- Site: Hinkley Point C
- IR number: 20-032
- Date: March/May 2021
- LC numbers: 19
Executive summary
Purpose of Intervention
Licence condition (LC) compliance interventions are an essential element of the Office for Nuclear Regulation’s (ONR's) overall intervention strategy which consists of a series of interventions. Each intervention is intended to establish that the licensee has adequate arrangements in place for compliance with a licence condition. Inter alia, LC 19 requires that:
'Where the licensee proposes to construct or install any new plant which may affect safety the licensee shall make and implement adequate arrangements to control the construction or installation.'
The aim of the intervention was to gain confidence that NNB Generation Company (HPC) Limited, the licensee, has adequate arrangements in place for compliance with LC 19, in relation to tensile testing of pressure circuit components and welds in order to substantiate their integrity and satisfy the regulatory expectations in ONR’s Safety Assessment Principles (SAPs). In addition, this intervention considered whether the sampled results from the tensile testing meet the requirements of the RCC-M standard and therefore the relevant fracture mechanics assessments remain demonstrably conservative.
Interventions carried out by ONR
The intervention was carried out in two parts:
- Part A: sampling of documentary evidence provided by the licensee for the main coolant line (MCL) and discussion with Framatome Jeumont.
- Part B: remote intervention via camera at the Jeumont laboratory where the tensile tests would be undertaken.
Key findings, inspector’s opinions and reasons for judgments made
My findings on the main aim of the intervention, to gain confidence that the licensee has adequate arrangements in place for compliance with LC 19, in relation to the tensile testing of pressure circuit components to substantiate assurance of nuclear safety of equipment/systems at Hinkley Point C are:
- The licensee demonstrated that it has adequate arrangements and procedures in place to undertake and control the tensile tests as required by RCC-M and other relevant ISO codes and standards.
- The licensee clearly highlighted effective control of identification and tracking of tensile test specimens from the MCL manufacturer’s facility to the test laboratory.
- From the data generated in the tests, the licensee demonstrated how that has been used to interpret the relevant tensile properties for the MCL material.
- The licensee also demonstrated through the testing of the MCL specimens that the tensile properties of material are well bounded by the recommended minimum properties in the RCC-M for the relevant temperatures (ambient and 350 °C).
- The licensee further demonstrated its intelligent customer capability by producing the relevant technical documents and providing the necessary oversight of the tests using suitably qualified and experienced personnel.
Conclusion of intervention
Overall, the conclusion of the intervention is that the licensee satisfactorily demonstrated adequate arrangements for compliance with LC 19, in relation to tensile testing of pressure circuit components and welds in order to substantiate their integrity and satisfy the regulatory expectations in ONR’s SAPs. An inspection rating of Green is appropriate for LC 19 (Construction or installation of new plant).