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US researchers develop zirconium-free alloy for nuclear fuel rods to enhance safety

EBR Staff Writer Published 16 April 2018

Researchers from the US Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL) have developed a custom-designed cladding for nuclear fuel rods in order to enhance safety.

The new material, which is an alloy of iron, chromium and aluminum, is intended to avoid zirconium, which is commonly preferred as base metal for fuel rods developed for civilian nuclear power plants.

Zirconium allows absorption of very few of the neutrons that drive a nuclear reactor, making its alloys suitable for fuel cladding as long as the reactor operated as planned.

However, once the reactor loses its cooling water, the zirconium makes a bad problem worse, the researchers said.

ORNL nuclear engineer Kurt Terrani said: “The issue is you have anywhere between 20 and 40 tons of zirconium metal in these reactor cores.

“Zirconium reacts with steam at high temperature, and when it reacts it produces a lot of heat and a lot of hydrogen.”

In order to address the issue, the team of researchers has developed the new zirconium-free alloy to provide substantially more time for plant operators to react to incidents such as a station blackout.

The new alloy, which has been developed using wide range of tools and expertise available at ORNL, can generate as little hydrogen as possible during incidents.

The researches have already tested the new cladding at ORNL’s High Flux Isotope Reactor and Idaho National Laboratory’s Advanced Test Reactor, as well as at the Halden research reactor in Norway.

Earlier this year, the new cladding was placed in a reactor at Southern Nuclear’s Hatch Nuclear Power Plant in Georgia for testing. Subsequent installations for the cladding are planned, Terrani noted.

Backed by DOE’s Office of Nuclear Energy, the research has leveraged ORNL’s High Flux Isotope Reactor, a DOE Office of Science User Facility.

Image: ORNL-designed nuclear fuel cladding. Photo: courtesy of Jason Richards/Oak Ridge National Laboratory, U.S. Dept. of Energy.