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Request pursuant to Subsection 12(2) of the General Nuclear Safety and Control Regulations: Darlington NGS – Impairment of the Public Address System

Directorate of Power Reactor Regulation

e-Doc 7167613
File 4.01.03
RIB 30850

November 17, 2023

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

Subject: Request pursuant to Subsection 12(2) of the General Nuclear Safety and Control Regulations: Darlington NGS – Impairment of the Public Address System

Dear Mr. Geofroy:

This letter is a request pursuant to subsection 12(2) of the General Nuclear Safety and Control Regulations related to a series of exchanges between Canadian Nuclear Safety Commission (CNSC) staff and Ontario Power Generation (OPG), from CNSC staff observations documented in DRPD-2023-FIR-18338: PA System Reactive Field Inspection [1] to OPG’s response to a subsequently raised Action Item, 2023-13-30850 [7].


During routine surveillance activities, CNSC staff have identified recurring issues of concern regarding the effectiveness of the Public Address (PA) System to perform its design intent. CNSC staff communicated these observations to OPG on August 29, 2023, in DRPD-2023-FIR-18338: PA System Reactive Field Inspection [1].

Following the issuance of the field inspection record, a series of exchanges, both written and verbal took place between CNSC staff and OPG. These are included in references [2-5] and detailed in the following action raised by CNSC staff [6].


  • On October 25, 2023, CNSC staff raised an Action Item 2023-13-30850, detailing the exchanges that took place on this issue and re-emphasizing concerns with the condition of the PA system, the audibility of emergency tones, the length of the established impairment and the urgency with which repairs and upgrades are being made [6]. OPG was requested to respond within ten (10) business days;
  • On November 9, 2023, OPG provided a response to CNSC’s letter, asserting that the compensatory measures put in place ensured OPG’s compliance with Licence Conditions 6.1, 10.1 and 10.2 [7].
  • OPG’s submission [7] also offered a high-level timeline for the upgrade of the PA system, targeted for completion in 2026 and committed to update CNSC staff on the cause of the length of the impairment by January 2024.

CNSC staff’s assessment of OPG’s responses and observations [8] [9] at Darlington Nuclear Generating Station (DNGS) note the following:

  • Emergency Response Team (ERT) sweeps: ERT response to fire emergencies is assessed against specific response times requirements in CSA N293-12. To demonstrate that clause 10.2.2 remains met, OPG has not provided any evidence that an assessment was performed to ensure that this task of alerting and escorting personnel will not impact the response times.
  • Accounting and Assembly Drills: In order to validate compensatory measures in place during the impairment of the PA system, OPG credited two (2) station-wide assembly and accounting drills and concluded that the results of these drills was that all occupants in the station were fully accounted for in less than 30 minutes. On November 4, 2023, CNSC staff observed one of the two drills. At the start of the drill, OPG indicated that 431 people were in the protected area and noted, in accordance with OPG procedures, that a best effort of manual accounting is completed. However, there is no measurable output (i.e., log/ record) demonstrating that 431 people were fully accounted.

Licence Condition 10.1 of PROL 13.03/2025 requires the licensee to implement and maintain an emergency preparedness program to ensure an effective response to any fire or emergency situation. Licence Condition 10.2 of PROL 13.03/2025 requires the licensee to implement and maintain a fire protection program to ensure the licensed activities do not result in unreasonable risk to the health and safety of persons and to the environment due to fire and to ensure that the licensee is able to efficiently and effectively respond to emergency fire situations.

Sections 10.1 and 10.2 of the LCH requires these programs comply with the requirements below:

REGDOC-2.10.1, Nuclear Emergency Preparedness and Response, section 2.2.2:

“All licensees shall have an ER plan and procedures that describe the immediate notification process and secondary communication methods to alert all onsite personnel, to initiate personnel assembly and accounting, and to activate the ERO and associated emergency response and support facilities.”

CSA N293-12, Fire protection for nuclear power plants, clause

“In addition to the requirements of the NBCC for fire alarm and voice communication systems, fire alarm systems with integrated, supervised, one-way voice communication shall be provided in all structures and exterior areas within the protected area, as well as structures and areas external to the protected area where SSCs directly support the plant.

The supervised one-way voice communication system shall provide main control room staff with a means to give one-way voice instruction to occupants during an emergency.

Where intelligible voice communication is not possible (e.g., in locations remote from buildings), audible and visual signal devices and voice communication shall be provided at building entrances.”

CSA N293-12, Fire protection for nuclear power plants, clause 8.3.2(a):

“When a fire protection system is out of service, compensatory measures shall be provided. Impairments to fire protection systems shall be managed through the development of an impairment plan. The impairment plan shall meet the following requirements:

  1. The duration of the impairment shall be the shorest period possible.”

CSA N293-12, Fire protection for nuclear power plants, clause 10.2.2:

“Industrial fire brigade members shall have no other plant duties that prevent immediate response to a fire.”

