Review of convergence acceleration methods in Monte Carlo criticality calculations for reactor analysis

The core problem of criticality calculations in nuclear analysis is to calculate the fission source distributions of systems. As the computing performance of hardware and software has advanced, Monte Carlo methods have been applied to the nuclear analysis of whole core problems, because the accuracy of the Monte Carlo calculations has been enhanced by its ability to use continuous energy nuclear data and to handle complex geometry information. When approaching whole core analyses, the Monte Carlo criticality calculations must handle some challenging problems, such as slow convergence, the stopping criteria of source convergence, and real variance estimations. Here, the theory and challenges of Monte Carlo criticality are introduced, and progress in convergence acceleration methods and variance reduction techniques is reviewed.