Performance analysis of a two-step calculation procedure based on Monte Carlo and pin-wise diffusion methods for PWR core design

This study introduces an efficient two-step calculation procedure for PWR core design by integrating Monte Carlo and pin-wise diffusion methods. The methodology combines Monte Carlo's high-fidelity cross-section generation with pin-wise diffusion's computational efficiency to model neutron flux and power distribution in reactor cores. The approach incorporates Super Homogenization (SPH) factors to enhance neutron flux heterogeneity modeling, addressing the complexities of modern reactor designs with advanced burnable absorbers and control rod strategies. Verification using the APR1400 benchmark demonstrates accuracy comparable to whole-core transport codes while maintaining computational efficiency. The methodology is also applied to innovative Small Modular Reactors (i-SMR), particularly evaluating cores with advanced fuel management and soluble boron-free operations. Results show accurate predictions of neutron flux and power distributions in i-SMR cores incorporating advanced burnable absorbers like HIGA (Highly Intensive and Discrete Gadolinium/Alumina Burnable Absorber). The approach effectively addresses i-SMR-specific challenges, including maintaining reactor criticality during extended operational periods. Through optimized parallelization, 3D reactor calculations are completed within seconds, ensuring practical applicability in various operational scenarios. This methodology represents a significant advancement in reactor core analysis, offering a high-precision, computationally efficient solution for modern PWR and i-SMR core designs, while maintaining exceptional accuracy in predicting core physics parameters.