THE BELGIAN RESEARCH, DEVELOPMENT AND DEMONSTRATION PROGRAM ON THE GEOLOGICAL DISPOSAL OF LONG-LIVED AND HIGH-LEVEL RADIOACTIVE WASTE AND SPENT FUEL IN A CLAY FORMATION: STATUS AND TRENDS

摘要

Within the Belgian program for the management of long- lived and high- level radioactive waste (HLW), the Boom Clay is studied as a potential host rock for deep disposal. This paper gives an update on progress and achievements of Research, Development & Demonstration (RD&D) programs at the Belgian Nuclear Research Center SCK·CEN. At SCK·CEN, large interdisciplinary RD&D programs combining underlying and applied science have contributed to extensive expertise on disposal in clay. In this paper, recent developments in a number of keyareas are highlighted. In particular, emphasis is on: 1. Investigations concerning the geological disposal of organic waste forms (bituminized reprocessing waste and alpha-contaminated cellulose waste); 2. The in situ testing of cement-clay interactions and the assessment of the consequences of these interactions for the development of the alkaline plume; 3. The CORALUS experiment, which is an integrated in situ experiment for the detailed investigation of the interaction of alpha-doped vitrified waste and various candidate backfill materials in the presence of heat and gamma radiation; 4. The in-depth geochemical study of trace elements and radionuclides, which are naturally present in the Boom Clay Formation, to gain insight in processes influencing the mobilization/immobilization of radionuclides in clay over geological time-periods; 5. Investigations on the compatibility of spent nuclear fuel with geological disposal in clay. During recent years, large-scale demonstration projects as RESEAL and PRACLAY have become increasingly important within the Belgian radioactive waste management program. In the RESEAL project, the feasibility of a shaft sealing technique is demonstrated. The PRACLAY project is intended to demonstrate the feasibility and overall safety of HLW disposal in a clay formation. As part of the PRACLAY project, the thermo-hydromechanical behavior of a simulated HLW repository in clay will be investigated into great detail. These demonstration projects contribute to building confidence in deep disposal in clay as a safe, feasible and environmentally responsible solution. New research areas where studies have recently started are: (i) the definition of alternative safety indicators, (ii) the evaluation of the technical, economical and institutional consequences of the retrievability concept, and (iii) the development of devices for the long-term environmental monitoring of a geological repository. In addition to scientific-technical aspects, non-technical issues including societal acceptance of geological disposal, risk perception, sustainable development, ethics, and communication have gained increased significance within the Belgian program on geological disposal. It is anticipated that the evaluation of the SAFIR-II safety assessment report will determine to a large extent the scientific-technical content of the Belgian waste disposal program from 2002 onwards.