NUMO-TR-07-02

The NUMO Structured Approach to
HLW Disposal in Japan
Staged Project Implementation at Volunteer Sites
Utilising a Requirements Management System

July 2007
Nuclear Waste Management Organization of Japan (NUMO)

2007 年 7 月 初版発行
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NUMO-TR-07-02

EXECUTIVE SUMMARY
The constraints set by the Japanese HLW disposal programme – particularly associated withthe decision to initiate siting by an open call for volunteers to host a geological repository –pose particular challenges for repository project management. In order to maintain theflexibility required to respond to the conditions found at volunteer sites, NUMO has not
published reference designs or site characterisation plans, as is normal for programmes
progressing by site nomination. Instead, we have developed a methodology – the NUMO
Structured Approach (NSA) described in this report – to allow such designs and plans to be
tailored to particular sites in a flexible, open and efficient manner, with the aim of producing
a site-specific process for design and operation of a demonstrably safe and practical facility.
The NSA has similarities to the adaptive staging framework developed and applied in someother national waste management programmes. However, the specific Japanese boundary
conditions and also the policies adopted by NUMO for its project work have led us todevelop and document a formalised structure and to emphasise particular aspects such as
flexibility, transparency and willingness to adapt concepts and to revise decisions in order toreflect the evolution of the project with time.
For a project involving stepwise implementation stretching until the end of the century, theflexibility provided by the NSA has great advantages; facilitating responses to the surprisesthat are almost inevitable in such projects and the changes in scientific and socio-politicalboundary conditions over this period. In addition, the emphasis on reversibility ofdecision-making has advantages for building dialogue with stakeholders – particularly local
communities. This fits well within our policy of establishing NUMO’s credibility as acompetent and trustworthy partner for potential volunteers.
Although the NSA description is rather abstract, its practical applicability is illustrated byexamples. It already forms the basis of tools that have been developed for selecting between
different options for site characterisation or repository design for specific siting locations.
While waiting for volunteers, these tools have been tested in a number of dry run exercises.
In order to implement the NSA in a clear and traceable manner, a special management tool isneeded. We are thus currently developing a Requirements Management System (RMS),
which will support – and help to document – the decision-making process at all hierarchicallevels within NUMO. The RMS, together with its relationship to other supporting
management infrastructure, is also outlined in this report.

iNUMO-TR-07-02

CONTENTS1INTRODUCTION........................................................................................................ 1

1.1

NUMO and its role .......................................................................................................... 1

1.2

The need for special programme management approaches........................................... 2

1.3

Structure of this document............................................................................................... 32

BACKGROUND AND BOUNDARY CONDITIONS........................................... 4

2.1

Staged project implementation and the basic approach to confidence-building........... 4

2.2

Enhancing technical credibility as the project progresses.............................................. 5

3

THE NUMO STRUCTURED APPROACH........................................................... 9

3.1

Structuring the development of repository concepts during the literature survey
stage .................................................................................................................................. 9

3.2

Decision-making within the NSA................................................................................. 12

3.3

Structured planning of the entire repository project ..................................................... 15

3.3.1

Application of the NSA during staged implementation............................................... 15

3.3.2

Response to surprises and unexpected changes in external conditions.......................17

4

CONCEPT OF REQUIREMENTS MANAGEMENT AND ITSAPPLICATION WITHIN THE NSA...................................................... 21

4.1

Hierarchical structure of decision-making within the NSA......................................... 22

4.2

Decision-making within the RMS ................................................................................ 23

4.3

Requirements management in the decision-making process....................................... 25

4.3.1

Terminology.............................................................................................................. 25iii

NUMO-TR-07-02

4.3.2

Outline of the NUMO's RMS........................................................................................25

4.4

Further development and implementation.................................................................... 30

5

CONCLUSIONS AND A LOOK TO THE FUTURE.......................................... 31

6

ACKNOWLEDGEMENTS ..................................................................................... 33

7

REFERENCES........................................................................................................... 34

APPENDIXILLUSTRATION OF HIERARCHICAL RANKING OFREQUIREMENTS ...................................................................................A-1

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NUMO-TR-07-02

1

INTRODUCTION

1.1

NUMO and its role

The Nuclear Waste Management Organization of Japan (NUMO) was established in 2000 to prepare
for and implement the geological disposal of “specified” waste – currently vitrified high-level
radioactive waste (HLW) resulting from the reprocessing of spent fuel from commercial nuclear power
plants. Legislation specifies particular constraints on such a repository in terms of depth and site
geological stability. It also defines a stepwise siting process (Figure 1-1), which proceeds from literature
survey to selection of preliminary investigation areas (PIAs), in which surface-based investigations will
provide the basis for selection of detailed investigation areas (DIAs). Detailed investigations will include
the construction of underground characterisation facilities and will then lead to the selection of a final
disposal site.
Volunteers

Literature survey

PIAs

DIAs

Final disposal site

Surface-based
investigations

Undergroundcharacteris ation facilities

Final disposal facility

Selection of PIAs

Figure 1-1:

Selection of DIAs

Selection of final
disposal site

The stepwise siting process.

Based on experience in Japan and elsewhere, NUMO has identified public acceptance as a critical issue
influencing the success of the repository project. We therefore decided to tackle this issue at the outset of
our work by choosing to initiate siting by a call for volunteers, issued to all municipalities in Japan in
2002 (Kitayama, 2003). Due to the complex geology and active tectonic setting of the Japanesearchipelago, we recognised that the assessment of the suitability of some volunteer siting areas could becomplex and technically challenging. Nevertheless, given NUMO’s commitment to openness andtransparency, we will strive to ensure that the process is as understandable as possible to all stakeholders.
Accordingly, we have already published the Siting factors that are used to exclude unsuitable sites andto compare sites in the case of multiple volunteers (NUMO, 2004a). The diversity of possible siting
environments requires flexibility in terms of repository design and, instead of specifying a reference
concept, we have therefore published a catalogue of options (NUMO, 2004b).

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NUMO-TR-07-02

1.2

The need for special programme management approaches

The volunteering process presents unique challenges for programme planning. Reference concepts areneeded to guide planning of site characterisation, repository design and safety assessment – and also,
importantly, to enable NUMO to communicate effectively with the broad public in Japan. However,
flexibility is essential to ensure that these concepts can be efficiently tailored to the specificenvironments presented by any volunteer. Fundamentally, NUMO has adopted a philosophy ofemphasising an open decision-making process, which allows decisions at all hierarchical levels to beeasily explained and, in particular, allows decisions to be revisited if particular boundary conditions
change. We consider this last point to be particularly important in the light of experience from othernational programmes, where implementing organisations have been reluctant to change early decisions
with regard to siting or repository design due to concerns about confusing the general public.
The process of iterative refinement of site models and associated repository designs and safety cases isformalised as the NUMO Structured Approach (NSA). This recognises that, over the many decades
until a repository is finally closed, science, technology and the socio-economic environment will evolveand the programme must be able to respond to the changes involved. Although such a concept isstraightforward in principle, it is challenging to implement in practice because of the complex,
multi-disciplinary network of requirements that influence key project decisions. Indeed, the challenge iseven greater because of the long lifetime of the project and the corresponding need for clear and explicit
documentation of the basis for all past decisions. Here NUMO has the distinct advantage of being ayoung organisation that does not face the task of retroactively documenting past decisions. On the other
hand, NUMO staff members are currently rotated on relatively short-term secondment, so that aneffective tool is needed to help guide and rigorously document technical decision-making. For thisreason, we have placed high priority on developing a Requirements Management System (RMS),
which will help with the day-to-day application of the NSA at all management levels.
The NSA has similarities to the adaptive staging framework developed and applied in various forms insome other national waste management programmes (e.g. NRC, 2003). However, the specific Japaneseboundary conditions and also the policies adopted by NUMO for its project work have led us to develop
and document a formalised structure for our iterative approach and to emphasise particular aspects thatare especially important in the Japanese context. These include:▪

Flexibility to cope with the diversity of siting conditions that may have to be considered;▪

Transparency and traceability (as required by Japanese law), with specific focus on thedecision-making processes;▪

Recognition that not only gradual, evolutional changes must be anticipated, but also major
surprises;▪ Willingness to adapt concepts and to revise decisions in order to reflect the evolution of the2

NUMO-TR-07-02

project with time and a readiness to accept stakeholder input.

1.3

Structure of this document

Chapter 2 expands on the boundary conditions on the NUMO programme, with particular emphasis on
the need for NUMO to establish the credibility required to attract volunteers and on the very tight timeschedule for the early stages of site selection. Chapter 3 describes the NSA, illustrating its initial
application to repository concept development and then discussing its wider application throughout ourprogramme. As such application is under development at present, specific examples are used to show
how it may actually be implemented. Chapter 4 outlines the RMS, which is being tested in prototype
form at present. This is planned to be a key management tool for NUMO and has a particular role instrengthening the interactions between the different technical groups involved in this complex project.
Finally, in Chapter 5, this work is summarised from the perspective of practical implementation of ourlong-term programme.

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NUMO-TR-07-02

2

BACKGROUND AND BOUNDARY CONDITIONS

2.1

Staged project implementation and the basic approach toconfidence-building

NUMO was established in October 2000 as the implementing organisation responsible for the safe
disposal of HLW, on the basis of the Specified Radioactive Waste Final Disposal Act (the “Final
Disposal Act”). In accordance with the provisions of the Final Disposal Act, the Japanese government
has issued ministerial ordinances on the Basic Policy for Disposal of Specified Radioactive Waste(MITI, 2000a) and the Plan for Disposal of Specified Radioactive Waste (MITI, 2000b). According tothis disposal plan, the repository site is to be selected between 2023 and 2027 allowing the disposal
facility to be commissioned around 2033-2037. The overall schedule for such staged implementation of
the project is illustrated in Figure 2-1.

