Office for Nuclear Regulation

Hinkley Point B Reactor 3 - Structural integrity outage inspection

Executive summary

Purpose of Intervention

This is a record of a planned intervention by the Office for Nuclear Regulation (ONR) at Hinkley Point B (HPB) Power Station during the 2019 periodic shutdown of Reactor 3.  The purpose was to inspect work by the Licensee, EDF Energy Nuclear Generation Limited, to comply with Licence Condition 28 (LC28), examination, inspection, maintenance and testing (EIMT).

Interventions Carried Out by ONR

I carried out a Structural Integrity inspection of Hinkley Point B (HPB) during the 2019 statutory outage of Reactor 3.  As ONR specialist inspector in structural integrity I met with Licensee staff and their contractors to examine compliance with LC28, sampled outage-related documentation and performed a walk-down of the plant. I concentrated on aspects of structural integrity that I judged important to nuclear safety.  I have taken cognisance of guidance provided by ONR in Safety Assessment Principles (SAPs) and Technical Assessment Guides (TAGs) relevant to structural integrity, in making my judgement. These are available on the ONR website.

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

The Vessel Entry Campaign has progressed smoothly with no significant findings and only one repair made.  I am content that the intent of the campaign, from a Structural Integrity viewpoint, has been met. 

Following the failure of a Highest Reliability weld at  Hunterston B, I sampled the work underway to ensure that components pertinent to safety at HPB are being managed suitably.  This position was, generally, positive, however, the sample of components for speculative inspection was limited to 10% of welds that were not in the highest reliability category.  It was not clear why the sample size was adequate or how the choice of locations were made.  I do not consider this to be a matter for restart of the reactor and will follow up through routine interactions ongoing in this area.

The corrosion management plan at HPB is being progressed and, during the walkdown, I was able to see signs of significant investment.  It is not clear, however, that there is sufficient control over management of the programme.  Specifically, the corrosion coordinator could not demonstrate that there was a proper set of timescales in place for delivery of corrosion mitigations, nor could a direct link to the requirements of the safety case could be demonstrated.  I do not consider this to be a matter for restart of the station.  This notwithstanding, I consider that a follow-up visit to site will be necessary to ensure that there is a robust position with regards to corrosion management at HPB.  This will be progressed separately from the outage.

 Inspection of the auxiliary steam system, following a steam release incident at Heysham 1 power station, appears to be being managed appropriately.  I reinforced that nuclear safety and conventional safety are both within ONR’s remit on nuclear licenced sites. 

The management of the seawater system at HPB appears to be of a good quality with the system engineer being particularly engaged and focussed on the system.  The performance in this area was good.

I performed a walk-down of selected areas of the plant.  I did not find any areas of specific safety concern that would prevent return to service, although housekeeping and corrosion management in certain areas could be improved.

I observed that there are components in the HPB Maintenance Schedule that refer out to the inspections required for Pressure Systems Safety Regulations 2000, and as such do not link directly to the Safety Case.  For the components sampled at HPB, the evidence I observed gave me confidence that the position is satisfactory to support return to service following the outage.

I sampled aspects of the management of Flow Assisted Corrosion (FAC) at HPB.  This appears to be in a good position, especially of note was the management of steam traps which compares positively with the rest of the AGR fleet.

I observed an Outage Assessment Panel (OAP), which is the main body for the sanctioning of Structural Integrity decisions for the outage.  The attendance at the meeting was in line with my expectations, and the individuals in attendance participated actively and provided challenge where appropriate.

I discussed the steam and feed steam with the system engineer.  The System Engineer demonstrated a good knowledge of the system, the operation of the plant and the condition of the hangers.  He was aware of observations of damaged hangers that I made during the plant walkdown, and was able to give me adequate assurance that remediation was underway.

I did not identify any return to service issues and assigned an indicative Green rating at the time of the intervention. 

Conclusion of Intervention

Based on evidence sampled, I conclude the Licensee has performed adequate examination, inspection, measurement and testing of structures systems and components (EIMT) to satisfy LC28. Based on ONR guidance, I award an inspection rating of Green. EIMT work planned by the Licensee during the periodic shutdown was not complete by the end of my inspection. I will monitor further progress and provide my judgement regarding return to service in my assessment report and use this as the vehicle to capture findings from the inspection. In particular I will consider the adequacy of corrosion management, and developments to address emergent work around the AGR fleet.