwater
formation processes based on fluid/rock reactions was also developed. Development of an evaluation method for deep hot
water has been conducted based on a geochemical approach.

Thermal history

Development of evaluation methods has been conducted, including methods for hydrothermal alteration history aroundnon-volcanic high temperature hot springs based on a method similar to the thermal age determination method that couples
several radioactive dating techniques and an analysis method that extrapolates the thermal effects of large-scale pyroclastic
flow on the deep underground by applying thermal history analysis based on the fission tracking method. The (U-Th)/He
dating technique has been applied to the analysis of low temperature (> 70 ºC) thermal history.

Effects from heatsource/volcanoes

Development has been conducted on a method to evaluate thermal flux and fluid velocity using a 1D heat transport model and3D hydrothermal simulation method using Magma 2002, an analysis code for calculating heat and hydrology around the ○ ○ ○magma chamber.

Probabilistic evaluation○: Most relevant stage○ ○R&D being conducted includes a method for predicting generation of volcanoes in the next one hundred thousand years
using a probabilistic model based on temporal and spatial distribution of volcanoes and geophysical information, a○ ○probabilistic evaluation method for independent monogenetic volcanoes and a method using a multiple inference model thatincorporates geophysical information on the Japan island scale into the probabilistic model using the Bayesian technique.

Table A.5-3 Summary of investigation/evaluation technologies for earthquake/fault activity (1/2)
Relevant stage
Evaluation items

Description

LS PI

DI

Existence of active faults

A- 3

The nationwide database developed after the H12 report includes geological structures in the marine area around Japan, adetailed active fault digital map, active fault database, Quaternary reverse fault atlas and active faults in urban areas.
Database○
An earthquake monitoring network (NIED) and GPS monitoring network (GEONET; GSI) have been established and areused to locate active faults.
High resolution topographic change analysis using the PALSAR system mounted with earth observation satellites and GPS
Geodetic technologies
continuous analysis revealed the presence of strain concentration zones. They also allowed simplified monitoring of strain ○(SAR,GPS)accumulation at plate boundaries.
Airborne radar surveys have been used to find faults in vegetation-covered areas and identification of faults based on analysisof minor displacement topography.
Geomorphic technologies
For areas where faults are clearly found at the ground surface, a lineament identification method has been proposed.
○ ○(tectonic relief)
Methods for finding and characterizing the activity of concealed active faults have been proposed, based on the distribution of
uplift level estimated from terrace distribution.
Methodologies developed include evaluating activity based on the progress of fracturing, deformation and alteration aroundthe fault or color of the fault gouge and based on the gouge age determination method that evaluates activity directly from
Geotectonic methodologies materials that constitute the fault (fault rock).
(geotectonic analysis, age
A method for evaluating activity history was developed based on the tectonic history, including investigations to determine○ ○determination)
thermal age.
An earthquake occurrence frequency analysis method has been developed based on detailed analysis of turbidite on the sea
bottom.
Applicability of the reflection survey method has been expanded and demonstrated, including development of the 2D
technique, application of the 3D technique in exploration of mineral resources, geotectonic analysis and investigation of active
faults, deposits and topography in marine areas and investigation of geology and ground in inland areas (small-scale faults).
The multi-channel sonic survey system has been developed to accurately determine tectonic structure in marine areas and has
been applied in the investigation of active faults.
Geophysical technologies
A marine electromagnetic exploration system for application in the foreshore at a depth of 200 m or less (expected to be used(reflection survey,
complementarily to acoustic exploration) has been developed and improved. In order to survey areas extending from coastal○ ○electromagnetic survey, seismic areas to marine areas, combination of the marine electromagnetic exploration system and other electromagnetic exploration
tomography)
systems has been developed.
The gravity exploration method has been considered for determining the length of active faults.
A method for identifying faults in active fold zones has been proposed, in which an earthquake source fault is estimated basedon distribution of corrected seismic sources and the estimated earthquake source fault is compared with the tectonic structureusing simulated movement analysis based on finite element analysis. For the evaluation of the seismic source fault model,
analysis of seismic waves such as tomography has been considered.
○: Most relevant stage