２０００

２０１０

２０３０

２０４０

２１００

ClosureOperation

Construction

Repository site
selection

DIA selection

Application

PIA selection

Solicitation

Figure 2-1:

２０２０

Planned schedule for project implementation (based on NUMO, 2004a).

As previously noted (see Figure 1-1), siting proceeds in three fundamental steps – but the first two areparticularly short. After volunteers apply, we have to make very sensitive decisions about which
potential siting areas will be carried forward as PIAs – and then which of these as DIAs – on the basis of
only a few years of work. There are clear technical challenges here but, as public acceptance is seen to
be a key factor, also challenges in the area of building confidence – in both the basic concept ofgeological disposal and in NUMO as a credible implementing organisation.
Our basic approach for building stakeholder confidence in the geological disposal project includes threecomponents:▪

Stepwise project development: Gradual focusing on a preferred site and associated repository
design proceeds in distinct stages and we make the decision to move to the next stage only withthe agreement of local communities;▪ Engaging communities: Ensuring that local communities not only have access to all informationthat they need, but are also encouraged to develop dialogue, which we feel is essential to having
them actively support the project;

4

NUMO-TR-07-02▪

Focusing on transparency: Providing all relevant information, particularly that supporting key
decisions, in an accurate and readily understandable manner.

Our decision to adopt an open solicitation procedure for the initiation of the siting process, based on
inviting municipalities from all over Japan to volunteer for initiation of the first literature survey stage, isa result of NUMO’s commitment to this approach. Although it is clearly difficult to attract volunteers,
we consider the effort involved in finding and motivating potentially interested communities to be
worthwhile in the context of a major, highly sensitive project extending in total over a period of ahundred years or more. Also in line with this approach, the call for volunteers was accompanied by apackage of supporting documents1, which provides interested municipalities with the background
required for informed decision-making. These documents outline the repository implementation process,the criteria used to exclude unsuitable sites and the outreach scheme for providing technical andfinancial support to volunteers.
Although there have been no formal applications to date that could proceed to the literature survey stage(as of the end of June 2007), we have received inquiries from a number of interested municipalities.
Efforts thus continue, at a national level, to raise awareness of the project in key stakeholder groups and,directly with interested communities, to enhance their understanding of the issues involved. The
national efforts utilise mass media, but the local interactions focus on personal contacts, for example byorganising briefing or study sessions with a view to establishing dialogue and raising local trust to thelevel needed for formal application as a volunteer PIA that could potentially become a repository host.

2.2

Enhancing technical credibility as the project progresses

Attracting volunteers is clearly a major challenge for the NUMO’s programme and a focus forcommunication efforts. Nevertheless, we consider it necessary to look beyond this point and plan for
future stages of work (Kitayama, 2006). Figure 2-2 illustrates this process, noting particular work
phases that overlap and extend beyond the strict stages of the site selection procedure. Planning ahead isimportant, especially for the short literature survey and preliminary investigation (PI) stages, in order toensure that all technical infrastructure needed for the work is available as and when needed, in order tomeet the tight deadlines. It is also important in terms of preparing the local communities for thepolitically sensitive decisions for selection of PIAs, DIAs and the final disposal site. For the local
populace, a key factor will be the credibility of NUMO as an organisation. Such credibility is based on
two components – our fundamental competence and our ability to communicate this to all relevant
audiences. We plan to enhance both these components during these work phases.

1

English translation of the documentation supporting the call for volunteers is available on the NUMO website
www.numo.or.jp

5

NUMO-TR-07-02[Project implementation]
Application
Establishment

Solicitation

Selectionof PIAs

Literature
surveySelectionof DIAs

Preliminary
investigations

Selection of arepository site
Detailed
investigations

Repository
construction[Establishing and enhancing technical credibility]
First phase

Second phase
Third phase

FutureFirst
First phase
phase (Establishment(Establishment-- Application)
Application)ÆÆEstablishing
Establishingcriticalcriticalinfrastructure:
infrastructure:technical
technicaladv
advisory
isory committees,committees, national
nationalandandinternational
internationalcollaboration
collaborationnetwo
network,
rk, inf
information
ormationmanagement
policy(opennessandtransparency
management policy (openness and transparency),),concepts
conceptsf fororquality
quality andandinfinformation
ormationmanagement
management

Thereafter
ThereafterÆContinuous improvement:

SecondSecondphase
phase(Solicitation(Solicitation-- Selection
Selectionofof PIAs)
PIAs)ÆÆEstablishing
Establishingtechnicaltechnicalmanagement
management concepts:
concepts:

NUMO
NUMO structured
structured approach,approach, requirements
requirements management,
management, internalinternal
workingworkingstandards,
standards, communication
communication

f urthering dialogue withstakeholders, f lexibility to respondto changing boundary conditions

Third
Thirdphase
phase(Application(Application-- Selection
Selectionofof aarepository
repository site)site)ÆÆApplication
Applicationof
oftechnicaltechnicalm
management
anagementtools:
tools:

dev
development
elopment ofof site-specificsite-specific projects
projects based
based onon thethe NUMO
NUMO structured
structured
approach,approach, establishingestablishing communication
communication with
with stakeholders
stakeholders andand buildingbuilding
partnership
with
local
communities
partnership with local communities

Figure 2-2:

Establishing and enhancing technical credibility during staged implementation.

(1) First phase
In the first phase, covering the time period from establishment of NUMO up to receipt of an applicationfrom a volunteer community, our emphasis has been on building the critical infrastructure fordemonstrating the competence of this new organisation. To begin with, a few competent andexperienced project staff members were delegated to NUMO from Japanese nuclear organisations inorder to take up the key management roles. Since then further staff positions have been filled bydelegated personnel who, although inexperienced at the start, have rapidly learned the technical andproject management approaches developed in NUMO. Unfortunately, the system of rotating external
staff into short term delegate positions has also led to some of the acquired knowledge and experience
being lost again. NUMO has now recognised the importance of building a permanent dedicated team.
At an early stage, measures were taken to build experience rapidly. High profile Domestic andInternational Technical Advisory Committees (DTAC, ITAC) were formed to obtain expert reviews, forexample of our technical activities and published documents (Kitayama et al., 2005a; DTAC, 2003).
ITAC also helps to facilitate our access to the extensive international expertise in geological disposal2. In
addition, NUMO has concluded technical cooperation agreements with other key domestic andinternational organisations active in this field and has worked with them in areas such as site selection
2

Summary records of ITAC meetings are available in English on the NUMO website.

6

NUMO-TR-07-02

procedures, repository engineering technology, engineered barrier concepts and performanceassessment methods (Kitayama et al., 2005a).
We have reported progress during this phase extensively in the technical literature, at national andinternational conferences and in technical reports (the NUMO-TR series). This has already been very
successful in bringing NUMO to the fore in the international waste management community, andfocused efforts continue to enhance awareness of the programme in Japanese technical, political andgeneral public audiences (Kitayama, 2006). Local government officials and opinion-leaders (bothindividuals and non-governmental organisations (NGOs)) have been identified as playing an essential
role here.
An important component of NUMO’s infrastructure, even in this early phase, is a Quality Management
System (QMS). This has already been used to ensure production of high-quality documents that areboth readily understandable and accurate from a scientific and technical point of view. This QMS will
be modified and expanded in further phases, so that it can be applied to all key tasks in theimplementation programme.
(2) Second phase
In the second phase, running from open solicitation to selection of PIAs (ongoing at present), we will
improve and expand our management toolkit in order to further enhance technical credibility. Becauseof the special boundary conditions imposed by the volunteering process, the NSA will play a key role indemonstrating our ability to respond to the challenges involved (Kitayama, 2005; Kitayama et al.,2005b and 2005c). Within only a few years, we must analyse literature information to determine the site
conditions that are critical first for ensuring that the location meets the geological stability criteria
required for qualification, and then for allowing evaluation of construction practicality and assessmentof long-term safety. If, as expected, several volunteers come forward, such literature surveys may run inparallel for different sites and, additionally, we may need to rank these sites in terms of suitability, if
there are more qualified volunteers than can be practically carried forward to the PIA stage.
The PIA selection decision is not only politically sensitive, but it also involves a major commitment of
our limited resources. Clear and transparent documentation of this decision – and all the supporting
argumentation behind it – should be facilitated by the NSA framework and the associated RMS tool
(Kitayama, 2005; Sakabe et al., 2005). Key decisions need to be based on explicit guidelines and project
goals. In the current absence of appropriate regulations, we are developing internal working standards
that specify targets in terms of safety, environmental protection, etc. These complement the rather
general PIA Siting factors, which we have already published (NUMO, 2004a).
In this phase, we wish to motivate volunteer municipalities to participate fully in the PIA selection
decision. To encourage involvement, it is important to make our activities understandable, as far as
7

NUMO-TR-07-02

possible, by the general public and local residents. To date, we have seen that traditional methods forestablishing dialogue have often proved to be insufficient for communicating to non-technical audiences
the rather complicated technical activities involved in geological disposal. Therefore, NUMO has
initiated development of new techniques for promoting technical understanding, and is also investing in
training to improve the communication and dialogue skills of key staff (Inatsugu et al., 2006).

