General Atomics – Electromagnetic Systems (GA-EMS) – with support from the US Department of Energy (DOE) – has developed silicon carbide nuclear fuel cladding tubes that can withstand extreme temperatures. DOE says this could completely transform the way industry makes future fuel.
Currently zirconium alloy is widely used as a nuclear fuel cladding because of its mechanical properties and corrosion resistance. While improvements have been made to zirconium alloy cladding over time, there is an interest in exploring and developing new cladding material to significantly improve the operating performance, economic efficiency, and safety of light water reactors.
GA-EMS is developing a new fuel cladding called SiGA with the help of funding, irradiation testing, and post irradiation examination support from DOE’s Accident Tolerant Fuel Programme. SiGA cladding is made from silicon carbide – a high-temperature ceramic material made of silicon and carbon in a high-purity crystalline composition.
Silicon carbide can survive temperatures hotter than molten lava but can be brittle in its pure form, historically limiting its use as a structural material. GA-EMS solved this problem by incorporating silicon carbide fibre into the cladding. The fibre reinforces the material similar to the way steel rebar is used to reinforce concrete.
The combination creates an tough and durable engineered silicon carbide composite material which can withstand temperatures up to 3800°F – some 500 degrees hotter than the melting point of zirconium alloy.
GA-EMS has already created 6-inch-long SiGA rodlets and 3-foot cladding samples that meet stringent nuclear power reactor-grade requirements and will undergo irradiation testing at DOE’s Idaho National Laboratory. Recent work has demonstrated the process is scalable to full-length 12-foot fuel rods.
SiGA cladding contains the solid fuel and any gasses that are produced during operation and features a novel sealing technology capable of withstanding pressures far beyond that typical of light-water reactor conditions. To make SiGA cladding a reality, GA-EMS will continue to scale up its manufacturing technology and further analyse SiGA both before and after irradiation. Accelerated fuel qualification methodology is underway using research reactors, commercial reactors, and modelling and simulation. GA-EMS believes that SiGA cladding could be demonstrated by the end of this decade, with commercialisation in early 2030. GA-EMS is also developing domestic manufacturing capability for SiGA.
Through the Accident Tolerant Fuel Programme, three of the largest US nuclear suppliers are working with DOE to develop other accident tolerant fuel concepts. DOE says these new fuel and cladding mixtures could help improve the overall economics and performance of today’s reactors – and allow for longer response times at high temperatures in accident situations.
