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 international cooperation in our development activities.

Sustained Availability of 99mTc: Possible Paths Forward

“…Conversion to LEU would reduce the 99 Mo yield per mass of uranium target to approximately 20% that from HEU, but this loss is partially offset by the use of denser uranium foil targets compatible with both acidic and alkaline dissolution processes (19,20). The commercial availability of LEU foils is one of the challenges for widescale deployment of this strategy.…”

Diagnostic Imaging Agents

“…According to Vandegrift [7,8], 25-fold more Pu-239 is produced in a LEU target than in a HEU target. On the other hand, when uranium is enriched for HEU (93% U-235), it is even more enriched in U-234.…”

The influence of radiopharmaceutical isotope production on the global radioxenon background

“…Then the rest of the different fission products is separated and purified. These chemical separation processes reach a 95% efficiency yield (Vandegrift and Snelgrove, 2000;Tabasi et al, 2005).…”

“…To reduce proliferation concerns, however, the planners are encouraged to use LEU targets (Vandegrift et al, 1999;IAEA, 2005), as done for example by the radiopharmaceutical facilities in Argentina (CNEA) and Australia (ANSTO). On the other hand, due to the high amount of 238 U in LEU there is a high production of 239 Pu during the irradiation (neutron capture by 238 U), which is also a proliferation concern.…”