Office for Nuclear Regulation

LC28 Plant Inspection, corrosion focused

Executive summary

Purpose of Intervention

This report records the findings of an inspection at Heysham 2 Power Station (HYB) that took place on 29 & 30 September 2020. Due to ongoing Covid-19 restrictions, it was decided that it would be appropriate and effective to conduct the inspection remotely via Skype. The inspection is a follow up to a plant material condition inspection that took place in January 2020. The January inspection resulted in a number of findings relating to team structure, oversight, leadership and the maintenance associated with the CO2 system; a regulatory issue was created to monitor progress. This inspection forms part of ONR’s oversight for this issue. 

Interventions Carried Out by ONR

This inspection focused upon improvements made by HYB since ONR’s inspection in January 2020, and also collected evidence that may be used to demonstrate closure of actions associated with the regulatory issue. The inspection covered; corrosion management team structure and process to prioritise defect remediation, transition to “normal business” in relation to corrosion and a review of CO2 system Examination, Inspection, Maintenance & Testing (EMIT).

To inform my sampling choices and provide a greater understanding of progress, prior to the inspection HYB provided an excerpt from HYB’s corrosion defect tracker, progress information related to the corrosion program (including key performance indicators (KPIs)) and updated maintenance schedule entries for the CO2 system. I was also provided with EDF company documents; company technical standard for environmental corrosion management, BEG/SPEC/ENG/CTS/031 and a branch instruction for corrosion assessment and remediation, E/PROC/ENG/BI/047.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable – not a System Based Inspection.

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

I am content that HYB has implemented improvements to its corrosion team structure since ONR’s inspection in January 2020. The team were knowledgeable, engaged and displayed a sound understanding of the corrosion mechanisms relevant to the plant at HYB, along with demonstrating an awareness of relevant EDF guidance documents. I consider that HYB has provided adequate responses and evidence to consider action 1 of the associated regulatory issue closed.

From my sample of the corrosion management process at HYB, I am content that improvements have been implemented since ONR’s last inspection in January 2020. The defect tracker is comprehensive and contains information to substantiate prioritisation for the remediation of defects.  Whilst I do not consider the following to be a significant shortfall, I have encouraged HYB to further enhance their defect tracker by quantifying the degree of corrosion identified and providing clearer links back to EDF guidance, in particular Branch Instruction 47. I am supportive of the recent CTO CTS031 waypoint audit, along with its findings. I consider that HYB has provided adequate responses and evidence to consider actions 2 & 3 of the associated regulatory issue closed.

I have sampled a draft system close out report for the Unit, Station & Generator Transformers and I consider that it contains an adequate level of detail and evidence to support judgements made with regards to prioritisation of future remediation. The corrosion team informed me that they intend to complete close out reports for all systems by March 2021. They also intend to demonstrate CTS031 compliance during 2021. I consider that the ambitions of the corrosion team are possible, however they will need ongoing support and focus from the station leadership team if they are to be successful.

Station-wide system engineer SQEP demonstration will be addressed via routine engagement with the ONR nominated site inspector. I am satisfied that the current CO2 system engineer demonstrated a sound knowledge of his system and the safety claims made against it. I am satisfied that for the CO2 system, HYB has embedded inspection and maintenance routines to inspect vessels, pipework and supports for LC28 and PSSR compliance demonstration. I was encouraged to see that the distribution pipework had been divided into clearly identified inspection zones, enabling visibility of which areas have been inspected and when. I also regard it as good practice that HYB has completely removed insulation from the CO2 distribution pipework to facilitate inspection; this will also mean that any future risk based inspection strategy can be informed by a sound benchmark of plant condition.

Conclusion of Intervention

The overall conclusion of this corrosion focussed LC28 inspection at HYB is that a GREEN rating is appropriate. As HYB has also been able to provide evidence to close all actions associated with the regulatory issue created following the January 2020 inspection, I recommend that it is closed.

I also recommend that ONR continue to monitor progress made by the corrosion management team at HYB, this may be via routine inspection activities during outages and system based inspections, or via future plant material condition thematic inspections.