Office for Nuclear Regulation

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Heysham 1 - Oxygen injection readiness inspection

Executive summary

Purpose of Intervention

Heysham 1 power station, Reactor 2, has been suffering from an increase in fuel pin failures, due to an increase in carbon deposition on the fuel pin surface. EDF Energy Nuclear Generation Limited (NGL) is proposing a modification which will inject oxygen (O2) enriched carbon dioxide (CO2) into the gas circulator arrangement which in turn will provide oxygen to the fuel channels. A small increase in oxygen concentration has been shown to be effective at clearing carbon deposition from fuel pin cladding surfaces at Windscale (prototype AGR) and boiler components at Heysham 2 and Torness.

This intervention record documents a readiness inspection to inform the permissioning activities related to oxygen injection at Heysham 1, Reactor 2. The main focus of the intervention was to ensure that EDF Energy NGL is in a position to commence the oxygen injection. The intervention focussed on recommendations raised as part of the technical assessments and information that was not available at the time of assessment.

Interventions Carried Out by ONR

This intervention focussed on EDF Energy NGL’s readiness to commence the project to inject oxygen enriched CO­2 into Heysham 1 Reactor 2 and the closure of the recommendations and other outputs of the specialist assessments. The readiness inspection also focussed on the equipment and procedures associated with oxygen injection. This included the following:

Explanation of Judgement if Safety System Not Judged to be Adequate

Not Applicable

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

The overall conclusion reached by the team of inspectors was that the EDF Energy NLG team were knowledgeable about the O2 injection project. While EDF Energy NGL is not currently in the position to begin oxygen injection, they are carrying out all of the activities that are expected as part of a Licence Condition 22 modification and that there were no significant shortfalls identified.

Due to the stage of the project, we were unable to witness the site acceptance testing (SAT) and support was sought from the Heysham 1 quality assurance engineer that adequate control and instrumentation commissioning activities have taken place.

Given the novelty of this activity the specialist human factors inspector considers it a sensible precautionary measure to observe either the SAT or commissioning activities to provide additional confidence in the management and conduct of this activity. This will be carried out in the future.

Conclusion of Intervention

The conclusions made from the intervention are that EDF Energy NGL is progressing well towards being ready to commence Oxygen injection at Heysham 1 Reactor 2. Whilst there is still some work to do, I do not foresee any issues with all activities being completed in time for commencement of the project.

A low level Regulatory issue was raised to bring about and track improvements in the Independent Nuclear Assurance (INA) concurrence hold point release arrangements.
There are a number of areas which require follow up by the specialist inspectors; these will be followed up via normal regulatory interactions.

The inspection outcome was rated as GREEN with no significant issues raised.