Nuclear's inherent dangers

Globe and Mail Letter to the Editor:.Gordon Edwards, President, Canadian Coalition for Nuclear Responsibility - Saturday, July 04, 2009

The president of the Canadian Nuclear Safety Commission writes that "contrary to many other reactor designs, CANDU reactors are protected by two fast-acting shutdown systems" (Nuclear's Place - letters, July 1).

The reason for this is the increased danger posed by the positive-reactivity feature. New reactor designs are required to eliminate this feature altogether. Some of the most spectacular nuclear accidents have been associated with positive reactivity, endemic to pressure-tube designs like the CANDU: the NRX reactor accident at Chalk River in 1952, the Lucens reactor accident in Switzerland in 1969, and the Chernobyl disaster in Ukraine in 1986.

The President's Commission on Three Mile Island found that a major cause of the TMI accident was the attitude by operators and regulators that nuclear power was safe because of engineering controls. The commission warned such a complacent attitude will bring about more accidents, and urged that nuclear power be regarded as inherently dangerous.


Edwards was responding to a letter by Michael Binder, President of the Canadian Nuclear Safety Commission, published in the Globe and Mail Last on Wednesday, Jul. 01, 2009:

"Candu reactors have operated safely for more than 30 years; the Canadian Nuclear Safety Commission has the regulatory responsibility for ensuring that they continue to do so (Reactor Design Puts Safety Of Plants Into Question - June 29).

"The positive-reactivity-feedback characteristic of Candu reactors is not a new discovery. It is well understood by the CNSC and nuclear power plant operators. Candu reactor safety systems were designed to respond to this characteristic and shut down the reactor before fuel fails. [see omitted sentences below]

"As the federal regulator, CNSC ensures that the safety cases for all reactors meet safety goals and that all nuclear power plant operators make adequate provision for the protection of the environment, the health and safety of persons, and the maintenance of national security."

Michael Binder, president and CEO, Canadian Nuclear Safety Commission


The globe and Mail did not publish the following sentence from Binder's letter, the complete version of which was posted on the CNSC web site:

"That is why, contrary to many other reactor designs, CANDU reactors are protected by two fast-acting shutdown systems, which are independent, diverse and fully-e ffective and would counteract any event related to the positive coefficient of reactivity."'


In turn, Michael Binder was responding to an article by Martin Mittelstaedt published in the Globe and Mail on June 29 2009:

Reactor design puts safety of nuclear plants into question. Feature speeds up rate of atomic reactions in event of a coolant leak. Regulators say they misjudged size of the problem.