High-burnup fuel rods arrive at PNNL for testing
Eleven high-burnup fuel rods manufactured by Global Nuclear Fuel have been delivered to Pacific Northwest National Laboratory for a battery of destructive tests. PNNL’s evaluation will provide GNF and the Department of Energy with information about the performance of the fuel, which—like other fuels developed through the DOE’s Accident Tolerant Fuel program— was engineered to handle longer operating cycles, improve fuel cycle economics, and support power uprates for existing light water reactors.
After six years of service in a power reactor core, fuel rods typically have time for cooling in a spent fuel pool. But these 11 rods were packed into a 60,000-pound stainless-steel rod carrying cask for a journey to PNNL that was “well-regulated, requiring complex logistical coordination between agencies over a span of 14 months,” according to GE Vernova. (GNF is a GE Vernova–led joint venture with Hitachi, Ltd.)
The fuel rods were manufactured at GNF’s Wilmington, N.C., facility then spent two operating cycles in the core of a boiling water reactor. Following those two operating cycles, according to GE Vernova, the same assemblies were licensed by the Nuclear Regulatory Commission for use as “high-burnup lead use assemblies” and “reloaded for an additional cycle to achieve operation in the reactor beyond current NRC licensing limits.” PNNL is now studying the impacts of the additional time in the core on the fuel and cladding performance.
The high-burnup motivation: “To draw more energy from these materials and increase plant power is like putting new generating capacity on the grid without having to build any new infrastructure,” said Mark Nutt, director of PNNL’s nuclear energy market sector. “That’s a useful thing for both fuel vendors and a nation that seeks to realize a fuller nuclear potential.”
The fuel shipped to PNNL is the same design that will be used in the initial core designs of the GE Vernova Hitachi Nuclear Energy BWRX-300 small modular reactor. GNF expects the data gained to support a potential extension of fuel cycle lengths for the BWRX-300 from 36 to 48 months.
“The examination of these rods is the next step in our continuous drive to develop higher efficiency fuels that are safer and more reliable,” said Craig Ranson, GE Vernova Hitachi Nuclear Energy’s Installed Base CEO.
The work is funded by the DOE Office of Nuclear Energy’s Accident Tolerant Fuel program. Frank Goldner, the DOE-NE’s Accident Tolerant Fuel federal program manager, said, “The development of this fuel could further support the Trump Administration’s executive order to facilitate five gigawatts of power uprates at existing power plants by 2030 and high-burnup fuels could be a big part of that.”
Inside a hot cell, a manipulator grasps and twists the tool that will puncture a fuel rod’s cladding, allowing researchers to measure the amount of xenon and krypton gases released. (Photo: Andrea Starr/PNNL)
Destructive testing: At PNNL’s Radiochemical Processing Laboratory (RPL)—a hazard category II nonreactor nuclear research facility—the rods are being punctured, cut, and mechanically stressed, according to the lab, with data collected before, during, and after those tests. Testing has included puncturing the cladding on a fuel rod inside a hot cell and capturing the released gases to understand the internal pressure inside the cladding.
“The RPL provides a unique opportunity where we can actually accept full-length high-burnup rods, perform the research in the hot cells, and take the material to different labs within the same space—without having to transfer buildings—for testing. It’s very efficient,” said PNNL chemist and project co-lead Susan Asmussen. “We have the ability to do work on materials—from post-irradiation examination to liquid-liquid separation chemistry—that few other facilities have.”
Debris generated from the disassembly of the rods will be used to train scientists who develop technology to detect and monitor nuclear activities, according to PNNL. Under the National Nuclear Security Administration’s Nonproliferation Stewardship Program, RPL staff will be able to study the debris to “understand how to characterize and monitor the movements of special nuclear materials like uranium and plutonium through a chemical separations process.”
