An advanced electron beam (EB) welding technology developed by Cambridge Vacuum Engineering (CVE) has the potential to transform the speed at which small nuclear power stations can be built.
In a trial conducted by Sheffield Forgemasters, Cambridge Vacuum Engineering’s Ebflow technology was deployed to cut the amount of time needed to weld a small modular reactor (SMR) pressure vessel demonstrator from more than a year to less than 24 hours – a move that could help reshape the future of nuclear reactor production worldwide and bridge the gap in the UK’s energy market.
As part of a Government-funded project, Sheffield Forgemasters incorporated Ebflow, operating under local vacuum, into a bespoke, large-scale EB facility at its Brightside Lane site to complete four thick nuclear-grade welds on vessels with a diameter of three meters and a wall thickness of 200mm. As well as reducing welding time by an astounding 99%, Ebflow also delivered the superior quality and precision of welds needed to ensure SMRs operate safely – setting a new standard for weld-joining thick-walled components.
How does it work?
Ebflow is a local vacuum electron beam welding system, which can be readily transported and operated on-site and applied to structures significantly larger than those that can be accommodated in a vacuum chamber. It eliminates the need for a vacuum chamber through
a local, coarse vacuum, which is established and maintained only where it is needed. The technology facilitates very high joint completion rates in thick-section metals and is 20-30 times faster than conventional submerged arc welding, achieving 200mm per minute in 150mm thick steel.
EB technology has the benefit of not requiring the use of a filler material (which can be costly) and retaining the base metal chemical composition leading to predictable corrosion performance and weld properties.
It also benefits from low, localised welding-induced stresses, which lowers the need for a minimum ferrite content in, for example, the welding of austenitic stainless steel grades and greatly reducing levels of welding-induced distortion.
Fusion welding
Ebflow is a highly advanced fusion welding process with applications across a wide range of industries, from oil and gas to nuclear power generation to shipbuilding and more. The technology utilises a focused beam of high-velocity electrons to join metal components together. The main difference to traditional welding methods is that no third-party material is introduced to make the join. This technique enables unparalleled levels of accuracy and efficiency, making it ideal for the intricate welding requirements of primary components used in mission-critical energy applications – including mini nuclear reactors.
Electron beam welding is a well-established welding process dating back to the late 1950s, when it was first used for welding Zircaloy nuclear fuel elements. However, the deployment of local vacuum technology to large structures has had limited adoption until now. CVE has spent around twenty years developing the technology, marked by intermittent pauses amid successful demonstration projects.
“The fusion welding
process reduced
welding time by 99%”
Bob Nicolson, Managing Director at CVE, said: “ We all know the clock is ticking when it comes to climate change. As more governments worldwide sign up to net zero emissions by 2050, the energy industry must embrace technologies – like Ebflow – that can help speed up the deployment of low carbon energy production.”
Tested on CRAs
Chris Punshon, Head of New Energy Applications at Cambridge Vacuum Engineering, explained: “Ebflow has undergone testing for welding numerous corrosion resistant alloys such as copper alloys, ferritic, martensitic and fully austenitic stainless steel grades, including precipitation hardened and duplex stainless steel grades. Additionally, it has been used on super and nitrogen alloyed austenitic grades. Commercially, pure titanium and alloys can also be welded readily, even at thickness above 150mm, along with numerous nickel alloys in various states of heat treatment.”
“Ebflow can be used to weld almost all metallic materials, although not always with weld properties meeting the application minimum requirements (this is rare however). Some metals can be EB vacuum brazed if not readily weldable.”
Large scale forgings
Sheffield Forgemasters is the only company in the UK with the capability to manufacture the large forgings required for SMRs, and now – thanks to Ebflow – it has years of developmental lead on global competitors in welding thick-walled assemblies. Dr Michael Blackmore, Senior Development Engineer and Project Lead at Sheffield Forgemasters, said: “The implication of industrialised Electron Beam Welding technology within the nuclear industry is monumental, potentially taking high-cost welding processes out of the equation.” Professor Jesus Talamantes-Silva, Research, Design and Technology Director at Sheffield Forgemasters, said: “We are delighted to have reached a significant milestone in assembling a nuclear vessel demonstrator, using electron beam welding for the first time at this scale, with 100 per cent success and no defects.”
About the companies
Cambridge Vacuum Engineering: Aquasium Technology Ltd, trading as Cambridge Vacuum Engineering (CVE), design and build process solutions and has over 60 years’ experience manufacturing electron beam (EB) systems in a range
of industrial sectors including aerospace, nuclear, automotive, oil and gas, and sensors. Sheffield Forgemasters: Sheffield Forgemasters specialises in the design and manufacture of high-integrity forgings and castings for complex engineering challenges. Some of the largest bespoke engineered steel products in the world are produced with capacity for castings of up to 350 tonnes and forgings of up to 200 tonnes finished weight. The company was acquired in August 2021 by the UK Ministry of Defence.
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