Oak Ridge National Laboratory, Tenn., announces that a team led by its researchers has developed an alloy of iron, chromium, and aluminum that does not contain zirconium. Zirconium absorbs very few of the neutrons that drive a nuclear reactor, so zirconium alloys make sense as a fuel cladding–as long as the reactor operates as planned. If a reactor were to lose its cooling water, however, zirconium would make a bad problem worse.
The fuel rods at civilian nuclear power plants have been sheathed with an evolving zirconium alloy for the past six decades. Zirconium as the preferred base metal was chosen in the 1950s by Hyman Rickover, then a captain and later an admiral, as he worked to take nuclear technology and use it to power ships and submarines. His choice of cladding, as well as the light-water reactors that powered these vessels, was adapted by the nuclear power industry and dominates plants throughout the world.
The issue is that 20 to 40 tons of zirconium metal are in these reactor cores, explains ORNL nuclear engineer Kurt Terrani, who heads up the project. “Zirconium reacts with steam at high temperatures, and when it reacts, it produces a lot of heat and a lot of hydrogen.”
The job for Terrani’s team, as the innovation engine of the consortium led by General Electric, was to create a zirconium-free alloy that would generate as little hydrogen as possible during incidents, while at the same time matching the performance of the nuclear fuel rod cladding that is in use today.
The team designed the new alloy from scratch with a diverse team that included experts in nuclear engineering, materials science, radiation effects, corrosion, thermomechanics, and alloy fabrication. The approach made use of the wide range of tools and expertise available at Oak Ridge, DOE’s biggest science and energy laboratory. The new cladding also underwent testing at ORNL’s High Flux Isotope Reactor and Idaho National Laboratory’s Advanced Test Reactor, as well as the Halden research reactor in Norway.
“This was by no means an Edisonian approach,” Dr. Terrani said, alluding to the trial-and-error approach made famous by Thomas Edison. “We worked with knowledge and tools that were not available in Rickover’s day. We designed an alloy that we knew was going to work. I’m not surprised that this alloy behaves so well under different conditions; we designed it to do so.”
It has now been turned over to the industry for testing and evaluation. The new cladding was placed in a reactor at Southern Nuclear’s Hatch Nuclear Power Plant in Georgia for testing in February, and subsequent installations are planned
https://ornl.gov/news/custom-designed-alloy-enhances-nuclear-safety
