Office for Nuclear Regulation

Adequacy of safety case decision-making processes (SCD26)

Executive summary

Purpose of Intervention

In accordance with the Office for Nuclear Regulation’s (ONR’s) Hinkley Point C (HPC) Construction intervention plan, ONR performs a series of planned compliance inspections of identified licence conditions (LC), to ensure that NNB Generation Company (HPC) Limited (NNB GenCo), is proportionately and adequately developing and implementing its LC arrangements commensurate to the current stage of the HPC project.

The intervention was an inspection on NNB GenCo’s safety case decision-making process related to HPC.

The purpose of the intervention was to:

Interventions Carried Out by ONR

LC17 requires licensees to establish and implement managements systems which give due priority to safety.

I carried out a one day LC17 intervention at NNB GenCo’s Bridgewater House Office in Bristol. This consisted of a mixture of review of documentation, discussion with relevant NNB GenCo staff and interviews with relevant senior managers.

The following guidance was used in this intervention:

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

Regarding the overall decision-making process I did not identify any significant shortfalls during this intervention against expectations in relevant guidance, and note that NNB GenCo already recognises the need to make improvements to ensure the process remains adequate for the next phases of the HPC project. However, it is noted that:

NNB GenCo senior managers generally considered the decision-making process to be effective and working, although recognised it needs to adapt for the changing phase of the HPC project, and that it involved appropriate people. It was emphasised that the decision-making committees do not overrule the safety case / modifications process, which ultimately has to make an adequate safety justification; the committees were seen as an interim part of the decision-making justification, with the safety case ultimately providing the final justification.

Whereas I accept the safety case provides the final justification, by that stage further options for necessary improvement, that may have been reasonably practicable if identified earlier, could have been foreclosed. It is therefore important that NNB GenCo ensures appropriate consideration of the as low as reasonably practicable duty at all stages in the decision-making, and that reasons for a decision are clearly recorded in meeting notes or minutes.

The intervention provided ONR with an improved understanding of the decision-making committees and their interactions.

The application of the design non-conformance report (NCR) process and its relationship to the site and manufacture NCR processes was not clear. As this was not a central part of this intervention, and requires further exploration before a judgement on the adequacy of the processes can be made, I recommend that a separate NCR intervention is considered.

Further consideration is required of the unit 2 replication strategy and the adequacy of its implementation in safety case decision-making. This will be taken forward through the regular NNB GenCo / ONR level 4 meetings.

Resolution of a number of nuclear vent and drain system sump issues, including application of the decision-making process, appears to have been non-optimum. However, as this was not a typical example of application of the decision-making process, and noting the low safety significance of the sumps, I did not consider the shortfalls relating to that particular decision-making to be generic or significant. However, I consider there will be significant benefit in NNB GenCo carrying out some form of learning review relating to decision-making around identification and resolution of all issues associated with the sumps, including application of relevant processes.. Given this is already planned by NNB GenCo it will be followed-up through routine level 4 meetings between NNB GenCo and ONR.

A number of minor areas for potential improvement were identified:

A level 4 Regulatory Issue has been raised to take these areas forward with NNB GenCo.

Conclusion of Intervention

Despite the minor shortfalls, I consider NNB GenCo’s LC17 arrangements and their implementation are adequate as regards decision-making within scope of NNB GenCo’s Technical Directorate. However, gathering further evidence will be considered through observation of relevant decision-making committees.

On the basis of the evidence gathered during this intervention, I judge that an inspection rating of GREEN (No formal action) is appropriate. This is because I found no significant shortfalls.