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Materials for nuclear environments

INOR-8, a nickel-molybdenum-chromium-iron alloy that resists aging, embrittlement, and corrosion from exposure to hot fluoride salts was developed to contain fuel used in the Molten Salt Reactor Experiment. Image credit: ORNL

75 years of science and technology

ORNL’s nuclear pioneers understood early on that this new technology would demand the hardiest of materials.

Nuclear reactors—with high temperatures and pressures, corrosive and oxidizing liquids, and heavy neutron bombardment—are a uniquely hostile environment for the materials that go into their fuels, reactor vessels and other equipment.

Eugene Wigner made the point in a 1946 paper in the Journal of Applied Physics: “Clearly, the collision of neutrons with the atoms of any substance placed into the pile will cause displacements of these atoms.”

As a result of these challenges, ORNL’s mission since the 1950s has included a focus on the materials used in nuclear environments.

“That’s something that ORNL has been in the forefront of ever since,” noted Jeremy Busby, director of the lab’s Materials Science and Technology Division. “We’ve worked on water reactors, molten-salt reactors, gas and sodium reactors, reactors for submarines and aircraft carriers. We’ve dabbled with aircraft and spacecraft applications. We’re a leading laboratory in the United States for fusion. So we have a wide range of expertise.”

In the 1970s and ’80s, the lab developed steel alloys containing chrome and molybdenum that made effective pressure vessels. More recently, the lab has worked with DOE, industry and regulators to assess extending the operating lives of America’s nuclear reactors.

Busby points to a combination of ORNL’s skills and facilities for promoting the lab’s preeminence

in nuclear materials. The High Flux Isotope Reactor and ORNL’s complex of hot cell and radiological facilities allow researchers to irradiate and analyze samples, while the lab’s strength in modeling and simulation helps promote a deeper understanding.

“I think pulling all of those pieces together has been a real bonus to solving some of these problems, developing a deeper understanding and providing solutions.”