Small heat exchangers present big welding challenge

The Nuclear AMRC has worked with heat exchanger specialist Thornhill Group to demonstrate a new welding method for small tube-to-tubesheet assemblies which could halve cycle time.

The project called on the Nuclear AMRC’s powerful disk laser welding cell, more often used on large components of up to three metre diameter. Using the laser on tubes measuring just 8mm diameter presented numerous challenges to the centre’s engineers, who successfully demonstrated that large-capacity welding machines can be used for nuclear components of all sizes.

Thornhill Group is the only UK provider of the complete cycle of heat exchanger services encompassing design, engineering, installation, repairs and servicing for clients in power generation, oil & gas, chemical and other demanding industries. Headquartered in Yorkshire, Thornhill employs around 150 people across its three sites.

One of Thornhill’s customers in the nuclear sector was looking to implement a tube-to-tubesheet joint within a restricted space, and asked the company to investigate how this could be designed and manufactured. To complement their own expertise in heat exchanger development and fabrication, the Thornhill team called on the Nuclear AMRC to help determine the feasibility of the customer’s design.

The study for Thornhill was one of the first commercial projects for the Nuclear AMRC’s disk laser welding cell, which was commissioned in early 2018. The cell was designed to develop high-speed welding techniques for large assemblies such as 3m3 nuclear waste containers, but is also capable of very fine narrow welds thanks to the high power density of the laser beam and fast travel speed of its gantry-mounted robot.

“Thornhill’s heat exchanger was much smaller than the assemblies we usually work with, and right at the limit of what our robot and welding head can handle,” says Dr Will Kyffin, head of the Nuclear AMRC’s welding team. “The size and inertial mass of the robot meant that programming it to perform an accurate circumferential weld of just 8mm diameter was extremely challenging, especially as this was a new facility and the team were still finding out what it could really do.”

The welding head had to be customised for the job, with the large gas nozzle and shield removed in favour of a separate gas shielding nozzle, and laser power was reduced to just 2kW from its maximum 16kW. Ensuring a high quality weld meant considering a host of factors, from angle and position of the weld head, to reducing the gas flow to avoid turbulence in the molten metal.

Initial trials showed that small tube-to-tubesheet welds could be successfully completed, with welding taking just over one second for each join. Allowing for movement time, a full tubesheet could be welded in a matter of minutes.

The project proved that a robotic laser welding cell can successfully join small tube-to-tubesheet assemblies, and the customer’s design can be manufactured to requirements.

Thornhill presented their full manufacturing proposal to their customer, secure in the knowledge that it had been practically tried and tested.

“While our heat exchanger design and manufacturing expertise has been proven over many years in the nuclear industry as well as other industry sectors, this project presented unique challenges,” says Sean Murphy, Thornhill’s business development director. “Sourcing independent, authoritative data from the Nuclear AMRC, one of the world’s leading research bodies in the nuclear field, on its feasibility was invaluable in presenting our solution to the customer.”

Nuclear Innovation UK

2–3 July, Sheffield.

The Nuclear AMRC and NNL present a major conference covering research supported by the government-funded Nuclear Innovation Programme.

The UK government is investing in an ambitious multi-year research and development programme to develop the next generation of nuclear technologies. The Nuclear Innovation Programme covers a host of technology areas which will provide real commercial opportunities to companies in the supply chain for nuclear and other high-value sectors.

Join the Nuclear AMRC, National Nuclear Laboratory and international industry experts in nuclear, digital manufacturing and R&D to discover the research so far, and learn more about the opportunities to come.

Confirmed speakers include:

  • Dr Tim Stone, Nuclear Industry Association
  • Allan Cook, High Value Manufacturing Catapult
  • Adriènne Kelbie, Office for Nuclear Regulation
  • Dr Fiona Rayment & Steve Napier, NIRO
  • Damitha Adikaari & Si Dilks, BEIS
  • Professor Ian Chapman, UKAEA
  • Duncan Steel, Sellafield Ltd
  • Andrew Storer & Adam Bond, Nuclear AMRC
  • Paul Howarth & Professor Andrew Sherry, NNL
  • Plus project leaders for all parts of the Nuclear Innovation Programme

For the latest information and registration, visit the Nuclear Innovation UK conference microsite.

Quality assurance requirements for nuclear facilities

24 June, Birchwood; 25 June, Sheffield; 27 June, Cumbria.

Swagelok Manchester presents an introduction to quality assurance requirements and regulatory commitments at nuclear facilities – a great opportunity for Fit For Nuclear participants to learn the essentials of nuclear quality.

Delegates will learn about general quality assurance requirements, and Swagelok’s top tips on how they can be applied to nuclear facilities:

  • Basic quality requirements – training and qualification, design, material traceability, continuous improvement.
  • ONR regulations and guides: categorisation of safety functions and SSCs, integrity of metal components and
    structures, safety systems.
  • Codes and standards: ASME Boiler and Pressure Vessel Code Section III, AFCEN RCC-M.
  • Quality requirements at specific sites: operating reactors such as Sizewell B, Torness, and Hinkley B; decommissioning sites such as Wylfa Newydd and Oldbury; non-power-producing sites such as Sellafield.

Companies can register for two free places at one of the three locations.

For more information, download the flyer or email

Wood to lead digital reactor research

Engineering group Wood is to lead the next phase of research into digital reactor design.

The research is backed by around £3.3 million from the Department of Business Energy and Industrial Strategy as part of the Nuclear Innovation Programme. The funding will allow experts from industry and academia to use collaborative virtual engineering and high-performance computing to demonstrate significant cost savings in the design, construction, operation and decommissioning of nuclear power reactors.

The Nuclear AMRC is part of the Digital Reactor Design Partnership led by Wood, and will integrate manufacturing data into digital models to better understand performance over the life of the reactor.

Other partners include EDF Energy, Rolls-Royce, National Nuclear Laboratory (NNL) and the University of Liverpool’s Virtual Engineering Centre.

The first phase of the Digital Reactor Design programme successfully demonstrated a proof of concept, by developing a computer-simulated design and management platform covering the whole nuclear life cycle.

The new second phase will focus on implementing digital tools in a software framework, using real project applications to demonstrate improved efficiency, enable supply chain collaboration, and deliver cultural change across the industry.

“This project has already been highly successful in proving the concept for a new and better way of designing and building nuclear power reactors,” said Bob MacDonald, CEO of Wood’s Specialist Technical Solutions business. “We’re looking forward to working with BEIS on the next stage and taking a very significant step towards achieving the cost reduction targets proposed by the UK Nuclear Sector Deal.”

Results from the first phase will be shared at the Nuclear Innovation UK conference in July. Organised by the Nuclear AMRC and NNL, the two-day conference will include technical presentations from the full range of projects supported by the Nuclear Innovation Programme, plus key speakers from industry and government.

Andrew Stephenson, the UK’s minister for nuclear, commented: “Using state-of-the-art virtual engineering and computing technology to design and build the next generation of nuclear reactors will position the UK at the cutting-edge of low-carbon energy innovation.

“Making simulations in a virtual world allows designers to take virtual risks, reducing design times and demonstrating cost savings across the nuclear life cycle, from design through to decommissioning. This is key to achieving the cost reduction targets in the Nuclear Sector Deal and part of our modern Industrial Strategy.”

Wood, which acquired Amec Foster Wheeler in 2017, also recently won a major contract to provide engineering design services to Sellafield Ltd over the next 20 years. The company was selected as design and engineering partner as part of Sellafield’s new Programme and Project Partners procurement model.