Office for Nuclear Regulation

Sizewell B – Inspection ID: 52183

Executive summary

Date(s) of inspection:

  • March 2023

Aim of inspection

The purpose of this inspection was to carry out licence compliance inspection at EDF Energy Nuclear Generation Limited’s Sizewell B power station in line with the planned inspection programme.

Site Licence Condition 30, Periodic Shutdown, requires EDF Energy Nuclear Generation Ltd, the licensee to periodically shutdown the reactors at its nuclear power stations for the purpose of undertaking the examination, inspection, maintenance and testing of items important to safety in accordance with the requirements of the plant maintenance strategy.

This inspection was to provide regulatory confidence in the examination, inspection, maintenance and testing undertaken or planned to be undertaken during reactor outage RO18 at Sizewell B from a mechanical engineering perspective. This intervention is in support of the ONR decision on plant restart.

Subject(s) of inspection

  • LC 28 – Examination, inspection, maintenance and testing – Rating: Green

Key findings, inspector’s opinions and reasons for judgement made

Based on my sampling, I am satisfied from a mechanical engineering perspective that during the Sizewell B 2023 (RO18) periodic shutdown, examination, inspection, maintenance and testing associated with:

  • Polar Crane,
  • Emergency Boration System,
  • Auxiliary Feedwater Turbine System,
  • Motor Operated Valves Programme

are being adequately controlled, in line with the requirements of the safety case.


From a mechanical engineering perspective and based on my sampling, I am satisfied that the LC28 arrangements in place for the Sizewell B RO18 refuelling outage are appropriate. I judge that an ONR inspection rating of GREEN is appropriate for this intervention. I support ONR granting permission under Licence Condition 30 to return Sizewell B to operation following its 2023 (RO18) periodic shutdown.