A Fast Variance Reduction Technique for Efficient Radiation Shielding Calculations in Nuclear Reactors

The increasing demand for cleaner and more sustainable energy sources has sparked significant interest in small modular reactors (SMRs). Due to their compact and modular design, SMRs pose unique challenges in radiation shielding, requiring a more refined approach. This study focuses on developing a new variance reduction technique (VRT) for radiation shielding analysis, specifically tailored for SMRs, to address the limitations of traditional methods such as surface source write/surface source read (SSW/SSR). The proposed VRT supports multi-threading and enhances computational efficiency by redefining source particles using a two-step method. The analysis is conducted using the Monte Carlo radiation transport code, MCNP6, and the effectiveness of the new VRT is evaluated through sensitivity analyses across various energy and directional divisions.