Date(s) of inspection
- August 2023
Aim of inspection
This inspection sought to gain assurance as to the adequacy of NNB Generation Company (HPC) Ltd’s (NNB GenCo) arrangements for the design of pipe supports for the nuclear island of unit 1 and for the technical galleries. The inspection considered both the civil engineering and mechanical engineering aspects of the design of the pipe supports and sought evidence that designs were sufficiently mature to justify safety prior to the start of construction.
The inspection targeted compliance with Licence Condition (LC) 14 in relation to the adequacy of the licensee’s arrangements for the design of pipe supports. It also considered compliance with arrangements for LC19, in particular that the safety case and detailed design produced under the LC 14 arrangements demonstrate the safety of each stage of construction before it commences.
Three pipe systems with varying degrees of importance to safety were sampled. As the design of the pipe supports and their connection to other structures is considered to be multi-disciplinary, both civil engineering and mechanical engineering inspectors participated in the inspection.
Subject(s) of inspection
- LC14 – Safety documentation – Rating: Green
- LC19 – Construction or installation of new plant – Rating: Green
Key findings, inspector’s opinions and reasons for judgement made
A significant quantity of evidence of NNB GenCo’s arrangements and examples of their implementation were provided in advance of the inspection.
Responses to questioning during the inspection provided confidence that the design, where sampled, was being adequately managed with due consideration of the risks involved.
Some further evidence was requested during the inspection, not all of which has been received or is available yet. In particular, an important aspect of the design was the subject of ongoing studies, with the concomitant risk that late design changes may be foreclosed. In order to manage progress with the delivery of the outstanding evidence, I have raised Regulatory Issue 11662.
On the basis of the evidence sampled, I was satisfied that the arrangements in place comply with LCs 14 and 19.
My overall judgement for the inspection is that, based on the evidence sampled, I was satisfied that arrangements in place address the key risks associated with the design of the pipe supports. Furthermore, those arrangements are under implementation and are consistent with relevant good practice.
This inspection highlighted no significant shortfalls but did identify some gaps in the evidence provided. These gaps include an acknowledged open point for which further studies are planned. As the outstanding information is not yet available, I have raised a level 4 regulatory issue (RI-11662) to oversee NNB GenCo’s progress. I judge that the absence of this evidence does not alter my judgement as to the rating of this inspection. As no significant shortfalls were found, the inspection was rated as GREEN against both LC14 and LC19.