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PRISM: Practical Illustration and Use of the Safety Case Concept in the Management of Near-Surface Disposal

First Technical Meeting

The first technical meeting of the project on Practical Illustration and Use of the Safety Case Concept in the Management of Near-Surface Disposal (PRISM) was held at IAEA headquarters from 30 March – 3 April 2009.

Watch Meeting SlideshowPRISM is the fourth in the series of near surface disposal projects that the Agency has organized since the late 1980s. Over this period there has been steady progress with implementation of safe solutions for near surface disposal of radioactive waste. Countries that were engaged in the early years of nuclear power development have made progress in dealing with "legacy" wastes from that period. Disposal of the increasing volumes of radioactive waste from the decommissioning of the early generation of nuclear power plants is taking place and some facility closures have taken place. The experience base for near surface disposal covers the entire lifecycle of facility development - from planning through to post closure monitoring and surveillance.

The PRISM meeting was attended by 60 participants from 30 countries and was chaired by Ms. Christine Gelles from the Department of Energy, United States of America.


It is widely recognised that the results of safety assessment calculations provide an important contribution to the safety arguments for a disposal facility, but cannot in themselves adequately demonstrate the safety of the disposal system. The safety assessment and a broader range of arguments and activities need to be considered holistically to justify radioactive waste disposal at any particular site. The term "safety case" is used to refer to this broad range of arguments and activities (see graphical illustration). Many disposal programmes are therefore moving towards the production of what has become known as a safety case.


The safety case is therefore a topical issue, where the exchange of information and communication of best practice is valuable. The current lack of a consistent interpretation of the safety case concept, particularly in respect of near-surface disposal, suggests that the project proposal for PRISM is timely.

The PRISM project is concerned with the nature and use of the safety case over the lifecycle of a near-surface disposal facility. It is a successor to the NSARS, ISAM and ASAM projects, which focused mainly on safety assessment methodologies and their application. Compared to these projects, the emphasis has shifted from safety assessment and calculations, to questions of practical implementation (i.e. how near-surface radioactive waste disposal can be managed using the Safety Case). The objective of this project is to share experience and communicate good practice from this perspective, in particular concerning:

  • The components and expectations of the safety case and their evolution over the lifecycle of a near-surface radioactive waste disposal facility
  • Decision making at different stages in the facility lifecycle, using the safety case

The project started with a plenary meeting at the end of March 2009 and will be completed in 2012.

Project Structure

Dedicated Task Groups have been established to address specific issues. The Task Groups address the following areas of concern:

  • Task Group 1: Understanding the safety case
  • Task Group 2: Disposal facility design
  • Task Group 3: Managing waste acceptance
  • Task Group 4: Managing uncertainty

In each of these tasks, the focus will be on the use of the safety case to take management decisions throughout the life cycle of the facility. It is envisaged that some quantitative analyses could be undertaken to illustrate the targeted use of calculations in decision-making processes.

A key project deliverable will be a project report based on the task group reports. In addition, a booklet, aimed at project managers responsible for implementing near-surface waste disposal, will be produced describing the use of the safety case in managing disposal at these facilities.

The project is open to professionals from Member States who are from operating and supporting organizations or regulatory organizations concerned with assessing, improving and managing the safety of near-surface radioactive waste disposal facilities. Participants are expected to contribute actively to the project by taking part in plenary discussions and Task Group activities.

Outcome of the First Technical Meeting

The agenda for the first PRISM meeting included plenary and breakout sessions where task group work was carried out. The project proposal, which was drafted over the course of two consultants meetings prior to the technical meeting, was accepted without modification. Each of the four task groups developed a work plan, listed below:

Task Group 1: Understanding the safety case

Task Group 2: Disposal facility design

Task Group 3: Managing waste acceptance

Task Group 4: Managing uncertainty

Task group meetings will be held in the period before the next plenary meeting to implement the work outlined at the first plenary meeting. The chairperson's summary report for the first PRISM technical meeting contains further detail.

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| Last update: Tuesday, 09 December, 2014.