Argonne National Laboratory chemist Amanda Youker purifies molybdenum-99 in 2015 as part of a research project conducted with SHINE Medical Technologies. SHINE is one of several US companies that plan to produce the medical isotope without the use of highly enriched uranium. Credit: Wes Agresta/Argonne National Laboratory, CC BY-NC-SA 2.0
Two nuclear nonproliferation watchdog groups and a pair of producers of the medical radioisotope molybdenum-99 have each urged the US Nuclear Regulatory Commission (NRC) to reject a Department of Energy application to export weapons-grade uranium to Europe. Their September 2019 petitions highlight DOE’s potentially conflicting missions to both end US exports of highly enriched uranium (HEU) and ensure an adequate supply of 99Mo, which decays into a gamma-emitting radioisotope that is used as a tracer in many medical imaging procedures. By law, the NRC must issue an export license for shipments of enriched uranium.
NorthStar Medical Radioisotopes, the sole US manufacturer of 99Mo, and Curium, a European producer, joined the Nuclear Threat Initiative and the Nuclear Proliferation Prevention Project in challenging DOE’s August 2019 request to ship 5 kg of HEU to supply the Belgium-based Institute for Radioelements. IRE says it needs one last shipment of HEU to satisfy the total demand for 99Mo and iodine-131, a less-used medical radioisotope, until it can complete a conversion to low-enriched uranium (LEU) processes next year. IRE claims to produce 30–40% of the 99Mo used in the US. The US is even more dependent on IRE for 131I, which is used in the treatment of thyroid cancer and other thyroid disorders.
At press time, the NRC had not acted on the opponents’ petitions to hold a public hearing on DOE’s license application. Energy Secretary Dan Brouillette further opened the export door this month by ruling, subject to NRC approval, that such HEU shipments can continue for another two years, on the grounds that the global supply of 99Mo produced without HEU isn’t yet sufficient to meet US patient needs.
Nonproliferation advocates and DOE share a goal of ending all US HEU exports, due to the threat of the material being diverted to nefarious purposes. But in the 2013 National Defense Authorization Act, Congress also handed DOE the task of maintaining an adequate supply of 99Mo. Brouillette noted that dual role when he approved extending the export period while also pledging to continue DOE’s efforts to nurture a domestic industry for 99Mo. The agency has provided $160 million since 2012 to subsidize a half dozen domestic companies that expect to produce 99Mo with non-HEU processes. DOE has also spent $140 million for related nonproprietary R&D. To date, Wisconsin-based NorthStar is the only US firm to have initiated production.
The 2013 legislation stipulated that a ban on HEU exports for the production of medical isotopes would commence in January 2020 if DOE certified that enough 99Mo was available to meet US demand. By definition, HEU is enriched in the fissionable uranium-235 isotope to 20% or more. The uranium used by IRE is weapons-grade, enriched to more than 93% 235U.
A “button” of highly enriched uranium. Credit: DOE
IRE is the only 99Mo supplier to the US that still uses targets fashioned from US-origin HEU. Other foreign suppliers to the US, including Curium, use targets made with LEU, which can’t be turned into a nuclear explosive. IRE CEO Erich Kollegger told the NRC last September that although the company has enough HEU to meet its 99Mo needs before production begins with LEU targets, it requires more HEU before it can convert its 131I recovery process. The 131I conversion is expected to be completed next year. DOE has provided $11 million since 2012 to help IRE convert to LEU targets.
Kollegger also told the NRC that IRE’s transition to LEU targets has been slowed in part because it has had to compensate for 99Mo shortages resulting from shutdowns of reactors in South Africa and Australia over the past two years. Given the small number of producers, global supply of 99Mo is notoriously unreliable, plagued by scheduled and unanticipated shutdowns of reactors as well as transportation delays. The isotope’s half-life of 66 hours precludes stockpiling.
Eleven nuclear security and public health experts had urged Brouillette in an 18 December letter to halt exports beginning this month. They maintained that current US patient needs for 99Mo can be met by a combination of foreign producers and NorthStar. Other US companies that won’t use HEU targets are expected to begin commercial production of 99Mo over the next several years. They include Northwest Medical Isotopes, SHINE Medical Technologies, Coquí RadioPharmaceuticals, and Niowave.
Alan Kuperman, director of the Nuclear Proliferation Prevention Project at the University of Texas at Austin, says that Brouillette could have chosen to accommodate only a final shipment to IRE rather than approving a two-year extension period. The extra time eases pressure on the Belgian company to speed conversion to LEU targets, Kuperman says, undercutting other foreign producers that have converted to LEU and the US startup companies that have been subsidized by DOE.
Once IRE completes its target conversion, only two facilities abroad will continue to require US weapons-grade uranium: the high-flux reactor at France’s Institut Laue-Langevin neutron source and Belgium’s BR2 research reactor. It’s likely that the French facility will require future HEU shipments, says Kuperman; officials with BR2 have committed to converting to LEU by the mid 2020s.
Opinions differ on the amount of HEU needed to build a nuclear explosive device. The International Atomic Energy Agency considers 25 kg of HEU enriched to 20% or more to be the approximate amount “for which the possibility of manufacturing a nuclear explosive device cannot be excluded.” Kuperman says the IAEA’s number is arbitrary. DOE considers even 1 kg of weapons-grade uranium to be a major concern and has paid to convert reactors using less than that amount in their cores, he says.
A 1995 analysis by the Natural Resources Defense Council concluded that a device yielding 20 kilotons—about the same as the Nagasaki bomb—could be fashioned from as little as 5 kg of weapons-grade material. Building such an implosion device would require a high level of sophistication, but it could be accomplished by a terrorist group with the help of scientists from some nation’s nuclear program, Kuperman says. HEU is considered the nuclear material of choice for terrorists because it is only mildly radioactive and far less hazardous than plutonium.
According to DOE’s license application, the HEU for IRE’s needs would be shipped—the mode of transport is classified—from the US stockpile located at the Y-12 National Security Complex in Oak Ridge, Tennessee, to the French company Framatome, which would fabricate it into reactor targets. The targets would be irradiated in research reactors located in Belgium, the Netherlands, Poland, and the Czech Republic. The irradiated targets containing the 99Mo and 131I fission products would then be shipped to IRE for extraction and purification of the isotopes.
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