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; this was followed by Unit 3, which was also refurbished and was returned to service in July 2023

Under licence condition 15.4 of the Darlington PROL (13.04/2025), OPG is required to obtain authorization from the Commission (or a person authorized by 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 unit-specific return-to-service-protocols. These protocols establish specific deliverables and schedules, which OPG must meet to fulfill the prerequisites for the removal of regulatory hold points for the return to service of each unit that has undergone a refurbishment.

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.

Figure 1 shows the timeline for the Darlington refurbishment schedule. — Figure 1 - Darlington Nuclear Generating Station refurbishment timeline

Next steps for Darlington

With the successful removal of the fourth and final regulatory hold point (RHP 4) at Darlington on November 14, 2024, OPG can now exceed 35% full operating power for the refurbished Unit 1 reactor. Throughout each stage of this process, CNSC staff continued their rigorous oversight to verify that the facility’s restart activities were completed safely and in accordance with the operating licence.

In parallel, OPG is progressing with the refurbishment of Unit 4. This project will be subject to the same regulatory oversight for return to service once all work has been completed.

Upon return to service of Unit 4, all 4 units at the Darlington Nuclear Generating Station will have been refurbished.

For more information about refurbishment activities at Darlington:

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.

Figure 2 shows the timeline for the Bruce Power refurbishment schedule. — Figure 2 – Bruce A and B Nuclear Generating Station refurbishment timeline

As of September 9, 2023, all regulatory hold points have been removed from Bruce B Unit 6 and the reactor has returned to full power operation.  CNSC staff continue to provide oversight of Unit 6 through the normal baseline compliance program.

What’s next for Bruce?

Bruce Power has begun the MCR outage for Unit 3. Fuel has been removed from the reactor, systems have been placed in a lay-up state and bulkheads have installed to separate the reactor from the containment system.  Work is underway to remove the major components, which will be followed by inspections and then re-installation of new components. Unit 3 will follow the same process for return to service once all work has been completed.

The Bruce A Unit 4 MCR outage is expected to start in early 2025.

For more information about the Bruce A and B nuclear generating station refurbishment, read:

Page details

Date modified:: 2024-11-18

Language selection

Search

You are here: