Office for Nuclear Regulation

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Sizewell B Power Station - System Based Inspection 13 - Accumulator Safety Injection System

Executive summary

Purpose of Intervention

The main purpose of this intervention was to undertake a system based inspection (SBI) at EdF Energy Nuclear Generation Ltd’s (EdF NGL) Sizewell B (SZB) power station. The inspection was conducted in line with the inspection programme contained in the SZB SBI plan for 2017/18.

Interventions Carried Out by ONR

Two ONR specialist structural integrity inspectors, which for the purpose of this intervention report shall be referred to as “I”, conducted a SBI on the Accumulator Safety Inspection System (ASIS) (SBI-13) at SZB nuclear power station.  Through examination of this system, I performed compliance inspections against the following licence conditions of the Nuclear Site Licence i.e. LC 10: Training; LC23: Operating Rules; LC24: Operating Instructions; LC27: Safety Mechanisms, Devices and Circuits and LC28: Examination, Inspection, Maintenance and Testing. The inspection was based on sampling the implementation of the arrangements in place at the station against each licence condition. Following discussion with the licensee it was judged that compliance inspection against LC34: Leakage and Escape of Radioactive Material for the ASIS was not applicable.

Explanation of Judgement if Safety System Not Judged to be Adequate

From the inspection I judged that overall, the ASIS met the requirements of the safety case and is adequate.

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

LC 10 (Training) - For this part of the inspection I chose to sample a range of employee training records for individuals with responsibility for the safe operation, maintenance and overall management of the ASIS. From the totality of the evidence gathered during the SBI, I consider that an ONR inspection rating of GREEN is appropriate for LC10.

LC 23 (Operating Rules) - I sampled the licensee’s compliance with a number of key accumulator operating rules under the site Technical Specifications (TS). The inspection confirmed that the station has made and implemented arrangements to ensure that plant is not operated unless the TS provided to implement the limits and conditions derived from the safety case are satisfied. I judged LC23 aspects of the SBI to be adequate, with the licensee having identified, implemented and demonstrated compliance with operating rules derived from the safety case, warranting a rating of GREEN.

LC 24 (Operating Instructions) - During this part of the inspection I sampled a number of the associated station and plant operating instructions, to confirm that operations important to safety are carried out in accordance with written instructions. This included a sample relating to the accumulator TS surveillance requirements. An appropriately clear link was established from the safety case through to operating instructions was evident. I found the operating instructions to be well presented, being in a systematic format and relevant to the tasks in hand. Accordingly, I judged that a rating of GREEN is appropriate.

LC 27 (Safety Mechanisms, Devices and Circuits) - The inspection reviewed records of Safety Mechanisms to establish how their availability is managed and good working order maintained. The station were able to provide adequate evidence that the devices sampled were maintained and available in line with safety case requirements, based on documented procedures and defined acceptance criteria. The records sampled were completed satisfactorily. Therefore, I judged the LC27 aspects of the SBI to be GREEN.

LC 28 (Examination, Inspection, Maintenance and Testing) - The inspection reviewed the procedures and arrangements in place to ensure Examination, Inspection, Maintenance and Testing (EIMT) is carried out appropriately for the accumulators and the associated pipework, valves and monitoring equipment. I reviewed the System Health Indication Programme (SHIP) system for an overall picture of system health and sampled further into maintenance and testing activities, conducted in support of the TS surveillance requirements. I was content that these represented adequate arrangements; in regard to reports and reviews of maintenance and demonstrated adequate control of the system EIMT requirements. A rating of GREEN was deemed appropriate for LC28.

LC 34 (Leakage and Escape of Radioactive Materials and Radioactive Waste) -Following discussion with the licensee and taking into consideration the operation and function of the ASIS, I did not consider the ASIS to be a relevant system for inspection under LC34, and therefore was not considered further as part of this SBI.

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

After considering all the evidence examined during the inspection, I considered that the ASIS met the requirements of the safety case.

From the information gathered and evidence obtained during this intervention, I judge that no matters have been identified that are likely to have significant impact on nuclear safety at this time. Therefore I consider that no additional regulatory action arising from this visit is necessary currently, and the interventions for SZB power station, set out in the integrated intervention strategy, should continue to be implemented as planned.