Modelling decisions for cementitious repository for long-lived il W (TRU)

Nirex has conducted a systematic evaluation of the modelling of the engineered barrier system (ERS) for its generic cementitious repository concept for long-lived intermediate level wastes. This paper sets out the current approach to modelling the EBS in a performance assessment and discusses the issues associated with this approach. A revised approach to performance assessment modelling is under consideration, based on time-frames defined by the safety functions of the various components of the multi-harrier system. In this revised approach, there would he a role for a more detailed representation of the EBS in the performance assessment models, particularly with a view to demonstrating the contribution of the EBS to safety in the early time-frames post-closure. (authors)