Chalk River: National Research Universal (NRU) Reactor Events
Letter to Ministers Lunn and Clement
December 10, 2007
The Honourable Gary Lunn, P.C., M.P.
Minister of Natural Resources
580 Booth Street, 21st Floor, Room C7-1
Ottawa ON K1A 0E4
The Honourable Tony Clement, P.C., M.P.
Minister of Health
Brooke Claxton Building, Tunney's Pasture
Postal Locator: 0906C
Ottawa ON K1A 0K9
Dear Minister Lunn and Minister Clement:
I am in receipt of your letter of December 10, 2007, regarding the current situation of the NRU reactor at Chalk River.
Please be assured that the Canadian Nuclear Safety Commission (CNSC) is acutely aware of the importance of the beneficial use of radioisotopes. The hospitals and clinics which
use radioisotopes are licensees of the CNSC and we are seeking to assist them with license amendments to use alternate supplies where available. We also have taken measures to facilitate the import of isotopes into Canada to increase the supply. In summary, the CNSC has taken actions within our mandate to assist the health sector to deal with the current situation.
The mandate of the CNSC is specified in the Nuclear Safety and Control Act (NSCA) to ensure the health, safety and security of Canadians and the protection of the environment and the implementation of international obligations to which the Government of Canada has agreed. The Commission is a quasi-judicial administrative tribunal and a court of
record and has a long record of regulating Canadian nuclear facilities and nuclear substances. As a quasi-judicial administrative tribunal, the Commission must act within the specific authority and powers delineated in the NSCA. To clarify this mandate as it applies to nuclear substances, our role is to insure the safety of nuclear substances. We perform this oversight by licensing and compliance activities related to the safe use, storage and transport of radioactive substances. As such, we regulate AECL as a nuclear reactor operator, and MDS Nordion as a processor. As stated earlier, we also regulate hospitals and clinics. The Commission will, in keeping with its mandate, ensure that all relevant factors coming within our mandate will be considered.
By way of background, the Commission had serious concerns regarding the safety of the 50 year-old NRU reactor when its former license was due to expire. When the Commission considered the licence renewal application in Spring 2006, it seriously questioned the safety of the NRU. Its decision, effective August 1, 2006, to grant the new licence in respect of the NRU, was based on specific assurances from AECL that its safety case was complete and that the seven safety upgrades were completed.
At the Meeting of the Commission on December 6, 2007, Mr. McGee, Senior Vice-President and Chief Nuclear Officer of AECL, recognized the level of risk resulting from the lack of connection of the two pumps and AECL voluntarily agreed to keep the NRU reactor in a shutdown state.
I wish to clarify that, contrary to your December 10, 2007 letter, the CNSC has not received a complete safety case for the single pump option. Presently, both AECL and CNSC staff are working on the material necessary to evaluate this safety case. CNSC staff notified me today that the work is ongoing and all efforts are being made to analyze the proposal as expeditiously as possible.
The Commission is committed to immediately convening a hearing to rule on this application once AECL submits a completed safety case with a request to amend its license and CNSC staff has submitted their assessment of the application. The Commission does not presently have the evidence required under subsection 24(4) of the NSCA to conduct an evaluation and therefore cannot yet convene a hearing.
As concerns the safety of the NRU reactor, under its current licence conditions, the Commission requires AECL to have all safety upgrades in place in order to operate safely under its license. These safety upgrades include the following:
- Second Trip System (STS) – to provide a second, independent trip system separate from the existing trip and control system;
- Qualified Emergency Response Centre (QUERC) – to provide, in the event of control room unavailability, an alternate, hazards-qualified location for the initiation and monitoring of all special safety systems;
- Liquid Confinement/Vented Confinement (LCVC) – to provide a defined boundary around the reactor and the primary coolant system to confine liquid and gaseous releases under accident conditions;
- Main Pump Flood Protection (MPFP) – to protect the main heavy water pumps from flooding due to major secondary coolant leaks;
- New Emergency Core Cooling (NECC) – to provide seismically-qualified, closed-circuit, long-term cooling of the reactor core after a loss of coolant accident (LOCA);
- Qualified Emergency Water Supply (QEWS) – to provide a back-up source of secondary cooling in the event of a loss of the primary heat-sink; and
- Emergency Power Supply (EPS) – to provide dedicated, seismically-qualified emergency back-up AC and DC power to the upgrades systems.
Each upgrade has a specific purpose; however, it is the integrated operation of all the upgrades that allows the critical safety functions to be delivered. In particular, the emergency power system (EPS) delivers emergency back-up power to all the upgrades systems such that each system can perform its desired function. Of specific note is the unique need for the NRU reactor to have forced (i.e., pumped) cooling at all times (even in non-accident conditions) as opposed to other reactor systems that can be cooled by thermo-siphoning if their cooling pumps become unavailable. Thus, the uninterrupted delivery of power to the motor starters of Main Heavy Water Pumps P-104 and P-105, as provided by the EPS, is essential for the safe operation of the NRU reactor. I trust that this responds to your specific question as to why it is essential that back-up power units be made operational for the safe operation of the NRU reactor. Additional details are available in AECL’s original safety case that was considered when the facility was last licensed.
The non-compliance revolves around the lack of connection of two heavy water pumps to an emergency power supply in order to avoid a fuel failure resulting in potential radioactive releases into the environment. The engineers and scientists at the CNSC have advised that the two backup pumps, included in the original safety case, are essential and are required pursuant to current industry standards and risk tolerance assessments. The Commission’s understanding is that both AECL and CNSC staff shared the view that these two pumps were essential up until November 30, 2007, when AECL first raised the one-pump proposal.
These pumps are required to provide essential safety assurance and are not just in place for earthquakes, but for all external design basis events. If AECL has additional evidence to support a different position, they are aware of the process to submit this information for evaluation by the CNSC staff.
For its part, the Commission tribunal stands ready to review any safety case and license amendment. The Commission is an expert quasi-judicial administrative tribunal and is prepared to respond expeditiously to these matters, with 24/7 availability. I must emphasize that the Commission cannot convene until it has received a complete application and safety case.
I have offered to the Deputy Minister of Natural Resources Canada (NRCan), in order to ensure effective communication on this important issue, that CNSC staff are available to meet government officials and AECL in one room to clarify matters on this issue. We remain ready and available to do so.
Original Signed by
Linda J. Keen, M.Sc