Establishing a neutronics design and equilibrium cycle analysis for the I2S-LWR reactor with UO2 and U3Si2 Fuel

Abstract

The Integral Inherently Safe (I2S-LWR) reactor was developed not only to enhance passive reactor safety performance, but also to improve reactor economics. This paper describes the steady-state and depletion analysis of the I2S-LWR core using both UO2 and U3Si2 fuel designs. The development and validation of the core models are described, to include the generation of HELIOS cross sections and comparison with the WEC lattice code PARAGON and the Monte Carlo code SERPENT. The few group homogenized cross sections were then prepared for the U.S. NRC PARCS core simulator using the GenPMAXS code. The multicycle capability in PARCS was used to determine the equilibrium core condition for three batch cores loaded with the UO2 and then with the U3Si2 fuel designs. Comparisons with the results from the WEC code ANC at beginning, middle, and end of cycle showed good agreement. Core conditions at beginning and end of cycle were then used to determine the converged steady-state conditions of a coupled RELAP5/PARCS model, which provided the initial condition for various transient accident simulations which are reported in a companion paper.