Comments on Monte Carlo Probability of Initiation Estimates for Neutron Fission Chains

This technical note shows that it is possible and effective to use Monte Carlo variance-reduction methods for the probability of initiation problem. The benefits are threefold. First, the proper use of variance reduction obviates using an arbitrary definition of a "divergent chain." Second, because chains of all lengths are allowed, there is no bias introduced by ignoring some long chains because they meet the divergent chain definition. Third, variance-reduction methods might drastically increase the efficiency of some of these calculations.