Letter to Ontario Power Generation regarding Regulatory Hold Point 2 – Darlington Unit 4

Regulatory Operations Branch

January 19, 2026

Mr. Allan Grace
Senior Vice President, Nuclear
Ontario Power Generation Inc.
1 Holt Road South, P.O. Box 4000
Bowmanville, ON L1C 3Z8

Mr. Vince Smyth
Senior Vice President, Refurbishment
Ontario Power Generation Inc
1855 Energy Drive, 3C14
Courtice, ON L1E 0E7

Subject: Darlington NGS - Unit 4 Return to Service: Request for CNSC Consent to Remove the Regulatory Hold Point for Prior To Removal of Guaranteed Shutdown State

Dear Mr. Grace and Mr. Smyth:

The purpose of this letter is to respond to Ontario Power Generation’s (OPG) submission [1], which requests removal of Regulatory Hold Point-2 (RHP-2), allowing the Guaranteed Shutdown State to be surrendered in the refurbished Darlington Unit 4 reactor.

Canadian Nuclear Safety Commission staff’s assessment [2] of OPG’s submission [1], as well as all supporting documentation, 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 Power Reactor Operating Licence 13.00/2045, I consent to remove RHP-2 and OPG may now proceed with surrendering GSS to restart the refurbished reactor at low power for testing and verification.

Yours sincerely,

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

CC: A. Viktorov, K.Lun, A. Mathai, M. Rickard, C. Loreti, E. Delgado, A. El-Merhi, C. Badal C. Brown, C. Chan, Darlington Site Office

References:

1. OPG Letter, A. Grace and V. Smyth to R. Jammal, “Darlington NGS Refurbishment – Unit 4 Return to Service: Request for CNSC Consent Prior to Guaranteed Shutdown State (GSS) Removal (RHP2)”, January 17, 2026
2. CNSC staff document entitled: “Request by Ontario Power Generation Inc. To Remove Regulatory Hold Point Prior to Surrender of the Guaranteed Shutdown State for Darlington Unit 4”, January 19, 2026