At Westinghouse Electric Company, a significant challenge is presented.
As the Russian invasion of Ukraine continues, the effects are being felt across Eastern Europe. Power supply is at risk, owed to the need for fuel at a series of Russian-designed VVER-440 nuclear reactors, of which Russia is the only source.
Westinghouse, an American supplier of nuclear technology, believes it has the potential to step in. The company had been working to develop a fully Western VVER-440 nuclear fuel in the background, but now there was a need to accelerate that work.
By the time Adam Travis, Westinghouse Senior Manager & Additive Manufacturing Program Leader, was accepting a TCT Award for this endeavour, the company had manufactured more than 1,000 units. Two components in every assembly – the top and bottom flow plates – are additively manufactured with laser powder bed fusion technology in Stainless Steel 316L. Westinghouse believes the two plates to be the first ever safety-related AM components to enter serial production.
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“We are very proud of the achievement that this application represents,” Travis said at the TCT Awards. “That’s the first in-core commercial nuclear AM component ever to go into serial production. This would not have been possible without the hard work and dedication of a global team. We were presented with a significant challenge to design, develop, qualify and deploy a safety-related AM component in 12 months to ensure continued energy security in Ukraine and Eastern Europe. The team answered that challenge and delivered something exceptional.”
That doesn’t come from nowhere. Westinghouse has been working with additive manufacturing technology now for several years, announcing in 2020 the successful installation of a 3D printed thimble plugging device inside a commercial nuclear reactor. This component is used to help lower fuel assemblies into nuclear reactor cores, and was deemed a ‘low-risk’ and low-volume’ application. At the time, it was perfect for where Westinghouse was on its AM journey.
It wouldn’t satisfy the demands of the sectors Westinghouse serves though. In 2022, the company installed its StrongHold AM 3D printed nuclear fuel debris filters in two Nordic Boiling Water Reactor (BWR) units, improving operational efficiency. The printed parts here were said to enhance capture features to prevent debris from entering fuel assembly, which could lead to expensive outages.
A year on from that and Westinghouse was delivering its VVER-440 fuel assemblies to locations in Eastern Europe. Due to Russian attacks on Ukraine’s energy system, lengthy power outages had occurred at the back end of 2022, with Ukraine anticipating a similarly difficult winter in 2023. For Westinghouse to manufacture bottom flow plates the conventional way would have required the fabrication of stamping dyes which, taking up to 12 months, would have significantly overshot its deadline. According to the company, AM was a ‘critical enabler’ in getting the parts developed, qualified and delivered on time.
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Westinghouse Electric Company
Westinghouse's TCT Award-winning VVER-440 flow plates
Produced with laser powder bed fusion technology, the top flow plates are consolidated from seven parts (six machined pins welded to a machined plate) to one, with the bottom plate being consolidated from two parts (a stamped skirt welded onto a machine plate) to one. Multiple welding and strap forming processes have been eliminated, with Westinghouse reporting the assembly is stronger as a result. The bottom flow plate is also said to improve fuel rod positioning, while the top flow plate provides a greater margin of safety in accident conditions. Westinghouse also says additive manufacturing is the most cost-effective method of manufacture for these components, though it could not identify a supplier that could commit to developing a compliant bottom flow plate manufactured with conventional methods anyway.
It has represented a significant milestone for Westinghouse.
“The [VVER-440] effort hugely impacted our organisational maturity in tolerancing for AM, as well as building operational efficiency around AM development efforts and deployment into serial production,” Travis said. “Even greater, the milestone of 1,000+ safety-related AM parts produced sends a message to the commercial nuclear industry that AM is not tomorrow’s novelty but today’s reality. It’s ready to start delivering value now.”
Westinghouse has wasted no time in proving that point. Less than a month after it was awarded the TCT Industrial Application Award for the successful development and deployment of its VVER440 fuel assemblies, the company had built on its prior debris capture progress by reporting a 30% improvement in the bottom nozzles of its Pressurised Water Reactor (PWR) fuel assemblies.
These PWR fuel assembly designs had been developed with conventional manufacturing methods and met both strength and pressure drop requirements for a nuclear fuel assembly. But Westinghouse had learnt from its prior applications of AM.
“Strategically, when we think about AM, we always look for opportunities to leverage AM as a design tool, not just a manufacturing tool,” Travis explained. “When looking at how we could improve even further for the next generation of bottom nozzles, it was clear that the design freedom of AM would be a crucial enabler, especially to improve debris catching efficiency over that achievable with conventional manufacturing methods – i.e. CNC.”
Westinghouse Electric Company
AMBN installed in lead use assembly
These nozzles, integrated into four Lead Test Assemblies and delivered to a nuclear plant operated by Southern Nuclear, were designed with a complex three dimensional filter geometry that is said to be highly efficient at debris capture and hydrodynamic. By decreasing the size of the debris that can pass through the filter by a factor of 13 and enabling the filter to retain a significant quantity of debris without clogging or affecting coolant flow characteristics, debris filtration efficiency has increased from 65% to 96%. It addresses the concern of loose debris in the closed primary coolant loop catching in the grids and wearing away the protective cladding on the fuel rods. Though rare, this could cause nuclear fuel to leak onto the coolant loop, leading to additional costs.
“When considering debris filtration in the reactor core, there is an unavoidable tradeoff between filtration efficiency – size and quantity of debris captured – and cooling loop hydrodynamics – pressure drop across the loop,” Travis explained. “Westinghouse pushed conventional bottom nozzles as far as possible in terms of maximising filtration efficiency without deleteriously affecting pressure drop. With the additively manufactured bottom nozzle, thanks to purpose-driven design enabled by AM, we were able to dramatically improve filtration efficiency even further, while delivering comparable pressure drop performance.”
With such additive manufacturing accomplishment, Westinghouse fancies itself as the leader when it comes to deploying the technology in the nuclear industry. Attention is already turning to what comes next, with the additively manufactured bottom nozzles scheduled to enter serial production once sufficient operational experience has been accumulated in the next couple of years. The company also expects a similar outcome for its Stronghold AM filters for Boiling Water Reactors, and then the company’s sights are being set on integrating AM technology into some of its most advanced products.
“The additively manufactured bottom nozzles, StrongHold AM, and VVER-440 Flow Plates are all drop-in improvements for the world’s existing fleet of Light Water Reactors (LWR),” Travis finished. “In the next few years, we’ll see more and more of those drop-in applications coming out. On a longer timescale, we’ll also see one or two truly revolutionary LWR AM applications, as well as design-enabling applications in Advanced Reactors like Westinghouse’s eVinci microreactor, the AstroVinci lunar/orbital reactor, and the AP300 Small Modular Reactor.”
This article originally appeared inside TCT Europe Edition Vol. 32 Issue 4 and TCT North American Edition Vol. 10 Issue 4. Subscribe here to receive your FREE print copy of TCT Magazine, delivered to your door six times a year.