NFPA 72-2007, National Fire Alarm Code, clause

“Where required, voice communications system shall be capable of reproduction of pre-recorded, synthesized, or live (e.g., microphone, telephone handset, and radio) messages with voice intelligibility.”

NFPA 72-2007, National Fire Alarm Code, clause

“To ensure that audible public mode signals are clearly heard, unless otherwise permitted by through, they shall have a sound level at least 15 dB above the average ambient sound level or 5 dB above the minimum sound level having a duration of at least 60 seconds, whichever is greater, measured at 1.5 m (5ft) above the floor in the area required to be served by the system using the A-weighted scale (dBA).”

CNSC staff assessment of the current performance of the PA system in the Darlington Nuclear Generating Station (NGS) and OPGs submission [7-9] find that OPG has not adequately demonstrated compliance with several regulatory requirements, and remains in non-compliance with Licence Conditions 10.1 and 10.2 of PROL 13.03/2025 and with Compliance Verification Criteria (CVC) prescribed in sections 10.1 and 10.2 of the Licence Conditions Handbook, LCH-PR-13.03/2025-R005.


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 OPG, by December 15, 2023, modify or install (upgrade) a Public Address System at Darlington NGS which meets current regulatory requirements, or provide an acceptable timeline to do so. In addition, OPG is required to perform the following assessments and provide the results while the upgrade activities are being completed:

  1. Current secondary communications mechanisms, validation methods and means of ongoing monitoring to confirm that these measures implemented by OPG remain effective for the duration of the PA system upgrade project, as set out under clause of CSA N293-12 and section 2.2.2 of REGDOC-2.10.1;
  2. A task analysis of the additional ERT duties to ensure that they do not impede response times or the capability of ERT staff to adequately perform their duties, as set out under clause 10.2.2 of CSA N293-12;
  3. A sound survey to determine audibility and intelligibility within the PA-equipped areas and in all adjacent buildings, as set out under clauses and of NFPA 72-2007;
  4. Results of the root cause analysis (REGM 28262844) to determine the cause and length of time the impairment existed on the Public Address System prior to the informal notification of the impairment to CNSC staff on October 12, 2023; and,
  5. A timeline to ensure the expedited resolution of the impairment such that it is the shortest period possible, as set out in clause 8.3.2 of CSA N293-12.

Please note that, in accordance with subsection 12(2) of the General Nuclear Safety and Control Regulations, OPG is required to file a report by November 30, 2023, with the Commission 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 related to this matter, please do not hesitate to contact Mr. Andrew Mathai, Director, Darlington Regulatory Program Division, at (289) 356-6785 or by e-mail at

Yours truly,

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

c.c.:      CNSC: K. Owen-Whitred, P. Elder, A. Mathai, S. Eisan-Kouznetsova, A. Stewart, C. Krasnaj, R. Tennant, T. Gulinski, A. Bounagui, J. Eduful, Darlington Site Office
OPG: S. Irvine, C. Axler, A. Bhardwaj


  1. CNSC Field Inspection Report – DRPD-2023-FIR-18338: PA System (Reactive), August 29, 2023. [e-doc 7106196]
  2. OPG email, M. Baytekin to A. Stewart, “CNSC Field Inspection Observations - DRPD-2023-FIR-18338- PA System (Reactive)”, September 15, 2023. [e-Doc 7127177]
  3. OPG email, C. Arnold to A. Stewart, “CNSC surveillance - Unit 2 Public Address System and Fire Tone”, October 13, 2023. [e-Doc 7147952]
  4. OPG email, A. Bhardwaj to C. Chan, “Update on Actions for Public Address System (PA) Impairment”, October 18, 2023. [NK38-CORR-00531-24921, e-Doc 7152823]
  5. OPG letter, R. Geofroy to A. Mathai, “Darlington NGS – Update on the Actions for the Public Address System”, October 24, 2023. [NK38-CORR-00531-24927, e-Doc 7153099]
  6. CNSC letter, A. Mathai to R. Geofroy, “Darlington NGS - Impairment of the Public Address System - New Action Item 2023-13-30850”, October 25, 2023.
  7. [NK38-CORR-00531-24930, e-Doc 7153576]
  8. OPG letter, R. Geofroy to A. Mathai, “Darlington NGS – OPG Response to Impairment of the Public Address System, Action Item 2023-13-30850”, November 9, 2023. [NK38-CORR-00531-24970, e-Doc 7164255]
  9. SODR Entry 23.0096, Observations from an Accounting and Assembly Drill, November 6, 2023.
  10. SODR Entry 23.0104, SCR D-2023-17793, EITER: Unplanned Unavailability of Public Address System Radio Bridge Contingency, November 9, 2023.

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