Office for Nuclear Regulation

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Sizewell B - LC22, LC26 and Outage Management

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake Licence Condition (LC) compliance inspections at EDF Energy Nuclear Generation Ltd's (NGL's) Sizewell B power station, in line with the planned inspection programme of the Operating Facilities Operating Reactors sub-programme intervention plan for 2017/18.

Interventions Carried Out by ONR

During this intervention, we reviewed activities undertaken in support of the Sizewell B statutory shutdown and measured compliance against the following Licence Conditions:

Explanation of Judgement if Safety System Not Judged to be Adequate

No system inspection was undertaken during this intervention.

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

This intervention reviewed a number of NGL's activities conducted during the Sizewell B periodic shutdown. During the shutdown, maintenance activities are conducted (in accordance with the plant maintenance schedule) and refuelling operations performed.

The compliance inspections focussed on the modification to replace a main steam isolation valve bypass isolation valve and some of the supporting pipework.

I reviewed the modification documentation and supporting implementation records. I found that the modification presented an effective solution to prevent problems during the installation of this valve.

The records for the off-line manufacture of the valve and pipe assembly demonstrated that the requisite standards had been achieved in a controlled environment. When the modification is completed it should ensure that valve and its supporting pipework meet the required integrity standards.

I observed the preparation and cutting out of the old valve and pipework. This work was conducted by Doosan and overseen by the EDF project engineer. The setting to work and pre-job briefs were thorough and enabled the work to be effectively controlled and conducted.

The supervision of the work by the EDF and Doosan staff provided effective oversight of the implementation of the modification and ensured the work was conducted to the required standard.

I continued engagement with EDF on the resolution of the emergent issue with steam generator D. The repair proposals were now being developed and qualified. The management of this issue by the station was considered appropriate.

The intervention was performed in line with ONR’s guidance requirements (as described in our technical inspection guides) in the areas inspected.

Conclusion of Intervention

I consider that based on the evidence acquired during this intervention, that an inspection rating of Green is appropriate for both LC 22 (Modification on existing plant) and LC 26 (Control and supervision of operations)