Development of a source term related to the geological disposal of spent nuclear fuel in Slovakia
26th Symposium of AER on VVER Reactor Physics and Reactor Safety (2016, Helsinki, Finland)
Intermediate storage of spent fuel decommissioning and radwaste / Spent fuel disposal and actinide transmutation
Abstract
DEVELOPMENT OF A SOURCE TERM RELATED TO THE GEOLOGICAL DISPOSAL OF SPENT NUCLEAR FUEL IN SLOVAKIADana Barátová, Branislav Vrban, Vladimír NečasInstitute of Nuclear and Physical Engineering, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology in BratislavaEmail: dana_baratova@stuba.sk, branislav.vrban@stuba.sk, vladimir.necas@stuba.skABSTRACTIn Slovakia, the preferred option how to manage a spent nuclear fuel (SNF) is a direct disposal of the SNF in a geological repository. It is considered that in the geological repository there will be disposed spent fuel assemblies from the operation of the Slovak nuclear power plants and also the radioactive waste which is not suitable for a disposal in the National Radioactive Waste Repository in Mochovce. Because of the fact that the isotopic composition of spent nuclear fuel and corresponding radionuclide activities are important parameters when developing a source term model of the geological repository, the isotopic composition and activities of individual radionuclides were calculated. Within this assessment the initial inventories of SNF assemblies were calculated for the fuel from VVER-440 reactors with different average initial enrichments of U-235 and different burn-up levels. Safety relevant radionuclides were identified based on the certain assumptions as relatively long half-lives, not negligible inventories, a presence of the instant release fraction (fraction of the inventory which is after water-contact released rapidly) and by using the international safety cases. Daughter nuclides with relatively short half-lives were assumed to be in equilibrium with their parent nuclides and were excluded from the radionuclide migration calculations. Stable isotopes were also included in the calculations as the isotopes of the same element share the solubility limit (the effect of reducing the solubility of safety relevant nuclides). Consequently the impact of different inventories of SNF assemblies on release rates (activity rates) in the radionuclide migration calculations was examined. Depletion calculations were realised by using the TRITON sequence of SCALE system and GoldSim simulation software was used for the radionuclide transport calculations. 26th Symposium of AER on VVER Reactor Physics and Reactor Safety 62 10 – 14 October 2016, Helsinki, Finland