Plutonium-238 Production Program Results, Implications, and Projections from Irradiation and Examination of Initial NpO₂ Test Targets for Improved Production

An alternative target design with potential improvements, including a major increase in ²³⁸Pu production rate and annual capacity; fewer targets to be fabricated, irradiated, and processed; and a significant replacement of a large volume of caustic-nitrate, aluminum-bearing radioactive liquid waste with a smaller volume of solid metal waste, has been conceived and evaluated using reactor physics and thermal-hydraulic analyses. The alternative target design uses pressed pellets of ²³⁷NpO₂, sintered to 92% to 93% of theoretical density, and stacked inside a Zircaloy-4 cladding tube. Four test targets were fabricated, irradiated, and examined. No melting or other potential problems were indicated. Projections from measured constituents indicated annual production could be increased by a factor of ~2, and the number of targets required to be fabricated, irradiated, and processed could be reduced by a factor of ~5.