Analysis of Bulk Shielding Experiments on Large SS316 Assemblies

Abstract

The fusion bulk shielding experiments on the cylindrical assemblies of 1.12 m in length and 1.20 m in diameter made of type 316 stainless steel have been carried out at the FNS facility in JAERI. This paper presents the analytical results for these experiments using the Sn code DOT3.5 and the Monte Carlo code MCNP with cross section libraries based on JENDL-3. The calculated results by both codes agree well with the measured values for threshold reactions and neutron energy spectra above 2 MeV. For the neutron energy spectra in keV energy region and fission rates of ²³⁵U, agreements between the measured data and the values by MCNP are pretty good, while the DOT3.5 calculation largely underestimated the measured values by a factor of 2–3 in deeper positions of the assemblies. For gamma-ray heating and gamma-ray spectra, relations between experiments and calculations are similar to those for low energy neutrons. A possible problem is pointed out in gamma-ray production processes when the DOT3.5 code and the FUSION-J3 library based on JENDL-3 are used.