Chalk River isotope reactor fully repaired: AECL

General Triad News

OTTAWA — After a $70-million breakdown, the world's oldest operating nuclear reactor is ready to resume service and medical isotope production, Atomic Energy of Canada Ltd. has announced.

The last of several complex repairs was completed on the weekend to the reactor's 65,000-litre containment vessel, which began slowly leaking radioactive heavy-water in May 2009, forcing AECL to shut down the NRU reactor at Chalk River, Ont., about 180 kilometres northwest of Ottawa.

"The vessel is fit for service, with its structural integrity assured for the next operating interval," AECL has informed the Canadian Nuclear Safety Commission. "Processes and procedures are in place to safely restart the reactor, and resume medical isotope production and research activities."

AECL is to appear before the commission June 28 to win the federal regulator's approval to completely refuel and restart the reactor.

The commission is expediting that hearing process to return the NRU, "to service as safely and as quickly as possible to support the production of medical isotopes for Canadian patients and health-care practitioners."

With commission approval and no further technical glitches, the world's largest machine for producing medical isotopes for treating cancer, cardiac problems and bone disease, is slated to return to commercial production at then end of July.

When injected into the body, medical isotopes emit harmless amounts of radiation that can be traced by special equipment and quickly reveal disease and illnesses.

Medical isotopes are to begin rolling out for processing and distribution within 10 days the restart, easing a global isotope shortage blamed for a 22 per cent decrease in nuclear medical diagnostic exams in Canada alone.

The estimated $70-million repair bill includes lost isotope revenue.

If all goes as planned, AECL is to expected to begin readying plans to go before the CNSC to request the 53-year-old reactor's operating licence, which expires in October 2011, be renewed through 2016.

In the year since Canada's main nuclear reactor was shut down doctors have developed ways to cope. But the long-term cost of the those strategies may be detrimental, said Dr. Jean-Luc Urbain, president of the Canadian Society of Nuclear Medicine.

His outlook is based on a concern that fewer patients have received diagnostic testing over the past year — a fact confirmed in a survey released Wednesday by the Canadian Institute for Health Information.

The health data agency reported a near 22 per cent decrease in the number of nuclear medical exams performed on Canadian patients' hearts, bones and lungs last October when compared to one year earlier — a total of 12,000 fewer exams overall.

"Medical isotopes are used in diagnostic imaging and enable very early diagnosis of diseases like cardiovascular disease and cancer," Urbain said. "If we don't do these tests because we don't have the isotopes, the diseases will continue to progress, many in a silent, insidious manner."

Consequently, he said, there will be an inevitable spike in advanced cardiovascular diseases and cancers over the next few years, among patients who were unable to undergo exams.

Since last spring, more than 300 engineers, skilled tradespeople, technicians and reactor operators have laboured over how to repair six spots in the NRU's vessel corroded by nitric acid, including the one responsible for the initial pinprick leak.

The work required building a full-scale NRU mock-up to develop and rehearse vessel cleaning and repair processes and designing specialized, remote-control tools to work in the vessel's confined and highly-radioactive environment.

Before and during repairs that began Dec. 12, a key consideration was learning and testing how the aluminum vessel would react to the welds. Ultra-sonic scanning was used to confirm they would hold under normal operating conditions.

In the end, the effort is being hailed as an enormous and unique feat of nuclear science and engineering that may someday serve other similarly stricken reactors.