R and D needs for accounting for the long term evolution of spent nuclear fuel in interim storage and geological disposal: objectives and programs

In order to satisfy the 1991 Law and the Government requests, CEA is currently supporting a wide project dealing with the long-term behavior of nuclear waste packages 2 (CLTC program), among which is the Spent Nuclear Fuel (SNF). The objectives of this research program is to study and assess the ability of the various types of waste packages (glass, spent fuels, bitumen- or concrete-based B types...) to maintain their functions in interim storage (whatever the duration can be) and geological disposal. Emphasis is put on total containment and recovery functions for duration up to hundreds years (long term 100 y. - or classical 50 y. - interim storage and/or frost reversible stages of geological disposal) and partial confinement function (controlled fluxes of RN) for 10.000's y. The final aims of this program is to get the right and reliable data concerning the long term behavior of the waste packages so that feasibility of interim storage and/or geological disposal can be assessed and demonstrated as well as optimized. The aim of this paper is to give an overview of the scientific objectives and researches performed on the particular topic of spent fuel in the CLTC program in CEA in close collaboration with and with the support of EDF (Electricity de France). Data acquired in this program are thus relevant to current industrial interim storage (- 50 y.), long term interim storage (line 3 of the French law) and geological disposal. The objective of the Research Program on the long term Evolution of Spent Fuel waste Packages (PRECCI) is to develop and build evolution models that will be able to predict the long term behavior of spent fuels in conditions of interim storage as well as geological disposal. Beyond these relative sophisticated models, more simple and robust models will also be developed and validated in order to confront the best state of the scientific knowledge to the initial operational needs which reflect the future industrial uses. These operational models will represent a strong involvement of the R and D people which will have to take the responsibility to define step by step for each boundary conditions, a easily understandable model that simultaneously reflects the actual and current expected evolution of spent fuels. In order to gain these ambitious objectives, the PRECCI transverse program gathers numerous studies Performed by teams belonging to different CEA divisions (DCC, DRN, DTA, DSM) and departments and working in most of the CEA research centers in France: Marcoule, Saclay, Cadarache. Research is carried out with EDF, and in close collaboration with other partners, particularly ANDRA The PRECCI program represents in 1999 an important CEA and EDF involvement with a significant increase with respect to previous years