Comparison of calculated bare critical masses between two versions of the Japanese Evaluated Nuclear Data Library, JENDL-5 and JENDL-4.0

Oizumi, Akito   

Research and development of the transuranium fuel cycle with accelerator-drive systems (ADSs) transmuting minor actinides (MAs) separated from commercial cycles has been continuously conducted by the Japan Atomic Energy Agency (JAEA) to reduce the high-level radioactive waste contained in the spent fuel discharged from nuclear power plants. To transmute MA with high efficiency, the ADS fuel contains a large amount of MA. The criticality safety design of facilities within the ADS cycle must rely on calculated values using the nuclear data library because there are no experimental or measured values for the critical mass of many MAs. Thus, it is crucial to figure out the impact of updating the evaluated nuclear data library on the critical mass calculation. This study compared the differences in the calculated critical masses of a bare metal sphere (BCMs) for each actinide isotope between two version of Japanese Evaluated Nuclear Data Library, JENDL-5 (released in December 2021) and JENDL-4.0 as a basic assessment. The study found that the differences in BCMs between JENDL-5 and JENDL-4.0 were less than 1% for U, U, Np, and Pu, which have the integral experimental data for metallic spheres registered in the International Criticality Safety Benchmark Evaluation Project (ICSBEP). On the other hands, the difference in BCMs between two nuclear data libraries was found to be almost 7-40% for nuclides such as Am, Am, Cm, and Cm, which have relatively limited or no integral experimental data registered in ICSBEP and International Handbook of Evaluated Reactor Physics Benchmark Experiments (IRPhEP). Furthermore, as a result of analyzing the nuclear data that influenced the difference in BCM, for example in the case of Cm, it was clarified that the update of fission reaction and prompt gave a significant contribution.