Vancouver scientists help solve world isotope dilemma
Intense beams of light may be able to generate material for nuclear medicine
Margaret Munro, Canwest News Service
Published: Monday, November 17, 2008
Vancouver-based scientists are at the forefront of a team who say they have hit on "a uniquely Canadian solution" to the world's medical isotopes woes.
The team, which includes scientists from Triumf, the national particle and nuclear physics laboratory at the University of B.C., say intense beams of light should be able to generate isotopes for nuclear medicine.
This would eliminate the security risks associated with making the medicines with weapons-grade uranium at the aging nuclear reactor in Chalk River, Ont.
A national task force report to be released Monday says creating isotopes using light beams from "photo-fission" accelerators, instead of the 51-year-old Chalk River reactor, could also help salvage Canada's reputation in the nuclear world after several misadventures.
The 58-page report, obtained by Canwest News Service, says that if photo-fission works, a half-dozen accelerators, which would cost upwards of $50 million each, could supply isotopes across North America.
Twenty-four leading physicists and nuclear medicine specialists from Canada and the U.S. sat on the task force. They describe photo fission as a promising alternative to the two "aging" nuclear reactors in Canada and Petten, the Netherlands, which now generate most of the world's medical isotopes.
The radioactive molecules, which are short-lived and considered harmless because they emit low levels of radiation, are given to about 40 million people a year, 1.5 million of them in Canada.
The isotopes make it possible to "see" inside the body to diagnose heart disease, locate tumours and follow cancer and its treatment.
The Chalk River reactor produces almost half the isotopes used in the world. It also generated an international crisis a year ago when the reactor was suddenly shut down over safety concerns.
Tens of thousands of people in Canada and the U.S. had heart and cancer tests cancelled because of the resulting isotope shortage.
"Accelerator-driven photo-fission is a uniquely Canadian solution and offers much potential," the team says.
The task force also notes that photo-fission "eliminates" the need for highly enriched uranium.
The weapons-grade uranium is now imported to Chalk River under tight security from labs in Oak Ridge, Tenn. The U.S. Nuclear Regulatory Commission licenses the exports but is under pressure to halt the shipments because of proliferation and terrorism concerns.
The enriched uranium is used in "targets" that are irradiated inside the Chalk River reactor to make Molybdenum-99. Moly-99, as it is often called, is used to make radioactive tracer molecules given to patients.
As they move around the body the molecules can reveal where tumours and cancer cells are lurking, and if organs are working properly.
The scientists say it should also be possible to make Moly-99 through "photo-fission" by bombarding natural uranium with streams of photons -- basically high-intensity light beams -- generated by an accelerator.
"We're proposing that instead of inserting a neutron [as occurs in the reactor when the uranium nucleus split to form Moly-99], you insert a photon," says Nigel Lockyer, task force co-chair and director of Triumf.
"We'd be able to get away from the weapons-grade uranium and use natural uranium," says Lockyer. "That's a huge plus."
The idea of using accelerators to make Moly-99 has been around for years, but had been written off as "an interesting curiosity," says Thomas Ruth, a senior scientist at Triumf. The machines just didn't seem capable of producing enough photons.
But the technology has advanced rapidly. And when Lockyer, an accelerator specialist, and Ruth, a nuclear medicine authority, got to talking it dawned on them that the type of accelerator now being designed at Triumf to study obscure physics and exploding stars might have significant down-to-earth applications.
By their calculation, such accelerators should also be able to produce Moly-99.
Ruth likens the reactors to old cars that are "sort of wobbling down the street."
International Atomic Energy Agency officials recently warned that relying on the aging reactors for medical isotopes could have "serious consequences."