Integral experiment on beryllium with DD neutrons for nuclear data benchmarking

Kondo, Keitaro; Ochiai, Kentaro; Tatebe, Yosuke; Yagi, Takahiro; Onishi, Seiki; Takakura, Kosuke; Sato, Satoshi; Konno, Chikara  

At the Fusion Neutronics Source (FNS) facility of JAEA we have conducted various integral experiments with DT neutrons for fusion reactor materials and have made a significant progress in the verification of their nuclear data. Recently we started a new series of integral experiments with DD neutrons at FNS in order to verify nuclear data relating to DD neutrons effectively. An integral experiment on beryllium with the DD neutron source will be presented in this conference. A beryllium pseudo-cylinder assembly of 45 cm in thickness and 63 cm in the diameter was built at the distance of 20 cm from the DD neutron source, and reaction rates of the In(n,n')In, Au(n,)Au and Li(n,)T reactions and a U fission rate were measured. The measured values were compared with calculations with the MCNP5 code and the latest nuclear data libraries; JENDL-3.3, ENDF/B-VII.0 and JEFF-3.1. A slight disagreement between the measurement and the calculation was found in the reaction rate of In, which is sensitive to neutrons above 0.3 MeV. We identified that the disagreement originated from the angular differential cross section data of the elastic scattering around 3 MeV and from the (n,2n) reaction cross section data near its threshold energy. The calculated reaction rates of Au, Li and U, which are sensitive to low energy neutrons, showed a large overestimation, which also appeared at the beryllium integral experiment with DT neutrons previously carried out at FNS. This problem has not been solved yet.