Ask Dr. Tatiana Ivanova, a long-time nuclear engineer and head of the Nuclear Science division at Paris-based intergovernmental organization Nuclear Energy Agency (NEA), why so much activity is ongoing to transform nuclear fuel — and her answer is simple: “It is the principal part of nuclear power plants.” Fuel design optimization is “a cornerstone for the industry to deploy new, modern fuel for light-water reactors [LWRs], advanced reactors, and small modular reactors,” she said. “Also, it is a very important part in storing, recycling, and disposing of used nuclear fuel. That is why a study of performance and reliability of nuclear fuel have remained a high priority in the research portfolios of all nuclear countries.”
What’s notable, she explained to POWER in February, is that all LWRs around the world currently use fuel systems comprising uranium oxide (UO2) encased within a zirconium-based alloy cladding (and to a much smaller degree, some reactors use uranium-plutonium oxide, or mixed-oxide [MOX] fuels). Over many decades, this oxide fuel-zircaloy system has been optimized, it has matured, and it has generally met all performance and safety requirements. But over the last 10 years, a rapidly changing sector has required a transformation — an urgent revival that starts at that core, with safety and economics as key priorities, she said.
Safety, perhaps, has been the foremost driver of rapid fuel design optimization. As Fukushima showed, “because of the highly exothermic nature of zirconium-steam reactions, under some low-frequency accidents [when core cooling is temporarily lost and part of the core is uncovered], low-probability accidents may lead to an excess generation of heat and hydrogen, resulting in undesirable core damage,” Ivanova said. That’s why in 2014, the NEA, a specialized agency within the Organisation for Economic Co-operation and Development (OECD), jumped into action to gauge the interest of its of its 33 member countries in the exploration of enhanced accident-tolerant fuels (ATF) for LWRs, she said.
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