[1G14-16] Analysis Method Development 3 Monte-Carlo Calculation

[1G15] Utility value of generalized extreme value statistics in Monte Carlo criticality calculation

*UEKI TARO¹ (1. JAEA)

Keywords:Monte Carlo, loosely-coupled system, criticality calculation, generalized extreme value statistics, neutron population, stationary fission source distribution

In the Monte Carlo criticality calculation of a loosely-coupled system, when the sampling from the fission source distribution (FSD) is conducted for small neutron population, the convergence toward stationarity of FSD occurs in an ill-conditioned manner and yields the biased estimate of the neutron effective multiplication factor (k_eff). This phenomenon is known as the k_eff-of-the-world problem and has been upgraded to a challenging problem under the current computing power. Based on this upgrading, the methodology of generalized extreme value is shown to effectively detect the transition from one stationary FSD to other stationary FSD under small neutron population.