Office for Nuclear Regulation

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Sizewell B LC28 inspection

Executive summary

Purpose of intervention

The pressurised water reactor at Sizewell is currently shutdown for the 2016 planned outage. Prior to restart, Nuclear Generation Limited, the operator of Sizewell B must apply to the Office for Nuclear Regulation for permission under licence condition 30.

The purpose of this intervention was to undertake a mechanical engineering focused inspection of examination, inspection, maintenance and testing work been carried out during the outage as required by licence condition 28. This intervention directly supports the licence condition 30 permissioning strategy.

Interventions Carried Out by ONR

My mechanical engineering inspection sampled work undertaken by the duty holder. The areas I considered as part of this intervention were based on their nuclear safety significance and association with recently reported events.

The areas selected were:

Whilst on site, and at the request of the nominated site Inspector, I took the opportunity to gather information on the following systems:

Key Findings, Inspector's Opinions and Reasons for Judgements Made

Based on the information sampled, I am satisfied that the work carried out on maintaining and testing the reactor coolant pumps is adequate. The work appears to be suitably controlled with handovers between Nuclear Generation limited and third party contract partners appearing to be well managed through the use of quality plans.

I am satisfied that the surveillances associated with the emergency boration system adequately demonstrate compliance with the relevant technical specification and provide a reasonable test of the integrity of the associated isolation valves.

I judge that the approach taken in managing issues associated with the emergency boration system actuator gas leaks is appropriate, demonstrating an appropriate and reasonable response to the problem. I am satisfied that the issue is being adequately monitored and controlled.

Following discussions recent issues relating to cooling water systems, emergency diesel generators and the reserve ultimate heat sink, I am satisfied that the approach taken by NGL in respect to these topics is reasonable and in-line with my expectations.

Conclusion of Intervention

Based on the sampling I have undertaken, I judge that maintenance activities carried out during the Sizewell B 2016 outage are being adequately controlled and support the requirements of the safety case. I therefore support the request under licence condition 30 to return the reactor at Sizewell B to operation.