Office for Nuclear Regulation

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Hunterston B - SBI05 - Reactor Circulating Water System

Executive summary

Purpose of Intervention

The purpose of this intervention was to conduct a system based inspection of EDF Energy Nuclear Generation Ltd’s (NGL) Hunterston B Power Station in relation to the Reactor Circulating Water System and Standby Cooling System. This was undertaken as part of a series of planned interventions that are listed in the Hunterston B Integrated Intervention Strategy (IIS) 2016/2017. The inspection was undertaken by two ONR Specialist Inspectors (Structural Integrity).

Interventions Carried Out by ONR

We performed a safety case informed, system based inspection of the Reactor Circulating Water System and Standby Cooling System. Through examination of these systems compliance inspections were performed against Licence Conditions (LC): LC10 (training), LC23 (operating rules), LC24 (operating instructions), LC27 (safety mechanisms, devices and circuits), LC28 (examination, inspection, maintenance and testing) and LC34 (leakage and escape of radioactive material and radioactive waste). The inspections were based on sampling the implementation of the arrangements in place at the station against each licence condition. The objective of the inspection was to determine whether the Licensee’s arrangements for plant operational limits, plant maintenance schedules, staff training requirements and third party inspection plans were in accordance with the system’s safety case requirements.

Explanation of Judgement if Safety System Not Judged to be Adequate

From this inspection, we judge that overall the safety provisions applicable to the Reactor Circulating Water System and Standby Cooling System inspected meet the requirements of the safety case and are adequate.

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

A system based inspection of the Reactor Circulating Water System and Standby Cooling System was carried out to judge the adequacy of the implementation of the station arrangements in place to ensure that relevant equipment can perform its requisite safety function. In deciding whether these safety systems have been adequately implemented, I inspected compliance with the licence conditions detailed above. LC34 relating to leakage/escape of radioactive material and waste was deemed to be not applicable to the systems inspected and hence excluded from the scope of the inspection.

During the course of this system based inspection it was found that Hunterston B Power Station has arrangements to ensure that the Reactor Circulating Water System and Standby Cooling System are maintained and, as necessary, operated in accordance with the safety case. The arrangements were deemed to be implemented in an adequate manner, on the basis of those areas sampled during the inspection. The inspection identified potential areas for minor improvement, however none gave rise to significant concern. Due to the limited significance of the observations I am content that HNB address these through their own arrangements. ONR has raised a regulatory issue to monitor outcome of the HNB Equipment Reliability Review for resolutions of observations made during this inspection with respect to the scope and periodicity of inspections.

In summary, the outcome from the system based inspection of the Reactor Circulating Water System and Standby Cooling System is that the arrangements and their implementation are deemed to be adequate, and therefore we have given an IIS rating of GREEN in respect of LCs 10, 23, 24, 27 and 28.

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

Conclusion of Intervention

After considering all the evidence examined during the inspection undertaken against LCs 10, 23, 24, 27 and 28, it was considered that the Reactor Circulating Water System and Standby Cooling System inspected met the requirements of the safety case.

There are no findings from this intervention that could significantly undermine nuclear safety.