Table A.5-4 Summary of investigation/evaluation technologies for earthquake/fault activity (2/2)
Relevant stage
Evaluation items

Description

LS PI

A- 4

Definition of deformation zone and affected
region around active faults

Existenceof actie faults

Development of a method to locate and characterize faults by measuring H2 gas generated due to fracturing of rocks and He
isotopes in groundwater, hot springs and gas in the soil has been conducted.
A method to evaluate active structures of the seismic source fault was proposed for areas where clear evidence of seismic
Comprehensive methodology faulting has not been observed at the ground surface; this is based on an analysis of micro-seismicity, airborne radar surveys ○and reflection surveys.
Fault-related fold analysis (e.g. growth strata) coupled with acoustic survey data was effective in identifying fault structures inmarine areas with sediments. Studies of formation mechanisms and categorization of active folds in Japan have been
conducted. Development processes of active fold/reverse fault zones and associated affected zones have been evaluated by
Determination of deformation
model experiments and evaluations based on the concept of fault-related folds have been conducted using existing geologicalzone○
data and the balanced cross-section method.
(e.g. active fold)Evaluation methods validated for their effectiveness for reverse and strike-slip faults include the method applying the balanced
cross-section based on geological investigation data and the method applying a numerical analysis program to estimate
deformation zones of rocks and topographic deformation in area around the fault.
An evaluation method for reverse faults has been developed based on an analysis of their development process using model
Development and extent of experiments.
○
faulting
Evaluation of strike-slip faults has been conducted by comparing development levels of major faults in the Chugoku andChubu areas as well as experiments/simulations.
Studies conducted include geological evaluation of damaged and process zones associated with faults that are relevant to
Characterization of fault fracturechanges in groundwater flow and the underground environment and evaluation of the extent of the damaged zone based on ○zones
resistivity obtained by MT surveys.
Fault activities in recent destructive earthquakes such as the 2003 Miyagi earthquake and the 2008 Iwate-Miyagi Inland
Evaluation of reactivation of active faults Earthquake and the Tachikawa fault in the southern part of Kanto area suggest potential reactivation of existing geological ○faults. The reactivation of geological faults has been studied by model experiments and numerical analyses.
A fault generation forecast method extending approximately one hundred thousand years into the future has been developed
based on strain velocity distribution and probability of exceeding the annual strain rate obtained from topographic change such
Probabilistic evaluation of fault activities as active faulting/uplift, GPS data and historical earthquake data.
○
Probabilistic seismic hazard analysis has been applied in forecast several tens of years into the future in the disaster prevention
areas.
○: Most relevant stage
Geochemical approach(H2, He)

DI

○
○

○

○

○

○

○

○

Table A.5-5 Summary of investigation/evaluation technologies related to uplift/erosion (climate/sea-level change)
Evaluation items

