Sheffield Forgemasters completes SMR nuclear vessel demonstrator

21 February 2024

Sheffield Forgemasters has completed weld-assembly of a full-size small modular reactor (SMR) nuclear vessel demonstrator using Local Electron-Beam Welding (LEBW). Sheffield Forgemasters Research, Design & Technology Director Jesus Talamantes-Silva said the company had achieved “a significant milestone in assembling a nuclear vessel demonstrator, using electron beam welding for the first time at this scale, with 100% success and no defects”.

Completing four, thick, nuclear-grade welds took less than 24 hours – work which typically requires a year. "With a diameter of three metres and a wall thickness of 200mm, construction of the vessel showcases the reliability and capabilities of LEBW, setting a dramatic new standard for weld-joining thick-walled components, previously untrialled in a demonstrator model," the company noted.

The operation deployed specially developed parameters, meticulously fine-tuned during the welding development stage, including innovative sloping-in and sloping-out techniques to start and finish the weld, ensuring a clean and complete weld-join.

Senior development engineer and project lead Michael Blackmore believes the implication of this technology within the nuclear industry is monumental, potentially taking high-cost welding processes out of the equation. "Not only does this reduce the need for weld-inspections, because the weld-join replicates the parent material, but it could also dramatically speed up the roll-out of SMR reactors across the UK and beyond, that's how disruptive the LEBW breakthrough is."

Sheffield Forgemasters said demonstrating LEBW technology's potential opens new horizons for "more efficient, low-cost and less time-heavy nuclear assemblies" with far-reaching implications for other projects which require thick-walled welded assemblies.

Jacob Pope, development engineer and LEBW machine tool installation lead said: “We thank the government's Department for Energy Security & Net Zero for enabling the project through its Nuclear Innovation Programme. We also thank our esteemed partner, Cambridge Vacuum Engineering, for their invaluable support throughout this endeavour. Their remote and on-site assistance played an instrumental role in the success of this milestone, highlighting the collaborative spirit that drives us forward."

Sheffield Forgemasters, which was acquired by the UK's Ministry of Defence in 2021, is the only UK company able to manufacture the large forgings required for SMRs. The company said future activities include a joint industrial project “supported by key participants from the USA and UK”. The aim is “to initiate a code case or multiple cases to facilitate the deployment of this technology in accordance with the standards set by the American Society of Mechanical Engineers (ASME)”.

In December, the company said it was on track to regain ASME status as a supplier of heavy forgings and castings to the civil nuclear market. An ASME Section III Division I NCA 3300, NCA 4000 and NQA-1 Code survey and audit, has recommended it for Material Organisation (MO), and welding (NPT) accreditations. This would allow it supply castings and forgings (material) for civil nuclear applications and also be qualified to carry out weld construction activities on these materials.

Sheffield Forgemasters has signed a number of agreements with SMR design companies. In October 2023 it signed a memorandum of understanding (MOU) with US X-energy and Cavendish Nuclear (a UK subsidiary of Babcock International) to explore opportunities around the deployment of a fleet of Xe-100 high temperature gas-cooled reactors (HTGRs) in the UK. Under the MOU, X-energy and Cavendish Nuclear will make use of Sheffield Forgemasters' extensive experience in developing nuclear forgings and castings. The companies plan to build up to 40 Xe-100s across the UK.

Earlier, in February 2023, the company signed an MOU with with Holtec Britain to design components for Holtec’s SMR-160 SMR and identify the best routes to manufacture. This followed similar agreements with other SMR developers. In July 2016, SFI and NuScale Power agreed to co-operate to develop the manufacturing techniques needed for the planned deployment of NuScale's SMR in the UK. Another MOU was signed in December 2021 with Rolls-Royce SMR to jointly explore commercial mechanisms for long-term collaboration on the supply of forgings to Rolls-Royce’s planned UK SMR fleet. In September 2022 SFI signed an MOU with GE Hitachi Nuclear Energy to support of the potential deployment of the BWRX-300 SMR in the UK.

Image: The ground-breaking welded SMR vessel at Sheffield Forgemasters (courtesy of Sheffield Forgemasters)

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