Darlington and Pickering NGS: Request pursuant to Subsection 12(2) of the General Nuclear Safety and Control Regulations: Issues Relating to Measurement of Hydrogen Concentration in Pressure Tubes

Directorate of Power Reactor Regulation

July 13, 2021

Mr. Steve Gregoris
Senior Vice President, Darlington
Ontario Power Generation Inc.
P.O. Box 4000
Bowmanville, ON L1C 3Z8

Mr. Jon Franke
Senior Vice President, Pickering
Ontario Power Generation Inc.
1675 Montgomery Park Road
Pickering, ON L1V 2R5

Subject: Darlington and Pickering NGS: Request pursuant to Subsection 12(2) of the General Nuclear Safety and Control Regulations: Issues Relating to Measurement of Hydrogen Concentration in Pressure Tubes

Messrs. Gregoris and Franke,

This letter is a formal request made pursuant to subsection 12(2) of the General Nuclear Safety and Control Regulations. Based on information reported to the Canadian Nuclear Safety Commission (CNSC) by Bruce Power, in relation to recent analysis of pressure tube sampling, it appears that the currently used models may under-predict the maximum hydrogen equivalent concentration in pressure tubes of CANDU reactors.

In accordance with Licence Condition G.1 of PROL 13.02/2025 and PROL 48.01/2028, and Section G.1 of Licence Condition Handbooks, licensed activities shall be conducted in accordance with the licensing basis. In addition, “for unapproved operation that is not in accordance with the licensing basis, the licensee shall take action as soon as practicable to return to a state consistent with the licensing basis, taking into account the risk significance of the situation.”

Pursuant to my authority as a person authorized by the Commission for the purposes of subsection 12(2) of the General Nuclear Safety and Control Regulations, I request that Ontario Power Generation (OPG) conduct analysis and review regarding pressure tube fitness for service, and make a report to the Commission, no later than July 30, 2021, in respect of the following actions:

1. Confirm receipt of the information from Bruce Power related to this discovery;
2. Analyze the impact of this information on the demonstration of pressure tube fitness for service;
3. Conduct necessary tests and analysis to verify that operation of all reactors at OPG stations remains within their licensing bases; and
4. Inform CNSC of any other measures taken in response to this information.

In addition, I request that OPG complete the following tests and analyses in the longer term (within 6 months of receipt of this letter), and make a report to the Commission:

5. Analysis of the hydrogen uptake model validity, reflecting new information.

Please note that, in accordance with subsection 12(2) of the General Nuclear Safety and Control Regulations, OPG is required to file a report with the Commission by July 19, 2021 that contains the following information:

1. confirmation that the request will or will not be carried out or will be carried out in part;
2. any action that OPG has taken to carry out the request or any part of it;
3. any reasons why the request or any part of it will not be carried out;
4. any proposed alternative means to achieve the objectives of the request; and
5. any proposed alternative period within which OPG proposes to carry out the request.

If you have any questions regarding this matter, please contact Stephanie Eisan-Kouznetsova at 613-897-0895 or at stephanie.eisan-kouznetsova@cnsc-ccsn.gc.ca or Milan Ducic at milan.ducic@cnsc-ccsn.gc.ca.

A similar letter has been sent to all CANDU reactor licensees that are subject to the requirements of the Nuclear Safety and Control Act.

Yours truly,

Alex Viktorov, PhD
Director General
Directorate of Power Reactor Regulation

c.c.: R. Jammal, P. Elder, M. Rinker, J. Burta, K. Campbell, V. Tavasoli, S. Eisan-Kouznetsova,
H. Overton, M. Ducic, J. Vecchiarelli, P. Herrera, S. Irvine, S. Kaufman