Office for Nuclear Regulation

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Inspection of weld defect

Executive summary

Purpose of intervention

I undertook a reactive inspection to undertake further enquiries into the circumstances surrounding an incident reported to ONR by EDF NGL in accordance with arrangements made under licence condition 7.

Interventions Carried Out by ONR

Supported by an ONR Specialist Inspector, I undertook an inspection to gather further information following the identification (by EDF NGL) of a weld defect in an instrument penetration forming part of a boiler at Hartlepool, Reactor 1. During the inspection, I held discussions with EDF NGL staff, examined operational records and examined plant equipment.

Explanation of Judgement if Safety System Not Judged to be Adequate

No system based inspections were undertaken during this intervention.

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

We are content that EDF NGL’s initial response to the identification of this defect has been appropriate. Furthermore, we are satisfied the Licensee is applying its Operational Experience process to identify relevant lessons learnt.

We examined the licensee’s safety case and quality assurance records for the manufacture and installation of the repaired instrument penetration.  We concluded that the weld repair was subject to appropriate controls and oversight in accordance with relevant good practice. We judged that an IIS rating of 3 (adequate) is appropriate against Licence Condition 22 (Control of modifications and experiments on existing plant).

We identified a shortfall in the safety case documentation for the instrument penetration transition weld prior to identification of the defect. We judge that an IIS rating of 4 (below standard) is appropriate against licence condition 23, which requires the licensee to produce an adequate safety case to demonstrate the safety of its operations. The anomaly has since been rectified by EDF NGL.

This intervention was performed in line with ONR’s guidance requirements (as described in ONR’s technical inspection guides, which can be found at www.onr.org.uk/operational/tech_insp_guides/index.htm) in the areas inspected.

Conclusion of Intervention

ONR will review the adequacy of EDF’s internal investigation to confirm that appropriate learning is identified following identification of the defect. There are no findings from this inspection that could significantly undermine nuclear safety and no change is necessary to the planned interventions and inspections at Hartlepool as a result.