Computational Thermal Hydraulics of a High-Performance Low-Enriched-Uranium Annular Target for HFIR Irradiation

Abstract

Molybdenum-99 has been historically generated via isolation from fission products of fissioned highly enriched uranium targets. The isotope is of significant demand due to its daily use across the planet in radiopharmaceutical medical procedures. The primary objective of this paper was to design and analyze an experimental target assembly containing one low enriched uranium annular target for irradiation at the High Flux Isotope Reactor. Efforts included incorporating spatially dependent energy sources from neutron and gamma interactions, quantifying thermal contact conductance at material interfaces, performing grid independent studies, comparing turbulence models, and simulating various steady-state and transient scenarios relevant for irradiation qualification and eventual insertion into the High Flux Isotope Reactor. The completion of the design for the target experimental assembly marks an exciting step towards addressing the nation’s domestic supply of Molybdenum-99. This pivotal experiment offers the opportunity to quantify important fuel performance metrics on the annular target. The irradiation can form the bedrock for a robust licensing basis.