Office for Nuclear Regulation

System Based Inspection SBI-02 - Data Processing and Auto Control Systems

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a system based inspection (SBI) at EDF Energy Nuclear Generation Limited’s (EDF NGL’s) Hunterston B power station in line with the planned inspection programme contained in the Hunterston B integrated intervention strategy (IIS) for 2018/2019.

Interventions carried out by ONR

The inspection was performed on the data processing system (DPS) and automatic control system (ACS) by two control and instrumentation (C&I) specialist inspectors and a human factors specialist inspector. For training purposes a nuclear graduate observed the inspection. 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 inspection was based on sampling the implementation of the licensee’s arrangements at Hunterston B against the LCs. The objective of the inspection was to determine whether the licensee’s arrangements were adequately implemented and in accordance with the systems’ safety case requirements

In conjunction with the inspection against the LCs mentioned above, an inspection of the physical, procedural and technical security controls of the DPS and ACS was undertaken by a specialist security inspector from the ONR Civil Nuclear Security division. The details of this inspection are captured in a separate intervention record (ONR-CNS-IR-18-012).

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

In addition to the inspection activities described above we also assessed progress against actions associated with Regulatory Issues related to the DPS raised in previous interventions. In particular, progress against completion of Regulatory Issue 5809 - “Use of laptops on site - NGL - OFD - Intervention Record - 17-126 - Hunterston ~ R4 C&I Statutory Outage” and Regulatory Issue 582 - “Medium Boiler Tube Failure (BTF) - Claim for Operator Action within 15 minutes of alarm being raised” were assessed.

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 DPS and ACS meet the requirements of the safety case.

Key findings, inspectors’ opinions and reasons for judgements made

Based on the areas sampled during this SBI, ONR judged that the licensee has implemented adequate arrangements to ensure that the DPS and ACS are maintained and operated in accordance with the safety case. This was supported by observations made by ONR inspectors during the plant walk down and discussions with the licensee’s staff.

The inspection identified a number of areas of good practice where EDF NGL were able to clearly articulate and demonstrate a comprehensive understanding and knowledge of their arrangements. In particular, the format of the compliance status logs which are utilised by operators to record the results of LCO surveillance activities, specifically, the inclusion of the limit / action level, compliance source. The proactive use of the simulator for verifying new or amended operating instructions and new operator interface equipment before being installed on plant. In addition, we considered the maintenance and test instructions for the systems sampled adequately specified tolerances and pass/fail criteria, had been suitably completed with clear sign-off by the system engineer where appropriate.

We noted areas for improvement with respect to the housekeeping associated with the DPS, and the capture and analysis of failure data for the DPS on the FLAIR system. EDF NGL should consider the resilience of the Hunterston B Nuclear Safety Group, in particular when key staff are unavailable. In addition, EDF NGL should ensure that maintenance and test instructions fully test the safety functions of the systems and that living safety documents unambiguously identify the safety functions required of those systems. A regulatory issue has been raised to track progress against the actions raised with the licensee. ONR will monitor progress for the resolution of this issue through normal regulatory business.

Overall we judged that the arrangements in respect of the DPS and ACS 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.

Following a review of evidence associated with the implementation of the action plan associated with regulatory issue 5809 we found that EDF NGL have made sufficient progress to close this issue. This regulatory issue was associated with a formal enforcement action [Ref. letter 2017/402525] in regard use of unauthorised laptops on site. ONR consider this action has been satisfactorily closed. In addition, through observation of a control room simulator session which demonstrated how boiler tube leaks are detected, diagnosed and managed by operators with support from engineered safety systems, we found that EDF NGL have made sufficient progress to close Regulatory Issue 582.

Conclusion of intervention

From the targeted sampling of documentation, discussions with the licensee staff and the plant walk down during the SBI; we consider that the DPS and ACS met the requirements of the safety case.

There were 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 Hunterston B Power Station.

We recommend that Regulatory Issues 582 and 5809 are closed.