Office for Nuclear Regulation

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Hunterston B - Planned Intervention

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake Licence Condition (LC) compliance inspections at EDF Nuclear Generation Limited's (NGL) Hunterston B (HNB) power station in line with the planned inspection programme contained in the Hunterston B Intervention Plan. Two further inspections were carried out in accordance with a fleet intervention and a readiness inspection. The compliance inspections and information exchange meetings were carried out by the Nominated Site Inspector, a specialist mechanical engineering inspector and a Structural Integrity Nuclear Associate.

Interventions Carried Out by ONR

We undertook a safety case informed System based Inspection [SBI-22] of the CO2 Storage and Distribution plant. The inspection sampled compliance against several licence conditions. These were LC10 (training), LC23 (operating rules), LC24 (operating instructions), LC27 (safety mechanisms, devices and circuits), LC28 (examination, maintenance, inspection and testing) and LC 34 (leakage and escape of radioactive material and radioactive waste). Following review of the system, it was judged that the CO2 storage and distribution plant was not applicable for inspection against the requirements of LC34 because the system only contained 'clean', non-contaminated gas, which is upstream of the reactor circuit.

The objective of the inspection was to determine whether the licensee's arrangements for plant operational limits, plant maintenance schedules, staff training requirements and inspection plans were adequate in accordance with safety case requirements.

The nominated site inspector undertook further planned and reactive information exchange meetings with Independent Nuclear Assurance, nuclear safety group to review outstanding regulatory issues, the Reactor 4 outage Manager and Safety Representatives. The nominated site inspector also attended a daily operational focus meeting.

Explanation of Judgement if Safety System Not Judged to be Adequate

Inspectors judged that the arrangements and their implementation, associated with CO2 storage and distribution plant, met the requirements of the safety case and are adequate.

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

From an LC10 perspective, staff training records and profiles were judged to be in accordance with the post training profile requirements. Therefore, we judged the LC10 element of this inspection to be adequate, warranting an associated Integrated Intervention Strategy (IIS) rating of 3 - Adequate.

From an LC23 and LC24 perspective, based on the evidence sampled during this inspection, the implementation of the technical specifications, commentaries, and schedules were judged to be consistent with the claims presented within the Hunterston B visible safety case for the CO2 storage and distribution plant. The licensee demonstrated adequate knowledge and understanding in the areas of the safety case and how they relate to the operating rules and instructions in place for the CO2 storage and distribution plant. We judged the LC23 and LC24 element of this inspection to be adequate, warranting an IIS rating of 3 - Adequate.

From an LC27 perspective, the duty holder was able to demonstrate an adequate level of compliance against LC 27 through demonstrable compliance with LC23, 24 and 28. We consider that the LC27 element of this inspection to be adequate, warranting an associated IIS rating of 3.

From an LC28 perspective, the licensee demonstrated that there are adequate processes, procedures and records in place for the examination, inspection, maintenance and testing of safety mechanisms, devices and circuits. Several samples were taken and suitable records were produced for each sample. We judged the LC28 compliance element of this inspection to be adequate, warranting an associated IIS rating of 3 - Adequate.

The nominated site inspector judged that Station's overall planning arrangements for the forthcoming Reactor 4 outage are advanced. Protocols for ONR - NGL engagement and communication during the outage were agreed and finalised. The nominated site inspector reviewed the weekly INA report and discussed a recent conventional safety incident. The site inspector advised he was content with NGL's investigation process awaiting completion of a Significant Adverse Condition Investigation in accordance with its arrangements under LC 7.

The licence conditions were inspected against ONR's published guidance requirements (as described in our technical inspection guides).

Conclusion of Intervention

From the evidence sampled, witnessed and collected during the inspection against LCs 10, 23, 24, 27 and 28, the structural integrity and mechanical engineering aspects for this system based inspection meet the requirements of the safety case and its implementation is considered adequate.

A number of observations were made as a result of this system based inspection, however, given that they are of minor nuclear safety significance, we are content that they will be addressed by the licensee in accordance with their own arrangements. There are no findings from this inspection that could significantly undermine nuclear safety.