Key Topic 1: Post-closure Safety Case

Overview

The purpose of the safety case is to gather all the scientific and technical arguments and evidence required to robustly support the safety claims of disposal facilities and systems. Safety is demonstrated by providing clear reasoning based on sound scientific and technological principles [i].  The safety case should be both robust and easily understandable.  Moreover, the safety case sets out the arguments and evidence seeking approval of the licensing documentation for specific nuclear waste disposal facilities and must therefore comply with the various requirements set out by the relevant national authorities. Attention should also be devoted to recommendations suggested by international organisations such as the IAEA and the OECD/NEA.

The safety case must describe the evolution of the repository in such a way that it provides a reasonable representation of the events that might occur, and that also provides a clear indication of the uncertainties included in the description.  This topic covers safety case and safety assessment issues related to the evaluation of the radiological impact of the whole repository on humans and the environment, and includes the evolution of the site over geological timescales (e.g. assessing the impact of processes such as erosion and climate change).  The impact of the repository and its components are covered under Key Topic 3.

[i]       OECD/NEA (2004). Post-closure safety case for geological repositories, Nature and purpose, NEA No. 3679, 2004.

Objective

The objectives of the research area, all of which are related to the “Safely Operate” pillar of the IGD-TP’s Vision 2040, are to:

  • Develop a broad view on the basis of the results of long-term safety assessments and enhance confidence in the concepts and the scenarios presented, thereby supporting development of the scope and content of subsequent safety cases for all IGD-TP participants.
  • Develop and refine the concepts and models applied to improve long-term safety assessments.
  • Improve the way in which sensitivities and uncertainties are addressed and communicated.
  • Further improve dialogue and engagement with the relevant authorities and other stakeholders.

Related Documents

Related Activities

There are existing co-operation and exchange forums, such as the Integration Group for Safety Case (IGSC) within the OECD/NEA, where national safety case experts meet regularly to keep up-to-date on recent achievements among the participating programmes.  Safety case discussions are also often discussed at international co-operation meetings held between various waste management organisations.  The IGD-TP maintains links with organisations such as the IGSC. A number of international projects have been undertaken that provide examples of process models and their role in safety assessment and feedback to design.  For example, the EU FORGE project and the Äspö Hard Rock Laboratory’s LASGIT project deal with gas production and transport in repositories, and the EU PEBS project deals with evolution of the engineered barrier system over time.

BELBaR

The BELBaR project aimed to increase knowledge of the processes that control clay colloid stability, generation and ability to transport radionuclides. The overall purpose of the project was to suggest a treatment of the issues in long-term safety assessment.
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FIRST-Nuclides

First-Nuclides aimed to improve the understanding of the fast / instantly released radionuclides from disposed high burn-up UO2 spent nuclear fuel. The outcome of the project is relevant for all types of host rocks in Europe.
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PEBS

PEBS aimed to evaluate the sealing and performance of the engineered barrier with time. The project involved experimentation and modelling, with consideration of the potential impacts on long-term safety functions.
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FORGE

Long-term radioactive waste management usually considers final disposal in a deep geological repository. This includes an engineered barrier system working in conjunction with the surrounding host rocks to minimise migration of radioactivity. As the repository system evolves, gases may be produced, such as hydrogen from the corrosion of metals and from the radiolysis of water, and radon from the radioactive decay of some of the waste. If present, biodegradable wastes can also produce carbon dioxide and methane. Understanding how these gases move in a repository setting is a topic identified for further study. The FORGE project, which ran from February 2009 to September 2013, studied key gas migration issues in repository performance assessment.
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SITEX

SITEX was a two-year project that aimed to establish and develop expertise among technical safety experts, and through this, support independent regulatory reviews of geological disposal safety at national levels. Attention was also paid to harmonising the policies and programmes among regulatory authorities, technical support organisations and waste management organisations.
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PAMINA

The PAMINA project (Performance Assessment Methodologies in Application to Guide the Development of the Safety Case) aimed to improve and develop a common understanding of integrated performance assessment (PA) methodologies for disposal concepts for spent fuel and other long-lived radioactive wastes in a range of geological environments. It was part of the Sixth Framework Programme of the European Commission. It brought together 25 organisations from ten European countries and one EC Joint Research Centre to improve and harmonise the methodologies and tools for demonstrating the safety of deep geological disposal.
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CROCK

CROCK was a two-and-a-half-year project that aimed to develop a methodology for decreasing the uncertainty in the long-term prediction of radionuclide migration in crystalline rocks. Work included sorption experiments on rock samples, including specially collected non-oxidised samples, and the development of transport simulations and models. Overall CROCK provided better understanding of key process of radionuclide migration and eliminated or reduced a number of uncertainties related to performance assessment.
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ERICA

The ERICA (Environmental Risk from Ionising Contaminants: Assessment and management) project was a three year project to provide an integrated approach to the assessment and management of environmental risks from ionising radiation.
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ARGONA

The ARGONA (Arenas for Risk GOverNAnce) project was a three year EU-funded research project started in 2006 which explored application of the concepts of public participation and transparency in nuclear waste management programmes.  The project included both theoretical and applied aspects and delivered a number of observations and recommendations on the role of participation and transparency in the arena of radioactive waste management.
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FUNMIG

FUNMIG (FUNdamental processes of radionuclide MIGration) was an Integrated Project (IP) that ran for four years and succeeded in its aim of improving understanding of the fundamental processes of radionuclide migration in rock.  The focus of the project was on rocks, radionuclides and processes relevant to the safety of deep underground nuclear waste repositories.
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NF-PRO

NF-PRO (Understanding and Physical and Numerical Modelling of the Key Processes in the Near-Field and their Coupling for Different Host Rocks and Repository Strategies) was an EU project to increase the understanding of the processes affecting radionuclide migration in the near-field of underground nuclear waste repositories.
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COWAM In Practice

COWAM In Practice was the third and final project in the Community Waste Management (COWAM) series of projects.  The COWAM project series was focused on developing a model for the inclusive governance of Radioactive Waste Management (RWM).  COWAM In Practice aimed to put into practice the results of the previous COWAM II project, and provided a framework for stakeholders in RWM to cooperate on an equal footing to identify and investigate important issues to them in the governance of RWM in their countries.  The project delivered guidance to the EU for the governance of RWM based on experience gained from this process.
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RED-IMPACT

The RED-IMPACT project (Impact of P&T and Waste Reduction Technologies on the Final Nuclear Waste Disposal) was a three and a half year EU project to assess the impacts of different partition and transmutation and other waste reduction technologies on the nuclear fuel cycle, with a focus on the effects on the final disposal of wastes.
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KiNa

The Kiruna Natural Analogue (KiNa) project aims to investigate the formations of smectite-rich clay occurring adjacent to magnetite deposits in the Kiruna mine in Sweden as a natural analogue to explore the long-term evolution of bentonite components of a geological disposal system for radioactive waste. The KiNa Project is a three-year IGD-TP project being undertaken by an international collaboration of waste management organisations including SKB, Nagra, Posiva, NWS, NUMO and NWMO.
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CCSC

The Climate Change in the Safety Case (CCSC) project is a collaborative project between European radioactive Waste Management Organisations to exchange information and best practice about modelling climate change and its implications for the safety case of a radioactive waste repository.
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PCCS

The Post-Closure Criticality Safety (PCCS) project is a collaborative project between Waste Management Organisations to exchange information, approaches and best practice with regards to the post-closure criticality safety of geological disposal facilities for radioactive waste.
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