The development of a multigroup Monte Carlo code for TRIGA reactors

Highlights: • New multigroup Monte Carlo code specifically designed for TRIGA reactor core design. • Complement other MC codes for functionalities that are less optimal. • Burnup calculations based on homogenized group cross sections. • Improved simulation performance in $k_{eff}$ and fission source convergence. - Abstract: This paper outlines the details of the development of TRIMON (TRIGA Monte Carlo Code), a next-generation reactor code that integrates diffusion-theory-type group cross sections into Monte Carlo method for TRIGA reactors. Such hybrid combination speeds up stochastic simulations via homogenization of complex local core regions. TRIGA reactors are currently installed in 24 different countries, thus, a robust core management code must be developed for their safety analysis. TRIMON includes important features that improve certain functionalities that are less optimal in most state-of-the-art Monte Carlo codes such as direct integration of local fuel burnup in core calculation, sophisticated reactor core design considerations and simulation time improvements in complex core configurations. TRIMON also eliminates the complicated jargon related to the core geometry and tally specifications imposed by most general multi-purpose Monte Carlo codes during the process of defining TRIGA core problems.