Metadata in Geological Disposal of Radioactive Waste:
The RepMet Libraries
1

CAMPHOUSE, Russell C., 2 CIAMBRELLA, Massimo; 1 MCMAHON, Kevin
1

Sandia National Laboratories
Performance Assessment and Decision Analysis Department
Carlsbad, New Mexico USA
2

Nuclear Energy Agency (NEA)
Radioactive Waste Management Division
Paris, France

Key words: repository, waste package, site characterisation, waste management

Abstract
The OECD Nuclear Energy Agency (NEA) launched the Radioactive Waste Repository Metadata
Management initiative (RepMet) in 2014 under the auspices of the Integration Group for the Safety Case
(IGSC) technical advisory body. The initiative involves programmes from over ten different countries
working on the formulation of a consistent set of guiding principles for capturing and generating metadata,
recommending a shortlist of selected relevant standards and guidelines on international good practices.
One of the main objectives of RepMet is to provide descriptions of conceptual data models and controlled
vocabularies, forming the so-called “libraries” in the project context, which support data and metadata use
for relevant topics within radioactive waste repository programmes. RepMet has developed a Site
Characterisation Library, a Waste Package Library, and a Repository Library. This paper describes thethree libraries and discusses their relationship to the overall RepMet initiative.
1. RepMet Introduction

RepMet developed conceptual designs of data andmetadata libraries in the three disciplines shown in
Table 1.

The Radioactive Waste Repository Metadata
Management (RepMet) is an initiative under the
Integration Group for the Safety Case (IGSC) of the
NEA Radioactive Waste Management Committee(RWMC).

Table 1: Disciplines and topics of the RepMet
data and metadata libraries
Disciplines

The IGSC launched the RepMet initiative in 2014
to investigate the metadata, a key tool of modern data
management, in order to bring about a better
understanding of their application within the national
programmes for the realisation of the radioactive
waste repositories. Several worldwide Radioactive
Waste Management Organisations (RWMOs) andresearch laboratories from NEA countries wereinvolved in the RepMet initiative: Andra (France),
Enresa (Spain), JAEA (Japan), Nagra (Switzerland),NDA (United Kingdom), NWMO (Canada),
ONDRAF/NIRAS (Belgium), Posiva (Finland),
PURAM (Hungary), Sandia National Laboratories(United States), SKB (Sweden), SÚRAO (Czech
Republic).

RepMet Libraries

TopicsRadioactive
WasteManagement

Waste Package
Library

Packaged waste andspent nuclear fuelready for final
disposal at therepository

Geoscience

Site
Characterisation
Library

Geological andgeophysicalcharacterisation of
the repository site

Engineering

Repository Design
Library

Repository
requirements andstructures at closure

1
6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan• Identification of methods and procedures for thegathering and management of data and metadata.

RepMet investigated metadata to foster a better
understanding of their application within RWMOs in
support of national programmes. Within thisframework, the main RepMet objectives are:• Justification of the sufficiency of the set of
metadata describing the identified data to support
use and re-use.

• the formulation of a consistent and sufficient set of
guiding principles for capturing and generating
metadata (policy guidance)• Relationship to safety assessment. The metadata
required for information captured “in the field”
will differ from that required for analysed andderived data that are often used within safetyassessment models. (Safety assessment models
are to be discussed in detail in future work.)• the identification of metadata sets that can be usedby national programmes to manage their repository
data, information and record, harmonised
internationally.

• Identification of methods and principles toguarantee the persistence in time of the above
procedures.

2. Metadata
National programmes for radioactive waste
repositories are collecting large amounts of data thathave to be managed throughout the entire period of
institutionalised oversight, spanning a considerable
length of time. The data, metadata, and related
records also increase in number, type, and quality as
programmes proceed through the successive stages ofrepository development: pre-siting, siting, sitecharacterisation, construction, operations, pre-closureand finally closure. Regulatory and societal approvals
are included in this sequence. Current programmes
are also documenting past repository programmes, sothat current and future generations are able tounderstand actions carried out in the past, by
retrospectively adding metadata to help organise andarrange programme records.

