Criticality computations for CANDU - 6 cell utilizing the SCALE system

The investigated CANDU - 6 cell was defined in the frame of a benchmark approach; the fuel pellets were of sintered UO2 (with natural uranium), the coolant and moderator are D2O of different purities, while the fuel element can, the pressure tube and the calandria are made of different zirconium based alloys. Utilising the modular system of SCALE codes for criticality computation in CANDU reactor is challenging from both the computation method (Monte Carlo) used and the nuclear data used, which are not specific to the CANDU reactor. For criticality computation the SAS1 (NITAWL, BONAMI, and KENO - VI modules) sequence of the SCALE system. The geometrical model used was is the one indicated in benchmark approach corresponding to the Final Safety Report for Cernavoda NPP Unit 1. Separate calculation with three nuclear data libraries were performed in order to evidence the influence of energy cutting (27, 44 and 238 groups, respectively) and of the nuclear data provenance. Sensitivity calculations aimed at investigating the influence of small variations in geometrical parameters and composition on the effective multiplication factor. Also, different variants of treating the leaks, ranging from the completely reflected cell up to the infinite lattice were studied