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Canadian nuclear reactor that makes isotopes for medical tests back online

August 17, 2010

A Canadian nuclear reactor that normally supplies about a third of the world's technetium-99m for medical imaging came back online this week after a 15-month shutdown for repairs that severely impaired physicians' ability to perform many needed tests. The situation was made even worse by the shutdown of a second reactor in the Netherlands that also produced significant amounts of the radioisotope. That reactor is expected to reopen next month.

The National Research Universal reactor in Chalk River, Canada, produces radioactive molybdenum-99, which has a half-life of only 66 hours and must be shipped immediately to hospitals and dispensing pharmacies throughout North America. It decays into technetium-99m, which has a half-life of only six hours and must be used quickly. That short half-life makes it ideal for many medical tests because it is eliminated from the body quickly, minimizing exposure to radiation.  Before the shutdown of the Canadian reactor, the isotope was used for tests on nearly 55,000 Americans each day, such as those monitoring the flow of blood through the heart or checking for the spread of cancer to the bones.

But on May 19 of last year, the Chalk River reactor was shut down because of corrosion caused by leakage of heavy water. Authorities had hopes of reopening it by the end of the year, but the complexity of the necessary repairs and the difficulties of working in a radioactive environment slowed progress. Preliminary tests last week at low reactor power levels were successful and the reactor began operating at full power this week. Atomic Energy of Canada, which operates the reactor, said it expects to begin shipping molybdenum-99 to distributors by the end of the week. The agency estimated the cost of the breakdown, including repairs and  lost sales, at $70 million.

The second major molybdenum source, the High Flux Reactor in Petten, the Netherlands, has been offline since February for routine maintenance and repairs to corroded pipes. It is expected to be back to full power by Sept. 9.

The restart of the Chalk River reactor will provide some breathing room for American physicians, who rely heavily on the nuclear medicine tests,  but the Society of Nuclear Medicine cautioned that the Canadian government plans to shut the reactor down permanently by 2016 and has no plans to replace it. The society is lobbying for the American Medical Isotopes Production Act, which would promote U.S. production of the valuable isotope, but the act has been hung up in the Senate.

Thomas H. Maugh II / Los Angeles Times

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