Description

Relevant stage
LS PI

DI

Nationwide database including the marine terrace atlas for Japan, uplift/subsidence distribution in the last 100,000 years, uplift rate○
distribution in the last 100,000 years and landslide topography distribution in Japan on a scale of 1 to 2 million.
A comprehensive approach for terrace correlation/chronology emphasizing topographic sequence, geological sequence and age
information was proposed to avoid erroneous interpretation of age data, which was validated using a detailed volcanic ash analysis
Terrace correlation/ method. Technologies that support the approach include quantification of terrace surfaces using DEM and its application to terrace○ ○chronology
correlation. The index of weathering for the cover and terrace gravel layer that constitute the terrace was revised. This contributed to
improving the reliability of the identification of terraces formed in the last stage of the marine oxygen isotope stage six (approximately
140,000 years ago) used for evaluating uplift in inland areas.
Evaluation of uplift
The applicability of the uplift estimation method of river terraces to inland areas was reviewed and causes of errors were identified. The
level in inland areas
estimate of uplift based on river terraces was verified by the balanced uplift between that estimated based on the throw of the active faults ○ ○based on riverand the uplift difference on both sides of the fault obtained from the relative height of the terrace.
terraces
Representation of Developed methodologies include estimating uplift/subsidence rates during the period from the past to present by comparing depth of the
uplift/subsidence formation (whose age is clear) when it was aggraded and current distribution elevation/sea-level and clarifying the paleogeography and○based on deposits development process of inland basins using the sequence sedimentary facies analysis method.
R&D being conducted includes topographic change forecast based on estimates of past erosion history and erosion depth obtained by
Forecast ofcomparing erosion topography on new and old marine terraces, combined with change in the climate/sea-level and that based on
topographic change,○ ○topographic change simulation of topographic change using diffusion equations. In addition, a method was proposed in which depth and volume of dissectedvalleysonthemarineterraceformedduringone
cycleof
glacial-interglacial
periods
areestimated
using
DEM
and,
using
these
values,model
incision rate and average erosion rate for the entire terrace are obtained.
Evaluation of
Developed methods include estimating uplift/erosion rate of the geology during a period of several million years based on the relationshiplong-term erosion
between the closure temperature and burial depth of minerals and using age determination technology to estimate uplift/erosion rate of(removal) level using○ ○age determination sediment layers based on thermal alteration of minerals and organics (e.g. transformation of silica minerals), aggraded depth and age andestimated geothermal gradient at the time of aggradation.
methodMeasurement ofA method to estimate denudation duration and erosion rate has been developed based on the type of in-situ cosmogenic nuclides generated
erosion rate using○
cosmogenic nuclides by the reaction between materials on the earth and cosmic rays and their generation rate in a year.
Representation of climate and Analysis of regional climate change and representation of evolution of vegetation have been conducted through the analysis of eolic○ ○sea-level change
deposits on terraces, analysis of sediment obtained by coring in inland basins and analysis of pollen.
○: Most relevant stage
Evaluation of erosion volume and rateA- 5Investigation/evaluation of
uplift/subsidence

Database

Table A.5-6 Summary of investigation/evaluation technologies for geological environment characteristics (1/3)

Geophysicalexploration

Description
For the reflection survey method (acoustic survey in the marine areas), the 2D data processing method has been improved. The reflection
survey technique has been used for resource exploration (3D method), geotectonic structure analysis, investigation of active faults,
sediments and topography in marine areas, investigation of geology/ground in inland areas (small faults with a throw of approximately 5m). A multi-channel acoustic survey system for accurate investigation of the tectonic structure in shallow marine areas has beendeveloped.
The marine electromagnetic exploration system for the foreshore at a depth of 200 m or less (expected to be used complementarily toacoustic exploration) has been developed. Technologies for surveying areas extending from coastal areas to marine areas and 3D analysis
methods have been developed. The stacking method has also been developed; this is important for obtaining high quality data required forthe analysis of the MT technique.

A system that allows control of drilling direction and angle, core sampling and borehole logging was developed and has been used for the
drilling in coastal areas.
R&D has been conducted on a method for estimating the spatial distribution of fracture density taking into account the relationship
Fracture analysis for
betweenfractures in the borehole and topography/fault of the bedrock for granitic rock and the multi-scale fracture distribution simulation
crystalline rocks
technology that allows consideration of regularity/correlation of fracture distribution on different scales.
The methodologies for analyzing 3D distribution of permeable features such as faults that are the basis for the hydrological analysis were
Fracture analysis fordeveloped for different scales. Also developed was an analytical fracture characterization method and site descriptive model development
sedimentary rocks (3Dmethod based on borehole investigation data, an investigation/analysis method for spatial distribution of highly permeable structures
structure)
based on rock mechanical stress calculations considering fault development mechanisms and an investigation/analysis method for the time
when the development of the anticline started based on diagenesis of silica minerals.
A series of methodologies have been developed for analysis of hydrological parameters such as permeability as part of the development ofHydrology insequential hydrological testing methods for deep underground rocks and a testing unit was developed for use for groundwater conditions
deep rocks
with dissolved gases in sedimentary rocks.
Methodologies developed include a method for identifying intake and outflowing water locations in the borehole with high sensitivity
Permeable
flowmeter logging, a method to identify/estimate permeable fractures with electrical conductivity logging and a water channel estimation
fractures/water
method using optical fiber temperature logging assuming the locations where flow velocity changes as locations where intake or
conduits
outflowing of water occurs.
Groundwater flow A flow direction /flow rate measurement method for extremely low flow rates was developed that allows measurement of flow direction
direction /flow rate /flow rate of 10-9 m/s by tracing the migration tracks of solid particles with ultrasonic sensors.
○: Most relevant stage
Borehole drilling

