A severe shortage in the supply of molybdenum-99, the precursor to the most commonly used medical radioisotope, is likely to arise once production ceases at a Canadian reactor next month, warns a committee of the National Academies of Sciences, Engineering, and Medicine. A 12 September report recommends that the US work with the Canadian government to resume output at the National Research Universal (NRU) reactor in Chalk River, Ontario, should disruptions occur at any of the world’s other current suppliers of 99Mo. The Mo isotope is the parent of technetium-99-metastable, which is commonly used in medical imaging procedures.
The Canadian government has announced that the 59-year-old NRU, the only North American source of 99Mo, is to end routine production of the isotope next month. The reactor will be kept on standby to serve as a supplier of last resort until March 2018, when it will be permanently shut down. The NRU, and several others in Europe, irradiate targets made of weapons-grade uranium (enriched to 93% 235U) to produce 99Mo.
The National Academies committee estimated a greater than 50% chance that a shortage will develop in the coming months. Several of the six remaining 99Mo-producing reactors are aging, and have had unplanned and extended outages in the recent past, the report said. Moreover, three of the four 99Mo refiners—the Australian Nuclear Science and Technology Organisation, Belgium’s Institute for Radioelements (IRE), and Mallinckrodt Pharmaceuticals in Ireland—are currently overhauling their facilities or processes, which could interrupt supply.
Because 99Mo has a half-life of 66 hours, the isotope can’t be stockpiled and must be delivered within a few days to the hospital or pharmacy. The daughter 99mTc, which has a half-life of six hours, is tapped at the location of use.
The US hasn’t produced 99Mo since the 1980s. But 99mTc is used in about 50 000 medical procedures each day in the US, according to the Department of Energy’s National Nuclear Security Administration (NNSA). The agency has been providing financial support to private companies to establish a domestic 99Mo capacity (see Physics Today, November 2015, page 20). It is specifically subsidizing production methods that don’t require the use of highly enriched uranium (HEU), which has 20% or more 235U.
None of the NNSA-supported companies are expected to begin operating until next year at the earliest. The National Academies report warns that the startups will face technical, financial, regulatory, and market penetration challenges, with the latter likely to increase as existing suppliers proceed with plans to boost production. The report notes that demand in the US—roughly half of the world’s total—has decreased by 25% for 2010–15. The committee predicted that US demand won’t increase significantly in the next five years and that most growth in demand will come from Asia.
As it encourages potential domestic 99Mo producers to spurn HEU, NNSA has continued to supply the Canadian production reactor, as well as European reactors, with weapons-grade uranium (see Physics Today, February 2011, page 17).
Days before release of the National Academies report, a group of 30 nuclear nonproliferation activists urged DOE and the Nuclear Regulatory Commission (NRC) to substantially reduce the quantity of weapons-grade uranium that NNSA has requested to export to France for 99Mo production. The proposed shipment of 7.2 kg of 93% 235U material would violate a commitment made by the US, France, Belgium, and the Netherlands at the 2012 Nuclear Security Summit in Seoul, South Korea, says the advocates’ 15 August open letter to Energy secretary Ernest Moniz and to the rule-making and adjudications department of the NRC. The agreement called for European 99Mo producers to use only low-enriched uranium (LEU; less than 20% 235U) by 2015.
“If the United States, the originator and leader of the summits, can violate its own commitment, why should other countries feel bound by theirs?” the advocates ask.
The US-exported HEU is to be fabricated into targets in France and irradiated in Dutch, Belgian, Czech, and Polish research reactors. Irradiated material containing 99Mo will then be refined and distributed by IRE. The HEU is sufficient for a year’s production of the isotope at IRE, according to NNSA’s application for an export license, which was published in the 15 August Federal Register.
The letter, whose signatories include Alan Kuperman, coordinator of the University of Texas at Austin’s Nuclear Proliferation Prevention Project, quoted the 2012 multilateral agreement: “the use of HEU will be completely eliminated for medical isotopes that are produced in Belgium, France, and the Netherlands and used in those countries and in the United States.” The letter warns against using weapons-grade uranium at civilian facilities in Europe “that cannot be protected like military facilities,” and says that minimizing HEU commerce “is essential to preventing nuclear proliferation and nuclear terrorism.”
“We urge you to reduce the amount of HEU in the proposed export license—to send a clear message that the United States intends to fulfill the spirit of its 2012 pledge by phasing out HEU exports to Europe for production of medical isotopes, and to incentivize IRE to expedite its conversion to LEU targets,” the letter states.
In a statement, an NNSA spokesperson cites an agreement signed during April’s Nuclear Security Summit in Washington, in which the European Union’s nuclear states pledged to ship enough HEU to the US, or dilute it to LEU, to decrease the total amount of HEU in circulation. Although Belgium and the Netherlands failed to meet their 2015 conversion goals, both countries “are currently executing technically complex LEU conversion projects that require multiple regulatory approvals in a number of different countries,” the statement says.
Kuperman says the April agreement simply reiterates a long-standing arrangement in which Europe is required to ship back US-origin HEU scrap from target and fuel fabrication in exchange for fresh US HEU. “When 30 experts criticized DOE for violating a 2012 commitment, they replied, ‘Don’t worry, we made a new commitment!’” Kuperman says. “DOE’s blithe violation of the 2012 agreement undermines the credibility of the new one. It’s like the old joke: Quitting smoking is easy, I’ve done it lots of times.”
The activists note in their letter that 99Mo producers in Argentina, Australia, and South Africa have gained regulatory approval. They also argue that neither US nor Belgian officials have provided evidence that IRE’s failure to convert to LEU is due to regulators.