(3) Third phase
In the third phase, from receipt of an application to selection of the final disposal site, the first intensive
contacts between NUMO and the volunteer municipalities occur. Dedicated NUMO teams will develop
projects for each site, with all activities being coordinated and integrated by the NSA. These teams willinteract strongly with local communities, with the clear aim of establishing a partnership, so that
residents identify with the project. In order to achieve this, it is clear that we cannot simply present a
finalised, fixed programme, but must be prepared to take public concerns into account and modify the
project as required. At the same time, we also have ethical responsibilities to ensure the safety of current
and future generations and to develop a project with a reasonable use of resources. We expect thatbalancing potentially contradictory programme requirements in a clear and transparent manner will behelped by the envisaged development of the RMS, but will, nevertheless, function only if carried out by
a competent and credible project team.
The requirement for flexibility with regard to these phases is illustrated for the case of Toyo-cho
community, the first formal volunteer, which later withdrew its application. Clearly, withdrawal is partof the inherent reversibility of the solicitation process and responding to such unforeseen events in a
way that reflects the values adopted by NUMO is a key role of the NSA.
(4) Future phases
After the selection of DIAs, there will be a long, intensive, period of fieldwork, with the ultimate aim ofdeveloping a repository implementation programme at the chosen site, should it prove suitable. We
recognise that, even after the local community accepts the decision to be a DIA, continuous active
dialogue is required to maintain commitment to the project and ensure that stakeholders buy into thedecisions that will be made as the project becomes more concrete. We are aware that, even late in the
programme, surprises in terms of site characteristics or changes in boundary conditions may occur. The
NSA provides a framework for responding to such events, and for a structured decision-making process
regarding the final site choice, but we feel it is important that the local communities understand theassociated issues and also become involved in developing possible responses and deciding on which
will be adopted.

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NUMO-TR-07-02

3

THE NUMO STRUCTURED APPROACH

The particular value of the NSA is most apparent when the boundary conditions of the Japanese HLW
programme are considered. To illustrate this, we describe the initial use of the NSA for planningrepository concept development during the literature survey phase of characterising a volunteer site. It
should be emphasised that NUMO uses a rather wide definition of Repository concept (RC), which
includes not only a design but also specification of operational procedures and assessment of safety(Box 1). The initial illustration of the NSA is then extended to show how the iterative development ofconcepts at later stages of the programme utilises the NSA. Here “Structuring factors” are introduced toillustrate how the relative weighting of top-level programmatic issues can lead to changes in emphasisof the specific design and Siting factors that are used in lower level decision-making. From this basis,wider application of the NSA within the NUMO programme is considered.
Box 1
Repository concept: Definition (from NUMO, 2004b)
NUMO defines a “Repository concept” (RC) as a design of all surface and underground repository
structures, along with a description of how the repository can be constructed, operated and sealed. This
also includes an evaluation of operational and long-term safety and an assessment of costs andsocio-political impacts. The concept is dynamic, evolving with our programme as it moves from early
generic studies through to siting and, eventually, licensing for construction and operation. Indeed,
continual evolution during the operational period is also possible, as experience is gained andtechnology develops.

3.1

Structuring the development of repository concepts during theliterature survey stage

Soon after a volunteer comes forward, we will need to develop a site-specific repository concept, toserve as a focus for structuring our work programme and for discussions with stakeholders. As
preparation for this, NUMO has reviewed the background provided by more than two decades ofgeneric R&D on this topic in Japan. We concluded that the fundamental engineered barrier systemcomponents featured in the reference case of the H12 feasibility study (JNC, 2000) – vitrified waste in a
thick steel overpack surrounded by a bentonite-based buffer – provided the basis for a robust safety case.
However, we have examined many design variants that would allow options to be tailored to theparticular characteristics of a wide range of volunteer sites (NUMO, 2004b). Furthermore, the catalogueof H12-based options is recognised as focusing on those technical areas where Japanese organisations
have built up extensive experience and is thus not comprehensive; thus, even more variants would bepossible based on experience gained in other national programmes.

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NUMO-TR-07-02

Given this background, our challenge is to efficiently and transparently select a preferred option for a
specific site. The approach developed is illustrated in Figure 3-1. The central part of the figure illustrates
the progressive steps taken to develop a site-specific repository concept. The left hand part indicates theincreasingly detailed site data that are needed for this, while the right hand blocks make clear that
non-technical aspects (e.g. land ownership) and engineering constraints must be considered in parallelwith the geotechnical issues. In both areas of development, the work may require specific R&D
activities to be carried out, as illustrated by the outermost blocks.
Some particular points to be noted are:▪

In the first step, the volunteer area is checked against the published exclusion factors; if it fails toqualify based on these site characteristics, it will be rejected;▪

As Japanese volunteer municipalities may be rather small, with complex geological structures,
existing data are used to identify the constraints on the potential location of the repository interms of the footprint (area) and thickness (host formation and depth constraints set by rockmechanics or geothermal gradients);▪ For any site with potentially suitable volumes of rock, available information on hydrogeology
and geochemistry is used to evaluate constraints on operational practicality and repository
design;▪ After these simple checks, literature information is synthesised into a site conceptual model; thebest understanding of the site is then integrated with an evaluation of design constraints to selectone or more concepts appropriate to the siting option(s) in a volunteer area;▪

A performance assessment (PA) is then carried out to check that the design shows promise interms of meeting long-term safety goals; if it does so, the site can then be considered as apotential PIA;▪

If there are problems in meeting safety goals with a particular design, there is the possibility toeither modify the design to increase safety margins or to drop the site. If the problems appear
insuperable, the site will be rejected. If it is considered that a safe repository at the site may befundamentally feasible but would require development of further designs, then the site may beconsidered as a reserve option – to possibly be evaluated further depending upon what othersiting options are available.

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NUMO-TR-07-02

Application
Prior confirmation ofgeological conditions(1)Check(1)Checkwith
withSiting
SitingFactors
FactorstotoqualifyqualifyasasPIA
PIA

Literature survey(2)Possible footprint & area
for surface facilities

Major faults / lineaments(3)Footprint version #2

Geological structures(4)Host formation

Rock mechanics(strength & stress)
temperature(5)Depth constraints
Design constraints

Hydrogeology(6)Design constraints
Operational constraints

Chemistry(7)Design & material constraints

Geosphere / biosphereinterface(8)Site conceptual model

Non-technical constraints on
footprint
Technical constraints, e.g.
respect distances from faults
Guidelines for host formation:geometry/size, continuity, etc.
Evaluation of temp. limits
Evaluation of mechanicalconstraints
Evaluation of hydrogeological constraints
Evaluation of geochemical
constraints

R&D programme

R&D programme

Topography/ land use

Repository design options(incl. data for PA)(9)Site-specific concepts
Geosynthesis

not(10)Performance assessment OK

Develop further repository
design options
Repository design notacceptable

Site information(11)Concepts that are OK

Engineering/PA

Next stage

Figure 3-1:

Illustration of the NUMO Structured Approach as applied to initial development of
repository concepts during the literature survey stage (based on NUMO, 2004b).

The NSA provides a generalised methodology that we can apply to sites that have very different
characteristics, which may result in diverse repository concepts. It thus serves as a basis for consistenttreatment of volunteers and facilitates the comparison that may be needed if sites have to be ranked. It
also helps us to document uncertainties and to prioritise R&D requirements in a structured manner. Thisis important because the residual levels of uncertainty and the requirements for additional R&D may
both be used as attributes to be considered in ranking sites in a multi-criteria assessment procedure.
It is important to recognise that, during this early stage, site information will be very limited and there
may be large uncertainties associated with key characteristics. The decisions we make at each of theindividual steps shown in Figure 3-1 are thus provisional, based on a number of caveats. We thusemphasise to stakeholders that we will certainly modify concepts – possibly in a major way – as site
understanding improves and as construction and operational aspects receive more consideration.
Consistency is, however, provided by the NSA methodology which is used to identify and justify
required changes – as discussed further below.
If there are only a limited number of volunteers, all sites with acceptable concepts may pass to the PIA
characterisation phase; open issues and uncertainties identified during the process shown in Figure 3-1
will help focus the R&D included in the site characterisation programme and supporting engineering /11

NUMO-TR-07-02

PA work programmes. In the case of a larger number of suitable volunteers, we need to rank them toallow the most favourable to be selected as PIAs and others to be either rejected or specified as reserves.
To help this process, we have defined specific Siting factors (“Favourable factors”) (NUMO, 2004a),
which include many of the characteristics that have an influence on the entire repository project (e.g.
land availability, transport infrastructure). Even then, strategic issues (e.g. balancing the regional
distribution of sites or the pros / cons of selecting locations with similar characteristics) need to be
included in the final decision process. Thus, this process will involve weighting of different project
attributes; ideally both the attributes themselves and the weighting factors to be applied will be
developed as a consensus with interested stakeholders.
It is emphasised that the ranking process above is not based on PA results alone and, indeed, at the levelof analysis carried out at this time, PA results may be one of the attributes that show little discrimination
between sites. A more useful concept in this regard may be the safety case. The term “safety case” asused by NUMO corresponds fairly well to that defined by the NEA (NEA, 2004); NUMO, however,emphasises that, at early stages, such a case is provisional and may involve much qualitativeargumentation and be based on many assumptions that have to be validated as the project develops(Kitayama et al., 2007). Nevertheless, the ease of safety case development may be a feature that
distinguishes between different sites.

