A university professor says the water-pumping problem Japanese nuclear officials are facing at the Fukushima plant is unlikely in the CANDU systems operating in Canada.
Japan’s earthquake on March 11 and the resulting tsunami damage to the Fukushima plant have some residents near nuclear-power plants in Ontario question their safety.
Dr. Glenn McRae, professor in the department of mechanical and aerospace engineering at Carleton University, says the reactors in Japan are significantly different than the CANDU (Canada Deuterium Uranium) reactors in Ontario.
“The reactor in Japan is a boiling water reactor similar to an electric tea kettle and a pressure cooker,” he said. “The CANDU reactor is different. It is not one large pressure vessel; instead it has pressurized horizontal fuel channels that sit in a big vessel of cold water. (CANDU reactors) already have the water; there’s no need to pump it in. If that fails we have other back up systems.”
The surrounding vessel of water is one of the major safety features of the CANDU reactor that the one in Japan doesn’t have, he said.
The boiling water reactor requires the water to be pumped in and that’s the issue facing Japanese nuclear workers now.
McRae points out that Japanese officials are dealing mainly with high temperature chemistry reactions, not nuclear reactions. At the first indication of the earthquake, the reactor safety systems would have shut down the reactor within seconds. The problem is that fuel within the reactor remains hot and must be cooled, he said.
The issue was that the cooling pumps did not work as they were supposed to when the tsunami cut off power, he said. He explained that if the fuel is not cooled, then the outer metal casing surrounding the fuel can become so hot that it reacts with water to produce hydrogen gas. If the concentration of hydrogen reaches its ignition point, it can explode.
But McRae emphasizes that this is a chemical reaction, not a nuclear reaction. The nuclear problem, he said, if the build-up of radioactive materials in the fuel and if that fuel breaches the metal casing around the reactor, then that material could reach the outside environment.
In an article by the Associated Press on March 18, 2011, the World Health Organization states that a 30-kilometre (18.6 mile) exclusion zone surrounds the Fukushima Dai-ichi nuclear complex. The radiation levels outside this radius are increasing, but there is no health risk, according the AP story.
In terms of public safety around Ontario nuclear facililties, there is a Provincial Nuclear Emergency Response Plan that describes the protocol in the case of an emergency.
Ted Gruetzner, a media representative for Ontario Power Generation, described the company’s role in case of an emergency.
“If we have an event, our responsibility is to manage the event within the facility,” Gruetzner said. “The first line of defense is the equipment and prevention. We have multiple back up shut down systems in place so the reactors are designed to shut off very quickly…”
“If there’s any disturbance, the station operator through working with some field staff, then determines what the nature of the event is and then has a series of procedures that they follow depending on what that event is.”