A time dependent Monte Carlo approach for nuclear reactor analysis in a 3-D arbitrary geometry

Highlights: • Development of a 3D Computer code for safety analysis of a nuclear reactor. • The Code works based on Monte Carlo method. • The restrictions of previous methods in transient analysis have been removed. • The Code is able to use either continuous or multi-group energy cross section libraries. • The Code is capable to simulate the systems with time-varying geometry and cross sections. -- Abstract: A highly reliable tool for transient simulation is vital in the safety analysis of a nuclear reactor. Despite this fact most tools still use diffusion theory and point-kinetics that involve many approximation such as discretization in space, energy, angle and time. However, Monte Carlo method inherently overcomes these restrictions and provides an appropriate foundation to accurately calculate the parameters of a reactor. In this paper fundamental parameters like multiplication factor (K_eff) and mean generation time (t_G) are calculated using Monte Carlo method and then employed in transient analysis for computing the neutron population, proportional to K_eff, during a generation time considering precursors decay. Based on this approach, a dynamic Monte Carlo code named MCSP (Monte Carlo dynamic Simulation of Particles tracking) is developed for both the steady state and time-dependent simulation of particle tracking in an arbitrary 3D geometry. MCSP is able to use either continuous or multi-group energy cross section libraries. To speed up the simulation, the MCSP was empowered with parallel processing as well. Several test problems such as C5G7, LMW and TWIGL are examined to assess the performance of the method.