New approach to qualifying nuclear reactor components rolling out this year

(Press-News.org) Contact: Kate McAlpine, 734-647-7087, kmca@umich.edu 

ANN ARBOR—A thousand times faster than conventional testing, an ion beam approach to qualifying materials for use in the cores of advanced nuclear reactors is advancing through stages of approval by the industry standards organization ASTM. 

The methodology, developed with leadership by University of Michigan Engineering, will be presented at a special event hosted by the Electric Power Research Institute, March 10-11 in Charlotte, North Carolina. 

Many have pinned hopes on advanced nuclear power to provide emissions-free electricity and power AI data centers, but the old way of ensuring materials can survive reactor cores can't keep up with the lifetime radiation doses inside advanced fission reactors and proposed fusion reactors.

Test reactors would take more than a decade to expose some advanced reactor components to enough radiation to simulate their design lifetimes. With ion beams, the same amount of damage can be achieved in a few days and at a fraction of the cost, enabling faster design iterations. The feasibility of using ion beams as a surrogate for test reactors has been under study for more than 35 years. 

The question was: Can the damage produced using ion beams truly mimic damage accumulation in a reactor? The answer seems to be yes. Now, the methodology is formalized as Qualification under Ion irradiation of Core Components, or QUICC. 

Key funders of the long journey to prove out this method include the U.S. Department of Energy, Electric Power Research Institute, Oak Ridge National Laboratory, Framatome and Rolls-Royce. The core team includes researchers from U-M, Pennsylvania State University, Oak Ridge National Laboratory and the University of Tennessee.

"The QUICC methodology, applied to two very different alloys, demonstrates that the critical changes to the materials under ion irradiation mimic those under reactor irradiation. The significance is that ion irradiation can be used to predict material behavior in reactors 1000 times faster than with test reactors and at one one-thousandth the cost," said Gary Was, U-M professor emeritus of nuclear engineering and radiological sciences, who led the development of QUICC.

The metric for radiation damage is displacements per atom, or dpa. Essentially, this is how many times, on average, each atom in the material gets knocked out of its location—either by a neutron from the reactor core or more often by a neighbor that took a hit. For some advanced reactors, core materials need to survive up to 200 dpa or even higher.

A lot can happen in 200 displacements. The metal's crystal lattice accumulates many disrupted spots where atoms aren't in the right place, forming various features that can make the metal brittle and vulnerable to cracking. Radiation damage can also create cavities in the material, causing it to swell. Transmutation products such as helium, which forms bubbles, can also enhance swelling. 

While neutron irradiation requires a test reactor, ion irradiation can be done with ion accelerators in laboratories. The key to mimicking the damage caused by test reactor irradiation, and at a much faster damage rate, is in the control of the ion irradiation conditions—this forms the methodology behind QUICC.

To emulate fission reactor damage, two beams are required. The bulk of the displacements come from irradiation with heavy ions, typically matching the dominant metal in the material so as not to induce chemical changes. To create helium bubbles, Was' team at the Michigan Ion Beam Laboratory added a helium ion beam. They also developed a target chamber in which the material to be tested is submerged in water heated to high temperature and under pressure to mimic the conditions in the reactor core, all while being irradiated.

The team also developed the methodology for fusion reactor environments. In these reactors, both helium and hydrogen will lodge in components along with radiation damage. This is simulated using triple beam irradiation—hydrogen, helium and heavy ion beams together—in the same proportions as in the fusion reactor.

The core team responsible for developing QUICC includes Was and Kevin Field, U-M associate professor of nuclear engineering and radiological sciences; Brian Wirth and Steven Zinkle, UT professors of nuclear engineering; Arthur Motta, Penn State professor of nuclear engineering; and Stephen Taller, staff scientist at Oak Ridge National Laboratory.

Was will also present on this method at the 2026 TMS meeting March 17 in San Diego.

Materials tested in the Michigan Ion Beam Laboratory were studied at the Michigan Center for Materials Characterization, both of which are operated and maintained with support from indirect cost allocations in federal grants. 

The team is working with U-M Innovation Partnerships to develop license agreements  to bring the technology to market. 

 

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