Office for Nuclear Regulation

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Hinkley Point B Planned Intervention, system based inspection SBI-029, Diverse Shutdown and hold down systems

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a system based inspection (SBI) of the diverse shutdown and hold down system at EDF Energy Nuclear Generation Limited's (NGL's) Hinkley Point B power station in line with the planned inspection programme contained in the Hinkley Point B Integrated Intervention Strategy (IIS) for 2017/18.

Interventions Carried Out by ONR

The Nominated Site Inspector for Hinkley Point B and an ONR C&I Specialist Inspector undertook a System Based Inspection of the diverse shutdown and hold down equipment to judge the system performance against its safety function. Through sampling of documentation, plant walk down and discussions with staff, we examined NGL's compliance with the following nuclear site licence conditions (LCs), which are applicable provisions of the Energy Act 2013:

We judged that LC34 - Leakage and escape of radioactive materials was not applicable to the system under consideration for the purpose of this inspection.

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

Explanation of Judgement if Safety System Not Judged to be Adequate

From the system based inspection, we judge that the implementation of the arrangements for the diverse shutdown and hold down system meet the requirements of the safety case.

Key findings, inspectors' opinions and reasons for judgements made

System based inspection - Diverse shutdown and hold down.

Based on the areas sampled during this system based inspection, we judged that the licensee has implemented adequate arrangements to ensure that the diverse shutdown and hold down system is maintained and operated in accordance with the safety case. This was supported by observations made by ONR Inspectors during the plant walk down.

The inspection identified a number of areas of good practice such as the system engineer's knowledge of the system and the associated safety case claims and the quality of the instructions associated with the nitrogen injection system.

A minor non-compliance was noted in relation to the identification of the maintenance requirements for the C&I equipment associated with the Nitrogen system on the Plant Maintenance Schedule (PMS)

We noted areas for improvement with respect to minor inconsistencies in testing of similar components, recording of maintenance test results and signoff. Moreover, the licensee should consider whether greater testing of some C&I components could be done to better identify ageing mechanisms that are taking place and leading to failures of components and equipment. A regulatory Issue has been raised to track progress against the actions raised with the licensee.

Overall we judged that the arrangements in respect of the diverse shutdown and hold down system generally met relevant good practice and therefore we have given an intervention rating of Green in relation to compliance with LCs 10, 23, 24, 27 and 28.

Conclusion of Intervention

From the targeted sampling of documentation, discussions with the licensee staff and the plant walk down during this SBI; we consider that the diverse shutdown and hold down system met the requirements of the safety case.

There are no findings from this inspection that could significantly undermine nuclear safety. At present, no additional regulatory action is needed over and above the planned interventions at the Hinkley Point B Power Station.