Monte Carlo Benchmark Calculations for 400MWth PBMR Core

Abstract – Benchmark calculations for the core of the 400MWth Pebble-bed Modular Reactor (PBMR), being developed in South Africa, were carried out by using MCNP5 code as a part of establishing Monte Carlo computation system for HTGR core analysis. After the detailed MCNP modeling of the whole facility, two neutronic benchmark problems, for fresh fuel and cold conditions(Case F-1), and first core loading with given number densities(Case F-2), proposed by the IAEA CRP5 was pursued. The resulting keff was calculated to be 1.2795±0.00052 and 1.1401±0.00055 for Case F-1 and F-2, respectively. It was found that these results were different with the results from other research group using MCNP4b, because 3 bottom cone regions and de-fueling chutes were assumed as the surfaces flattened in MCNP4b calculations while these were modeled explicitly in this study. This study can be contributed and utilized directly in the establishment of benchmark problems to develop deterministic neutronics analysis tools and methods, which lagged behind the state of the art compared to other reactor technologies, to design and analyze PBMR