Office for Nuclear Regulation

Hinkley Point B Reactor 3 graphite core inspection arrangements during its 2019 statutory outage

Executive summary

Purpose of Intervention

Hinkley Point B (HPB) Reactor 3 (R3) was shut down for a statutory outage in March 2019.  During this outage, EDF Energy Nuclear Generation Limited (NGL) has been carrying out a series of inspection activities on the graphite core. This work is required under License Condition (LC) 28 and includes visual inspection, dimensional measurements and materials sampling of the fuel and control rod channels.  EDF NGL have also been performing inspections in excess of those required under the LC28 obligations, which I have also sampled.

The objectives of this intervention were:

I judged the adequacy of NGL’s inspection based on the findings of the intervention, the quality of the data I observed and the knowledge and experience of the licensee’s staff. This intervention will inform the ONR decision on granting consent for the return to service of HPB R3 following its 2019 periodic shutdown.

Interventions Carried Out by ONR

This intervention was performed to determine that EDF NGL was compliant with its requirements under LC28 in respect of its graphite inspection work.  ONR inspectors performed the following activities:

This intervention report does not comment on the significance of the inspection findings, which will be addressed by a separate assessment of the outage findings once the inspection has been completed. That assessment will, however, take note of the findings of this intervention.

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

At the time of the visit, the licensee had completed just over 25% of the visual fuel channel inspections and bore measurements.  During the graphite core inspections, the first observed Keyway Root Crack (KWRC) at HPB R3 was observed and sentenced in line with NGL’s due process.

I consider that the licensee’s arrangements with regards to graphite core inspection during this outage are both suitable and adequate. In my opinion, the visual records and the data that I sampled were of adequate quality for NGL to form a judgement and sentence the cracks. At the time of my intervention, although there had been a 48 hour delay to the start of the graphite inspection, the schedule for the graphite core was on target and, at the time of my inspection, there was no reason to believe that the schedule would not be completed fully.

The licensee personnel that I met at station were knowledgeable and the training records that I sampled were up-to-date. From the training records that I sampled, I consider that the personnel involved in undertaking inspections and measurements have adequate training and experience to perform their various tasks. I judge that junior staff were receiving adequate support and mentoring from the more experienced staff.

NGL informed me of some issues with tilt-measurement equipment reliability.  NGL were able to provide adequate information and evidence to assure me that there would be no significant effect on the quantity or quality of the completed inspections.

Conclusion of Intervention

I conclude that the licensee is in a good position to complete its full scheduled programme of graphite inspection.

Based on my inspection, I judge that the licensee’s graphite core inspection arrangements are adequate. Therefore, I consider that NGL is complying with the requirement of LC28. I have allocated an ONR rating of ‘Green’ – Adequate.