Continuous-energy Monte Carlo method for reactor transient analysis based on quasi-static methods

Abstract

As computing power increases, the Monte Carlo method becomes popular in nuclear reactor physics analysis due to its capability of scalable parallelization and handling complex geometry and continuous-energy nuclear data. This paper describes and compares the Monte Carlo method for reactor transient analysis based on two quasi-static methods; 1) the improved quasi-static method and 2) the predictor-corrector quasi-static method. In both methods, a linear approximation of fission source distributions during a macro-time interval is used to provide the analytic solution to delayed neutron source, and fission source iteration is used to solve the transient fixed-source problem. To solve the transient fixed-source problem via Monte Carlo method, the conventional particle-tracking method is modified. In numerical results, the two quasi-static methods in Monte Carlo calculation are compared with the direct time-dependent method of characteristics (MOC) on a TWIGL two-group problem for verification of the computer code. Then, transient analyses via the two quasi-static methods are presented and compared on a continuous-energy problem.