Office for Nuclear Regulation

LC 17 - MSC 12 Manufacturing Assurance - Start of equipment manufacture - Pump house pumps (3252)

Executive summary

Purpose of Intervention

This intervention was to observe the implementation of NNB Generation Company (HPC) Limited’s (NNB GenCo) Engineering Readiness Review (ERR) process. It was to give ONR confidence that this process ensures that the manufacturers’ Design Package Release Notes (DPRN) are suitably ready to support start of manufacturing and that the procured equipment will fulfil the associated safety case requirements.

Interventions Carried Out by ONR

This was a Licence Condition (LC) 17 observation at NNB GenCo’s Bridgwater House Offices and through teleconference.

LC 17 requires that licensees make and implement management systems that give due priority to safety. It also requires the licensee to implement adequate quality management arrangements to all activities that may affect safety.

ONR observed the project’s review meetings associated with the release to manufacturing for the essential service water system (SEC) pump casings noting that the formal point of release to manufacture is the Pre-Inspection Meeting (PIM) which includes a mandatory check of the status of the DPRN, reviewed at earlier ERRs, and any associated limitations / conditions associated with the DPRN. The intervention included the observation of the following three meetings:

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

The first ERR was conducted in a professional manner with an atmosphere that encouraged open technical and safety case discussion and challenge. The attendees appeared to be knowledgeable in their respective areas and understood the objectives of the review. The NNB GenCo Project Manager was not seen to be exerting undue pressure on the other attendees to approve the manufacturer’s DPRN.

At this first ERR, I am satisfied that due consideration was given to design modifications affecting the pump casings. The review also sought to identify the maturity of any design packages for interfacing works and the potential for future changes in these works that could impact the pump casings.

This ERR concluded that the original DPRN was not ‘fit for purpose’ to support the release for manufacture of the pump casings. This was due to the ‘not accepted’ status of a number of documents and the need to update the general assembly drawings to reflect the modifications. It was also noted that a material exemption request for the pump casings had not been formally accepted, although the change had been previously discussed and agreed within the project.  I am satisfied that NNB GenCo’s decision was appropriate in the circumstances and reflected conservative decision making with due consideration given to the stability of the design.

ONR is particularly interested in establishing that the safety case requirements are appropriately reflected in procurement documentation such that equipment will be designed / manufactured to fulfil these requirements. For the SEC pumps it was clear from the DPRN that the procurement documents are at ‘accepted’ status and therefore the implication is that NNB GenCo is satisfied that the safety case requirements are adequately captured. ONR will give consideration to a future intervention to sample the relevant parts of the SEC pump specifications along with the associated review and acceptance records to gain confidence that the safety case requirements are in fact captured.

The second ERR was well chaired and there was good context setting by NNB GenCo’s Project Manager. The amended DPRN was significantly improved with only three documents remaining as ‘not accepted’ for which additional controls / limitations were identified. It was also noted that the material exemption request had been formally accepted. The ERR concluded that with the additional controls / limitations in place that the DPRN was now ‘fit for purpose’. I consider the basis for the final decision on the DPRN to be reasonable, and any risks going forward appear to have been adequately mitigated.

I consider that the PIM, chaired by the manufacturer, was well conducted with good challenges from NNB GenCo’s Technical Management and Acceptance (TMA) representative. The output from the second ERR was clearly communicated resulting in the manufacturer agreeing to add a hold point to their surveillance Follow Up Document (FUD) preventing any weld repairs until the relevant procedure is accepted. The meeting concluded that the start of manufacturing hold point could be released; I am satisfied that the decision was appropriate.

Conclusion of Intervention

I have taken confidence from the application of the ERR process. ONR observed that NNB GenCo did not accept a substandard DPRN at the first meeting. At the second ERR meeting, the DPRN was accepted with conditions. I observed that these conditions were clearly communicated to the contractor during the Pre-Inspection Meeting. There was evidence of conservative decision making in the reviews with due consideration given to the stability of the design. As a result I am satisfied that this aspect of NNB GenCo’s arrangements is adequate. Therefore, I have rated this intervention GREEN, no further action.

ONR will consider a future intervention to sample the detailed relevant parts of the SEC pump procurement specifications, along with the associated NNB GenCo review and acceptance records. This is for ONR to gain confidence that the safety case requirements are adequately reflected.