Nuclear and thermal hydraulic calculation of a representative I2S-LWR first core

Abstract

The Integral Inherently Safe Light Water Reactor (I2S-LWR) concept developed by Georgia Tech is a novel PWR reactor delivering electric power of 1000 MWe while implementing inherent safety features typical for Generation III+ small modular reactors. The main safety feature is based on integral primary circuit configuration, bringing together compact design of the reactor core (121 fuel assembly), control rod drive mechanism (CRDM), 8 primary heat exchangers (PHE), 4 passive decay heat removal systems (DHRS), 8 pumps, and other integral components. A high power density core based on silicide fuel and APMT (FeCrAl) stainless steel cladding is selected to achieve a high thermal power. Initial representative first core nuclear design is proposed by Westinghouse. Full core 3D depletion calculation was performed using PARCS code. The cross section library is prepared using FA2D code and verified using Polaris sequence from SCALE 6.2 beta5. The axial and radial reflectors are assumed to be homogeneous water-APMT mixtures. The axial reflectors are both assumed to be 12 inch (30.48 cm) sections composed of 30% APMT steel by volume. The radial reflector is assumed to be 90% APMT steel by volume. The reflector constants were calculated using SCALE TRITON sequence. The thermal hydraulic part of the model is based on COBRA subchannel code coupled to PARCS code. Initial depletion calculation is based on one thermal hydraulics channel per fuel assembly approach. The hot fuel assembly is determined using separate pin-by-pin COBRA subchannel model and pin power reconstruction data from PARCS. The objective of the paper is demonstration of LWR design methodology applicability to silicide fuel and identification of possible improvements in the first core design.