In 2011 the nuclear energy industry faced one of its greatest challenges. Koroush Shirvan, assistant professor in the MIT Department of Nuclear Science and Engineering rose to the challenge. Shirvan has seized on an innovative nuclear fuel concept that addresses key safety issues while offering potential improvements in reactor performance.
From the start, Shirvan’s team sought both fuel and cladding alternatives. “In Fukushima, there were hydrogen explosions because of interactions between the conventional zirconium-based fuel cladding (the outer layer of fuel rods) and high temperature steam produced when the safety system failed and coolant water heated up,” he says. Hydrogen leaked out of the core and detonated in the reactor building itself. “Our goal was to come up with fuels that can last longer during potential heat-up events and reactor cladding materials that won’t generate much combustible hydrogen as quickly as zirconium.”
Collaboration with Free Form Fibers, a company co-founded by former Stanford University materials scientist Pegna, a pioneer in additive manufacturing, the firm approached Shirvan several years ago with an idea for using their patented 3D laser printing technique to create a new fuel. “They proposed using chemical vapor deposition (CVD) to create fuel fibers in which protective material coats each fiber, layer by layer,” says Shirvan. “This enables the fuel to serve as its own containment.”
The concept was to pack these CVD-fabricated, cylindrically shaped fuel particles into a bundle that fits into a typical fuel rod, and replace the conventional zirconium fuel rod cladding with silicon carbide composite, to slow down hydrogen generation. This would hypothetically enable “retrofitting” current nuclear plants with new and safer materials.
The base of each uranium nitride fuel, which is coated with a soft buffer layer made out of porous carbon, followed by denser carbon, followed by silicon carbide — a material with a very high melting point. Spaces are filled by more silicon carbide, with bundles stacked on top of each other vertically, then placed inside a cladding also made out of silicon carbide or other ATF material. These uranium and carbon fuel cylinders wrapped in silicon carbide, stuffed into a silicon carbide-clad fuel rod, can theoretically survive temperatures up to 1,800 degrees Celsius, which might enable nuclear reactors to run at higher power levels
Samyak is the IT Manager at IYNS. He is currently in Mumbai, pursuing his PhD in Experimental and CFD simulations of ablation behaviour of sacrificial material by molten corium for design of IPWR Core Catcher, from Homi Bhabha National Institute, Bhabha Atomic Research Centre, Mumbai. He is an Applied Nuclear enthusiast and always has time for a good Old School Shayari. Additionally, his interests include Severe Accidents, learning new software, reciting Shayaris and debating.