Diagram showing the structure of Lightbridge Fuel. (Image: Lightbridge)
Lightbridge Corporation has fabricated samples of nuclear fuel materials made of an enriched uranium-zirconium alloy, matching the composition of the alloy that the company intends to use for its future commercial Lightbridge Fuel product. The fuel is designed to improve the performance, safety, and proliferation resistance of nuclear reactors, according to the company. The enriched coupon samples will now be placed into capsules for irradiation testing in Idaho National Laboratory’s Advanced Test Reactor.
Characteristics: The fuel has three components that are metallurgically bonded during the fabrication process to improve fuel rod integrity and thermal conductivity, as well as to eliminate a source of fission product release during any bonded barrier breach.
The fuel core is made of a uranium-zirconium alloy with high thermal conductivity and low irradiation-induced swelling. The metallurgically bonded barrier is made of a corrosion-resistant zirconium-niobium alloy “with variable thickness to increase protection at the lobe tips,” according to the company.
The fuel also has a unique shape, with a “helical multi-lobe fuel rod which increases fuel surface area. At the same time, it reduces the distance it takes heat generated in the fuel rod to reach water, improving fuel coolability. Swelling occurs primarily in the valleys between the lobes to maintain the fuel rod diameter,” the company noted.
Advantages: According to Lightbridge, its fuel product allows reactors to “operate at significantly lower temperatures while extracting more heat from the fuel core and delivering greater electricity output,” resulting in improved economics.
The safety benefits from the fuel come from the substantially lower temperature of the fuel rods (>1000°C cooler), compared with standard nuclear fuel, and the 35-percent greater fuel surface area, which leaves “considerably more margin to fuel failure.”
The company stated that its initial fuel enrichment level is in the range of 15 percent to 20 percent, “making it the lowest strategic value for proliferation potential.” The fuel “contains significantly less plutonium than conventional uranium oxide fuel and consumes more uranium during its operating cycle.”
Testing at INL: The next step is to test the enriched coupon samples in the ATR as part of a cooperative research and development agreement between INL and Lightbridge. The irradiation testing, including post-irradiation examination activities, will generate performance data for the Lightbridge Fuel. These data, stated Lightbridge, “will play a key role in supporting the company’s regulatory licensing and commercialization efforts for deployment of Lightbridge Fuel.”