3.2

Decision-making within the NSA

Within the process outlined in Figure 3-1, the selection of site-specific concepts (step 9) is particularly
tricky, as the pros and cons of a number of different options need to be balanced against each other. To
facilitate this process and aid decision transparency, we have also defined a specific set of attributes that
we label as “Design factors” (Umeki et al., 2003; Ueda et al., 2004). These factors represent global
characteristics of the repository concepts, which we consider when evaluating options, including:long-term safety, operational safety, engineering feasibility/quality assurance, engineering reliability,
site characterisation and monitoring, retrievability, environmental impact and socio-economic aspects.
Because of limited information during the literature survey stage, the extent of quantitative assessmentof any concept is inherently limited; the achievable level at this stage may be similar to that in H12 (JNC,
2000) – i.e. idealised feasibility and post-closure safety assessment, with very limited evaluation ofeither practicality or operational safety.
We can use such Design factors in an absolute sense, to assess the fundamental acceptability ofrepository concepts for specific site conditions, or relatively, in order to compare alternative design
options. We have previously described the procedures for using these factors, involving either a matrix
presentation (bottom-up approach) or a multi-attribute analysis (top-down approach) (NUMO, 2004b).
Indeed, both of these have been applied to a number of “dry run” test cases, to confirm their applicability.
It has been seen that evaluating concepts in terms of their performance with regard to individual factors
is predominantly a technical challenge: however, the weighting of different factors to produce an
12

NUMO-TR-07-02

integrated evaluation requires top-level strategic input.
In addition to the technical Siting factors for site ranking and Design factors for repository concept
ranking, we have defined a top-level set of programme “Structuring factors”. Although the term usedhere is analogous to the siting and Design factors previously discussed, Structuring factors are of a rather
different nature. They represent key aspects of the overall NUMO programme whose importance must
be pragmatically weighted as the programme progresses in order to focus the overall effort, as illustrated
below (see also Box 2). Unlike technical factors, the Structuring factors and their weightings are
inherently subjective in nature and represent a strategic consensus of NUMO management – guided asmuch as possible by discussions with key stakeholders. Although a very rough indication of the way inwhich such factors may develop with time can be produced (e.g. Figure 3-2), this will certainly besensitive to the type and number of volunteer sites, national and international political developments,
advances in science and technology, etc.

Box 2Transparent decision-making
When comparing different options for sites, designs, etc., it aids transparency when the factors to be
used in assessing them are clearly defined in advance. NUMO has already published the Design
factors used for evaluating RCs and the Favourable factors used to select PIAs. These attributes canbe evaluated either quantitatively or using expert judgement. In order to rank options, “weightings”
have to be established that indicate the relative importance of different factors. Such weightings willchange as the programme develops; NUMO has attempted to provide some guidance for setting theweightings on Design and Siting factors by identifying overarching programme aspects, labelled
Structuring factors, and by indicating how the importance of these varies during repository
development. The specific Structuring factors used may be different at different programme stages.
The relative and absolute importance attached to these key aspects will affect the weightings on siting
and Design factors at any decision stage – but subjectively rather than in an objective, quantitativeway.

The later stages of the project, as represented in Figure 3-2, should not be over interpreted, but some
important messages to be communicated to stakeholders in early stages are indicated. Between theestablishment of NUMO and the start of open solicitation, we place major weight on general risk
communication: not consideration of a specific site, but rather the fundamental issues associated withthe safety of deep geological disposal. Even at the stage of selection of PIAs, it is likely (but not known
for certain until all volunteers come forward) that site information will be very limited and hence our
focus will continue to be on general issues influencing risk (e.g. arguments for geological stability)
rather than rigorous post-closure safety assessment. We also place significant weight on engineering
13

NUMO-TR-07-02

practicality (on the basis of current technology) and associated operational safety, even though it isunlikely that these aspects can be quantitatively assessed with the information base available from theliterature survey. This is because, in Japan, these topics are likely to be of concern to stakeholders andhave not been examined much in the past (e.g. within the H12 project). Therefore, we assign relatively
high weightings to siting and Design factors associated with these issues when comparing options,while R&D to support this work is given high priority. On the other hand, recognising that post-closure
safety can be well quantified only after extensive site investigation leads to this factor having a verystrong influence only later in the programme.
Site characterisation
Operational safety

Quality assurance

Post-closure safety
Risk communication

Engineering Technology

Relative weighting of factor

PIAｓ: Preliminary Investigation Areas
DIAｓ: Detailed investigation Areas
RS : Final repository site
Project completion

Post-closureManagement (monitoring?)

ClosureSite selection process (3 stages)
Repository design and performanceassessment

Operation

Selection ofRS

Construction

Selectionof DIAs

LicensingOpen solicitation initiatedEstablishment of NUMO

Figure 3-2:

Selectionof PIAs

Illustration of potential changes in relative weighting of Structuring factors influencing therepository programme.

The figure includes quality assurance (QA) as a Structuring factor, which gradually increases in relative
weight as the project develops. It must be emphasised that this does not mean that we do not consider
quality to be important at early stages; rather it recognises the reality that, initially, the programme must
utilise a lot of material that may not yet be fully quality assured. For example, the literature survey will
simply have to make best use of whatever is available for a particular location. Nevertheless, even at thisstage, QA measures will be applied to material identified as critical project input. At later stages, the QA
programme will be more comprehensive but, even here, we recognise that we cannot aim for an“perfect” QA system that covers all possible system components, but have to define one that is sufficientfor our purposes. This is especially the case if measures to assure QA compliance involve possible risks
to operational staff; here a very careful balance has to be achieved.

14

NUMO-TR-07-02

For the specific case of comparison of sites and associated repository design options at the stage of PIA
selection, the Structuring factors indicate the weighting we give to the different Design factors / Siting
factors when used in multi-attribute analysis. This leads to a consistent assessment for this particular
stage of the programme, while acknowledging that these will change in the future – with possible
changes in relative ranking of sites and / or repository design options.

3.3

Structured planning of the entire repository project

3.3.1

Application of the NSA during staged implementation

Although Figure 3-1 focused on RC development during the literature survey phase, the NSA also
serves to provide a structure for the planning and analysis of the field characterisation work. The figure
can thus be generalised (Figure 3-3) to include all the technical decision-making associated with thestaged siting process. Further, this process can actually be iterated at each of the implementation stages,
taking into account the changes in the relative weighting of different issues as represented by the
Structuring factors (Figure 3-2). In contrast to the approach in many other national programmes, the key
feature here is that, during each iteration, we reassess the entire sequence of decisions (as indicated for
RC development in Figure 3-1) in the light of improved knowledge, advances in science andtechnology and strategic weighting of Design factors and Siting factors.
Factors influencing project development(Structuring factors)
Input fromprevious stageEngineering
technology&&
PA technology

D

D

Site descriptivemodel and tailoredRC
Documentation
for move tonext stage

Figure 3-3:

R

R

Site conditions

Decisions on sitecharacteris ation
and repository
design/PA： Flow of requirements
and inf ormation

Generalised application of the NSA to guide site characterisation and repository design /PA at any siting stage.

The details vary somewhat, but we consider that the fundamental NSA is fully applicable to phases aftersite selection, including construction, operation and closure as indicated in Figure 3-4 (for simplicity andcomparison with Figure 3-1, this illustration focuses on RC development). Between PIA selection andlicensing of the chosen site, knowledge about the geological environment will have improved
considerably and we will tailor the RC to the best available model of the site. The design will, however,15

NUMO-TR-07-02

also have to be optimised in terms of not only long-term safety, but also operational safety / practicality(especially in the light of remaining site uncertainties) and quality assurance procedures. We have thus
decided that establishing the methodology for carrying out such optimisation is a priority for R&D in
the intervening period. For example, the post-closure safety case will initially concentrate on near-fieldprocesses and a robust engineering barrier system, as a pragmatic response to the limited geologicalinformation at early stages. The basic PA modelling capability needs to be extended, however, to allow amore realistic assessment of total system performance, which will be needed to compare options. In
addition, efforts are underway to rigorously assess operational phase safety and the practicality ofassuring quality of the constructed engineered barriers. These are key components of the total safetycase which are identified as being in need of particular attention now, as they may better discriminate
between sites while information is still limited (Kitayama et al, 2007).
A basic principle of the NSA is that decisions are never frozen and can always be reassessed as required.
Even after licensing, site understanding and technology will evolve further during the decades of
construction and operation and hence further optimisation may be introduced. During construction andoperation, operational safety and quality assurance are particularly important and experience gained
from this “first-of-kind” project in Japan is expected to allow us to make continuous improvements.
Even at the final stage of licensing for closure, we will make use of the experience gained during all
previous stages to optimise the final closure concept – which may well be very different to thatenvisaged in the original construction license. This step will certainly involve some discussion of
post-closure monitoring. At present, there is no technology that could directly monitor safety-relevant
performance of a repository without risking perturbation of the key safety barriers. This could, of course,
be completely different at the end of the 21st century. On the other hand, either advanced safetyassessment technology or growth in public confidence in repository safety might make such monitoring
unnecessary. The NSA allows for such uncertain boundary conditions and provides a method for
ensuring that we will find an optimum solution based on state-of-the-art understanding of the issues
involved at the time when the decision finally has to be made.

16

NUMO-TR-07-02•Flexibility to adopt new technology at any stage

Requirements for very long term
projects•Flexibility to respond to stakeholders’ wishes-Progress of science andtechnology-Public involvement-Risk communication-Requirements of stakeholders

Structuring
factors

RC prior to
closure stage

Structuring
factors

RC fromprevious
step

Structuring
factors

R&D

Site
conditions

Generic RC

R&D

Confirmsite conditions

Confirm
designEngineering
technology

Closureconcept

Re-evaluationof design

Engineering
technology

Optimized RC

PAtechnology

R&D

PA
technology

Progress

Closure license

Closure ※R&D

Operations
Construction

R&D

Site
conditions

Site assessment
RC design
Site selection
Site specific RC

Engineering
technology

License application

Licensing ※R&D

PAtechnology

Selection of final repository

DIA selection
Site selection and RC reports

PIA selection ※2000 Establishment of ＮＵＭＯ

Figure 3-4:

3.3.2

Operation steps※ Milestones illustrated

RC: Repository concept

Illustration of potential changes in weighting within the NSA as the project develops.