Hydrology

Groundwater hydrology

A- 6

Geology/ geological structure

Evaluation items

Relevant stage
LS PI DI

○ ○

○ ○
○ ○

○ ○

○ ○

○ ○

○ ○

Table A.5-7 Summary of investigation/evaluation technologies for geological environment characteristics (2/3)
Evaluation items

Relevant stage
LS PI DI

Development of the GEOMASS system that integrates processes from the development of numerical models to evaluate groundwater flow inthe rock to groundwater flow analysis has been conducted.

○ ○Synthesis of data obtained by investigations from the ground surface using groundwater flow analysis, analysis for sedimentary rock areas
Sedimentary
where saline groundwater with dissolved gases is distributed and modeling of the stability of groundwater depending of the bonding level (pF)rockof the groundwater in the pores of rocks have been conducted.

○ ○Modeling of For coastal areas where sedimentary rocks are distributed, long-term groundwater flow evaluation considering long-term evolution of thelong-term climate and sea-level as temporal evolution boundary conditions27) and groundwater flow analysis during the period from the past to present
evolution using paleotopographic distribution models have been conducted.

○ ○Water chemistry, Surveys of technologies for sampling and analysis of groundwater were conducted. A method for identifying fossil seawater based onage determination groundwater age determined using 36Cl generated in underground rocks and data on stable isotopes are proposed.

○ ○Groundwaterchemistry modelThis includes M3 analysis (Multivariate Mixing and Mass balance modeling analysis) that combines primary element analysis andmixing/mass balance calculations to evaluate the range and extent of the temporal evolution of the groundwater chemistry and determinationof ion concentration in the porewater extracted from rock cores to analyze the correlation with groundwater flow.

○

Mechanicalproperties

The rock evaluation method using three factors (uniaxial compressive strength, ROQ and fracture condition) as indices was proposed. With
regard to rock pressure measurement methods, the overcoring method for measuring stress in soft rocks and the downward compact
conical-ended borehole overcoring technique for in-situ rock stress in deep boreholes have been developed.
The difference in uniaxial compressive strength due to the difference in mineral composition in granite samples has been analyzed andmechanical characteristics of the granite have been compiled in terms of mechanical and rock properties. Rock stress measurement methods
are being studied based on change in tangential Young’s modulus. In the Mizunami URL, boreholes have been drilled from the ground surface
to develop a mechanical conceptual model of rocks.

○ ○Groundwaterhydrology
structuremodel/groundwater flow
Groundwaterchemistry

A- 7

Rock properties

Crystallinerock

Description

Data on rock properties (physical, mechanical, hydraulic and thermal) under high and low temperatures were collected based on literature
Thermal properties surveys and compiled into a database44). Mechanical properties of sedimentary rocks (soft rock) in a high temperature environment(temperature dependence of three axial compressive strength and creep characteristics) have been shown.
By compiling existing data, criteria for evaluating extrusion of the ground and a design guide for tunnel construction methods based on
Evaluation ofgeological information obtained in advance were presented and a method for evaluating the likelihood of encountering difficult constructiondifficultconditions based on information obtained up to the PI stage was proposed. Safe construction methods against failure of the liner that is likely toconstructions
occur during shaft construction in fault/ fracture zones have been proposed.
○: Most relevant stage

○ ○

○ ○

Table A.5-8 Summary of investigation/evaluation technologies for geological environment characteristics (3/3)
Description

Mass transport
properties

Thermodynamic, sorption and diffusion databases have been developed. Studies have been conducted on processes and fieldstructures that control migration or retardation of radionuclides in permeable fractures in crystalline rocks and in-situ testing
methods and modeling methodologies have been developed.

