Office for Nuclear Regulation

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Hinkley Point C - Severe accident analysis safety case

Executive summary

Purpose of Intervention

The purpose of this intervention was to gain confidence in the adequacy of AREVA’s arrangements, a key supporting organisation to NNB GenCo, covering the development and control, validation and verification, and utilisation of codes and methods in support of severe accident analysis for the Hinkley Point C (HPC) safety case.

Interventions Carried Out by ONR

Office for Nuclear Regulation (ONR) severe accident analysis and reactor chemistry specialist inspectors supported by an ONR technical support contractor visited AREVA’s offices in Germany to form a judgement on the arrangements associated with severe accident analysis codes and methods. This ONR intervention was carried out in collaboration with a representative of NNB GenCo’s internal regulator (Independent Technical Assessment).

The relevant ONR Safety Assessment Principles, FA.15, 16, 25 (applicable to severe accident analysis), and AV.1-6 (relevant to code validation and sensitivity studies), were used to inform ONR’s judgement during this intervention.

During this intervention, the main evidence was provided by AREVA, concerning its processes for managing codes and methods. Future interventions on this topic will consider NNB GenCo’s and the Responsible Designer’s arrangements in more detail.

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

Based on the evidence gathered, a number of good practices in the codes and methods area were observed demonstrating that adequate arrangements are in place, and competent personnel are available:

However, a number of observations were noted for further consideration by NNB GenCo during the development of its review and acceptance arrangements.

Conclusion of Intervention

Based on the objective and the information presented, I conclude that an intervention rating of GREEN is the appropriate rating for this intervention.

The following recommendation resulted from this intervention, to be taken forward as part of routine interactions in the severe accident topic stream and future planned interventions:

NNB GenCo to consider rationalisation of the severe accident codes, methods and tools used to develop HPC site specific analyses to be presented within the HPC pre-commissioning safety report.