Publication Laka-library:
The FEBEX project. General overview
| Author | ENRESA |
| Date | |
| Classification | 2.12.4.10/13 (SWITZERLAND - WASTE (NAGRA)) |
| Front | 
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From the publication:
INTRODUCTION The engineered barrier system (EBS) is a key component of the current ENRESA safety concept for the final disposal of spent fuel. The EBS provides the primary containment of the wastes and consists of the waste form, encapsulated in carbon steel canisters, surrounded by bentonite and emplaced horizontally in disposal galleries. The releases from the waste form are constrained by its high structural stability and low corrosion rates and by the low solubility of many radionuclides. The canister isolates the waste for a minimum lifetime of 1,000 years and its corrosion products act as a chemical redox buffer, which ensures low solubility of many radionuclides. The bentonite has the multiple purpose of providing mechanical protection for the canister against rock movements, retarding the migration of radionuclides due to sorption processes, and acting as a chemical buffer, ensuring adequate pH and reducing conditions in the near-field. The disturbed rock zone should provide low groundwater flowrates around the disposal galleries to restrict the rate of diffusive transport through the bentonite, and should ensure reducing conditions and have adequate thermomechanical stability. A consequence of the ambition of having the EBS carry a large part of the safety burden of the repository is that there will be higher demands on the understanding of the processes involved, on the quality of the data base and on the modelling of the processes involved. As a response to these demands, ENRESA devised the FEBEX project, the goal of which is to study the performance of the EBS through a full-scale experiment in a realistic environment. The experiment has three major parts: 1) an "In situ" test, under natural conditions and at full scale [1]; 2) a "Mock-up" test, at almost full scale [2]; and 3) a set of experimental laboratory tests, to complement the information from the two large-scale tests [3,4]. The experiment is based on the Spanish reference concept for crystalline rock, in which the waste canisters are placed in horizontal drifts surrounded by a clay barrier formed from compacted bentonite blocks [5]. The complete project, of about seven years in duration, has been divided into four sequential stages: pre-operational (planning, design, installation, and predictive modelling); operational (heating, monitoring, and cooling); dismantling (extracting, sampling, and testing the materials); and final evaluation of the entire experiment. The project is currently in the operational stage.
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