Others

Evaluation items

It is known that fluid that causes eruption of mud volcanoes ascends from a depth of 2,000 m and dehydration of clay minerals
plays a key role in the formation of the fluid; the fluid contains hydrocarbons generated by decomposition of biogenic
Mud volcanoes organics. Data on activation period and volume of ejecta for mud volcanoes have been collected from cases in other countries.
Underground structures and distribution/scale have been estimated based on geodetic or geophysical techniques. Mechanismsof volcano formation and its scale have been studied based on knowledge of Miocene mud diapirs.
A method for predicting potential large collapse in the Mino Terrain was developed, in which frequency of the collapse isestimated based on age determination (based on 14C) of the sediments in a dammed lake formed by large-scale collapse of Mt.
Mass movement
Ibuki. Large-scale landslides during earthquakes are also reported.

A- 8
Monitoring○: Most relevant stage

Measurements of groundwater pressure and long-term monitoring of water chemistry have been conducted using boreholes in
the Mizunami and Horonobe URLs. At JAEA Tokai, development of technologies and verification of their applicability havebeen conducted to monitor the performance of the engineered barriers. Other R&D includes preparing technology options(technology menu) for data transmission, sensors and measurement technologies.

Relevant stage
LS

PI

DI

○

○

○

○

○

○

Base
metal

A- 9

Weld

Table A.6-1 Current status of scientific knowledge on corrosion behavior of the base metal and weld
Behaviors
Description
Data on corrosion rate were accumulated. Decrease of the corrosion rate in a long-term perspective was shown
General corrosion behavior
by experiments.
It was shown that the passivation could be prevented by the pH buffering effect of the buffer materials or by
Local corrosion,using of low-pH cement. Test data on local corrosion were accumulated, which indicates that the local corrosion
passivation
would not be significant as to affect to the corrosion life.
Effects of radiolysis
Insignificant effects of radiolysis product of groundwater (e.g. hydrogen peroxide) due to γ-ray from HLW glass
products on corrosion
was validated by tests, indicating conservativeness of the radiation shielding allowance of 150 mm that has been
resistancetaken into account in the design to prevent local corrosions.
Reduction of activities of sulfate-reducing microbes with the increase of bentonite/water ratio was validated byMicrobiological effect onlaboratory tests. Effects of microbes such as sulfate reducing microbes are considered to be small because
corrosion
migration of the microbes will be prevented by the filtration effect of the compacted bentonite, restricting their
inhabitation or activities.
Preferential corrosion was observed under oxidizing conditions; however, there is a prospect that it could be
General corrosion
solved by changing welding materials. It was also shown that the corrosion resistance of the weld is equivalent
to or better than the base metal.
SCC, hydrogen
Sensitivity to SCC was tested in the carbonate solution and sensitivity to hydrogen embrittlement evaluatedembrittlement
under simulated saline water, showing less sensitivity than the base metal.

A- 10

Table A.6-2 Current status of scientific knowledge on basic properties, long-term behavior and interaction of buffer materials (1/2)
Behaviors
Description
The swelling pressures decreases with the increase of salinity, but its difference from that under fresh water is
Effects of saline water
not significant at the effective density of 1.5Mg/m3 or higher. The volume swelling ratio increases with theincrease of effective density of the clay but it is less with the increase of the salinity.
Transformation to
The groundwater passing through the concrete support or plug could become Ca ion rich composition. Studies
Ca-bentonite of clay have been conducted on potential alteration of Na-smectite to Ca- smectite by ion exchange, resulting increase
minerals in the buffer of permeability and decrease of swelling pressure, when it contact with the buffer material.
It is a phenomenon that the smectite, a main mineral that constitutes the buffer material, dissolves into the
Dissolution of clay
groundwater, as reported in literatures. Formulation the phenomenon has been conducted using pH and
Cement-bentonite minerals in the buffertemperature as parameters.
interaction
It is a phenomenon that the smectite, a main mineral that constitutes the buffer material, forms secondary
Sedimentation ofminerals and is replaced with it, which could result in change in swelling properties and permeability. Thissecondary minerals
phenomenon could be significant under the condition where the smectite becomes mineralogically unstable.
It is a phenomenon that could occur around the cement-bentonite interface where secondary minerals
Cementation
precipitate and fill the pores in both materials. This could cause change in swelling properties and permeability.

