Office for Nuclear Regulation

Emergency Generation SBI, IIS Compliance Inspection at Hunterston 'B'

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake Licence Condition (LC) compliance inspections at EDF Energy Nuclear Generation Limited’s (NGL’s) Hunterston B power station in line with the planned inspection programme contained in the Hunterston B Integrated Intervention Strategy (IIS).

Interventions Carried Out by ONR

We undertook a safety case informed System Based Inspection (SBI) of the Emergency Power Generation systems at Hunterston B Power Station. The inspection sampled compliance against several licence conditions. These were LC10 (training), LC23 (operating rules), LC24 (operating instructions), LC27 (safety mechanisms, devices and circuits) and LC28 (examination, maintenance, inspection and testing).

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 the system’s safety case requirements.

We also undertook a Licence Condition 22 compliance inspection, during which we examined the arrangements for, and implementation of, modifications to existing plant.

Explanation of Judgement if Safety System Not Judged to be Adequate

We were satisfied that the Hunterston B arrangements and their implementation associated with Emergency Power Generation meet the requirements of the safety case and are adequate.

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

From an LC10 perspective, the station demonstrated adequate arrangements for training. However, we advised the station of potential improvements associated with system specific training. Work is already underway to address this gap. On this basis we allocated an IIS rating of 3 - Adequate

From an LC23, 24 and 27 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 Station Safety Report (SSR) for the Emergency Power Generation systems. 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 Emergency Power Generation Systems. We therefore allocated IIS ratings of 3 – Adequate for LC23, LC24 and LC27 elements of the inspection.

From an LC28 perspective, the licensee demonstrated that adequate processes, procedures and records are in place for the examination, inspection, maintenance and testing of nuclear safety significant plant. Whilst suitable records were produced for each of the system inspected safety significant areas sampled, these are not currently scanned and attached to the digital maintenance records. This has been raised as an Area for Improvement by NGL’s internal regulator, Independent Nuclear Assurance (INA) and will be monitored through the station’s own arrangements. This is a repeat observation from previous system inspections, and we were satisfied the licensee has an appropriate programme by which to address this backlog. We allocated an IIS rating of 3 – Adequate for LC28 arrangements.

A number of observations were made as a result of this system based inspection. These are of minor nuclear safety significance, which have been raised by INA and are to be addressed through the station’s own arrangements. I will monitor progress through my normal regulatory interactions with the Station

Based on samples of LC22 plant modifications examined, we were satisfied the licensee is demonstrably compliant with arrangements for conception, classification, safety assessment, verification, implementation and closure of modifications to plant. We further sampled the implementation of a modification undertaken by a term contract partner; we were satisfied the work was undertaken with appropriate control and oversight by the station and in accordance with the company arrangements.

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

From the evidence sampled, witnessed and collected during the inspection of the Emergency Power Generation against LCs 10, 23, 24, 27 and 28, we concluded that the operation and maintenance of the system meet the requirements of the safety case, and its implementation is considered adequate. We were satisfied that the minor shortfalls identified during this inspection should be addressed by the licensee in accordance with their own arrangements, and that there are no findings from this inspection that could significantly undermine nuclear safety.

We concluded that the station is demonstrably compliant with its arrangements made under licence Condition 22 for control of modifications to plant.