• Guidelines for metadata management.
• Controlled dictionaries and policy as a means of
ensuring consistency and reliability of data andcataloguing.
• Use of metadata to support data auditability,
verification methods and, if needed, modification.
• Provision of a basis for the exchange and sharingof data between organisations, stakeholders andmember nations, which may be separated crossgenerations.
• Identification of methods and procedures for thedata and metadata gathering and management.
RepMet does not intend to promote any
commercial products or services for managing
metadata.

The available data, information and records areaccessed and updated according to management
systems, with the underlying repository allowing
users to locate what they require through searches offull text or the associated metadata.

4. RepMet Deliverables
Figure 1 illustrates the structure of the RepMet
initiative deliverables that were produced during theinitiative from its launch in 2014 to 2017.

Metadata allows context to be stored with dataand provide additional information so that it can belocated, used and reused. It can also be a useful tool
to help a waste management organisation todemonstrate that their programmes are appropriately
driven. Such context setting information may include
information on quality checking or approval;
provenance or ownership.

Figure 1: RepMet Deliverables

When considering metadata for a particulardomain (as for RepMet), metadata are typicallyassociated with a set of predefined digital or physicalobjects, for example an ID for a waste package orsigning date of a quality log. It is important toremember, however, that metadata also cover how
these elements are to be constructed and related to
one another (for example how a waste package
relates to a packaging campaign), the type and rangeof values they may take (for example, a package
weight must be greater than 0 kg).
3. RepMet Scope
The scope of the RepMet initiative includes thefollowing:

The first document of the deliverables deals withthe application of metadata in the field of radioactive

2
6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japanwaste geological disposal from a general, high-level
point of view:

discuss and present the three RepMet libraries inmore detail.

• RepMet/01 – “Metadata in Geological Disposal”
provides an overview and brief summary of
RepMet goals, deliverables, various aspects ofmetadata implementation and issues forconsideration.

5. RepMet Libraries
The RepMet Libraries provide the conceptual designof databases about the topics of interest reported inTable 1. They report the CDMs2 of the databases, i.e.
the organisation and the structure of the databases interms of objects of interest (i.e. entities) together with
their descriptive characteristics (i.e. attributes) andthe logical associations among them (i.e.
relationships). It is out of the RepMet scope toidentify the software and hardware technology for therealisation of such databases.

The following three deliverable documents, theso-called “Libraries”, adopted a more technical pointof view. They discuss the key aspects of data andrelated metadata for selected topics of different
scientific and technical disciplines involved in therealisation of a radioactive waste repository. The
Libraries include conceptual data models (CDMs),
descriptions of data entities, attributes, associatedmetadata and other relevant information:

The main feature of the RepMet Libraries is theimplementation in the database’s conceptual designof metadata sets to support the long-term
management of the information built on the dataassociated with the entities and the attributes in thelibrary. These metadata:• RepMet/02 – “Site Characterisation Library”
deals with data and related metadata that areconsidered during the selection of thecharacterisation of a site investigated andsurveyed for suitability for radioactive waste
disposal purposes leading up to site selection;• indicate the source of the data: who?, what?,
when?, where?, why? and how?;• RepMet/03 – “Waste Package Library” deals withdata and related metadata about packaged waste
and spent nuclear fuel that, after proper treatment
and conditioning processes, are ready for final
disposal at the repository;• provide context to facilitate the accurateinterpretation and use of data;• describe data quality (e.g. uncertainty);• add additional information about the data ina structured and detailed way;

• RepMet/04 – “Repository Library” deals withdata and related metadata which relate to theengineered structures and waste acceptancerequirements of the radioactive waste repositories.

• help users quickly find the data object thatthey are looking for; and• support the search for information (e.g.
promote scientific research, engineering,safety assessment).

The above Libraries can be used independently ofeach other, however utilising all of the libraries andthe approach outlined in these documents provides
the additional benefit of having a uniform approach todata and metadata management.

5.1. Site Characterisation Library
Site characterisation requires knowledge about rockstability and isolation properties that are controlled
by surface and underground conditions close to therepository and in the wider environment. A complex
model of the geological environment including
information on composition, structure and processes
are needed. This knowledge is improved by using
geoscience, a wide discipline that includes many
scientific areas, like traditional geology, geophysics,
hydrogeology, geochemistry, satellite imagery, etc. It
is not enough to collect data once. It is essential to do
monitoring, i.e. repeating observations on a regularbasis.

