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Intervention on the adequacy of welding, non-destructive testing and surveillance (WN1)

  • Site: Hinkley Point C
  • IR number: 19-025
  • Date: October 2019
  • 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 and consist of a series of interventions 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.

Welding requires high levels of control to ensure quality requirements are met and hence ONR seeks to ensure the licensee has developed appropriate arrangements to ensure welded items are manufactured to the appropriate quality. Therefore, it was deemed proportionate to conduct a planned intervention to gain confidence that the licensee has adequate arrangements in place for compliance with LC 19, in relation to welding, non-destructive testing (NDT) and surveillance of components manufactured at Framatome St Marcel facility intended for the Hinkley Point C (HPC) project.

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:

Part 1 (Bristol) covering the following topics relating to welding and NDT:

  • Weld cladding operational experience (OPEX);
  • Welder training and qualification arrangements;
  • Root cause analysis process;
  • Welding consumable storage, control and issue;
  • Weld cladding NDT;
  • Surveillance frequencies.

Part 2 (St Marcel) covering the following topics relating to welding and NDT:

  • Management of surveillance (the licensee and Direction Industrielle); 
  • Consultation with the Independent Third Party Inspection Agency (ITPIA);
  • Welding consumable warehouse visit;
  • Observation of NDT ultrasonic testing (UT) cladding blocks;
  • Observation of weld cladding operation;
  • Reactor pressure vessel (RPV) lower head to transition ring weld;
  • Nuclear safety culture.

The aim of the intervention was to gain confidence that the licensee has adequate arrangements in place for compliance with LC 19, in relation to welding, NDT and surveillance of components manufactured at Framatome St Marcel facility intended for the HPC project.

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

The key findings are that:

  • The licensee and Direction Industrielle appeared to have an adequate process in place to perform appropriate levels of surveillance for weld cladding operations.
  • Framatome appeared to have tighter controls over welding consumable storage compared with previous interventions.
  • The licensee appeared to have an adequate level of control and oversight of welder training and qualification arrangements at Framatome St Marcel.
  • The licensee did not appear to have adequate control and oversight of Framatome’s root cause analysis process, in particular over the early decision making stage. An action has been placed on the licensee to demonstrate an adequate level of control and oversight which will be tracked via a Level 4 Regulatory Issue.
  • It is not clear if there are adequate toughness properties for high integrity components which have been subjected to interpass temperatures higher than that which has been qualified. An action has been placed on the licensee to provide a technical justification. This will be tracked via a Level 4 Regulatory Issue.
  • It appears that Framatome and the licensee are not responding promptly to concerns raised by ITPIA. This will be monitored via the ONR Nuclear Steam Supply System (NSSS) work-stream.
  • The NDT requirements and frequencies for weld cladding operations appear to be adequately specified.

Conclusion of Intervention

The licensee appeared to have adequate arrangements in place for surveillance, consumable storage, welder training and non-destructive testing of weld cladding within its supply chain at the Framatome St Marcel facility.

An action has been placed on the licensee to address the findings regarding root cause analysis and interpass temperature. 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.