Response to surprises and unexpected changes in external conditions

Figure 3-4 emphasises the planned development of a project, where gradual changes in Structuring
factors can be taken into account at project milestones or regular evaluation points within longer stages(e.g. every 5-10 years). We consider it very important, based on international experience, to also allow
for surprises – which may either be technical (unpredicted geology, sudden technologicalbreakthroughs) or socio-political (new concerns of local communities, social disruption). Such surprises,
if significant, should result in a rapid response at an appropriate level, regardless of whether areassessment milestone has been reached or not. Potentially the most disruptive would be events that
influence the entire programme (Figure 3-5). Basically, however, any event can be reflected in a change
in the Structuring factors, allowing the NSA to be directly applied.
For example, the scenario of a high profile accident in an underground construction project in Japan
could be the trigger for a reassessment of the programme. Here, much higher weighting than previously
used might be placed on site uncertainties (determining any similarities with the accident location) andoperational safety. The output might involve both changes in the site characterisation plan (to improveassessment of similar risks under expected conditions) and the repository design (including both barrierfeatures such as tunnel liners and operational procedures / infrastructure such as emplacement
17

NUMO-TR-07-02

methodology, ventilation and drainage). The explicit consideration of such cases in the NSA allows
responses to be implemented rapidly and readily communicated to stakeholders.
External changes

Better defined boundary conditions

Increase in site understanding+ input from R&D
Reconsideration due toexternal changes

Engineering / PA technology
advances + input from R&D

5∼10 years

Figure 3-5:

Application of the NSA between implementation stages.

Surprises may be categorised in terms of their impact. Some may clearly require an immediate andcomplete reassessment of the entire project; others may be more limited in scope and would primarily
affect only a component of the technical programme – e.g. many types of unexpected geologicalfindings. The latter are more probable and we can take them into account by applying the NSA to areassessment of only the influenced components of the project. We can evaluate borderline cases
between these two extremes qualitatively, by determining the extent to which “current” Structuring
factors would be changed and assessing the impact of such changes on the programme.
For example (Figure 3-6), major advances in site characterisation technology could greatly reduce
uncertainties – allowing improvement of the model of geological structures, including safety-relevant
major faults and associated geochemistry – and could thus improve the assurance of performance of thenatural barrier. Such improved understanding of the geosphere allows a change in the relative weightingof the Structuring factors, which might then allow us to optimise the engineered barriers, relaxing
previous thermal, mechanical and chemical constraints. Again, this would be a structured response to aforeseeable development and should be able to be communicated as learning from experience, not to be
confused with a simple “cost-cutting” measure, which might cause public concern.

18

NUMO-TR-07-02

Modified ‘Structuring facto r s’ in respon se to ex ternalchanges

Assessment of impact
on site understanding

Assessment of impact
on design and saf ety

Engineer ing

Site conditions････

Thermal constraints

Geological structure････

Mechanical constraints

････
････

Major f aults

PA
････

････
Geochemistry

Chemical constraints

････

････

: Area influenced by modification of the ‘Structuring factors’

Figure 3-6:

Example of the process of responding to external changes; modification of theStructuring factors leading to reassessment of assumptions and boundary conditions.

The optimisation process is indicated in Figure 3-7. The management decision that we have to make iswhether the changes involved are so critical that an immediate re-focusing of the project is needed, orwhether they can be accommodated by minor changes of component work packages – with complete
reassessment postponed until the next planned project milestone. Whatever the case, the analysis
involved and the resultant decisions are documented in a consistent manner that will be transparent to(or even include input from) local communities.

Modified ‘Structurin g factors’

RC from previous stage

Site conditions････
Geological structure

R&D

････
････

Engineer ing
Reassessmen t b asedo n n ew r eq u ir emen ts& kn o wled g e

Thermal constraints････
Mechanical constraints

Major f aults････
Geochemistry

････

PA
Mo d i fied d eci sio n s o n si teselecti o n , ch ar acteri satio n
p l an , tail or ed RC, etc.

R&D

････
Chemical constraints････

Revised report on site selection and RC: Area influenced by modification of the ‘Structuring factors’: Flow of modified requirements and know ledge

Figure 3-7:

Example of the process of responding to external changes; project optimisation.

19

NUMO-TR-07-02

In overview, the development of a volunteer site might look quite different to the nomination of sites fora reference repository concept, as is the case in most other national programmes. For example, on thebasis of the literature survey, three particular host rock / repository designs might be considered for a site.
During PI, one option could be abandoned (e.g. if the host rock is not found at a depth accessible withexisting technology) while another might be expanded into variants (e.g. if a potential host rock wasstronger / more homogeneous than expected). By the detailed investigation (DI) stage, increased
understanding and greater weight on operational safety may cause further reassessment of options –merging variants or postponing further consideration of options which appear more problematic. At any
point, however, a change in external conditions (e.g. a social requirement for ease of retrievability) cancause modification of an option or, indeed, reconsideration of past decisions (e.g. mobilising reservesites, revisiting abandoned designs which may become feasible on the basis of improved technology).
The structure of the process described is illustrated in Figure 3-8. In effect, this emphasises both
flexibility and the concept of the “reversibility” of decisions. These are features that are considered to beimportant in most national programmes that focus on staged implementation, but we consider them
particularly critical for NUMO’s special boundary conditions. Emphasis of this process from the
beginning should show NUMO’s preparedness to respond to changes and encourage the participation ofinterested parties in developing a consensus response.
The NSA provides a clear methodological framework for developing projects in a flexible manner,
identifying the key decisions to be made and placing them in context. In itself, however, it provides little
direct support for the various decisions that have to be made on a regular basis and at various
hierarchical levels. Nevertheless, by identifying the factors that have to be considered and theweightings to be applied to them, the requirements to be considered when reaching and documenting
decisions can be specified. This can assist our application of an appropriate management tool to guidecomplex, multi-disciplinary decision-making – the RMS described in the following chapter. Indeed,with the emphasis on flexible responses to changes and reversibility of decisions, the RMS is consideredessential for practical implementation of the NSA – especially given the long duration of the repository
project and the inevitable changes in personnel and boundary conditions that will occur over this period.
Original
options

Advances in technology /Reserve changed boundary conditions

BranchOption A

ModifyOption D

Option A2

Option B
Option Co

Option A1

Merge
Abandonx

Progress in site characterisation

Figure 3-8:

Process overview – maintaining flexibility and focus.

20

Option E

New Option F

NUMO-TR-07-02

4

CONCEPT OF REQUIREMENTS MANAGEMENT AND ITSAPPLICATION WITHIN THE NSA

As any project grows in complexity, maintaining the overview needed for informed decision-making
becomes more difficult. By the end of the 20th century, this was already acknowledged to be a particular
problem in major, high-technology projects (a good example being the aerospace industry), especiallywhen these might extend over decades and be subject to continuously changing regulatory andsocio-economic boundary conditions and to steadily advancing science and technology. This has led tothe evolution of the field of “requirements management” (see Box 3) and the development of many
tools to assist implementation of various types of formal Requirements Management Systems (RMS).
Box 3
Requirements management
The term “requirement” as used here applies to any project constraint, i.e. to any quantitative or
qualitative boundary condition or goal to be satisfied by the project. The challenge is to optimise theproject with regard to such requirements – a task which increases in complexity as the number ofrequirements increases, as requirements change with time and as the project is defined in more
technical detail.
“Requirements management” can be defined as a systematic approach to identifying, organising,communicating and responding to changing requirements during design, development, licensing andimplementation. A critical task for all projects is to establish a solid set of baseline requirements andrigorously manage the changes in these as a project matures. Another key element of requirements
management is the ability to define requirements at the correct level of detail for a specificapplication, taking into consideration both technical needs and external boundary conditions. The
overall process of specifying and managing requirements is sometimes termed “requirements
engineering”.
The deep geological disposal of HLW might be regarded as a rather low-technology project in terms ofpractical implementation, but it is supported by state-of-the-art science in a wider diversity of technicaldisciplines than almost any other industry. Particularly when the long project duration is considered –around a century or more – repository implementation is clearly an appropriate field for the use of anRMS. The high priority we assign to development of such a system for the NUMO programme results,
however, from the constraints set by the practical implementation of the NSA – requiring regular
iterations of making (or reviewing) decisions at a range of hierarchical levels. In addition, ourcommitment to openness and transparency requires that such decisions should, wherever possible,
include input from involved stakeholders and, in all cases, be clearly documented. The final
consideration which gives urgency to this initiative is the current situation where many of our key staff
members are only on relatively short attachments to NUMO; providing them with the background to beable to evaluate the basis for decisions and ensuring that all such decisions are comprehensively
recorded is thus critical.
21

NUMO-TR-07-02

4.1

Hierarchical structure of decision-making within the NSA

As emphasised in the previous chapter, we make decisions in many different technical areas and at a
range of hierarchical levels – from relatively frequent modifications of site characterisation plans orrepository designs to the major site selection and licensing decisions made at project milestones. Thissituation is illustrated in Figure 4-1, which indicates also the important coupling between decisions.
Thus, for example, a decision on the design of a waste overpack is coupled to decisions on the host rockchosen to be the focus of site characterisation and also on how compliance with regulatory guidance
will be assured. Indeed, it can be even more complex as, even at a detailed technical level, decisions
may interact with socio-economic issues such as public acceptance and cost. Coupling may extend not
only horizontally, but may also directly link decisions at different hierarchical levels.
Top-level decision-making(policy, strategy)

NSA for the entire NUMO
programme

Socio-economic issues

Decision-making on top-leveltechnical issues
Decision-making on
specific technical topics

NSA for technical issues

NSA for specific issues

coupling
Site characterisation

Figure 4-1:

Engineering and PA

Compliancewith regulatory
guidance

Hierarchical structure of decision-making within the NSA.

