Lead Benchmark Experiment with DT Neutrons at JAEA/FNS

A new benchmark experiment on lead with DT neutrons was designed and carried out with a large lead assembly covered with Li₂O blocks at JAEA/FNS to validate nuclear data of lead for measurement of reaction rates without impact of background neutrons. The experiment was analyzed by using the MCNP5-1.40 code with the latest nuclear data libraries, ENDF/B-VII.1, JEFF-3.2 and JENDL-4.0. The calculated reaction rates underestimated the measured ones with the depth. Moreover, the tendencies of C/Es were different among the nuclear data libraries. In order to find out the reasons of the differences, we examined reaction cross-sections of lead in the nuclear data libraries in detail. The potential reactions to cause the underestimation issue of the calculated reaction rates were indicated through this study.