On effective delayed neutron fraction calculations with iterated fission probability

Chiba, Go; Nagaya, Yasunobu  ; Mori, Takamasa

The effective delayed neutron fraction can be accurately calculated with the continuous-energy Monte Carlo method using the iterated fission probability (IFP) if the sufficiently large number of generations is considered. In order to deterministically quantify the required number of generations in the IFP-based calculations, the concept of the generation-dependent importance functions is introduced to calculations. Furthermore, the most appropriate reactor property used in the IFP calculations, which reduces the required number of generations, is theoretically derived. Through numerical calculations, it is shown that the several generations are required in the IFP-based calculations and that the use of the appropriate reactor property can reduce the required number of generations. An efficient procedure for the IFP-based calculations with the Monte Carlo method is also proposed.