Buffeted by geopolitics from afar and the needs of patients at home, the United States is moving on two fronts to secure the supply of isotopes vital in medical imaging but dangerous in the wrong hands.
No longer able to depend on the traditional Canadian and Dutch suppliers, Washington is accelerating efforts to jump-start domestic production of the molybdenum-99 isotope. At the same time, policy-makers want to wean the world off of the weapons-grade uranium used to make isotopes and achieve conversion to low-enriched uranium, a promising but unproven path to solving the global isotope shortage.
This tricky juggling act is incorporated in legislation before the US Congress. It was spurred by the indefinite loss of supplies from Canada’s National Research Universal (NRU) reactor in Chalk River, Ontario, and extended interruptions from the other major source, in the Netherlands.
The House of Representatives passed a bill in November 2009, with overwhelming support from both parties, which would release US$163 million over five years to find means of producing the isotope from low-enriched uranium.
The legislation also would ban the export of highly enriched uranium in seven to 11 years, putting pressure on foreign producers to stop using materials that can be diverted to nuclear weapons development. A similar bill cleared a Senate committee in January, then stalled as a senator sought further study.
This, as supplies have plunged over the past year to 20%–30% of needed levels, leaving caregivers scrambling to keep up in the diagnosis and treatment of cancer, heart disease and other medical conditions. The US found short-term alternatives when the Chalk River reactor was shut down but now the High Flux Reactor in Petter, the Netherlands, is closed for repairs until August.
“It’s not a very good situation,” says Dr. Michael M. Graham, president of the US Society of Nuclear Medicine. Society members are expecting they’ll soon face soon face widespread disruptions of imaging studies. The US consumes half the world’s supply of molybdenum-99 — from which the radioistotope technetium-99m is fabricated for use in imaging — of which some 60% has traditionally been supplied by the NRU.
President Barack Obama’s administration isn’t waiting for the legislation to grind through Congress. The Energy Department recently announced seed money for two pilot projects aimed at coaxing elusive molybdenum-99 from existing commercial reactors and a low-enrichment mini-reactor. Still, a new and reliable supply chain is years off.
The US National Academy of Sciences provided an impetus to move from bomb-grade uranium last year in a report that concluded low-enriched uranium —not suitable for weapons — could technically be used in the production of adequate supplies of medical isotopes over time (http://dels.nas.edu/dels/viewreport.cgi?id=5559). Argentina and Australia are already producing limited quantities of molybdenum-99 isotopes using low-enrichment uranium.
If the technology is feasible, though, it’s still formative. “As new reactors get designed and begin to get built there’s very definitely going to be an effort to shift to LEU [low-enriched uranium],” says Graham.
The search for stable, safe supplies is playing out as the US and Iran engage in diplomatic brinkmanship over Tehran’s nuclear program. It’s a standoff at the intersection of nuclear medicine and apocalyptic weaponry —Iran insisting on its right to produce medical isotopes, the global community suspicious that it’s a cover for development of nuclear weapons.
Iran declared this month that it has begun enriching uranium to 20% purity, up from 3.5%, for the production of medical isotopes. From there, it’s not an impossible leap to the purity required in a bomb. For the US, that’s emblematic of the need to find a benign alternative to a tried-and-true material that saves lives but comes with a dark side, in a world going rogue.
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Previously published at www.cmaj.ca