Bruce Nuclear radiation incident shows safety gap
Published Thursday, February 18, 2010 4:35PM EST
OTTAWA - An incident that exposed hundreds of workers at an Ontario power station to low levels of radiation has revealed an apparent gap in safety procedures at Canadian nuclear facilities.
Officials from Bruce Power told a public hearing Thursday they did not anticipate or test for airborne alpha radioactivity in one of the reactors currently being refurbished at the Bruce A nuclear station on the shores of Lake Huron.
They said they're always on the lookout for beta radioactivity, operating on the assumption that protecting against one will protect against the other.
That assumption -- which Canadian Nuclear Safety Commission officials said is a common, industry-wide assumption -- proved false late last year when unanticipated alpha contamination was discovered in the reactor vault where up to 563 people had been working.
The company eventually concluded that 195 workers had been sufficiently exposed to warrant testing.
Preliminary results on 14 of the workers deemed to have been among the most exposed have so far found alpha radiation levels that are less than half the safe limit prescribed by the nuclear safety watchdog.
At Thursday's CNSC hearing into the incident, agency inspectors said they've found no evidence that the radiation leaked beyond the reactor vault or endangered the public.
Commission member Ronald Barriault suggested Bruce Power, the country's only private nuclear station operator, was lucky the incident wasn't far more serious.
"It's more by good fortune than by good industrial hygiene management that you don't have a serious problem in the sense of radiation sickness," he said.
Company officials acknowledged they could have done better but contended they took steps that minimized the risk. Barriault conceded the point and withdrew his comment.
The trouble started late last November as workers, using special tools designed to minimize dust, were grinding the pipes that carry coolant to the Unit 1 reactor, which has been shut down for almost 15 years. They'd done the same job on the Unit 2 reactor a month before without incident and assumed the same procedures would be sufficient.
"With hindsight, it would have been prudent to revisit these underlying assumptions," Norman Sawyer, executive vice-president and chief nuclear officer at the Bruce A plant, told the hearing.
Sawyer said beta radiation levels in nuclear plants are typically 10,000 times that of alpha levels. Hence, they routinely monitor for beta, even though exposure to alpha particles is actually more dangerous.
However, in this instance they eventually found the ratio of beta to alpha was significantly reduced -- only seven to one -- due to the fact that the reactor had been idle for years and beta decays faster.
"There is a bit of a mindset issue here in that we're looking for the beta and not directly for the alpha," conceded Frank Saunders, vice-president of oversight and regulatory affairs.
Compounding the problem, the company could not quickly assess how dangerous the exposure to its workers had been because there is only one accredited facility in Canada -- at Chalk River -- that conducts the time-consuming tests.
It intends to test all 195 workers deemed to have been at risk, plus any other workers who ask for it, but it will take another 18 weeks to get all results. The company is working with CNSC to find an American lab that could do some of the work.
Since the incident, the company has installed alpha air monitoring devices and purchased alpha detection scanners for employees. And it is setting up its own on-site testing facilities.
Both CNSC members and Bruce Power officials expressed some mystification at the media interest in the incident.
Murray Elston, the company's vice president of corporate affairs, later insisted Bruce Power acted quickly and responsibly, escalating its protective measures as confirmation of contamination came in.
Still, he acknowledged: "For us, this is a huge event . . . The issue is we've identified we can do better."