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 modernize 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 its life by several decades.

CNSC mandatory checkpoints built in throughout the process

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 operators.

An important part of these conditions is the use of regulatory hold points, a series of mandatory checkpoints that require review and verification by CNSC staff.

The refurbishment of 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 CNSC 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 four Darlington reactor units, starting with Unit 2 in 2016.

Under Licence Condition 15.4 of the Darlington PROL (13.02/2025), OPG is required to obtain authorization from the CNSC to remove the pre-established regulatory hold points before proceeding to the next step in return-to-service activities. In support of this project, CNSC and OPG staff concluded the Unit 2 Return to Service Protocol, a document that establishes specific deliverables and schedules that OPG must manage in order to obtain the removal of each regulatory hold point.

Reactor operation cannot proceed past each of the four hold points, without approval delegated by the Commission to the CNSC’s Executive Vice-President and Chief Regulatory Operations Officer.

These four regulatory hold points require the operator to stop and seek authorization prior to:

  1. Loading fuel into the reactor.
  2. Removing the guaranteed shutdown state and starting the reactor.
  3. Exceeding 1% full power.
  4. Exceeding 35% full power.

CNSC oversight and support continues throughout the process

Throughout the process, CNSC staff have also developed and followed a compliance-monitoring plan that aligns with OPG’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 OPG prerequisites, 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.

What’s next for Darlington?

In accordance with the Darlington licence condition handbook, OPG will submit special documentation for each regulatory hold point, known as the completion assurance documentation. 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.

Regulatory oversight by CNSC staff also continues with testing above 35% to ensure that all conditions for high-power testing are met, as detailed in REGDOC-2.3.1, Conduct of Licensed Activities: Construction and Commissioning Programs.

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