How regulatory hold points contribute to the safe and successful restart of a newly refurbished reactor
All buildings and facilities in Canada eventually come to a stage where they need to be modernized if they are to maintain safe operations. In the life of a nuclear power plant, this modernization comes in the form of refurbishment – an enhancement of equipment and systems that can extend a plant’s life by several decades.
CNSC mandatory checkpoints
When seeking to refurbish a facility, the first step is to have the power reactor operating licence (PROL) updated and amended by the Commission. Licence conditions to govern the refurbishment activities are set by the Commission and must be met by the operator.
An important part of these conditions is the use of regulatory hold points (RHP), a series of 4 mandatory checkpoints that require review and verification by CNSC staff.
Reactor operation cannot proceed past any of the 4 hold points without approval, which is delegated by the Commission to the CNSC’s Executive Vice-President and Chief Regulatory Operations Officer.
The 4 regulatory hold points require the operator to seek authorization prior to:
- loading fuel into the reactor
- removing the guaranteed shutdown state (GSS) and starting the reactor
- exceeding 1% full power
- exceeding 35% full power
Ongoing CNSC oversight and support
Throughout the refurbishment process, CNSC staff follow a compliance monitoring plan that aligns with the licensee’s planned activities and schedule. CNSC site staff work closely with other CNSC experts in Ottawa to conduct inspections, technical reviews and compliance monitoring activities.
In addition to the CNSC prerequisites for releasing hold points, these inspections and surveillance activities help inform staff recommendations to the Executive Vice-President and Chief Regulatory Operations Officer on the removal of each regulatory hold point.
Refurbishment of nuclear generating stations
Darlington Nuclear Generating Station
An excellent example of how regulatory hold points help the CNSC maintain rigorous safety standards in Canada is the current refurbishment of the Darlington Nuclear Generating Station in southern Ontario. In December 2015, the Commission renewed the 10-year operating licence for this facility and authorized the licence holder, Ontario Power Generation (OPG), to undertake the refurbishment and life extension of all 4 Darlington reactor units. In 2016, Unit 2 underwent a 3‑and-half-year refurbishment outage, resuming commercial operation in June 2020.
Under licence condition 15.4 of the Darlington PROL (13.02/2025), OPG is required to obtain authorization from the Commission to remove the pre-established regulatory hold points before proceeding to the next step in return-to-service activities. In support of this refurbishment project, CNSC and OPG staff created a unit-specific Return to Service Protocol, which is a document that establishes specific deliverables and schedules that OPG must meet to fulfill the prerequisites for the removal of each regulatory hold point.
In accordance with the Darlington licence conditions handbook, OPG will submit special documentation, known as completion assurance documentation, for each regulatory hold point. In addition, once sustained operation is at 100% full power, OPG will be required to submit further documentation specifying what activities were completed between the return from 35% to 100% full power.
What’s next for Darlington?
The next hold point for OPG is scheduled for Q2 2023, which is for the removal of the guaranteed shutdown state. Since regulatory hold point 1, OPG has been conducting commissioning and testing to declare systems available for service, conducting training, and ensuring procedures are validated to proceed to the next hold point. Throughout this process, CNSC staff have continued to conduct compliance verification activities, which includes witnessing commissioning tests, conducting walkdowns of systems, and ensuring staff have the necessary training to proceed past the guaranteed shutdown state.
In parallel, OPG has begun the refurbishment of Unit 1. This project is proceeding with the installation phase and will follow the same process for return to service once all work has been completed.
For more information about the Darlington Unit 3 refurbishment, read:
- CNSC letter to OPG regarding regulatory hold point 4 for Unit 3
- CNSC letter to OPG regarding regulatory hold point 3 for Unit 3
- CNSC letter to OPG regarding regulatory hold point 2 for Unit 3
- CNSC letter to OPG regarding regulatory hold point 1 for Unit 3
- CNSC letter to OPG regarding regulatory hold point 4 for Unit 2
- Record of Proceedings for the 2016 Darlington licence renewal
Bruce A and B nuclear generating stations
In 2018, the CNSC renewed the 10-year operating licence for the Bruce A and B nuclear generating stations, which authorized the licence holder, Bruce Power, to undertake the refurbishment – referred to as Major Component Replacement (MCR) outages – of 6 of the reactor units, starting with Unit 6 in 2020.
Under licence condition 15.5 of the Bruce PROL (18.02/2028), Bruce Power is required to obtain authorization from the Commission to remove the pre-established regulatory hold points before proceeding to the next step in return-to-service activities. In support of this refurbishment project, the CNSC approved the deliverables and schedule for the activities needed to meet the prerequisites for releasing the hold points.
In June 2023, Bruce Power requested the removal of the third and fourth hold points to exceed 1% and 35% of full power respectively for the refurbished reactor.
What’s next for Bruce?
Bruce Power will continue with work to have the remaining hold points lifted to bring the systems back online. Throughout this process, CNSC staff will be reviewing Bruce Power’s work, witnessing commissioning tests and ensuring that staff have the necessary training, before removing the subsequent hold points and continuing with the return to service of Unit 6.
In parallel, Bruce Power has begun the MCR outage for Unit 3. That project is in the initial phases, with the removal of major components series expected to begin later this year after systems have been placed in a lay-up state. Unit 3 will follow the same process for return to service once all work has been completed there.
For more information about the Bruce A and B nuclear generating station refurbishment, read:
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