Advanced radiation shielding methodology for small modular reactors using a multithreaded two-step source approach

The increasing demand for compact and efficient radiation shielding in advanced nuclear systems, such as small modular reactors in nuclear-powered ships, necessitates the development of improved radiation shielding techniques. This study presents an advanced methodology using a multithreaded surface source approach for radiation shielding analysis and applies it to the URANUS lead-bismuth cooled fast reactor. Unlike traditional surface source write/read (SSW/SSR) methods, which do not support multithreading and often suffer from prolonged computation times to reduce relative error, the proposed method ensures consistent statistical accuracy and computational efficiency. By using MCNP6's advanced capabilities, this approach overcomes prior limitations and enables more reliable and effective shielding analysis. Comparative analyses with conventional shielding methods, energy and directional sensitivity studies, and preliminary optimization results demonstrate the effectiveness of the newly developed methodology in enhancing radiation shielding performance for space-constrained nuclear systems.