A fifth document includes common techniques andtools that RepMet has adopted for the development ofmultiple libraries and which are deemed useful for
relevant RWMO activities and initiatives:• RepMet/05 – RepMet Tools & Guidelines
supports the libraries providing a number of usefultools, methods, metadata standards, guidelines,
and approaches that were either used indeveloping the Libraries or are useful for the
RWMO when adopting and implementing the
Libraries.
RepMet will close its activities in 2017. The
above deliverable documents will be made available
publicly in electronic form on the RepMet webpage 1
on the NEA website in the next months. We now

All this involves handling large amount of datawith heterogeneous structure and content.
Heterogeneity may arise for methodological,

2. The CDMs cannot be shown in this document as a resultof their size, but will be displayed and discussed during thepresentation, and can be seen in the RepMet libraries
themselves.

1. www.oecd-nea.org/rwm/igsc/repmet.

3
6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japanhistorical and/or practical reasons. In the last decade,considerable effort has been devoted to harmonisingdata related to knowledge about the natural andartificial environment. One of the biggest initiatives
in Europe is the INSPIRE (Internet Spatial
Infrastructure for Europe) directive that integrates
34 environmental themes into one uniform CDM. It
is based on a long list of open standards andharmonised web services. The proposed CDM for the
RepMet Geoscience Library is largely based on the
INSPIRE principles and data models.

The RepMet group developed the Waste Package
Library with the purpose of presenting sets of data
and metadata that national programmes may use forthe data, information and records management,
specifically with respect to the waste packages readyfor disposal at the final repository. Low Level Waste(LLW), Intermediate Level Waste (ILW), HighLevel Waste (HLW) and Spent Nuclear Fuel (SNF)
from commercial light water reactors (LWRs) are allconsidered.
The CDM for packaged radioactive waste and
SNF is an original RepMet product and it is based oneleven entities. These entities, together with theirdefinitions, draw on definitions from the IAEA
(2006). However, a number have been modified inorder to ensure consistency within the data modelthat has been developed, and add flexibility to theCDM, thereby allowing it to meet the needs of thediverse range of packaging solutions adopted by
WMOs worldwide.

Figure 2. Geoscience domains as definedin EU INSPIRE Directive

The entities and their definitions are listed below:
1.

2.
There are six schemas in the INSPIRE data modelthat are most relevant to Site Characterisation.
Figure 2 shows the scientific domains and theirrelations as they are represented in the existing
standard. These are:3.

•

Geology••

Hydrogeology
Geomorphology••

Geophysics
Environmental Monitoring; and5.

•

Sampling

6.

4.

Geology, Hydrogeology, Geomorphology andGeophysics belong together in the Geology spatial
data theme of INSPIRE. Environmental Monitoringis defined in a separate theme. Monitoring facilities
often collect information about geological andgeophysical phenomena as well. The common
building block is the Observation and Measurements(O&M) standard that creates an important bridge
between seemingly separate domains. The O&M
concept allows geosciences and environmental
monitoring to be integrated into one generic CDM
that RepMet adopted to cover the geoscientificaspects of site characterisation relevant to nuclear
waste disposal facilities. Hierarchical dictionaries ofphysical property and observation process names arepart of the INSPIRE framework and are used as
attributes for the RepMet Site Characterisation
Library CDM.

7.

8.

Buffer – additional material or a mix of materials
that contribute to preventing or reducing the
migration of radionuclides from the disposal
module.
Disposal container – container into which one ormore waste packages, and optional filler orbuffer, may be placed.
Disposal module – ensemble of one or morewaste packages together with their disposal
container, optional filler(s) and buffer, suitablefor handling, transport, storage and disposal.
Filler – material or a mix of materials that is
added to the disposal container filling the void
spaces.
Overpack – container into which the wasteform
container may be placed.
Stabiliser – material or mix of materials that isused in treatment and conditioning processes tostabilise, either physically and/or chemically, one
or more wastes, or one or more spent nuclear
fuel, to give a wasteform.
Spent nuclear fuel – nuclear fuel removed from areactor following irradiation that is no longer
usable in its present form.
Waste – raw material in gaseous, liquid or solid
form that is intended for storage and disposal
after proper treatment and conditioning. Waste
materials conditioned into containers that areconsidered unfit3 for disposal are also waste, as
they require further treatment before disposal.