Table A.6-2 Current status of scientific knowledge on basic properties, long-term behavior and interaction of buffer materials (2/2)
Behaviors
Description

Interaction
between carbon
steel corrosion
products andbentoniteA- 11

Exchange of
exchangeableinterlayer cation with
Fe-ionExchangeable interlayer cation (Na+) in the smectite could be exchanged with Fe2+ ion, which could result inchange of swelling properties, permeability and sorption capability of the bentonite.

Chemical alterationof minerals

At the increased portion of Fe2+, minerals such as pseudo chlorite/Fe-chlorite, berthierine, nontronite,Fe-saponite could be formed. Alteration to pseudo chlorite/Fe-chlorite and berthierine that do not have wellingcapability could cause change of swelling properties, permeability and sorption capability of the bentonite.

Cementation bycorrosion products

Sedimentation of the iron corrosion product or chemical reaction of minerals could cause secondary
sedimentation of other minerals, resulting closure of pores. It could cause change in swelling properties,
permeability and sorption capability.

Illitization
Erosion of buffer material

It is proven that the illitization could not occur below the temperature of 130 ºC, thus has insignificant impact
to the safety functions of the buffer.
Erosion is the phenomenon that need to be noted under the fresh groundwater condition, but it is proven that,
under the saline groundwater condition, it effect is insignificant. Under the fresh groundwater condition,
appropriate measure will be required based on the analysis of effects of fractures contacting with the buffer on
the erosion behavior of the buffer material.

Table A.7-1 Progress of R&D relevant to safety assessment since the H12 report (1/4)
R&D area

Effective scenario
development
methodology

A- 12

Scenariodevelopment

FEP-based scenario
development
methodology andcompilation of FEP
information
Determination ofsystem conditions
and scenario
development
methodology
considering
long-term evolution
Scenariodevelopment
methodology fordisruptive natural
phenomena

Description

Relevant technologyarea
EBS
○

NB
○

○

○

○

○

○

○

○

○

○

○

○

○

Development of a methodology for defining nuclide migration analysis model parameters by compilinggeoscientific knowledge on features of relevant phenomena, focusing on changes in thermal /hydrogeological / mechanical / chemical conditions.

○○

Development of a methodology for handling “what if?” scenarios for events that should be avoided by site
selection or EBS design.

○○

Development of a methodology for evaluating potentially significant natural events.

○○

Development of a scenario development methodology based on safety functions and on FEPs.
Development of methodology to improve completeness and efficiency, based on hierarchical relationships
between FEPs and safety functions.
Development of a tool to express correlations between FEPs in a matrix.
Development of a concept for revising scenarios in the light of advances in R&D and preparation for
application cases.
Development of a concept for classifying events based on the significance of their consequences byanalysis of links between safety functions and nuclide migration parameters.
Compilation of knowledge in a FEP list based on literature information (for engineered barriers andgroundwater transport scenarios for geological environments typical of Japan).
From correlations between FEPs, judgment on whether or not to include in key scenarios.
Compilation of FEP data for the safety assessment of the geological disposal of TRU waste.
Development of a methodology for determining system conditions taking into account the long-term
evolution of the coastal geological environment.
Development of a scenario development methodology taking into account long-term evolution of thenear-field environment.

[Relevant technology areas] EBS: Engineered barriers,

NB: Host rock (natural barrier), BIO: Biosphere

BIOTable A.7-2 Progress of R&D relevant to safety assessment since the H12 report (2/4)
R&D area

