Sizewell C reactor vessel non-conformances vs Hinkley: ONR lessons for engineers
Reviewed by Joe Ashwell
First reported on New Civil Engineer
30 Second Briefing
Quality issues in the manufacture of Sizewell C’s reactor pressure vessels have been identified by the Office for Nuclear Regulation during a recent inspection, with more non-conformances reported than for the equivalent Hinkley Point C components. The findings relate to fabrication of the large forged steel RPV shells, which must meet stringent fracture toughness, weld integrity and dimensional tolerance requirements for EPR reactors. ONR scrutiny of welding procedures, heat treatment records and material traceability signals tighter oversight of nuclear-grade pressure boundary components before site installation.
Technical Brief
- For other nuclear new-builds, the case reinforces early, intensive regulator engagement with pressure boundary component supply chains.
Our Take
The Office for Nuclear Regulation has featured repeatedly in recent UK Infrastructure coverage, including asbestos-related improvement notices at Torness and Hartlepool, signalling a period of heightened enforcement attention that will colour how any Sizewell C manufacturing deviations are interpreted by project insurers and lenders.
In our database of 887 Infrastructure stories, only a subset combine the Safety and Standard/Guideline tags with nuclear new-build projects, so ONR’s updated licensing guidance from May 2026 is likely to be a key reference point for how manufacturing non-conformances on Sizewell C’s reactor vessels are managed and documented.
The contrast between issues at Sizewell C and the earlier Hinkley Point C build will be closely watched by UK regulators given recent scrutiny of ONR’s oversight at Hinkley; any perception of inconsistent treatment could feed into political and community debates around future nuclear projects in the United Kingdom.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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