Modification of Targets and Processes for Conversion of 99Mo Production from High- to Low-Enriched Uranium

Abstract

As part of the U.S. nonproliferation effort, we are investigating the conversion of the production of fission-product 99Mo from use of high-enriched uranium (HEU) to low-enriched uranium (LEU). Successful conversion from HEU to LEU (<20% 235U) requires an irradiation target that contains 5 times more uranium but minimizes changes to target geometry and processing. The LEU target being developed uses thin foils of uranium metal that can be removed from the target hardware for dissolution and processing. This paper describes our recent successes in target fabrication, irradiation, and processing. Target fabrication has been improved by (1) heat-treating the uranium foil to produce a random, small-grain structure and (2) electrodepositing zinc and nickel fission-fragment barriers onto the foil. These fission-fragment barriers have been found to be stable during transport of the targets following irradiation. Recent irradiation tests have shown that the concept is sound. Progress was also made in broadening i...