Target and Core Optimization for an Electron Accelerator-Driven Transmutation Facility

Abstract

The current statutory limit for Yucca Mountain is quickly being met by waste produced at the reactors operating in the United States. A possible method of modifying reactor waste for more efficient storage in Yucca Mountain is transmutation. This study analyzes the use of an electron accelerator targeting its beam on a neutron producing target within a subcritical reactor fueled with transuranic waste from power reactor operations.

To maximize the transmutation effectiveness of the design, several loading patterns were analyzed for neutronics behavior and transmutation effectiveness. Designs utilizing multiple batches of fuel or multiple targets within the core were also analyzed.

The loading pattern analysis showed no clear beneficial loading pattern for the neutronics of the core; however, the results indicated that placing Curium within the innermost fuel assemblies improved the transmutation effectiveness of the core. The most effective loading pattern in terms of neutronics and transmutation effectiveness utilized Curium assemblies in the innermost locations, Americium assemblies in the second ring, and Neptunium and Plutonium assemblies in the outermost locations.

The use of multiple batches in the core layout demonstrated superior neutronics behavior but lacked in transmutation effectiveness. On the other hand, the use of multiple targets in the core did not exhibit the lower peaking factors expected and also performed poorly in the area of transmutation effectiveness. Most likely, these core designs should be combined with more effective loading patterns to maximize their benefits.

When comparing electron accelerator based systems with proton accelerator based systems, the proton based systems have a significant advantage due to the higher neutron production efficiency within the target. However, economic and timeline considerations make the deployment of electron based systems attractive in specific scenarios.