Impact of Revised Thermal Neutron Capture Cross Section of Carbon Stored in JENDL-4.0 on HTTR Criticality Calculation

The effect of revised thermal neutron capture cross-section of carbon stored in JENDL-4.0 on HTTR criticality calculation is examined. The HTTR is a graphite-moderated and helium gas-cooled block-type HTGR, situated at JAEA-Oarai Research and Development Center. It has 30MW thermal power and its outlet coolant temperature, which can be used for nuclear heat utilization, is 850°C in rated power operation. The critical approach of the HTTR was carried out by the fuel addition method at room temperature. In the critical approach, dummy graphite blocks previously placed in the core were replaced with fresh fuel blocks from the outer core region in the form of fuel columns. The discrepancies between the experimental and calculation results on the following two issues were resolved as expected by replacing the nuclear data libraries with JENDL-4.0, in which the thermal capture cross section of carbon was revised for the first time in 21 years.