Letter to Ontario Power Generation regarding Regulatory Hold Point 1 – Darlington Unit 4

Regulatory Operations Branch

August 28, 2025

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

Mr. Boris Vulanovic
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 Fuel Load

Dear Mr. Grace and Mr. Vulanovic:

The purpose of this letter is to respond to Ontario Power Generation’s (OPG) submission [1], which requests removal of Regulatory Hold Point-1 (RHP-1), allowing fuel to be loaded in the refurbished Darlington Unit 4 reactor core, and provides the associated Completion Assurance Document.

Canadian Nuclear Safety Commission (CNSC) 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-1. 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 13.06/2025, consent to remove RHP-1 is hereby granted, and fuel may now be loaded into the Unit 4 core.

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 B. Vulanovic to K. Owen-Whitred, “Darlington NGS Refurbishment: Unit 4 Return to Service: Request for CNSC Consent Prior to Fuel Load (RHP1)”, dated August 22, 2025.
2. CNSC staff document entitled: “Request by Ontario Power Generation Inc. to Remove Regulatory Hold Point for Prior To Fuel Load for Unit 4”, dated August 28, 2025.