Computational mapping of neutron flux distributions in the PRR-1 SATER using PHITS

Abstract

Optimizing the experimental potential of the Philippine Research Reactor-1 (PRR-1) Subcritical Assembly for Training, Education, and Research (SATER) requires a  computational model capable of simulating complex reactor geometries and detailed radiation transport. In this work, the facility was modeled using the Particle and Heavy Ion Transport code System (PHITS) code to establish a computational basis for subsequent reaction rate calculations. The spatial distribution of the neutron flux across the horizontal plane was mapped according to fast, epithermal, and thermal neutron energy ranges. Results confirm a highly localized fast neutron flux within the central fuel lattice, whereas thermal neutrons are more broadly distributed in the surrounding water moderator. These preliminary spatial neutron flux profiles show reasonable agreement with a previously established OpenMC computational model, providing a useful basis for subsequent neutron reaction simulations using PHITS.