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The Canadian Nuclear FAQ  

by Dr. Jeremy Whitlock


Published on AECL's website, 2008 January 29:

AECL Clarifies Inaccurate Statements by Former CNSC CEO Linda Keen

Chalk River, 2008 January 29 Comments by former CNSC President & CEO Linda Keen today at the House of Commons Standing Committee on Natural Resources were erroneous and misleading. Ms. Keen said that the chance of fuel failure in the NRU research reactor, without starter motors for two coolant pumps hooked up to a seismically-qualified, third back-up power system, is one-in-one-thousand. She further stated that the international standard is one-in-one-million.

Ms Keen was wrong on several counts.

  1. There are no international standards related to one-in-one million for fuel failures.

  2. All reactors experience fuel failures from time to time and there are no safety consequences to the public, employees or the reactor.

  3. No nuclear designer in the world incorporates a one-in-one million year earthquake scenario.

The frequency for a severe earthquake at NRU is assumed to be 1 in 1000 years. For this to lead to fuel failure, the following would all have to happen in sequence:

  • A severe earthquake occurs with its epicentre directly under the NRU reactor at Chalk River (there is no record of such an earthquake in the Upper Ottawa Valley);

  • The provincial power grid fails;

  • Back-up diesel power, and back-up battery power supplies are knocked out;

  • No NRU operating staff takes any action;

  • After about 0.5 hour the reactor coolant begins to boil;

  • After about 1.0 hour the reactor coolant has boiled away;

  • The onset of fuel failures begins.

NRU is a small research reactor operating at low temperature and low pressure. Therefore, even in this worst-case scenario, the radiation exposure to workers is less than half the radiation exposure received from a CT Scan, and the radiation exposure to the public is less than half the radiation exposure received from a cardiovascular diagnostic treatment.

The safety of the reactor has been endorsed by the CNSC, which has licensed the reactor to operate this way for the past 50 years.


The NRU reactor is a 135 MW thermal research reactor that entered service in 1957. The fuel in the reactor is cooled by eight pumps that are powered from the electrical grid. In addition, four of the pumps have an independent backup power supply from diesel generators on site. These pumps also have (DC) motor backups powered by battery. Any one of these four pumps provides sufficient cooling flow when the reactor is shut down during an outage.

The Emergency Power System, or EPS, is an additional power system that is qualified to withstand severe seismic activity. EPS is designed to provide additional backup power to two of the coolant pumps, pumps 104 and 105. At the time Bill C-38 was passed, EPS was in the process of being connected to pump 105.

The work on pump 105 was completed safely on December 14, and the reactor was restarted on December 16. Production of medical radioisotopes resumed on December 18, 2007.

Under the auspices of Bill C-38, AECL is now completing the connection of the EPS to the second coolant pump (pump 104).

For further information:

Dale Coffin
Director, Corporate Communications
Telephone: (905) 403-7457