IMPORTANCE OF SELF-SHIELDING EFFECT ON SHIELDING DESIGN OF FUSION DEVICES

Abstract

Through analyses of the bulk-shielding experiment on large type 316 stainless steel assemblies performed at FNS / JAERI, importance of the self-shielding effect on shielding designs of large-scale fusion devices is studied. When the self-shielding effect is not considered, DOT calculations largely underestimate resonance energy neutrons up to a factor of 2.5 at a depth of 0.91 m and overestimate gamma-ray production 35 % larger against MCNP calculations. DOT calculations with self-shielding corrected cross sections agree well with MCNP calculations for both neutron and gamma-ray production. Since DOT with self-shielding correction and MCNP agree with experiment within a few tens of percentage, validity of the used nuclear data library, JENDL-3, is confirmed. It is pointed out that the self-shielding correction is required in response functions for shielding design parameters, such as activation, displacement damage and neutron dose. In conclusion, it is inevitable for shielding designs of large-scale fusion devices to take the self-shielding correction.