Chilled machining to reduce stress

The Nuclear AMRC is exploring the use of cryogenic coolant for civil nuclear machining, with the aim of improving machining efficiency and increasing tool life while minimising the risk of component failure.

cryo machining

Cryogenic cooling uses extremely cold gas or liquid to control the heat generated during machining. Benefits can include reduced residual stress and thermal damage, improved surface roughness and longer tool life.

Nuclear AMRC machining researchers have installed a carbon dioxide cooling system to the Hermle C60, a flexible five-axis mill-turn centre, and investigating its use in cutting a range of hard-to-machine metals, including steels, titanium and nickel alloys. CO2 can replace conventional coolant for many cutting tasks, and can potentially benefit processes which are usually run dry.

The ChilAire Aero system delivers a controlled stream of carbon dioxide gas and CO2 ice particles through the machine spindle or external nozzles.

As it expands, the CO2 reaches temperatures as low as –78°C. This is not as cold as temperatures achieved with liquid nitrogen, the standard for cryogenic cooling, but is more controllable and reduces the risk of adverse material effects.

cryo spindle

“We are looking to develop this environmentally-friendly technology for nuclear applications,” says Dr Krystian Wika, advanced cooling technology lead at the Nuclear AMRC. “One of the major benefits of cryogenic machining is that it has the potential to reduce residual stress and help prevent stress corrosion cracking.

“With carbon dioxide, our aim is to optimise the key process variables so we can control the cooling and improve the surface integrity. If you can obtain favourable compressive stresses instead of tensile stresses, you can help stop crack initiation and propagation and extend the life of nuclear components.”

Initial research is benchmarking carbon dioxide against conventional coolant, and seek to understand how it behaves under different application modes, flow rates, pressures and machining parameters.

Carbon dioxide avoids the chemical hazards of conventional coolants, and can be used in non-enclosed portable machining tools, but the gas does bring its own risks in the workplace. The Nuclear AMRC has introduced additional safety measures around the Hermle during trials, including CO2 alarms and personal exposure monitors.

The researchers are also using another recent addition to the machining group’s R&D armoury, a state-of-the-art high-speed thermal camera.

The Flir X6580sc cryo-cooled medium wavelength infrared camera can visualise and quantify changes in surface temperature and heat dissipation during machining processes, including drilling, milling and turning.

The camera is fully calibrated from –20° to 1500°C and can take up to 355 frames per second at 640×512 pixel resolution.

“This is probably the fastest thermal camera on the market with this level of detail, and has a range of unique features,” says Wika. “It will help us reach a deeper understanding of cryogenic cooling and many other challenging issues in high-performance machining.”

  • nl21 frontFor more news on how the Nuclear AMRC is supporting industry through manufacturing R&D and supplier development, download our Q4 newsletter (4MB pdf).

The power of additive

26 January 2016.


The Nuclear AMRC invites you to explore the state of the art in bulk additive manufacturing processes for the energy industry.

This special event will focus on additive manufacturing technologies and applications for civil nuclear, oil and gas, renewables and other innovative power generation sectors.

Metal additive manufacturing can bring significant commercial benefits to the power generation industry, including reduced lead time and production cost, while avoiding problems with transportation and supply chain capability and capacity.

New additive techniques can also help overcome technical challenges including microstructural inhomogeneity, defect occurance and detection, and size and geometric limitations.

Discover how major companies are already developing and implementing bulk additive manufacturing techniques, and find out how your business could benefit from these new capabilities.

To register, got to

For more information, contact

Civil Nuclear Showcase

19-21 January 2016, London.

UK Trade & Investment (UKTI) and the Nuclear Industry Association (NIA) present the UK’s leading international networking event for the nuclear industry.

The Civil Nuclear Showcase takes place over three days in central London and aims to provide valuable insights into the civil nuclear marketplace while connecting the industry with key stakeholders.

The event offers a tailored conference programme covering trade and investment opportunities across the UK nuclear sector, plus a networking reception and one-to-one meetings to connect with UK industry and international stakeholders.

For more information, visit UKTI’s Civil Nuclear Showcase 2016 website.

