Manufacturing Issues Identified During Sizewell C Reactor Vessel Production

The Office for Nuclear Regulation (ONR) has identified a number of manufacturing quality issues during the production of reactor pressure vessels (RPVs) for the Sizewell C nuclear power station, following a regulatory inspection of Framatome's manufacturing facility in France.

The findings, published in an inspection report released on 22 June, relate to work being carried out at Framatome St Marcel, where the critical reactor components are being manufactured for the Suffolk nuclear project.

According to the regulator, the number of non-conformance reports (NCRs) recorded during production has increased compared with those identified during the manufacture of equivalent components for Hinkley Point C.

The inspection formed part of the ONR's ongoing oversight of Sizewell C's supply chain and manufacturing arrangements, assessing whether appropriate controls are in place for the production of one of the most safety-critical components within the nuclear plant.

The reactor pressure vessel forms the heart of the reactor's primary circuit and is classified as a Nuclear Safety Class 1 component. Within the Sizewell C safety case it is also designated as a High Integrity Component, meaning any structural failure during operation is considered unacceptable.

In its report, the regulator said the purpose of the inspection was to determine whether Sizewell C's arrangements for specifying, monitoring and overseeing manufacture at Framatome complied with Licence Conditions 12 and 19, which relate to suitably qualified personnel and the control of construction and installation activities.

During the inspection, ONR officials received an update from Sizewell C on quality performance at the manufacturing facility.

The report stated: "Sizewell C gave an overview of reactor pressure vessel manufacturing quality issues at Framatome St Marcel, explaining that the number of non-conformance reports has increased when compared to Hinkley Point C."

According to the regulator, investigations undertaken by both Sizewell C and Framatome have identified human performance as the principal cause of the recorded issues.

In response, Framatome has developed a site-wide human performance improvement programme designed to strengthen manufacturing practices across its St Marcel facility.

The ONR said it had shared the findings with its own supply chain, quality assurance and human factors specialists to ensure the improvement programme receives appropriate regulatory oversight.

Despite the increase in non-conformance reports, the regulator did not identify any immediate safety concerns requiring formal enforcement action.

Sizewell C said the findings demonstrate the value of beginning manufacturing activities earlier in the programme, allowing potential issues to be identified and addressed before components progress further through production.

A spokesperson for the company said:

"Replication means doing things better and that is exactly what is happening at Sizewell C. The overall quality of our nuclear components has improved thanks to the learning and experience gained at Hinkley Point C.

"Our early manufacturing approach means we can spot any problems quickly and deal with them. As the ONR inspectors' report makes clear, a plan is in place to address the specific issues at St Marcel, and we will rigorously monitor its implementation."

The Sizewell C project has consistently promoted the replication of Hinkley Point C's European Pressurised Reactor (EPR) design as a means of reducing cost, improving delivery certainty and shortening construction schedules by applying lessons learned from the UK's first new nuclear power station in a generation.

However, campaign group Together Against Sizewell C said the regulator's findings highlight the importance of maintaining rigorous quality assurance throughout the manufacturing process.

A spokesperson for the group said the reported increase in non-conformance records warranted close scrutiny, particularly given previous manufacturing challenges encountered on other EPR projects overseas.

The comments referenced issues experienced during construction of France's Flamanville 3 nuclear power station, where manufacturing defects and quality assurance failures contributed to substantial cost increases and significant programme delays.

Framatome had not issued a public response at the time of publication.

The ONR will continue monitoring manufacturing progress as production of the reactor pressure vessels advances, with ongoing regulatory inspections expected throughout the construction programme to ensure quality standards continue to meet the stringent requirements expected of nuclear safety-critical components.