Request pursuant to Subsection 12(2) of the General Nuclear Safety and Control Regulations: Darlington Emergency Exercise "Unified Command 2025"

Directorate of Power Reactor Regulation

November 6, 2025

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

Dear Mr. Grace:

This letter is a request being issued to Ontario Power Generation (OPG) Inc., pursuant to subsection 12(2) of the General Nuclear Safety and Control Regulations (GNSCR). It pertains to observations made during a CNSC Type II inspection of the emergency exercise “Unified Command 2025” at the Darlington Nuclear Generating Station (DNGS).

OPG did not meet the exercise objectives of adequately deploying Phase 1 and 2 Emergency Mitigating Equipment (EME) and did not validate the adequacy of Phase 2 EME deployment guide. As a result, OPG has not demonstrated the deployment and functional operation of EME as required by licence condition 10.1 of PROL 13.06/2025, REGDOC-2.10.1, Nuclear Emergency Preparedness and Response, Version 2 (Sections 2.1, 2.2.6, 2.2.9, 2.3.1, 2.3.2 and 2.3.3) and REGDOC-2.3.2, Accident Management, Version 2 (Sections 3.2, 3.4 and 3.5).  It is important to note that EME plays a critical role in mitigating risks to the health and safety of workers and the public by helping to prevent the release of radioactive material in case of a beyond design basis event.

During the inspection, CNSC staff identified significant gaps requiring corrective actions in OPG’s deployment of EME, including: 

• Failure to demonstrate that EME can be successfully deployed in order to fulfill its purpose (e.g., by providing cooling water from the forebay and providing electricity to repower key indications and components)  
• Inadequate maintenance of equipment essential to emergency response (e.g., 4 out of 5 Portable Uninterruptable Power Supplies (PUPS) being unavailable, seals on the dry-riser enhancements not adequately maintained) 
• Lack of staff proficiency in the deployment, operation and connection of EME 
• Failure to validate the adequacy of the Phase 2 EME deployment guide 

These issues were communicated to OPG’s senior management, and immediate corrective actions were taken by OPG in response ^{Footnote 1}. CNSC staff expect that sustained efforts will be made to ensure the long-term sustainability and effectiveness of the emergency management program. The detailed inspection findings will be issued to OPG in a separate letter in the near future. 

Requests 

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 hereby request OPG to submit the following information, confirming that OPG will comprehensively address the observed deficiencies in the EME deployment during the exercise:

1. Gap analysis on training for personnel deploying and operating the EME: A comprehensive review of the existing EME training to ensure that its design, development and implementation is in accordance with the requirements of REGDOC-2.2.2, Personnel Training, Version 2 (Section 5.1.2, 5.3.2, 5.5). This shall include a description of how OPG will ensure that the staff required to deploy, operate and troubleshoot Phase 1 and 2 EME are qualified and proficient, along with measures to maintain that proficiency. 
2. Plans to validate the Phase 2 EME Guides(s): Develop a plan and validate the Phase 2 EME guide(s) and demonstrate to CNSC staff that OPG can successfully and safely deploy, troubleshoot and operate, all Phase 1 and 2 EME, including the deployment of PUPS.     
3. Evaluation of the existing maintenance program for EME:Assess the current EME maintenance program to identify any changes necessary to ensure the continued availability and operational readiness of all EME (such as PUPS, generators, etc.), including associated components such as fittings and connection points. 
4. Evaluation of the extent of condition and required improvements, including those at Pickering NGS: A summary of the extent of condition and any improvements that are required for both Darlington and Pickering NGS to address similar issues.  

As part of a graduated enforcement plan, failure to act and/or respond to a request under subsection 12(2) of the General Nuclear Safety and Control Regulations may lead to further enforcement action.

Please note that, in accordance with subsection 12(2) of the General Nuclear Safety and Control Regulations, every licensee who receives a request from the Commission or a person who is authorized by the Commission for the purposes of this subsection, to conduct a test, analysis, inventory or inspection in respect of the licensed activity or to review or to modify a design, to modify equipment, to modify procedures or to install a new system or new equipment shall file, within the time specified in the request, a report with the Commission that contains the following information:

• a) confirmation that the request will or will not be carried out or will be carried out in part
• b) any action that OPG has taken to carry out the request or any part of it;
• c) any reasons why the request or any part of it will not be carried out;
• d) any proposed alternative means to achieve the objectives of the request; and
• e) any proposed alternative period within which OPG proposes to carry out the request.

OPG is hereby requested to provide a response, by December 19, 2025, acknowledging receipt of this letter and summarizing the actions taken or planned to be taken by OPG.

If you have any questions related to this matter, please do not hesitate to contact Mr. Kenneth Lun, Acting Director, Darlington Regulatory Program Division, at 613-795-9146 or by e-mail at kenneth.lun@cnsc-ccsn.gc.ca.

Yours truly,
Alexandre Viktorov, Ph.D.
Director General
Directorate of Power Reactor Regulation 

c.c.: CNSC: R. Jammal, D. Moroz, K. Lun, M. Hitchon, E. Delgado, R. Tennant, T. Gulinski, A. Stewart (HOPD), L. Hagen, R. Richardson, D. Mendoza, Darlington RPD 
OPG: S. Irvine, C. Axler, C. Bedard