Safety Case Development & Performance Assessment

In 2017, the Dutch radioactive waste management agency (COVRA) completed its major, five-year research programme on the feasibility of disposal of the national inventory of higher-activity wastes into the Boom Clay (the OPERA Programme).  Neil Chapman and Charles McCombie were members of the Safety Case Steering Group during the project and are co-authors of the final OPERA Safety Case report and Summary, published in December 2017.

In 2014 MCM supported Japanese Nuclear Safety Research Association (NSRA) with development of a structured approach to safety case production for long-lived intermediate level waste (TRU-waste), in particular, bituminised nitrate waste. MCM work included:

•  Critical review of the international literature on bituminisation to determine if further relevant information on high temperature reaction is available and assess potential sources of data to support post-closure safety case development (relevant abstracts provided separately).
• Support of development of a structured approach to safety case production for specific Japanese boundary conditions and waste properties, with initial focus on an argumentation model that identifies potentially relevant perturbation scenarios.
• Identification of open issues requiring further R&D.

Tara worked with Wood (formerly AMEC Foster Wheeler) and NDA and Subject Matter Experts to further understanding of the potential disposal of U₃0₈ – primarily with regards to its chemical composition – a material which is likely to arise from the processing of the significant amount of depleted Uranium in the UK waste inventory. The findings were presented at a conference on behalf of the NDA.

In 2010 RWM published a generic Disposal System Safety Case (gDSSC) to demonstrate that a disposal facility for UK higher activity radioactive waste will be safe to operate, will remain safe after it has closed, and will meet all applicable regulatory safety requirements. In support of this programme of work, MCM partners and staff were responsible for:

• Lead-author of the Near-field Evolution Status Report - a report providing a synthesis of state of the art R&D on the post-closure chemical, physical and thermal evolution of the repository engineered barriers. Covering a range of geologies,, concepts options and waste types (ILW/HLW and spent field), it required in depth knowledge of international RD&D programmes and their representation of key features, events and processes in environmental safety cases and performance assessments for a range of scenarios.
• Member of the Environmental Safety Case (ESC) Advisory Panel – providing strategic direction and periodic review throughout the ESC development.
• Managing international expert peer review of the suite of 8 R&D Status Reports an evaluation of the overall peer review process specified by RWM.
• Peer review of all generic GDF Design reports and of the generic Disposal System Technical Specification.