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LC19 Oversight of site welding: Class 1/2 systems (WN3)

  • Site: Hinkley Point C
  • IR number: 20-021
  • Date: October 2020
  • LC numbers: 19

Executive summary

Purpose of Intervention

Licence condition (LC) compliance interventions are an essential element of the Office for Nuclear Regulation’s (ONR's) overall intervention strategy which consists of a series of interventions. Each intervention is intended to establish that the licensee has adequate arrangements in place for compliance with a licence condition. Inter alia, LC 19 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.'

The aim of the intervention was to gain confidence that the licensee had adequate arrangements in place for compliance with LC 19, in relation to the welding of class 1/2 components at Hinkley Point C (HPC). While this was the main focus of the intervention, given observations on possible exposure to welding fume from previous inspections, I also made checks on those aspects of the welding.

Interventions carried out by ONR

The intervention comprised a launch meeting to agree on the approach, a site visit to gather evidence on the effectiveness of the licensee's arrangements for site welding and a close out meeting. During the intervention, ONR asked for and the licensee supplied documents which ONR checked against its expectations for site welding.

Key findings, inspector’s opinions and reasons for judgements made

My findings on the main aim of the intervention, to gain confidence that the licensee had adequate arrangements in place for compliance with LC 19, in relation to the welding of class 1/2 components at HPC are:

  • The licensee has met the expectation that it has an approved welding procedure specification (WPS) supported by a welding procedure qualification record (WPQR).
  • The licensee demonstrated effective controls on the competence and qualification of welders.
  • The contractor, Darchem's, arrangements for weld consumable storage aligned with the licensee's requirements and did not give cause for concern.
  • The licensee's documentation on the control of non-destructive testing (NDT) that I sampled was fit for purpose.
  • The licensee's demonstrated surveillance of welding and NDT which was consistent with its requirements and did not give cause for concern.
  • The licensee's arrangements for the management of the contractor's activities aligned with its requirements and appeared to be effective.
  • The licensee's documentation linked the requirements of the extant safety case to the welding operations.
  • The licensee's document setting out the strategy of the installation surveillance team (IST) was out of date.

My conventional safety findings are:

  • The weld process that was under way, tungsten inert gas (TIG) welding of stainless steel, can produce significant quantities of ozone. The risks of exposure to ozone were addressed by controls in the working area; however, there was no ozone monitoring in place and there was a proposal to provide a dispensation to allow welding without local exhaust ventilation. I will liaise with conventional safety inspectors to inform them of the situation so that they can take it forwards within their ongoing engagements.
  • The Control of Substances Hazardous to Health (COSHH) assessment for the welding was produced on 28 Oct 2020 and issued after my visit.
  • The licensee's precautions against COVID-19 seemed thorough and reasonable.

Conclusion of intervention

Overall, the conclusion of the intervention is that the licensee demonstrated adequate arrangements for compliance with LC 19, in relation to the welding of class 1/2 components at Hinkley Point C, with only minor areas for improvement identified. An inspection rating of Green is appropriate for LC 19 (Construction or installation of new plant).