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Over the last 10 or so years, the IAEA has coordinated two international projects on the development and use of the safety case for near surface disposal of radioactive wastes.  These projects were known as the PRISM and PRISMA projects.  These projects have now been completed with the publication of a single combined summary report.

Both projects involved professionals from operating organizations, regulatory bodies and supporting organizations concerned with managing and ensuring the safety of near-surface radioactive waste disposal facilities.

PRISM project - PRactical Illustration of the use of the Safety case concept in the Management of near surface disposal

General Information

The PRISM project ran from 2009 to 2012 and considered the components of the safety case and its use to aid decision-making during the lifetime of a near-surface disposal facility.  Dedicated Task Groups were established to address specific issues:

  • Task Group 1: Understanding the safety case
  • Tast Group 2: Disposal Facility Design (draft WG report)
  • Task Group 3: Managing waste acceptance
  • Task Group 4: Managing uncertainty

In each of these task groups, the focus was on the use of the safety case to make management decisions throughout the life cycle of the facility.

PRISM involved 4 plenary and 6 technical meetings. More than 60 participants from over 30 member states took part in PRISM.

Overview of outcomes

In the context of radioactive waste disposal, the safety case is defined as ‘a collection of scientific, technical, administrative and managerial arguments and evidence in support of the safety of a disposal facility covering the suitability of the site and the design, construction, and operation of the facility, the closure and the post-closure, the assessment of radiation risks and assurance of the adequacy and quality of all the safety related work associated with the disposal facility’ (Disposal of Radioactive Waste, IAEA Safety Standards No.SSR-5, IAEA, Vienna, 2011). The components of the safety case for a disposal facility are illustrated in Figure 1.

Figure 1: Components of the Safety Case

The PRISM project elaborated the content of the safety case and discussed its development for a near-surface disposal facility in the context of a series of decisions which typically have to be made in the licensing, development, operation and closure of such a facility (Figure 2).

Figure 2: The Typical Sequence of Key Decisions in the Development of a Repository

The decision to move from one phase of facility development to another is a strategic step in which it is necessary to consider a range of factors, including safety, legal requirements, costs and available resources, schedules, and stakeholder views.

The PRISM project documented the main components and subcomponents of the safety case at each decision step within the development of a radioactive waste disposal facility. The safety case arguments were presented in a matrix – the Matrix of Arguments for a Safety Case, or MASC Matrix. The MASC matrix is valuable tool which can be used to help develop and review a safety case.

PRISMA - PRISM in Application

General Information

The PRISMA project ran from 2013 to 2016 and used the MASC matrix from the PRISM project to develop example safety case arguments for two hypothetical near surface disposal facilities.  A generic country setting was developed to provide the required framework for the two safety cases.  PRISMA concentrated on documenting the basis for decisions made in developing the content of a safety case.
PRISMA involved 4 plenary and 5 consultancy meetings. Over 20 Member States were represented during the different meetings.

  • Operator Groups 1 & 2, which developed and documented the basis for the content of the two cases.
  • Regulator/Government Group, which provided the criteria and the considerations used in evaluating the safety case examples.

During the role-play, participants went through all the major safety case components required for the development of a near surface disposal facility and at the end of each step they made a final decision in order to move or not to the next step. The detailed safety cases for the hypothetical disposal facilities are described in the final project report.

PRISMA involved hands-on, role-playing exercises as described below. The participants formed groups with various assigned roles, as if they were representing particular counterparts involved in the process of developing a near surface disposal facility.

Overview of Outcomes

The generic country description developed had the following characteristics. The country is of medium size, with a humid to semiarid climate.  It is not overpopulated and has a developed infrastructure. Three distinct areas (Sites A, B & C) were selected in the country, based on their geological, climate and hydrological setting, as well as socio-economic factors. The generic country had two nuclear power plants (each with two reactors) and one research reactor in operation. An agreement has been made with another country, in which they will manage HLW, ILW and Spent Fuel, therefore the generic country only has to deal with LLW.

Each decision step in the PRISM methodology was considered in a subsequent PRISMA meeting. The following table provides a record of each of the decision steps considered.

The different meetings of PRISMA tested the safety case up to the step 5 - operational license in order to achieve the best result within the time allocated to this project. A more detailed description of the decision steps is provided in the final combined report.

Step # Decision
  Operator Group 1 Operator Group 2 Operator Group 3
1. Need for action Go for disposal Go for disposal Approved conditionally
2. Disposal concept One single sub-surface disposal facility Two facilities located at the same site regarding short or long-lived low-level waste facility -group 1: acceptable -group 2: conditionally accepted
3. Site selection and Engineering design Site C + single repository with a tunnel design Site B with a one-entrance subsurface design with two separate facilities Both acceptable but subject to a list of conditions
4. Construction Apply for construction licence on site C Apply for construction licence on site B Both acceptable but subject to a list of conditions
5. Operation Complete construction after issues solved and applied for permission to operate the repository Face to public opinion changing, group 1 developed a monitoring plan and submitted it Both proposals have been approved

Related projects

The PRISM and PRISMA projects were complementary to other IAEA activities in the Waste Management field, such as the HIDRA project (Human Intrusion in the context of Disposal of Radioactive Waste) and the GEOSAF projects (International Intercomparison and Harmonisation Project on Demonstrating the Safety of Geological Disposal).

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| Last update: Wednesday, 28 June, 2017.