Calculations of Kobayashi benchmark problems with a neutron transport simulation code system CBG

Chiba, Go

In order to evaluate applicability of a neutron transport simulation code system CBG to shielding problems, calculations are performed with CBG for the Kobayashi benchmark problem which has been proposed for validations of neutron shielding calculations. In fully-absorbed shielding problems, it is shown that angular quadrature sets which have limitations on the angular order result in large discrepancy to the reference solutions in neutron flux due to the ray effect and that angular quadrature sets which have no limitations on the order reproduce well the reference neutron flux. In partly-absorbed shielding problems, it is shown that the high-order Tri_DPT set reproduces well the reference neutron flux. In addition, a multi-step S method is proposed, and it is shown that it can drastically reduce calculation time without losing calculation accuracy.