The need to make decisions influenced by a complex range of factors was recognised at an early stage
by NUMO; this has also been well documented in other national programmes – particularly associatedwith site selection. To gain experience with practical support tools for making such decisions, we havebeen carrying out case studies using a fairly standard Multi-Attribute Analysis (MAA) approach(NUMO, 2004b; Tsuchi et al., 2007) and have also examined alternative methods such as Evidential
Support Logic (ESL) (Tsuchi et al., 2003).
For decisions such as selection of preferred host rocks, sites or repository designs, we can base theattributes on the defined Siting factors / Design factors, while weightings of these would be based on therelative Structuring factor weightings appropriate to the particular stage of the programme (see Box 2).
These methods can thus be useful for supporting major decisions at project milestones, but are of22

NUMO-TR-07-02

limited applicability to lower-level technical decisions of the type that are made on a regular basis. A
further inherent limitation is that both these methods are passive – they do not provide any kind of active
feedback to indicate when reassessment of the decision may be needed (a key component of the NSA)
and they do not link different decisions. Such tools are thus necessary, but not sufficient, for our
implementation of the NSA.

4.2

Decision-making within the RMS

Basically, the NSA provides a logical sequence for stepwise development of plans – leading to a
network of decisions that, in general, become more technically detailed as they are traced to lower
hierarchical levels. An example is indicated in Figure 4-2, which is a representation of the componentsof the decision hierarchy associated with repository design. Although appearing complex, this is actuallya considerable simplification of the true situation, where the previously mentioned coupling between
decisions is important – as indicated in Figure 4-3.
These figures also illustrate the common basis of any decision – which is reached from some kind of
consideration of a number of different requirements that have to be met. Each requirement, in turn, isassociated with certain arguments – or assumptions – that define its applicability. The requirements
overlap between decisions and can be used to define the coupling between them. Thus, although interestis usually focused on decisions, requirements are more fundamental and hence form the basis for the
RMS, which aids the decision-making process. It should also be noted that, although decisions maychange over a short time period, in particular when knowledge about a site is increasing rapidly, thebasic requirements change much more slowly and, indeed, some may alter little over the entire period ofdevelopment of the project.
Examination of Figures 4-2 and 4-3 allows some of the key attributes that an RMS must have in orderto support the NSA to be highlighted:▪

The hierarchy of decisions must be established and these must be able to be followed (andevaluated) in both a top-down and bottom-up fashion;▪

The considerations for decision-making (i.e. the specific basis on which the decision rests) mustbe fully recorded, particularly the weightings assigned to the different (potentially contradictory)
requirements involved;▪

The potential need to reassess any decision should be flagged automatically in the case ofchanges in either top-level considerations (e.g. due to a change in Structuring factors), thearguments supporting the requirements (e.g. due to a change in a lower-level decision) or the
emergence of new requirements (e.g. due to a surprise external change).

23

NUMO-TR-07-02

D: Decisions
Selection of
PIA

D

C: Considerations for decision-making

C

R: Requirements

R

R

A

D

Selection of site
specific RC

R

A: Arguments forming the basis forrequirements

A

C
R

A

A

D
R

Establishingdisposaltunnel pitch

R

Figure 4-2:

R

A

D

Establishing
repository
depth

C

A

D

C
R

A

R

A

C
R

A

A

Example of the hierarchical structure of decision-making.

R
Conforms withsiting factors
for long-term
geologicalstability

D
R

R

A

A

Uplift not a threat torepository safety

C
R

D
R

R

A

A

D

C

Selection of
PIA

A

R

A

D

C

Selection of site
specific RC

AR

Decisions coupled bycommon require ments

C
R

A

D
R

A

Establishingdisposaltunnel pitch

Example of coupling of decisions.

24

A

Establishing
repository
depth

C
R

A

D
R

Figure 4-3:

Establishingwaste package
pitch

A

D

C
R

A

R

A

Establishing
C waste package
pitch

R

A

NUMO-TR-07-02

4.3

Requirements management in the decision-making process

4.3.1

Terminology

To avoid confusion, it must be emphasised that the term “requirement” as used in the RMS field is a
general term applied to any project constraint (see Box 3) and not a hard “necessity” as implied bycolloquial English. For a geological disposal project, requirements may be quantitative (40,000 waste
package inventory for repository) or qualitative (desire for a simple geological setting), externallyimposed (e.g. 300 m minimum depth) or NUMO decisions (volunteering approach), well-defined(exclusion distance from Quaternary volcanoes) or provisional assumptions (maximum acceptable
uplift rate). Requirements can also be structured hierarchically, the top-level set by legislation and policy
leading to lower-level, derived requirements – leading eventually to detailed work or productspecifications. This is formalised within an RMS; in principle, however, the process is similar to the
traditional use of hierarchies of reports to describe a project and, indeed, some RMS software utilises
such documentation to structure the implementation of a practical system for the management of
requirements.
The decisions illustrated in Figures 4-1 and 4-2 involve assessment of information, which may be used
to determine the extent to which requirements are met. As emphasised before, such information may bevery uncertain in the early stages of the project and an improvement in understanding may be a trigger
for us to reassess a decision. Alternatively, lack of knowledge of key system characteristics may require
us to make a provisional assumption, with resolution of specific issues identified as priority topics for
R&D. As the amount of information – which can generally be classed as “knowledge” – expands in a
project, its management also becomes a challenge. This has been recognised by the Japan Atomic
Energy Agency (JAEA), which is currently developing advanced concepts for a Knowledge
Management System (JNC, 2005) that could, in principle, provide support for the NUMO’s RMS. Suchdevelopments are being actively followed by NUMO but, at present, are less critical than establishing
the basic RMS infrastructure and putting a QMS in place for the key knowledge that will be generated
by NUMO as soon as the siting process commences.
4.3.2

Outline of the NUMO’s RMS(1) Hierarchy of requirements
At a top hierarchical level, it is clear that NUMO has to develop a repository project that conforms to therequirements specified in laws and regulations. To date, the main law of relevance is the Final Disposal
Act, which is complemented by outlines of policies and implementation plans produced by the Atomic
Energy Commission (AEC) and the Nuclear Safety Commission (NSC). These will be expanded on ata national level as the repository project moves towards implementation and will, as siting progresses,
also include regulations or guidelines that may be specified at a more local level by the prefecture or themunicipality.
25

NUMO-TR-07-02

Although it is only intended to be illustrative (the actual hierarchical structure to be used in the RMS iscurrently under development), the appendix indicates how the top-level legal requirement can be broken
down into sub-requirements – which can be separated pragmatically into those relating to the site andthose focused on the repository concept. At an even lower level, design requirements can be split into
those that are related to operational safety, those more relevant to post-closure safety and those
associated with environmental impact. It should be emphasised, however, that there are clear links
between such requirements and that this process can be continued to several lower, more detailed
hierarchical levels.
In addition to legal requirements, there are also technical constraints on the NUMO programme andpractical requirements associated with credibility – not only of the programme, but also of NUMO as
the implementing organisation (as highlighted in Chapter 2). Again, such top-level requirements can be
broken down in increasing detail. It is interesting to note that the NSA, and the RMS itself, arise
naturally as important components of NUMO’s programme to respond to these requirements.
(2) NUMO’s technical basis for implementing the RMS
The appendix not only lists examples of requirements, but also provides comments that indicate theparticular approaches, infrastructure, tools or focused R&D that NUMO will use to satisfy them.
Although the RMS development is ongoing at present, significant progress has already been made inensuring that the technical basis for implementing the RMS will be available as and when needed. The
management structures associated with the NSA have already been discussed, and the overarching
QMS has been mentioned. This section thus summarises progress in technical areas - broken down into
site selection / site evaluation, repository concept development and compliance with regulatory
guidance (Figure 4-4).
With regard to siting, we have already published Siting factors for the selection of PIAs (NUMO,
2004a), which include the legal requirements for site selection as laid down in, for example, the Final
Disposal Act. Similar, more detailed Siting factors are scheduled to be published in advance of thesubsequent selection phases and these will reflect the changes in weightings in the programme andadvances in site understanding as indicated by the structured approach. We have developed methods fortechnical evaluation of factors associated with site suitability and have also prepared associateddatabases. These include, for example, a geographic information system (NUMO-GIS) and a geologicalenvironment data management system. We are also examining an “information flow diagram” approachfor the literature survey, which effectively provides a method for defining the links between required
assessment information and the investigation methods used (Noda et al., 2007). We will update these
databases and the associated information flow diagram on the basis of increasing information as the
project advances, or, as emphasised by the NSA, in response to surprises or changes in boundary
conditions.

26

NUMO-TR-07-02

We will establish appropriate, tailored repository concepts by iterating repository design andperformance assessment on the basis of site conditions; initially, comparison of various options will be
aided by Design factors, which we have already published (Umeki et al., 2003; Ueda et al., 2004). The
selection of site-specific reference concepts will also be guided by the NSA and reassessed at project
milestones and in the event of any changes in boundary conditions. To assist re-evaluation, we havebeen looking at a computer-assisted repository concept development system (NUMO, 2004b), whichallows repository design and performance assessment to be conducted systematically and efficiently forspecifically defined site conditions.
Overlapping these two technical areas, we have, as previously mentioned, examined the applicability ofcomparison and evaluation methods based on MAA and ESL to allow ranking of sites and / orrepository concepts.
Due to the absence of regulatory guidelines to date, we have placed a high priority on establishinginternal working standards. These will effectively define our goals and code of conduct for early project
phases, until the official safety regulations for geological disposal and any other relevant legislation (e.g.
on environmental protection) are established in the future. In line with the NSA, these standards will
evolve with the progress of the project and will be key requirements to be applied in site selection,
establishment of repository concepts and construction, operation and closure of the repository.
Given the importance we assign to involvement of stakeholders in the entire process, efforts towards
developing improved methods of risk communication has wide applicability. This is complemented bytechnical work to establish methods, using relational databases, for communicating and archiving key
knowledge and information that support our evolving safety case.
We expect that such a comprehensive toolkit, utilised in combination with the RMS, will facilitate our
implementation of practical and efficient projects within the overall framework set by the NSA.

