Mechanisms governing the release of radionuclides from spent nuclear fuel in geological repository: major outcomes of th
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Mechanisms governing the release of radionuclides from spent nuclear fuel in geological repository: major outcomes of the European Project SFS. Christophe Poinssot 1, *, Cécile Ferry 1, Bernd Grambow 2, Manfred Kelm 3, Kastriot Spahiu 4, Aurora Martinez 5, Lawrence Johnson 6, Esther Cera 7, Joan de Pablo 8, Javier Quinones 9, Detlef Wegen 10, Karel Lemmens 11, Thomas McMenamin 12 1
CEA Nuclear Energy Division, Department of Physics and Chemistry, DPC/SECR, F-91191 Gif Sur Yvette cedex, France. 2 SUBATECH Laboratory, School of Mines, 41 rue A. Kastler, La Chantrerie, BP20722, F-44307 Nantes, France. 3 INE, Forschung Zentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Germany. 4 SKB, Brahegatan 47, box 5864, S 102 40 Stockholm, Sweden. 5 ENRESA, Emilio Vargas 7, E-28043 Madrid, Spain. 6 NAGRA, Hardstrasse 73, CH-5430 Wettingen, Switzerland. 7 ENVIROS SPAIN, Passeig de Rubi, 29-31 Valldoreix, E-08197 Barcelona, Spain. 8 UPC, Barcelona, Spain. 9 CIEMAT, MONCLOA center, Avda. Complutense, 22, E - 28040 Madrid, Spain. 10 European Commission, JRC, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe, Germany. 11 SCK-CEN, Boeretang 200, B-2400 Mol, Belgium. 12 European Commission, Bruxelles, Belgium.
ABSTRACT European Commission supported a wide research project entitled "Spent Fuel Stability under repository conditions" (SFS) within the 5th FWP, the aim of which was to develop a common understanding of the radionuclides release from spent nuclear fuel in geological disposal and build a RN release model in order to assess the fuel performance. This project achieved by the end of 2004 focuses both on the Instant Release Fraction (IRF) model and the Matrix Alteration Model (MAM). A new IRF model was developed based on the anticipated performances of the various fuel microstructures (gap, rim, grains boundaries) and the potential diffusion of RN before the canister breaching. However, this model lets the choice to the end-user about the degree of conservativeness to consider. In addition, fuel alteration has been demonstrated to be linked to the production of radiolytic oxidants by water radiolysis at the fuel interface, the oxidation of the fuel interface by radiolytic oxidants and the subsequent release of uranium under the influence of aqueous ligands. A large set of experimental data was therefore acquired in order (i) to upgrade the current radiolytic kinetic scheme, (ii) to experimentally correlate the fuel alteration rate and the fuel specific alpha activity by performing experiments on alpha doped samples, (iii) to experimentally test the potential inhibitor effect of hydrogen on fuel dissolution. Based on these results, a new MAM was developed, which was also calibrated using the experiments on inactive UO2 samples. This model was finally applied to representative granitic, salt and clayey environment to predict spent fuel long-term fuel performance.
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Contact author: email. : [email protected]
INTRODUCTION Direct disposal of spent nuclear fuel is a reference option for many European c
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