UKTI tech


The economic case for SMRs

In his autumn statement and spending review, chancellor of the exchequer George Osborne announced new funding to develop small modular reactors in the UK. Mike Tynan, Nuclear AMRC chief executive, explores the economic case for SMRs.

NuScale plant

There’s been a lot of talk about small modular reactors (SMRs) recently. Proponents say that SMRs present the UK with the opportunity to regain a global lead in reactor technology, while meeting the country’s need for affordable and secure low-carbon electricity.

But why would a small nuclear reactor be any more efficient or economic to build and operate than a reactor 10 or 20 times its size? The answer is that it’s not necessarily more efficient – however, it is much more affordable.

The global reactor vendors have focused on developing and building very large output nuclear reactors. Each has its own branded technology – Areva’s EPR, Westinghouse’s AP1000 and GE’s ESBWR – all varieties of light water reactor generating between 1100 and 1700 megawatt. The premise is the bigger the better, particularly for markets like the UK where nuclear forms part of baseload generation.

The case for economies of scale was partly based on a high initial capital cost followed by 60 years of low operating costs, providing excellent revenue streams with good return on a safe investment. Reality for the large reactors has not proved so simple. Initial capital costs are significantly higher than originally expected, and the cost of financing such a multi-billion pound investment can be prohibitive. This severely impacts the business model for large units – witness the difficulties in attracting investors for Hinkley Point C.

To compare electricity prices between technologies, we need to calculate a levelised cost of electricity (LCOE). The current wholesale price of electricity in the UK is around £45 per megawatt hour, while the agreed price for electricity from the planned new nuclear station at Hinkley Point C is £92.50/MWh. This price is driven, in large part, by the expense of financing the project. Many have argued that this strike price is too expensive, and it is higher than originally expected. However, it is in line with the estimated full cost of new gas generation by 2025 – £85-95/MWh, according to the UK’s independent Committee on Climate Change.

SMR developers claim that their LCOE could be in the region of current electricity market prices, thanks largely to the much lower capital cost. Realistically, I expect that cost to be in the region of £60-75/MWh, but anything lower will be a real bonus. In an assessment of SMRs led by the National Nuclear Laboratory and published in December 2014, the best estimate was in excess of £80/MWh – not hugely different from the strike price for the EPR at Hinkley Point.

So what would make SMRs more affordable than the gigawatt-scale reactors? It all comes down to how we make them. Because SMRs will be built in relatively high volumes in factory conditions, there are a number of very practical steps that would significantly reduce their capital cost. These include modular construction of the reactor unit; modularisation of concrete infrastructure; design for manufacturing; and the use of advanced production processes such as electron beam welding and hot isostatic pressing.

Significantly reducing SMR production costs is eminently achievable – but it’s no less important to ensure a strong route to market at home and abroad, and a UK supply chain that delivers high-value sustainable jobs in the long term. To achieve the best economic value for the UK, technology vendors will need to create UK entities that deliver indigenous intellectual property. It is this issue, rather than the technology itself, that will stir UK government and industry into action on SMRs.

The Nuclear AMRC is working with the principal SMR technology vendors in support of their drive for a UK SMR. We have the technology, expertise and experience to de-risk SMR programmes, support design for manufacturing, develop innovative solutions for SMR manufacture and deliver high-value complex components, large and small. We are also working with the UK civil nuclear supply chain to ensure that UK suppliers can deliver competitive products and services for SMR technology vendors.

EIC Connect Energy

24-25 November, Manchester.

EIC Energy15

EIC Connect Energy aims to highlight potentially lucrative global opportunities and identify UK capability on major power, nuclear and renewable energy projects around the world.

For 2015, the EIC’s flagship event will look to directly contribute to the export of UK companies through a series of informative presentations by the major energy sector operating companies and their contractors.

The two-day event will focus on the search for new and innovative technologies and cost-saving products, and explore the foreign markets relevant to the nuclear, renewable and conventional power markets.

The Nuclear AMRC is supporting the event, and our Fit For Nuclear team will be offering one-to-one consultations with SMEs to help them seize the opportunities of nuclear. Our MD Andy Storer is also chairing Wednesday’s Nuclear Outlook conference session and a discussion of skills issues across the energy sector.

For more information and to register, go to the EIC Connect Energy homepage.