THE TCA BENCHMARK FOR VALIDATION OF TEMPERATURE FEEDBACK CALCULATIONS

Abstract

The TCA benchmark was investigated as a possible candidate for validation of temperature feedback calculations. This benchmark has low-enriched uranium fuel, light water moderation and reflection, and a temperature range of 20–60 °C. The use of three different nuclear data libraries was considered, viz. ENDF/B-VIII.0, JEFF-3.3, and JENDL-4.0. Since the results were not as good as hoped for, additional studies were performed to identify the cause(s) of discrepancies. The benchmark values depend on a choice of delayed neutron data, so it was investigated whether this could be the cause of discrepancies. Also, an assessment was made based on critical configurations only, i.e. avoiding the use of delayed neutron data, whether the calculations exhibit a bias in relation to the benchmark in the results for the effect of temperature. Indications were found that such a bias exists. It is concluded that the choice of delayed neutron data has a significant effect on the benchmark values themselves. The use of three major nuclear data libraries leads to a range of benchmark values for each configuration, rather than one value. Also, one has to take into account the possibility of a bias in the calculation of temperature effects. It is not clear at this point what the cause of the bias is.