Office for Nuclear Regulation

Sizewell B – Inspection ID: 52177

Executive summary

Date(s) of inspection:

  • March 2023

Aim of inspection

This inspection will consider aspects of the Sizewell B (SZB) refuelling outage (RO) 18 activities undertaken. This was a planned intervention and part of the 2022/2023 ONR integrated intervention strategy for operating reactors.

Subject(s) of inspection

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

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


The inspection activities undertaken at Sizewell B (SZB) focused on the arrangements that have been established for the completion of the SZB refuelling outage (RO) 18 and their implementation. The aim was to provide ONR with regulatory confidence in the implementation the arrangements established for the SZB RO18. This inspection considered the electrical engineering (EE) structures, systems and components (SSCs) that are being maintained during the SZB RO18 in compliance with licence condition 28.

This inspection also provided ONR with the opportunity to follow up on conventional electrical safety event investigation undertaken by EDF Energy NGL


From the sample inspected, EDF Energy NGL adequately demonstrated the implementation of the arrangements established for the SZB RO18 activities, including inspection and observation of the actual condition of the station’s electrical SSCs, progress against the station’s RO18 plan, management of emergent issues and completion of work order cards, in accordance with licence condition 28.


On the basis of the evidence sampled at the time of each inspection:

For the Refuelling Outage 18 Activities inspection, I judge that EDF Energy NGL were able to adequately demonstrate the implementation of the arrangements in compliance with licence condition 28 at SZB. Noting ONR guidance on inspection ratings, it is my opinion that an inspection rating of GREEN – no formal action is merited here. Based on this inspection there were no issues identified from electrical work activities which would prevent ONR granting consent for SZB to return to service at this point. This is subject to the completion of the planned examination, maintenance, inspection and test (EIMT) work and the assessment of any EMIT activity deferrals.