3. E.g. legacy waste packages that cannot be disposed ofaccording to the current policies and practices; drums to besupercompacted and then inserted in a bigger container forvolume reduction.

5.2 Waste Package Library

4
6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, JapanWaste package – ensemble of one or morewasteforms together with their wasteform
container and optional overpack(s), suitable forhandling, transport, storage and/or disposal.
10. Wasteform – waste, or the spent nuclear fuel, in
the physically and chemically stable form inwhich it will be disposed of, including any
stabilisers and container furniture 4 , but notincluding the wasteform container.
11. Wasteform container – container into which one
or more wasteforms are made or placed.
The attributes of the Waste Package Library are
structured and arranged in the form of an originalcontrolled dictionary according to the RDF/SKOS
format. It is included in the library final report.

Waste Containers, including such elements as
disposal modules, overpack or other physical barriers
included with the waste package, the waste package isdesigned to contain the contents during storage,transportation and emplacement in a repository.
Repository Engineered Barrier Systems (EBS) may
be added around or near the waste package emplacedin the repository to further contain radioactive and/or
chemical contaminants in the area near the waste
package. Repository Natural Barrier Systems may beconsidered and used by the repository host rock
media to ensure additional containment ofradionuclide or chemical contaminates that may havebreached a waste package and the EBS.

9.

For the RepMet CDM of a radioactive waste
repository, six entities have been identified. These
entity selections were developed for a repository at
the time of closure, based on the assumption that the
metadata requirements will be known in totality(maturity) at this time. They are based on theexperience of subject matter experts involved in
RepMet as well as a review of selected reports on thedevelopment of radioactive waste repositories.

5.3. Repository Library
The purpose of the repository library is to present setsof metadata that can be used by national programmes
for information and records management, specificallywith respect to radioactive waste repositories.
Repositories for LLW, ILW, HLW and commercial
LWR SNF are all considered, and this document isintended to be a registry on RWM repository subjectsof common interest based on the practices currently
in use internationally. The content of this library has
been developed from the exchange of experienceamong project members, and discussions withexternal experts and constituencies.

The entities and their definitions are listed below:
1. Facility information – a nuclear facility wherewaste is placed for disposal:
o Geological repository – A facility for radioactive
waste disposal located underground (usually
several hundred metres or more below the surface)in a stable geological formation to provide
long-term isolation of radionuclides from thebiosphere.

Figure 3. Multiple Barriers of a Repository

surface repository – A facility forradioactive waste disposal located at or withina few tens of metres of the Earth’s surface.

o Near

2. Repository

engineered
barriersystem(R-EBS) – manufactured physical obstructionthat contributes to the containment, retardation
and/or isolation of (radioactive or chemical)
contaminants present in the waste that is part of
the repository facility or is created by/in therepository facility.

3. Repository

naturalbarriersystem(R-NBS) – naturally
occurring
physicalobstruction that contributes to the containment,
retardation and/or isolation of (radioactive or
chemical) contaminants present in the waste.
Data for this entity comes from the RepMet Site
Characterisation Library.

A RWM repository’s primary objective is toensure that radioactive and chemical releases to theenvironment are mitigated to levels at or below thecognizant regulatory requirements. A repository may
accomplish this through a combination of engineered
and natural barriers that contribute to the containment,
retardation and/or isolation of (radioactive or
chemical) contaminants present in the waste.

4. Repository monitoring system – systems andprocesses implemented in the repository tomonitor any aspect of repository performance,
including radionuclide release, chemical release
and/or heat release to the near field, far field andthe biosphere.

Figure 3 provides a graphical representation ofmultiple barriers in a repository contributing to thecontainment of radioactive and/or chemical
contaminants present in the waste. Beginning with the

4. E.g. dewatering tubes, in-drum mixing puddles.

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6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan5. Waste acceptance criteria (WAC) – quantitative

While RepMet has completed key deliverables in its
initial phase, the group recognises the following
outstanding work:or qualitative criteria specified by the regulatory
body, or specified by an operator and approvedby the regulatory body, for radioactive waste tobe accepted by the operator of a repository fordisposal, or by the operator of a storage facility
for storage. Waste acceptance criteria might
include, for example, restrictions on the activity
concentration or the total activity of particularradionuclides (or types of radionuclide) in thewaste or requirements concerning the waste
form or waste package.

