Mobilization/Retention of Radionuclides during Corrosion of High Burnup Spent Fuel and Backfill Materials in Salt Brines
- PDF / 61,609 Bytes
- 7 Pages / 595 x 842 pts (A4) Page_size
- 54 Downloads / 183 Views
II8.2.1
Mobilization/Retention of Radionuclides during Corrosion of High Burnup Spent Fuel and Backfill Materials in Salt Brines Andreas Loida, Bernhard Kienzler, Horst Geckeis Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung, P.O.Box 3640, D-76021 Karlsruhe, Germany ABSTRACT With respect to the assessment of the long-term behavior of the waste form spent fuel it is of high importance to study the fuel alteration in contact with groundwater and near field materials. The aim of this work is to evaluate the impact of candidate backfill materials hydroxylapatite and magnetite on the overall corrosion behavior of this waste form in salt brine; both materials are used in corrosion tests together with spent fuel. The instant releases and the matrix dissolution rates appear to be similar in presence and in absence of any backfill material under study. However, Am,Np,Pu,U and Sr are retained at different ratios on the hydroxylapatite, on the magnetite and on the fuel sample, indicating possibly the formation of different radionuclide containing new solid phases. INTRODUCTION The long-term safety of a repository containing spent nuclear fuel will be guaranteed by the “multibarrier system”, consisting of the canistered spent fuel itself, possible backfill materials, borehole sealings, the host rock formation and its overburden. All barriers contribute to isolate the radionuclides from the biosphere. Backfill materials should provide prevention of groundwater access, retardation of radionuclide transport, control of the geochemical conditions, and distinguished retention capacity for radionuclides. Assuming that groundwater would find access to the waste packages, they will corrode, and after breaching of the container and the cladding the groundwater will interact with the spent fuel. Performance assessment of spent nuclear fuel disposal requires careful quantification of its long-term ability to retain individual radioelements, either by retention upon the surfaces of the solid phases present in the system, or incorporated in newly formed secondary phases. Related research comprises analyses of the (geo)chemical interactions of spent fuel with aqueous solutions (groundwater, brine), host rocks and near field components. Many experimental data on the dissolution rate of the spent fuel itself, in absence and presence of container material (Fe) and the associated release/retention of radioelements were obtained by extensive laboratory test programs. In the frame of our work they were mainly related to a rock salt environment [1, 2], which was considered to be the host rock for a repository for high-level waste in Germany. Aim of this work is to study the impact of candidate backfill materials on the overall corrosion behavior of spent fuel in salt brine. The candidate backfill materials hydroxylapatite (HAP - Ca5OH(PO4)3) and magnetite (MT - Fe3O4) were selected to be used in corrosion tests together with high burnup spent fuel pellets. Both of these materials are characterized by their ability to incorporate, or
Data Loading...
