Neutronic calculations for steel-reflected fast critical systems with the sub-group S method

Chiba, Go; Kugo, Teruhiko 

We perform neutronic calculations for steel-reflected fast critical systems with the sub-group S method. In the present sub-group S calculations, we do not assume the narrow resonance approximation and do consider sub-group to sub-group transfer probabilities for in-group scattering sources. In addition, sub-group dependence of out-group scattering sources, which has been ignored in previous studies, is also taken into account. The present sub-group S method is applied to neutronic calculations for several steel-reflected fast systems included in the ICSBEP handbook. It is shown that the present sub-group SN method reproduces quite well the reference Monte-Carlo solutions for the effective multiplication factor and neutron flux spatial distribution above 0.1 MeV in reflector regions.