Terrorist-resistant ‘source’ of moly-99 hits the U.S.

Molybdenum-99 is the radioactive feedstock for the most widely used diagnostic nuclear-medicine isotope. On December 6, the first commercial batch of moly-99 that had been produced using a terrorist-resistant process arrived in the United States from a reactor in South Africa.

Instead of using highly enriched — i.e. weapons-grade  — uranium, or HEU, the new process relies on low-enriched uranium. Although nuclear security experts have advocated this switch to LEU for decades, isotope producers had balked, saying it would increase their costs and would likely create regulatory hurdles, such as a need to demonstrate that the new moly product was as safe as the existing isotope.

But with a $25 million supplemental investment from the Department of Energy earlier this year, the South African Nuclear Energy Corp, or NECSA, was able to retool moly-99 production at its Safari reactor and NTP Radioisotopes Ltd. of South Africa was able to help secure approval from the U.S. Food and Drug Administration for moly-99 made without HEU. This cleared the way for NTP to become the world’s first commercial-scale source of LEU-based moly-99.

Lantheus Medical Imaging of North Billerica, Mass., received the first shipment of that moly. It met the day’s “normal Monday demand,” a company spokesperson said.

NTP informed Lantheus that it plans to transition all of its production of moly-99 from HEU to LEU in the near future. Lantheus has additional commercial sources of moly-99, and “many of these suppliers are also moving to LEU-based moly-99 but are doing so on different schedules,” the spokeswoman told me. “Therefore, we cannot predict when we expect to be at full capacity in terms of using only LEU-produced moly-99.”

Moving to LEU virtually eliminates the risk that uranium-coated targets, the tiny plates that get irradiated in reactors, can be diverted by terrorists and used to make bombs. That threat has been a pervasive concern as these targets regularly travel through airports around the world en route to and from the few reactors that have been licensed to irradiate them.

Because moly-99 is a short (66-hour) half-life isotope, new stocks must continually be generated. And that means HEU targets today travel frequently and in huge numbers to sate the needs of nuclear medicine. Physicians perform some 60,000 diagnostic procedures each weekday using moly-99’s even shorter-lived product: technetium-99m.

“We applaud South Africa’s world leadership on minimizing the use of highly enriched uranium,” according to a prepared statement issued on December 6 by Gary Samore, the White House coordinator on issues related to weapons of mass destruction and a leader of the April 2010 Nuclear Security Summit in Washington, D.C. South Africa’s “choice to move towards LEU-based medical isotope production shows an important confluence between peaceful uses of nuclear technology and nuclear security goals.”

NTP and NECSA currently produce about a quarter of the world’s moly-99 demand. Safari is one of only a handful of reactors, most of them around a half-century old, licensed to make moly-99. Although U.S. procedures use roughly half of the global supply, there are no sources (at least yet) in the United States.

In some ways, NECSA had it somewhat easier to make the LEU conversion than other moly-99 sources, notes Parrish Staples of the Energy Department’s National Nuclear Security Administration in Washington, D.C. The Safari reactor had already transitioned to a medium-enriched fuel. It’s about 40 to 50 percent enriched uranium, versus 90 percent in the other moly-production reactors. This made working with LEU targets easier he said.

It will require processing somewhat more targets for the South African process to achieve the same yield of moly-99 as before, Staples says, but not the five-times more targets that had been projected for HEU-fueled reactors.