Spent fuel criticality and compositions evaluation for long-term disposal in a generic cask

The Nuclear Energy Agency (NEA) Expert Group on Burn-up Credit Criticality Safety published a Benchmark with results obtained from simulations with some nuclear codes for a PWR-UO2 nuclear fuel disposed of in a cask. The same situations were simulated at the Departamento de Engenharia Nuclear/Universidade Federal de Minas Gerais (DEN/UFMG) with the SCALE 6.0 (KENOVI/ORIGENS), MCNPX 2.6.0/CINDER and Monteburns (MCNP5/ORIGEN2.1). Combinations of codes and nuclear data are slightly different from those used by the organizations who participate of the Benchmark. For keff time evolution, the results are very similar to the values obtained by the benchmark participants. For decay time evolution, the results obtained for several nuclides presented the expected behavior. Nevertheless, differences in the composition increase during the time specially using the Monteburns code. These differences may be attributed to the libraries and methodology for choosing libraries to decay calculation and the number of days to a year considered to calculations.