CRITICALITY SAFETY ANALYSIS OF SPENT FUEL STORAGE POOL FOR NPP MOCHOVCE
29th Symposium of AER on VVER Reactor Physics and Reactor Safety (2019, Energoland, Mochovce NPP, Slovakia)
spent fuel disposal and actinide transmutation
Abstract
This article is devoted to an optimization scenario of the spent nuclear fuel storage pool located at NPP Mochovce site, which, due to safety and legislation, has 71 empty positions (without fuel assemblies). The calculation was performed using MCNP5 and Serpent 2 codes using the nuclear section library ENDF / B-VII. The safety analysis was performed on a three-dimensional model of the storage pool loaded with VVER-440 W-type fuel assemblies with a nominal average enrichment of 4.87 wt.%. The sensitivity of the multiplication factor to the change in the lattice spacing of the fuel rods, the pitch of the fuel assembly, the temperature of the coolant, the density of the fuel and the mass of boron in ATABOR absorbing steel is analyzed. Parametric analysis showed that the propagating properties of the system are negatively affected by an increase in the pitch of the lattice of the fuel rods, an increase in the fuel density, a decrease in the pitch of the absorbing pipes, a decrease in the temperature of the coolant and a decrease in the boron content in the absorbing pipes. Then, the results of the parametric analysiss are used in the spent fuel storage model to propose an optimized scenario for loading the storage using absorbing parts of the VVER-440 control assemblies – so the storage can be fully loaded. In terms of the efficiency of using the maximum number of empty positions in the storage pool and the minimum number of absorber parts loaded, the scenario K_M3-09, in which only 9 pieces of absorbers are used.