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| The turbine hall of Bruce A unit 2 (Image: Bruce Power) |
Officials discovered the leak in the moderator system early Saturday.
"Somewhere within that system a valve or part of a valve did fail and that's what led to the leak," company spokesman John Peevers said Monday.
"They isolated it, the repairs are underway and as part of our operating procedures we returned to what is called a guaranteed shutdown stage, which we were just coming out of."
The Canadian Nuclear Safety Commission posted a statement on its website that says "there was no release to the environment and no plant worker received any dose (of radiation)...The other units in the Bruce A station were not affected."
Peevers said the setback "was not entirely unexpected."
"We are going to be heating up systems and starting up equipment that hasn't been operational for 17 years. We knew we were going to hit some bumps along the road. That's why we're taking a slow, steady, safety-first approach," he said.
Peevers said it's not expected to be a complicated repair job, but he couldn't say how much the repairs will cost.
On Friday, Bruce Power received permission from the CNSC to remove the reactor shutdown guarantees on the Unit 2 reactor, which allowed the company to start it up for final checks before bringing it online.
When it's fully operational and online, the Unit 2 reactor will be capable of producing enough electricity to power 500,000 homes.
When the Unit 1 and 2 restart project was originally announced in 2005, the cost of the program was estimated at $2.75 billion, with electricity production to begin by late 2009 or early 2010.
The cost has risen to $4.8 billion.
The power plant is located about 240 km northwest of Toronto on the eastern shore of Lake Huron.
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OTTAWA — With the approaching anniversary of the Fukushima nuclear disaster as a backdrop, Ontario's top energy executive is urging Canada's nuclear industry not to retreat in the face of renewed public skepticism.
"While other jurisdictions may be scaling back their nuclear energy commitment because of Fukushima, we are not," Tom Mitchell, president and CEO of Ontario Power Generation (OPG), declared in an address Thursday to several hundred Ottawa delegates at the Canadian Nuclear Association's annual conference.
Nations around the world are reconsidering plans for increased reliance on nuclear power, while others, such as Germany, have vowed to pull the plug on nuclear power altogether as a result of Fukushima.
But instead of retrenching, Mitchell told the crowd that the worst nuclear accident in 25 years has given the industry "a great opportunity."
"It's once again made people aware of nuclear energy. It may have put some aspects of the industry on the spot. But it's also put us in the spotlight."
OPG owns and operates 10 CANDU reactors at Ontario's Darlington and Pickering nuclear stations, and Mitchell said the public utility is pressing ahead with plans to refurbish and to expand Darlington.
Combined with eight other OPG-owned reactors leased to the private operator, Bruce Power at Kincardine, Ont., nuclear generation now supplies close to 60 per cent of Ontario's energy needs.
Following Fukushima, the Canadian Nuclear Safety Commission ordered OPG and other nuclear operators to thoroughly assess the safety of their operations.
"What we will do — and are doing — is incorporating the lessons of Fukushima into our refurbishment and new build planning and design. That is a definite commitment on our part," Mitchell said.
One key lesson is "the absolute necessity to guard against external events, specifically those that threaten to overwhelm the design basis of the plant's systems and equipment," as the tsunami did at Fukushima. (When the Tohoku earthquake hit that day, all three of the plant's operating reactors shut down automatically as designed and emergency generators operated until sea water disabled them.)
Mitchell said OPG has almost a dozen Fukushima-related projects underway or planned by the end of 2016.
Already, equipment that operates independently of any electrical source has been installed at one Pickering reactor to help mitigate potential and dangerous hydrogen gas buildups, as happened at Fukushima. Three other Pickering reactors are to be similarly upgraded this year.
Mitchell said "significant progress" also has been made securing emergency, portable diesel generators and pumps that can supply critical electrical power for essential fuel cooling. Four new diesel-driven pumps and a diesel generator are now stationed at Darlington.
The crisis at the Fukushima Daiichi power plant began unfolding last March 11 when the 9.0-magnitude earthquake triggered a wild series of tsunamis along Japan's northeast coast. More than 25,000 people were killed, injured or went missing.
A 15-metre-high wall of sea water flooded the plant and knocked out the emergency cooling systems for three reactor cores, causing the uranium fuel to overheat. Over the following three days, the cores largely melted down. Additional systems used to cool thousands of deadly spent fuel rods also failed.
The resulting buildup of hydrogen gas soon detonated, destroyed one of the reactor buildings and spewed radioactive contamination over a wide swath of the countryside. Contaminated sea water also escaped. Cleanup costs are estimated at hundreds of billions of dollars.
This week, scientists reported the contamination has been detected as far as 640 kilometres off Japan in the Pacific Ocean, with water showing readings of up to 1,000 times more than prior levels.
But those results for the radioactive isotope cesium-137 are far below the levels generally considered harmful, either to marine animals or people who eat seafood, said Ken Buesseler of the Woods Hole Oceanographic Institution.
Mitchell said the renewed attention on nuclear power is an opportunity to address some "misconceptions" about the industry and nuclear science.
"Like the fact that the management of nuclear waste is somehow this big vulnerability in our industry — and not one of our greatest strengths. Which it is."
Investing for the future management of that nuclear waste has been less successful. For the nine months ended Sept. 30, 2011, OPG's net income decreased by $278 million compared to the same period in 2010, primarily as a result of lower investment earnings from $11 billion in funds set aside for future nuclear plant decommissioning and for nuclear waste disposal.
Mitchell said there is also considerable misinformation on the issue of radiation.
"Yes, we need to respect even small quantities of radiation. Our industry always has. But we also need to convey to people that it's been proven that radiation can be measured, controlled and handled very safely in ways that deliver huge benefits to society, in science, in medicine and in energy," he said.
"Three Mile Island, Chernobyl, Fukushima. These words are perpetual reminders that we can never be complacent, and that safety, despite our industry's excellent record, can never be taken for granted.
"As an industry, we have not been complacent. We are a better and safer industry after (Three Mile Island in 1979), than before. We are a better and safer industry after Chernobyl (in 1986), than before. And we are — and will be — a better and safer industry after Fukushima, than before.
"Which is why I believe our industry will not fade. It will not grow obsolete. It will thrive."
