Office for Nuclear Regulation

This website uses non-intrusive cookies to improve your user experience. You can visit our cookie privacy page for more information.

Structural Integrity Level 4 Meeting

Executive summary

Purpose of intervention

I attended the meeting to monitor and influence progress by NNB GenCo on the structural integrity of the Hinkley Point C (HPC) UK EPR™ Nuclear Steam Supply System (NSSS). I was supported at this meeting by an ONR structural integrity inspector in the team implementing the ONR HPC NSSS Construction and Commissioning Intervention Strategy.

Interventions Carried Out by ONR

This meeting's focus was the examination of NNB GenCo's compliance with two licence conditions: LC19 (Construction or installation of new plant) and LC14 (Safety documentation). Some of the intervention was relevant to LC17 (Management Systems).

NNB GenCo provided updates on:

I provided feedback to NNB GenCo on the progress update and requested supporting documents where judged necessary.

There was no representative at the meeting from the Assurance Department of NNB GenCo's Safety Directorate.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable

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

Key findings are as follows:

Inspection Strategy

ONR has previously requested that NNB GenCo reconsider its proposal not to use an independent agency to undertake repeat inspections. NNB GenCo intend to apply its Monitoring and Decision-making process (MODEM) to inform a decision on independent repeat inspections later in the year, currently scheduled for the end of Q2 2014.

In the interim NNB GenCo has requested feedback from ONR on the proposals contained in the optioneering summary document (HPC-NNBOSL-XX-000-REP-000037, 13 May 2014), relating to the repeat inspection strategy for High Integrity Component forgings and welds prior to the production of the MODEM paper.

On the inspection strategy for HIC forgings and welds, I judge that NNB GenCo has responded in a positive manner to ONR's request that NNB GenCo reconsider its proposal not to use an independent agency to undertake repeat inspections.

Tubesheet Fracture Toughness Testing

On tubesheet fracture toughness testing (FTT), NNB GenCo gave an update on the proposed test programme. Additional FTT activities have been identified by NNB GenCo as Forward Work Activities and linked to ONR recommendations (TRIM 2014/52316 refers). The Safety Case Implications Document (SCID) has now been updated and finalised to reflect ONR's previous comments and recommendations which closes Action 1791.

To complement the above, I asked NNB GenCo to deliver a presentation on the substantiation of the claims for the fracture toughness of tubesheet at the structural integrity Level 4 progress meeting currently scheduled for 24 June 2014.

I judge that NNB GenCo is addressing the structural integrity issues relating to tubesheet fracture toughness and the concomitant test programme in a satisfactory manner.

GDA Assessment Findings, Capability Statements and Technical Specifications

I judge that NNB GenCo has demonstrated significant progress in the production of resolution plans to address GDA assessment findings, and in the production of inspection capability statements and technical specifications for Nuclear Steam Supply System (NSSS) components.

Conclusion of Intervention

I judge that significant progress has been made by NNB GenCo on issues in the following structural integrity topic areas (i) repeat inspection strategy, (ii) inspection capability, and (iii) fracture toughness of thick section forgings.