27

NUMO-TR-07-02

Overall quality assured by QMS
Management/planning of overall programme - integrated by NSA / coordinated by RMS
Technical work – weighted by
Structuring factors

Site
selection

Management/planningof technical work

Development of
repository concepts

Site evaluation

Technical reports

Compliance withregulatory guidanceTechnical toolkit

Siting factors(infrastructure)
Support tools for
decision-making(MAA, ESL etc)

Figure 4-4:

Geologicalenvironment data
management
system and
NUMO-GIS

Working
standards
Information
Flow Diagramfor LS & PI

Structuring factors

Risk communication
methodology

RC catalogue

SA codes &Repository concept
development system

Overall perspective of NUMO’s technical programme.

(3) Practical constraints on development of the RMS
We intend the RMS to be a practical tool that will assist in the implementation of decision-making
within the NSA – both for day-to-day technical decisions and major project reassessments, either atplanned milestones or in the case of surprises. Indeed, as previously noted, ideally the RMS should
actively identify links between decisions and flag cases where past decisions might need to be
re-evaluated.
The major objectives behind developing an advanced software RMS tool include (Sakabe et al., 2005):▪

Ensuring transparency and traceability in decision-making processes;▪

Recording project decisions, considerations that influenced them and requirements andarguments behind these decisions;▪

Anticipation and support of future decision-making;▪

Identifying the consequences of changes in decisions or boundary conditions;▪

Supporting R&D planning by establishing needs and setting priorities.

28

NUMO-TR-07-02

With the above objectives in mind, the resulting RMS tool should have functions that include (Sakabe etal., 2005):▪

Taking full account of the interconnected nature, hierarchy and cross-relationships between
decisions and requirements;▪

Being flexible enough to allow for the changing nature of requirements and the possibility ofrevising or reversing decisions as the project progresses;▪

Accepting and recording changes in a controlled, orderly and well structured manner, supervised
by a system administrator;▪

Incorporating the concept of “ ownership” - each user is authorised to propose modifications to alimited subset of requirements and decisions;▪

Actively providing input to, and accepting feedback from, users (NUMO staff) affected by any
decision/information changes;▪

User-friendliness: simple, self-evident commands and operations incorporated into an interface
allowing ease of use by even non-technical staff;▪

Providing adequate security - allowing only limited access to sensitive information and assuringa robust system of archive backups;▪

Being centrally hosted so that only the current version is always running.

It must be emphasised that such a system does not make decisions – it merely ensures thatdecision-makers have ready access to all of the information relating to any issue and are fully aware of
the consequences of different available options. Together with the support tools for evaluating complex
decisions (MAA, ESL), this will aid openness and transparency and, ideally, also involvement of
stakeholders in developing a consensus on key issues.
Practical implementation within an evolving project is illustrated in Figure 4-5. The RMS represents any
decision in a standardised manner. In the case of any change in an external decision / requirement /argument linked to this decision, the influences are clearly highlighted and their effect on theconsiderations behind it are noted. This allows the decision-making process to be modified and thejustification for the new decision to be documented. In fact, as the entire process is recorded, theevolution of a project can be readily traced. Termed “change management”, this has been identified as a
key function of our RMS.

29

NUMO-TR-07-02

Original form

Di C

Transitional stage

Modified form

D’i C’

D”i C”

R’i1 A’i1 R’im A’im

R”i1 A”i1 R”ik A”ikDs
i

Ri1 Ai1 Rin Ain

influenceii

influence

Rs1
Isolated initial decision made bya specific consideration of
relevant requirements andarguments

Figure 4-5:

Clear definition of changes driven byexternal decisions or requirements
The correction is iterated byevaluation of any changes to theconsideration process and associatedrequirements / arguments.

Refined specification of
the modified decisionmaking process

An example of record preservation for the modification of a decision in response tochanging knowledge or requirements.

The RMS thus identifies gaps in knowledge or uncertainties which make a decision provisional,
depending on particular assumptions. These assumptions can serve to focus and prioritise R&D and,based on the results of improved understanding, either lead to confirmation of the decision or else flag it
for reconsideration as described above. In the future, it may be that this latter function can be
implemented by a supporting Knowledge Management System; although this does not currently seem
practical on the basis of existing technology, developments in this area will be followed with interest.

4.4

Further development and implementation

The rather detailed description of the fundamentals of the decision-making process, as we intend to
implement it within our RMS, highlights the logical structure involved. It is presented in such detail not
only to show its flexibility in terms of application to all parts of our programme, but also to emphasise
the role of change management, which – as is clear from the earlier NSA discussion – is a critical issue
in our programme. From this basis we need to develop dialogue with key stakeholders so that they cansee how decisions are made and how such decisions might change in the future – particularly as a resultof surprises. Ideally, stakeholders will actively participate in this process.
In the interim, the main role of the RMS will be within NUMO, helping our staff to prepare forvolunteers and to move forward efficiently as soon as potential sites appear. Here, it is essential that thetheoretical structure presented above works in practice. Thus, development of a prototype RMS tool
proceeds iteratively with checks of practicality for specific test cases. Such a procedure is, of course, inline with the NSA concept; we accept that our RMS may need to be modified in the light of experience
to ensure that it is tailored to our particular needs.
30

NUMO-TR-07-02

5

CONCLUSIONS AND A LOOK TO THE FUTURE

This report has outlined the special boundary conditions on the NUMO programme. These result
predominantly from the flexibility needed to implement geological disposal of HLW based on the
NUMO volunteer approach to siting and on the strict Japanese requirements for transparency andtraceability, but due also to the inherent constraints set by a complex, highly sensitive project that willdevelop over a period of a century or more. Rather than the conventional emphasis on a reference
repository design and host rock – as is typical of most national programmes – we have concentrated on
the process of optimally tailoring a technical project to the particular conditions encountered, as
formulated in the NSA. The use of the NSA has been illustrated by its application to the development ofsite-specific repository concepts during the literature survey phase, but it will be applied to our entire
programme. To assist in its application, we are in the process of developing a formal RMS.
The NSA places particular emphasis on the provisional nature of decisions made when uncertainties arelarge, particularly at early stages of site characterisation. The system allows for ease of reassessment or,indeed, reversal of decisions – a key attribute of adaptive staging. Further, within the RMS, theevolution of system understanding and boundary conditions can be followed automatically anddecisions that may need such re-evaluation can be identified. The NSA applies to the expecteddevelopment of the project, allowing for changes in the weighting of particular issues at different stages– as indicated by Structuring factors. This flexibility also allows the consequences of technical surprises
or unexpected changes in boundary conditions to be readily incorporated into the NSA process.
Apart from practical advantages, the application of the NSA and the supporting RMS are a deliberatepart of our strategy to develop technical credibility. This area is one where we feel a need to be at theforefront of the state-of-the-art, demonstrating an ability to respond to the complex challenges in theJapanese HLW programme and illustrating our commitment to open and transparent decision-making.
In addition to the RMS, we are developing a range of supporting management tools that will assist withcompiling and assessing the large volume of information that will accumulate during this project – andrefining it into a form suitable to support the decision-making process. Of particular importance here is
the overarching Quality Management System; although this is clearly essential and urgent, ourdevelopment of this system is proceeding in a stepwise manner to ensure that it is properly tailored to
NUMO’s particular requirements.
For the immediate future, the main challenge is clearly to motivate and support volunteer communities.
The investment in improving communication tools and efforts to develop dialogue with interested
communities and key opinion-formers is expected to bear fruit only if NUMO can be seen to be atechnically credible, honest partner. The NSA may be difficult to implement, but it shows a commitment
to flexibility and preparedness to change plans to meet the desires of stakeholders, which we thinkwould be difficult to demonstrate using conventional approaches. Implementing and operating theformal RMS may also be expected to result in challenges but, from the perspective of the entire project31

NUMO-TR-07-02

duration, an intensive effort now may yield benefits at later stages of the programme – particularly whenwork pressure and deadlines might be more critical than at present.
With the advantage of being a young organisation, NUMO has been able to incorporate the NSA as a
keystone of our corporate culture. This is apparent in the way that flexibility and reversibility are beingemphasised in all our planning documents, in marked contrast to the rather rigid planning approaches
formerly used in the nuclear field and common still in other industrial areas. It is one of the firstsuccesses of our work in this area that, even prior to implementation of the RMS, our staff members are
effectively applying the principles of the NSA in their daily work – even if do not always make explicit
reference to the formalised structures involved.

32

NUMO-TR-07-02

6

ACKNOWLEDGEMENTS

This report records concepts developed by NUMO, which have been refined by extensive discussion
with other Japanese organisations and with our international partners. In particular, we would like toacknowledge the role of our International Technical Advisory Committee, whose extensive andperceptive review of an earlier draft led to extensive modifications reflected herein.