•

Development of a complete metadata
structure/database for a safety assessment
tailor-made for the needs of the nuclear waste
industry. Extension of the use of the developed
metadata structure developed by RepMet toencompass also the data related to the safety caseand its “models” (abstract, geometric, stochastic,
deterministic).

•

Creation of new RepMet Libraries including
different topics for waste management
pre-closure, e.g. “waste treatment andconditioning”, “plant operations”, “interim
storage of the waste package”.

•

Extension of the current RepMet Libraries (e.g.
maturing, increasing the level of detail).

Similar to the Waste Package Library, the attributesof the Repository Library are structured and arrangedin the form of an original controlled dictionary
according to the RDF/SKOS format. It is included in
the library final report.

•

Application of the O&M standard that RepMet
has adopted to support safety assessment process
chains and for the development of the safety case(e.g. new and dedicated RDF/SKOS controlled
dictionaries and models).

6. Closing Remarks•

Definition of RDF/SKOS controlled dictionaries
for the IGSC FEP Task Group.

•

Definition of conceptual requirements for thecreation of a central metadata database to allow
data from multiple databases (e.g. commercial
off the shelf [COTS] offerings) to be extracted
and combined from a single query. These
requirements should take into account thepossible conflicts of interest when handling
metadata.

•

Formulation of data dictionaries for RWMO
modelling.

6. Waste package emplacement - describes the way
waste packages are placed in the repository forfinal disposal. Such placement may include
vertical or horizontal placement in drifts, orplacement in boreholes (for example). Much of
the data for this entity is derived from the
RepMet Waste Package Library.

Metadata enables RWMOs to manage their data in awell-organisedmanner,meeting
statutory
requirements and ensuring that data quality is noteroded, confidence in the stored data is maintained,that it remains suitable for support of their future
decisions and operations efforts and meets therequirements of their designated communities now
and in the future.
RepMet has formulated a consistent set of
guiding principles for metadata management in thecontext of geological repositories; the results of thework are useful to operators, regulators and otherrelevant actors. The Libraries and associateddocuments have been prepared with the intent toprovide generic models, processes and descriptions
that can be tailored to the needs of virtually any
RWMO. These can be regarded as a common basis
for the development of metadata.

7. Disclosure
Sandia National Laboratories is a multi-mission
laboratory managed and operated by National
Technology and Engineering Solutions of Sandia
LLC, a wholly owned subsidiary of Honeywell
International Inc. for the US Department of Energy’s
National Nuclear Security Administration undercontract DE-NA0003525. SAND2017-11944 C.

RepMet recognises that each RWMO’s activities
are in many respects unique, and that eachradioactive waste site has characteristics that are
exclusive to that particular site. However, there arealso many common and general aspects ofradioactive waste management and final disposal.

The opinions expressed and arguments employedherein are those of the authors and do not necessarilyreflect the official views of the OECD, the NEA or of
the governments of their member countries.

Each RWMO needs to adapt the provided
models, processes and descriptions to ensure that theadapted constituents meet the requirements of local
regulations, the RWMO’s individual needs, and theindividual characteristics and the applied technologyof the individual radioactive waste management
operations.

8. References
International Atomic Energy Agency (IAEA) (2006),
Development of Specifications for Radioactive Waste
Packages, Vienna, Austria, IAEA-TECDOC-1515.
Directive 2007/2/EC of the European Parliament andof the Council of 14 March 2007 establishing an

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6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan

Infrastructure for Spatial Information in the European
Community (INSPIRE), European Union, 25 April
2007, Official Journal of the European Union.
OGC (Open Geospatial Consortium), Geographic
information – Metadata. [Online] www.iso.org/obp/
ui/#iso:std:iso:19115:ed-1:v1:en.
World Wide Web Consortium, SKOS Simple
Knowledge Organization System Primer, [Online]
www.w3.org/TR/skos-primer.

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6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan