Atomic Energy of Canada Ltd., which misplaced the part while working on the multi-billion-dollar restart of the plant, failed to notify officials at Bruce Power about the incident.
The federal nuclear regulator wants to know why the loss of the part was kept quiet until it was accidentally discovered.
A spokesperson for the Canadian Nuclear Safety Commission said Bruce Power has until Aug. 8 to file a detailed report of what happened at Unit 2. Industry experts say it's just the latest in a string of events that reflect poorly on AECL.
"AECL became aware of the problem on April 23 that a calandria tube insert was unaccounted for, however they failed to notify the RP (radiation protection) department of this fact," according to an incident briefing filed on June 24 by Bruce Power to the regulator. "The increased hazard would have existed from that time."
The document said the worker, who discovered the radioactive part on June 22, followed proper procedure and kept his radiation exposure to safe limits.
The reactor contains hundreds of calandria tubes, which contain heavy water. Collectively, these metal tubes form the core of a Candu nuclear reactor.
Duncan Hawthorne, chief executive officer of Bruce Power, dismissed the seriousness of the incident when contacted by the Star. "It's not a story," he said. "It's a bull---- story. There is no issue."
Federally owned AECL is a key contractor in the Bruce restart project and a supplier of Candu reactor technology that lies at the heart of all nuclear plants in Ontario. Spokesperson Dale Coffin acknowledged it took too long for the company to alert officials.
"We're disappointed we didn't notify Bruce Power sooner," he said.
Coffin explained that the work AECL was doing is all automated, done by remote control outside of the vault area and monitored through TV cameras. A robot removes and destroys the old calandria tubes and tube inserts, which are chopped up and disposed of in a shielded waste bin. A single reactor has 960 metal tube inserts.
He said the company was aware of an "accounting discrepancy" with regards to the parts that were handled.
"We were going back and verifying whether or not (the part) was still in the tube or placed in the bin. It did not add up. We were in the process of verifying that," Coffin said.
Frank Greening, a nuclear scientist and consultant with more than three decades of industry experience, equated the incident to a doctor leaving a scalpel inside a patient, knowing about it, but taking two months before saying anything.
"They seem to have a habit of not reporting stuff, then they have to talk their way out of it when it finally is reported," he said. "There's a bit of a pattern here of sloppy bookkeeping and reporting."
Norm Rubin, director of nuclear research at Energy Probe, which is critical of nuclear power, said it's standard practice to immediately report such events. "Obviously, things that are carcinogenic and lethal shouldn't be left around, no matter what field you're in," said Rubin.
Bruce Power is trying to restart reactor units 1 and 2 at its Bruce A site, a project originally estimated at $2.75 billion. The nuclear power generator is now expecting costs in the range of $3.1 billion to $3.4 billion under a contract with the government that will see Ontario electricity consumers pay for $237.5 million of budget overruns so far.
TransCanada Pipelines Ltd., a financial partner in the Bruce restart project, told shareholders in April that AECL has been largely responsible for the delay and added rebuilding costs.
AECL is among three bidders hoping to win the chance to build two new nuclear reactors at the Darlington site, a decision the Ontario government delayed by three months to March 2009.
The incident at Bruce is just the latest in a series of troubles for the Crown corporation, currently the subject of a federal government review that could result in its privatization.
Last November, AECL's research reactor at its Chalk River laboratory was shut down after regulators found problems with an emergency backup system. This led to a prolonged outage that put the world's medical isotope supply at risk and resulted in the federal government bypassing the authority of the regulator.
Earlier this month, life sciences companies MDS Inc. launched a $1.6 billion lawsuit against AECL after it decided to cancel a 12-year-old project for two new research reactors at Chalk River. Those reactors were supposed to guarantee a long-term supply of medical isotopes to MDS but AECL couldn't get them to work properly.