The Enresa 2003 performance assessment exercises for clay

Clay is one of the candidate lithologies considered by ENRESA for the disposal of High-Level Radioactive Waste. Up to now, three Performance Assessment exercises have been developed by ENRESA: ENRESA 97 (Granite), ENRESA 98 (Clay) and ENRESA 2000 (granite). With the experience gained with these exercises and with the results provided by the R and D programme, a new exercise for a clay formation is presently underway. This new PA exercise will be finished at the end of 2003. The main objectives of the PA for clay are: - To increase the structuring and accessibility of ENRESA's knowledge, data and evaluation methodologies, adapted to the Spanish context; - To test the numerical codes and tools developed in the R and D programme; - Integration in the PA exercises of the research people directly involved in the R and D; - To obtain criteria and dates to be considered in the site studies, guidance R and D programme and repository design. The safety bases of the exercise consider the post-closure period and the effects of the operational phase on the long-term safety. The site is a 'generic site', elaborated with direct information of real Spanish clay formations. The repository reference concept and design is adapted from ENRESA 98. Several scenarios are in consideration (normal and altered) and two approaches for consequence analysis are included (deterministic and probabilistic in scope). Sensitivity analyses will be carried out on the calculation results. For the objectives of this workshop, the main contribution of the ongoing ENRESA 2003 is related to the use of geological data -for the construction of the site conceptual model and the managing of the interaction between different teams for the evaluation. (author)