Investigation on present status of thermal neutron scattering law for beryllium metal and hydrogen in light water

Imaizumi, Tomomi; Takemoto, Noriyuki ; Nagao, Yoshiharu  ; Kawamura, Hiroshi

For the neutronic calculation in JMTR, an error of only thermal-neutron-flux tends to extend in specific region, i.e. an irradiation region in beryllium reflectors surrounding the fuel region. From our former investigation, the reason is thought to be the neutron scattering and absorption in the thermal energy region. Therefore, the effect on the thermal neutron scattering law S(,) to hydrogen in light water and to beryllium metal was investigated. As a result, it was confirmed that the error could be caused by the treatment in inelastic scattering within coherent scattering in the beryllium metal, whereas no error factor was found to the hydrogen in light water.