33

NUMO-TR-07-02

7

REFERENCES

Special Radioactive Waste Final Disposal Act, 2000 (in Japanese).
DTAC (2003): Report on the technical review of “Siting factors for the selection of Preliminary Investigation
Areas” and “Repository concepts”, Domestic Technical Advisory Committee, 8 May 2003 (in Japanese).
Inatsugu, S., Takeuchi, M., Kato, T. (2006): Public Perspectives in the Japanese HLW Disposal Program, Proc.
VALDOR 2006, -VALues in Decision On Risk, 14-18 May 2006, Stockholm, Sweden, pp.82-89.
JNC (2000): H12 Project to Establish the Scientific and Technical Basis for HLW Disposal in Japan, Project
Overview Report, 2nd Progress Report on Research and Development for the Geological Disposal of HLW
in Japan, JNC Technical Report TN1410 2000 001, Japan Nuclear Cycle Development Institute (JNC),
Tokai-mura, Japan.
JNC (2005): H17: Development and management of the technical knowledge base for the geological disposal Knowledge Management Report. JNC Technical Report JNC TN1400 2005-022, Japan Nuclear Cycle
Development Institute (JNC), Tokai-mura, Japan.
Kitayama, K. (2003): NUMO’s open solicitation of volunteer municipalities for a potential disposal site, Proc.
ICEM ‘03: The 9th International Conference on Radioactive Waste Management and Environmental
Remediation, 21–25 September 2003, Oxford, England.
Kitayama, K., McCombie, C., Ohe, T. (2005a): Strategies for Technical Confidence Building in the NUMO HLW
Disposal Programme, International Conference on the Safety of Radioactive Waste Disposal, 3-7 October
2005, Tokyo, Japan.
Kitayama, K., Umeki, H., Ueda, H., McKinley, I. G., Kaku, K. (2005b): A structured approach for stepwise
tailoring of repository concepts to volunteer sites, Proc. ICEM'05, The 10th International Conference on
Environmental Remediation and Radioactive Waste Management, 4-8 September 2005, Glasgow, Scotland.
Kitayama, K., Ueda, H., Sakabe, Y., Umeki, H., McKinley, I. G., Kaku, K. (2005c): A structured approach for
stepwise design of HLW repositories tailored to volunteer sites, Proc. International Conference on the Safetyof Radioactive Waste Disposal, 3-7 October 2005, Tokyo, Japan.
Kitayama, K. (2005): NUMO structured approach for implementing a HLW repository, The 2nd Japan-Korea
Joint Workshop on Radioactive Waste Disposal 2005: Interaction between NBS and EBS, 6-7 October 2005,
Tokyo, Japan.
Kitayama, K. (2006): NUMO’s Winning Team: a goal-oriented approach to gain the confidence of all stakeholders,Radioactive Waste Management, 12-14 June 2006, London, UK.
Kitayama, K., Ishiguro, K., Takeuchi, M., Tsuchi, H., Kato, T., Sakabe, Y. and Wakasugi, K. (2007): Strategy forsafety case development: Impact of volunteering approach to siting a Japanese HLW repository, OECD
Nuclear Energy Agency International Symposium: Safety Cases for the Deep Disposal of Radioactive
Waste: Where do we stand?, 23-25 January 2007 , Paris, France.
MITI (2000a): Basic Policy for Specified Radioactive Waste, Ministry of Economy, Trade and Industry (MITI)
Notification No.591 (in Japanese).
MITI (2000b): Final Disposal Plan for Specified Radioactive Waste, Ministry of Economy, Trade and Industry

34

NUMO-TR-07-02(MITI) Notification No.592 (in Japanese).
NEA (2004): Post-closure safety case for a geological repository, Nature and purpose, NEA Rep. No. 3679,
OECD/Nuclear Energy Agency, Paris, France.
Noda, M., Sato, S., Tsuchi, H., Koike, A., Ueda, T. (2007): Concept and Development of Information Flow
Diagram for Literature Survey (IFDLS), Proceedings of the 11th International Conference on Environmental
Remediation and Radioactive Waste Management, ICEM2007, 2-6 September 2007, Oud Sint-Jan Hospital
Conference Center, Bruges, Belgium (to be published).
NRC（2003）：One Step at a Time, The Staged Development of Geologic Repositories for High-level Radioactive
Waste, Committee on Principles and Operational Strategies for Staged Repository Systems, Board on Earthand Life Studies, National Research Council of the National Academies, the National Academy Press,
Washington, D.C.
NUMO (2004a): Evaluating Site Suitability for a HLW Repository, Scientific Background and Practical
Application of NUMO’s Siting Factors, NUMO Technical Report NUMO-TR-04-04, Nuclear Waste
Management Organization of Japan, August 2004, Tokyo, Japan.
NUMO (2004b): Development of Repository Concepts for Volunteer Siting Environments, NUMO Technical
Report NUMO-TR-04-03, Nuclear Waste Management Organization of Japan, August 2004, Tokyo, Japan.
Sakabe, Y., Ueda, H.,. Hyodo, H., Ishiguro, K., Kitayama, K., McKinley, I. G., Kaku, K. (2005): Implementationof a Requirements Management System for the Japanese HLW programme, International Conference on the
Safety of Radioactive Waste Disposal, 3-7 October 2005, Tokyo, Japan.
Tsuchi, H., Seo, T., Metcalfe, R., Kawano, K., Takase, H., Suyama, Y., Toida, M., Furuichi,. M. (2003): Study on a
Decision Making Methodology with Uncertainties in the Selection Process of Preliminary Investigation
Areas, Proc. MRS 2003 Scientific Basis for Radioactive Waste Management XXVII, 15-18 June 2003,
Kalmar, Sweden, pp.21-26.
Tsuchi, H., Koike, A., Sato, S., Kawamura, H. (2007): A Study on the Enhanced Methodology for theComparative Assessment between Potential Repository Concepts and Locations, Proceedings of the 11th
International Conference on Environmental Remediation and Radioactive Waste Management, ICEM2007,
2-6 September 2007, Oud Sint-Jan Hospital Conference Center, Bruges, Belgium (to be published).
Ueda, H., Umeki, H., Konishi, T., Naito, M. and Danda, H. (2004): Design Factors for Filtering HLW Repository
Concepts, Proc. Disposal Technologies and Concepts (DisTec) 2004, 26-28 April 2004, Berlin Germany,
pp.143-148.
Umeki, H., Ueda, H., Naito, M., Konishi, T. and Danda, H. (2003): The NUMO Approach for Development of
Repository Concepts, Proc. 10th International High-Level Radioactive Waste Management Conference(IHLRWM 2003), 30 March - 2 April 2003, Las Vegas NV USA, pp.1019 - 1024.

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NUMO-TR-07-02

36

NUMO TR 07-02

APPENDIXILLUSTRATION OF HIERARCHICAL RANKING OFREQUIREMENTS

The table below illustrates the way in which top-level (1) requirements can be refined to produce
lower-level (2, 3) requirements. This process can be continued further to derive technical specifications
for individual processes or repository components. This is only a small subset of the set of requirementsthat is currently being assembled for our prototype RMS. The challenge is to ensure that the complete
set of requirements is comprehensive, is specified at the appropriate hierarchical levels for specificapplications and is kept up to date, with any changes being properly recorded. As discussed in Chapter 4,
such requirements are the basis for decisions made within the programme. As many requirements may
influence a specific decision, explicitly representing this in the RMS allows more open, transparent andconsistent decision-making.
Requirement Requirement title
Level
1
Project meets legal
requirements
2
Site meets legal requirements

2
3
3

3

1
2

2

2

Comment

Repository design meets legal
requirements
Site-specific design meets
post-closure safety guidelines
Site-specific design meets
operational safety guidelines
Site-specific design meetsenvironmental protection
guidelines
Repository project istechnically credible
Post-closure safety is assured
by a passive system of robust
barriers
Construction and operation of
the repository is practical andsafe
The site and design minimise
the risk of disruptive scenarios

Requirements defined in existing and future laws
and regulatory guidance
Current law reflected in “Evaluation factors for
qualification”; future requirements anticipated in
Siting factors and working standards
No current legislation; assumed to be covered byoperational and long-term safety requirements
Anticipated requirements included in working
standards
Includes exploration, construction and operation:
anticipated requirements included in working
standards
Includes exploration, construction and operation:
anticipated requirements included in working
standards
The entire programme corresponds to the technicalstate-of-the-art
The safety case is built on a well-understood EBS
tailored to a well-characterised host rock
Efficient, robust and fail-safe procedures tailored tosite characteristics
Siting and Design factors reduce both theprobability of disruptive processes and events andthe consequences of any perturbations that might
occur

A-1

NUMO TR 07-02

3

3

3

3

3

1

The EBS provides complete
containment for the period ofhighest waste toxicity
After complete containment,
RN releases from the EBS arevery low
Releases from the EBS are
reduced and delayed by the
NBS
Performance of the repository
is assured by rigorous QA

The fundamental components of the EBS are basedon H12 (JNC, 2000), tailored to assure 1000 years
containment at any site
Set by constraints on release from glass matrix,
solubility limits, retardation processes, etc.
The natural geological barrier reduces releases byretardation (decay), dilution and dispersion
Both operational and post-closure safety are assured
by QA procedures which ensure that materials andoperations conform to tightly defined specifications
Manpower and financial resources needed should beappropriate to the national significance of the project

The repository can be
developed with acceptable useof resources
NUMO is credible as animplementing organisation

2

Staged project implementation

2

Active support of hostcommunities

2

Well-structured and transparent
programme
Criteria for decision-making
are open and transparent
Clear ranking of options
Open decision-making process

3
3
3
3

Clear procedure for responding
to surprises

EBS – engineered barrier system
MAA – Multi-Attribute Analysis
NSA –NUMO structured approach
RMS – requirement management system

Active establishment of national and international
reputation and rigorous plans for developing internal
competence in key areas
Stepwise site selection and licensing with fullreversibility of decisions and evolving programme
focus as specified by Structuring factors
Active and comprehensive programme developing
dialogue to encourage full participation in key
decision-making processes
Incorporated in the NSA and overviewed in thisreportPublication of Siting factors, Design factors, etc. inadvance of key milestones
Use of established MAA and ESL methodology
NUMO’s RMS allows efficient and open
documentation of decision-making
Key advantage explicitly provided by the NSA

ESL – Evidential Support Logic
NBS – natural barrier system
QA – quality assurance
RN – radionuclide

A-2