Description

Development of a 2D model for evaluation of nuclide migration and retardation in the EDZ.
Development of a 3D nuclide migration model for evaluation of the effects of heterogeneity of host rocks anddesign options.
Development of an approach to optimize repository layout (maximize number of waste packages emplaced,
use of better quality rock), based on spatial distribution of geological characteristics.
Development of an approach to improve performance of the repository by laying out the repository in better
quality rock.
Development of a methodology for incorporating information on heterogeneous migration pathways obtainedby groundwater flow analysis into the nuclide migration analysis models.
Improvement of Development of a biosphere evaluation model and related dose conversion factors addressing the effect of
nuclide migration climate change by focusing on the reduction of precipitationb in cool temperate and cold desert zones,
analysis methods changing parameters such as irrigation water volume, penetration/run-off rate and ingestion of foodstuffs.
taking into account Development of a model development methodology for incorporating hydrology/mass transport at thelong-term
geosphere / biosphere interface.
evolution of thesurface
Development of a methodology for incorporating features of the geological environment in coastal regions
environment andtogether with their long-term evolution into nuclide migration models.
geologicalenvironment
Development of Improvement of groundwater analysis code (FEGM) and nuclide migration code (FERM) and theireffective
application in groundwater analysis/chloride ion concentration analysis at the Äspö URL.
calculation
Development of a statistical nuclide migration analysis model using GoldSim.
methods forDevelopment of effective nuclide migration analysis tools considering temporal evolution of parameters.
nuclide migration
Derivation of approximation solutions that facilitate obtaining the response of thegeological disposal system.
analysis
Construction of a glass dissolution database
Construction of a thermodynamic database
Compilation data
Construction of a sorption database
Construction of a diffusion database

Improvement of
nuclide migration
analysis methods
taking into accountthe heterogeneityof host rocks anddesign options

A- 13

Model
development

Development
of datasets[Relevant technology areas] EBS: Engineered barriers,

NB: Host rock (natural barrier), BIO: Biosphere

Relevant technologyarea
EBS NB BIO
○
○

○

○

○

○

○

○
○

○

○
○
○
○
○

○
○

○

Table A.7-3 Progress of R&D relevant to safety assessment since the H12 report (3/4)
R&D area

Description

A- 14

Review of dose conversion factors for radionuclides selected for biosphere evaluation in the current
regulations, reflecting ICRP Recommendation 1990 (for HLW and TRU waste).
Data compilation Standardization of measurement methodologies for sorption and diffusion data.
Compilation of nuclide migration data in the natural environment.
Tentative setting of sorption distribution coefficients for actual geological environments and development ofDevelopment
methodology for using the JAEA sorption database.
of safety
Establishmentof a procedure for defining biosphere parameters considering the significance of the parameters,
assessment
significance,
progressof database construction and availability of data.
datasets
Compilation of
Formulation of strategies for collecting knowledge and parameter setting for parameters relevant to civil
datasets
engineering from those used in the groundwater scenario for the safety assessment of geological disposal.
Tentative compilation of a dataset using actually obtained geological environment data (porewater chemistry,
distribution coefficients).
Development of datasets for the safety assessment of the geological disposal of TRU waste.
Identification and quantification of parameters that have significant effects on the evaluation results.
Sensitivity analysis
Compilation of uncertainty factors for the geosphere-biosphere interface that impact on biosphere evaluation.
methodology
Development of a methodology for identifying important parameters in biosphere evaluation.
SafetyDevelopmentof a methodology for reducing uncertainties associated with dilution by comparing theanalysisComplementary radionuclide flux at groundwater discharge points from fault fracture zones with natural fluxes.
indicators
Collection and compilation of data on concentration and flux of natural origin radionuclides and developmentof calculation methods for natural origin radionuclides focusing on drainage basins.
[Relevant technology areas] EBS: Engineered barriers,

NB: Host rock (natural barrier), BIO: Biosphere

Relevant technologyarea
EBS

NB

BIO
○

○

○
○
○
○

○

○

○

○

○

○
○

○

○

○

Table A.7-4 Progress of R&D relevant to safety assessment since the H12 report (4/4)
R&D area
Coordination with othertechnology areas

Comprehensive safety assessment(including methodologies)

Description
Presentation of procedures/methods leading from investigation/evaluation of the geological environment tonuclide migration analysis to be applied for specific sites.
Development of a safety assessment methodology considering uncertainties conducted as part of the
Horonobe URL project.
Comprehensive safety assessment of the geological disposal of TRU waste for geological disposal undergeneric geological environment conditions in Japan.
Evaluation of the robustness and feasibility of the geological disposal system based on analysis of issues
proposed in the 2nd TRU report and using additionally obtained data.

[Relevant technology areas] EBS: Engineered barriers,

NB: Host rock (natural barrier), BIO: Biosphere

Relevant technologyarea
EBS

NB

○

○

BIO

○
○

○

○

○

○

○

A- 15