Filling technical gaps and fueling the advancing nuclear supply chain at SRNL
Ensuring energy resilience for our nation is on the minds of leaders and citizens alike. Advances in nuclear power technologies are increasing needs within the nuclear industry supply chain. Savannah River National Laboratory’s decades of experience in nuclear materials processing makes the lab uniquely qualified to meet the current and future challenges of the nuclear fuel cycle.
SRNL has demonstrated expertise in developing solutions for tristructural isotropic (TRISO) fuel processing, high-assay low-enriched uranium (HALEU) feedstock, and molten salt reactor fuel development. Our capabilities are poised to accelerate broad adoption of advanced small modular reactors by addressing fuel cycle needs.
Advanced SMRs and microreactors are key to the future of reliable and secure energy. While these reactors offer many benefits, a viable solution is needed to both support fuel supply-chain needs and handle the resulting spent nuclear fuel.
“SRNL is excited to be engaged in solving technical challenges to enable deployment of advanced nuclear reactors,” said Bill Bates, SRNL’s deputy associate laboratory director. “Helping to fill technical gaps in both the front and back ends of the fuel cycle is very important work for SRNL and our industry partners.”
TRISO
The core of a TRISO particle is surrounded by four layers: buffer, inner pyrolytic carbon, silicon carbide, and outer pyrolytic carbon. (Image: Alphonzo James/ SRNL)
Recovered TRISO fuel particles. (Photo: Robert Pierce/ SRNL)
The Department of Energy identified several new reactor designs that will require TRISO fuel before coming on line by 2030. TRISO fuel particles, which are more structurally sound and resilient than typical reactor fuel, are encased in graphite moderator. However, a TRISO-based reactor typically discharges the largest volume of SNF in the industry—roughly 10 to 15 times that of traditional light water reactors—per unit of energy produced.
SRNL’s patented vapor digestion process provides a 60 percent overall reduction of TRISO SNF volume by removing the graphite binder in which the small particles of fuel are dispersed. This reduction process generates carbon dioxide, which must be treated to meet regulatory requirements. SRNL and the University of South Carolina have partnered to develop a process to capture the CO2 and convert the gas into a solid form so it can be disposed of as low-level waste. The patented vapor digestion technology can also be leveraged to maximize optimization of the nation’s HALEU supplies through its use in the recovery of HALEU from fresh fuel scrap during fuel fabrication or recovery of HALEU from irradiated spent nuclear fuel.
Project collaborators and funding partners include the DOE Office of Technology Transitions, the DOE Advanced Research Projects Agency–Energy (ARPA-E), the University of South Carolina, and Westinghouse.
HALEU
Many of the new reactors will require a supply of HALEU fuel, which contains a higher relative percentage of uranium-235 than what is used in existing commercial reactors. Unfortunately, in the near term, the current U.S. industry projected demand for HALEU far exceeds the available supply.
Through work sponsored by the DOE Office of Nuclear Energy, SRNL is using its extensive capabilities and competencies in radiochemical analysis to determine compatibility of existing high-enriched uranium inventories at the Savannah River Site for use in HALEU production to meet fuel fabricator specifications.
Although fabrication and reprocessing of fuel are vital components in supporting the nuclear fuel supply chain of the future, the ability to safely transport these fuel materials must not be overlooked. The produced HALEU is in a liquid solution known as uranyl nitrate. SRNL is also working closely with an industry partner to conduct an analysis that will allow shipment of this solution using a licensed shipping package. SRNL has extensive expertise in packaging and transportation technologies and is leading the effort to obtain a license to transport this material at the higher U-235 levels found in HALEU. This will allow the transport of HALEU to a fuel fabrication facility that will produce new fuel for advanced SMRs.
MSR Fuels
Loaded crucibles in a process tube prior to insertion into the tube furnace for a chlorination technique experiment. (Photo: Bryan Foley/SRNL)
Scientists at SRNL are testing a new technology for processing SNF from existing LWRs for use in MSRs, which are gaining attention for their increased efficiency and reduced waste volumes, compared with conventional reactors. In this scenario, cladding is removed from commercial SNF sourced from traditional nuclear power plants, and the fuel is converted into a salt that can be used as MSR fuel. While the reprocessing of the SNF serves the back end of the commercial nuclear fuel cycle, the creation of the salt supports the front-end supply chain for MSRs.
In theory, SNF from any existing commercial reactor could be converted into fuel for MSRs by using a molten, salt-based chlorination technique patented by Metatomic Energy Inc. SRNL is collaborating with Metatomic to perform proof-of-concept experiments to assess the viability of this technique. This effort has been supported through an award from the DOE-NE’s Gateway for Accelerated Innovation in Nuclear (GAIN) program.
As the energy landscape evolves and nuclear fuel needs rise, the lack of an appropriate nuclear fuel supply chain and gaps in available process technologies for fuel processing pose challenges that SRNL is well positioned to overcome.
Catelyn Folkert is an environmental management communications specialist at Savannah River National Laboratory.