[3J12-14] Criticality Safety

[3J14] Calculation Method of Estimated Criticality Lower-Limit Multiplication Factor Using the Bootstrap Method

*Takuto Hayashi¹, Tomohiro Endo¹, Akio Yamamoto¹ (1. Nagoya Univ.)

Keywords:nuclear criticality safety, estimated criticality lower-limit multiplication factor, bootstrap method, Whisper-1.1

In the conventional method, the normal distribution is assumed as calculation errors of effective multiplication factors to evaluate estimated criticality lower-limit multiplication factor (ECLLMF). To propose a methodology without the assumption of normal distribution, an estimation method of the ECLLMF was newly developed using the Bootstrap method, where the assumption of the normal distribution is not necessary. The critical benchmark experiment analysis data were chosen by Whisper-1.1 for a unit cell of a UO₂ sphere with a radius of 1.0 cm surrounded by a water moderator, where the fuel to moderation ratio was almost optimum. The ECLLMF was calculated using effective multiplication factors obtained by the analysis. It was confirmed that the estimation result using the Bootstrap method was comparable with that using the conventional method.