Office for Nuclear Regulation

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Hinkley Point C planned inspection

Executive summary

Purpose of intervention

To conduct a planned inspection of compliance with the nuclear site licence in relation to the design, testing and production of concrete that will be used in the construction of nuclear safety related civil engineering structures.

Interventions Carried Out by ONR

Inspection of NNB GenCo's implementation of arrangements for compliance with Licence Condition 14: Safety documentation. The inspection was focussed on the arrangements for the design and specification of concrete mixes for the main civil works contract.

Inspection of NNB GenCo's implementation of arrangements for compliance with Licence Compliance 19: Construction or installation of new plant. The inspection was focussed on the arrangements for production and compliance testing of concrete for the main civil works contract.

Information gathering inspection in relation to:

The intervention was attended by a civil engineering specialist inspector supported by a technical support contractor specialising in concrete materials.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable, as this was not a system based inspection.

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

Licence Condition 14

I found that adequate arrangements are in place for the design and specification of concrete mixes for the main civil works contract. My judgement is based on sampling the designs and laboratory test records for concrete Mix 6S which were found to have been very thorough and met the requirements of relevant good practice. On the basis of my findings I have allocated a rating of Green to this inspection.

Licence Condition 19

I found that adequate arrangements are in place to produce concrete to the required quality for nuclear safety related construction for use in relation to the main civil works. My judgement is based on my inspection of Batching Plant 1 which found that, based on the areas sampled, that the plant has been designed and is being operated in accordance with relevant good practice and is staffed by suitably qualified and experienced personnel.

I found that adequate arrangements are in place for compliance testing of concrete to the required quality for nuclear safety related construction. My judgement is based on my inspection of the contractor's site laboratory which found that, based on the areas sampled, that an adequate management system was in place to operate the laboratory and appropriate independent accreditation has been obtained.

I found that adequate arrangements are in place for the final approval of concrete mixes for nuclear safety related construction on the main civil works contract. My judgement is based on my inspection of the final suitability trials for concrete mix 6S, which found that thorough site tests are being undertaken to approve each concrete mix for production from each batching plant. Based on examination of the production records, and from witnessing the initial laboratory tests, I found that the concrete mix complied with the design requirements.

On the basis of my findings I have allocated a rating of Green to this inspection.

Conclusion of Intervention

I consider that the concrete mix design and trials process for mix 6S has been very thorough and is in accordance with relevant good practice, with some aspects meeting best practice.

I consider that Batching Plant 1 and the site laboratory are adequate for the production and compliance testing of concrete for nuclear safety related purposes.

No issues were raised, but one observation was raised on NNB GenCo's document "Surveillance Guideline for Concreting of a reinforced concrete structure". ONR considered that the requirements for curing are not in accordance with relevant good practice. NNB GenCo agreed with the ONR comment and will review the guideline.

I recommend that ONR continues its engagement with the concrete mix design and production topic. In particular I recommend that the focus of its interventions is transferred to the proposed offsite production facility for the marine works contract.

I recommend that ONR engages with the proposed work to construct a mock-up of a section of technical gallery, in order for ONR to verify that the licensee's arrangements for placing the approved concrete mixes comply with relevant good practice.