Office for Nuclear Regulation

Hinkley Point C - Oversight of site welding - Containment liner (WN2)

Executive summary

Purpose of Intervention

License Condition (LC) compliance inspections are an essential element of the Office for Nuclear Regulation’s (ONR’s) overall intervention strategy and consist of a series of inspections which are each intended to establish whether NNB Generation Company (HPC) Ltd (hereafter known as ‘the licensee’) has adequate arrangements in place for compliance with a specific LC.

This intervention is informed by regulatory intelligence on the Flamanville 3 (FA3) & Olkiluoto 3 (OL3) containment liners where issues were encountered. Therefore, it was deemed proportionate to conduct a planned intervention on the implementation of licensee arrangements linked to LC 19 for welding of the HPC containment liner.

Interventions Carried Out by ONR

LC19 requires that “Where the licensee proposes to construct or install any new plant which may affect safety the licensee shall make and implement adequate arrangements to control the construction or installation”.

ONR carried out the following LC19 : Construction or installation of new plant inspection:

A one day inspection at HPC covering the following topics relating to welding:

The aim of the intervention was to gain confidence that the licensee had adequate arrangements in place for compliance with Licence Condition (LC) 19, in relation to welding of the Hinkley Point C (HPC) containment liner.

Explanation of Judgement if Safety System Not Judged to be Adequate

N/A as this was not a safety systems inspection.

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

Conclusion of Intervention

The licensee appeared to be taking into consideration the operating experience from Flamanville 3 and ensuring appropriate mitigation measures are put in place for welding the HPC containment liner. The licensee also appeared to have adequate arrangements in place for welder training, surveillance and non-destructive testing of welds on the HPC inner containment liner.

However, the finding in relation to consumable control requires justification. An action has been placed on the licensee to justify and resolve the finding in a timely manner. A Level 4 regulatory issue has been raised to capture the action.

An inspection rating of GREEN is appropriate at this stage for LC19 (Construction or installation of new plant) as only minor shortfalls were identified. The aspects relating to COSHH requirements will be considered as necessary by the ONR Conventional Health & Safety team.