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Letter to Ontario Power Generation regarding Regulatory Hold Point 2

Regulatory Operations Branch

April 5, 2020

Mr. Dietmar Reiner
Senior Vice President, Nuclear Projects
Ontario Power Generation Inc.
1855 Energy Drive, 3C14
Courtice, ON L1E 0E7
Mr. Steve Gregoris
Senior Vice President, Darlington Nuclear
Ontario Power Generation Inc.
P.O. Box 4000
Bowmanville, ON L1C 3Z8

SUBJECT: Darlington NGS - Unit 2 Return to Service: Request for CNSC Consent to Remove the Regulatory Hold Point for Guaranteed Shutdown State New Action Item 2020-13-20750

Dear Messrs. Reiner and Gregoris,

The purpose of this letter is to respond to Ontario Power Generation’s (OPG) request [1] to remove Regulatory Hold Point (RHP-2), allowing Guaranteed Shutdown State to be removed in the refurbished Darlington Unit 2 reactor.

Canadian Nuclear Safety Commission (CNSC) staff’s assessments [2, 3] concluded that OPG has met all the pre-requisites established by the Commission to remove RHP-2. Therefore, as the person authorized by the Commission and pursuant to Licence Condition 15.4 of the Darlington Nuclear Generating Station (DNGS) Power Reactor Operating Licence 13.01/2025, I hereby consent to the removal of RHP-2, allowing OPG to surrender the Guaranteed Shutdown State in Unit 2. This authorization is with a special condition pertaining to the Emergency Coolant Injection (ECI) flow transmitters that must be rectified prior to the Primary Heat Transport System (PHTS) reaching 90°C and having a fully functioning ECI to the satisfaction of CNSC staff.

My consent is based on a Risk Informed Decision, used in special circumstances, taking into account CNSC staff’s assessment [3], indicating that the resolution for a small number of ECI flow transmitters will be carried out as captured in Design Engineering Change (DEC) 123592. In their assessment, CNSC staff conclude that this open item can be closed post RHP-2 removal but must be rectified prior to the PHTS reaching 90°C.

As a result, Action Item 2020-13-20750 has been raised to track completion of this work to the satisfaction of CNSC staff. If the inaccurate flow transmitter indications cannot be resolved prior to the PHTS reaching 90°C, OPG shall return Unit 2 to a Guaranteed Shutdown State until full resolution of the problem has been confirmed to the CNSC’s satisfaction.

Yours sincerely,

Ramzi Jammal
Executive Vice-President and
Chief Regulatory Operations Officer
Regulatory Operations Branch

c.c: G. Frappier, J. Burta, P. Elder, D. Newland, G. Lamarre, M. Rinker, K. Heppell-Masys, H.Tadros, C. Loreti, D. Desjardins, D. Nguyen, N. Abonasara, K. Hazelton, A. Mathai, C. Yacoub, Darlington Site Office


  1. OPG Letter, D. Reiner and S. Gregoris to R. Jammal, “Darlington NGS Refurbishment – Unit 2 Return to Service: Request for CNSC Consent Prior to Guaranteed Shutdown State (GSS) Removal (RHP 2)”, April 3, 2020, NK38-CORR-00531-21509.
  2. CNSC staff document entitled: “Request by Ontario Power Generation Inc. to Remove Regulatory Hold Point for Prior to Guaranteed Shutdown State for Unit 2”, March 26, 2020.
  3. CNSC memorandum: “Removal of Regulatory Hold Point 2 – Prior to GSS Removal for Darlington NGS Unit 2”, April 5, 2020.

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