Executive summary
Date(s) of inspection:
March 2026
Aim of inspection
The aim of the inspection was to inspect NNB Generation Company (HPC) Ltd's (NNB GenCo) arrangements for compliance with Licence Condition 19 (LC 19), construction or installation of new plant, in relation to civil engineering construction assurance. LC 19 requires that where the licensee proposes to construct or install any new plant, which may affect safety, the licensee makes and implements adequate arrangements to control the construction or installation.
The objective of the inspection was to obtain evidence in relation to the adequacy of NNB GenCo’s arrangements for the control of the gamma tendon post-tensioning of the unit 1 inner containment reinforced concrete. The particular focus of the inspection was on the implementation of arrangements to ensure conformant construction of civil engineering elements, in accordance with the design intent and safety case.
Evidence of conformance with technical relevant good practice in the management and execution of civil engineering works was also sought. The gamma tendons are first of a kind in the UK and the inspection aimed to gain confidence that they are to be installed without latent defects that might undermine safety case claims on the containment structure.
Subject(s) of inspection
- CDM 15 - Rating: GREEN
- LC19 - Construction or installation of new plant - Rating: GREEN
Key findings, inspector's opinions and reasons for judgement made
This Licence Condition (LC) 19 (construction or installation of new plant) compliance inspection was carried out on Monday 16th March and Tuesday 17th March at Hinkley Point C (HPC).
The inspection focused on the Unit 1 reactor building (HR), post-tensioning manufacturing warehouse and grout batching plant. The inspection initially comprised of an office based discussion on the progress of Unit 1 post-tensioning works and preparation for the installation of gamma tendons. The discussion was followed by a site walkdown, where we visited the Unit 1 HR inner containment post tensioning work area, Unit 1 post tensioning stressing gallery, post tensioning manufacturing warehouse and grouting batching plant. The remainder of the inspection was office based where evidence was sampled.
The objective of the inspection was to obtain evidence and gain confidence in the adequacy of NNB GenCo's arrangements for the control of the gamma tendon PT installation in Unit 1. The focus of the inspection was implementation of the LC19 arrangements and readiness for NNB GenCo to undertake gamma tendon PT works on site.
Overall, on the basis of the inspection and evidence sampled, I judge that LC19 arrangements, in relation to the installation of gamma tendons, are being implemented appropriately and preparations for site works are progressing in accordance with expectations.
The inspection highlighted no significant regulatory issues on the day but it was recognised that an open-point existed in that an ongoing Independent Technical Assessment (ITA) review of a Field Change Request (FCR) to re-sequence the order of post tensioning ran contemporaneously. A level 4 regulatory issue RI-13015 was raised after the inspection with the purpose of tracking the closure of the open-point and linking findings of the FCR review to this inspection.
A small number of observations were made during the inspection and where appropriate, actions were set to address them.
Conclusion
On the basis of the evidence sampled, I judge that NNB GenCo have implemented their LC19 (construction or installation of new plant) arrangements for the installation of the first nuclear safety gamma tendons being carried out at site.
In relation to the specific areas sampled, I judge that NNB GenCo’s development and implementation of arrangements for the planning, management and execution of the implementation of gamma tendon PT works in the U1 inner containment structure were adequately controlled.
Upon consideration of the ONR guidance in relation to inspection ratings, I judge that a rating of Green (no formal action) is appropriate.
RI-13015 has been raised after the inspection to track the post tensioning injection grout pressure change and tendon installation order re-sequence open-points to closure.
Actions and observations have been raised for the duty holder to consider and address after the inspection, which will be monitored through routine regulatory business.