Office for Nuclear Regulation

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Sizewell B - Inspection Week

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 undertook a themed compliance inspection examining the control and supervision of operations and maintenance on the station. During this inspection, we measured compliance against the following relevant statutory provisions of the Energy Act (2013):

Also during this intervention I attended the Suffolk Emergency Planning Consultative Committee (EPCC) in Ipswich on 14th June 2017. This was also attended by an emergency preparedness & response (EP&R) inspector. 

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

We made the following principal findings in relation to the control and supervision of operations and maintenance:

In relation to LC 23 (Operating rules) we were satisfied that the station is demonstrably compliant with the limits and conditions set out within its Technical Specifications; technical specification action condition entries are tracked and logged with appropriate rigour. Through the Work Management Process and mature safety rules arrangements, nuclear risk appears to be well managed to ensure sustained compliance with Technical Specification requirements. Based on these findings, we therefore assigned a rating of Green for LC 23 (no formal action).

In relation to LC 24 (Operating instructions) we observed work activities to have been undertaken in accordance with appropriate written instructions, and isolations generated and performed according to checklists produced in a systematic manner.  Based on these findings, we have assigned a rating of Green for LC 24 (no formal action). 

In relation to LC 25 (Operational records) we sampled a range of operational logs which monitor Technical Specification compliance (notably the equipment inoperability log which is comprehensive in ensuring plant status is appropriately visible). We suggested opportunities to improve visibility by which Technical Specification entries could progress in more onerous situations. Overall, we therefore assigned a rating of Green for LC 25 (no formal action).

In relation to LC 26 (Control and supervision of operations), we observed a number of work activities including the pre-job briefs and setting to work activities.  In all cases the level of control and supervision was commensurate with the safety significance of the task.  We also examined the safety rules process and were satisfied the station is managing isolations and de-isolations according to mature and appropriate arrangements. This is supported by improved return to service arrangements and earlier development of return to service strategies timelier major plant items. Based on these findings, we have assigned a rating of Green for LC 26 (no formal action). 

In relation to LC 27 (Safety mechanisms, devices and circuits), we were satisfied that the station’s approach to managing nuclear risk through the work management process is effective and mature. There has been a discernible effort from the station to enhance the integration of operations and engineering personnel into the work planning process in order to ensure fit for purpose sequencing of activities to ensure loss of defence in depth during planned and emergent work is minimised. There has been a clear operational focus on improving nuclear safety related chiller availability. Notwithstanding this, at the time of inspection it was evident that ongoing issues with poor reliability continue to challenge defence in depth, due to a combination of planned work and emergent defects concurrent with high ambient temperatures.  The station’s long term plan for replacement of the fourteen chiller units has gathered maturity and appears to have appropriate resources. However, further assurance is required from the station that all reasonably practicable measures are being implemented to ensure availability of HVAC chillers before all fourteen chillers are replaced within the next two years. In view of the ongoing reliability issues challenging availability of nuclear safety related chillers, we have assigned a rating of Amber for LC 27. We will write to NGL seeking improvement. An entry on the ONR Issues database has been created to track resolution of this issue.

In relation to LC 28 (Examination, inspection, maintenance and testing), We sampled the arrangements for work planning and management of emergent work and observed improved engineering and operations engagement at the daily work review meetings to ensure optimal prioritisation of emergent work against planned. The work activities sampled were conducted by suitably qualified and experienced persons in accordance with written schemes of work and under a level of control and supervision commensurate with the nuclear safety significance of the task being undertaken. We therefore assigned a rating of Green (no formal action).

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 inspection, we concluded that the station is implementing adequate arrangements associated with the control and supervision of operations and maintenance are adequate (as measured through observation of plant status control, work management work planning and work executions and supervision).

Improvement is being sought, through a Level 3 regulatory issue, for improved interim reliability and availability of nuclear safety related chillers pending a replacement project.