Development and validation of new algorithms for control rods insertion modeling in the RAPID code system using the JSI TRIGA Mark-II reactor

Abstract The Real-time Analysis for Particle-transport and In-situ Detection (RAPID) Code System, developed based on the Multi-stage Response-function Transport (MRT) methodology, allows for real-time simulation of nuclear systems such as reactor cores, spent nuclear fuel pools and casks, and subcritical facilities. This paper presents a novel methodology for modeling control rods movement within the RAPID’s Fission Matrix (FM) formulation. This methodology, referred to as FM Control Rods “deltas” (FM-CRd), allows for combination and interpolation of RAPID’s FM coefficients to take into account the effect of inserting the control rods into the reactor core, while simultaneously limiting the amount of pre-calculations required. The FM-CRd methodology is benchmarked against experimental data from the JSI TRIGA ICSBEP benchmark and reference Serpent continuous-energy Monte Carlo calculations. The results show that RAPID’s FM-CRd can accurately calculate 3-D fission source distribution and k eff in the JSI TRIGA in a matter of seconds, hence constituting a powerful analysis tool for online analysis of the reactor during experiments.