October 12, 2023, 12:00PMNuclear News
Idaho National Laboratory's TREAT reactor. (Photo: INL)

Researchers at Idaho National Laboratory have a new experimental tool to study nuclear fuel under simulated loss of coolant accident (LOCA) conditions in INL’s Transient Reactor Test (TREAT) Facility. A specialized experiment holder called a TWIST capsule holds a fuel sample surrounded by water, which can rapidly drain away during testing, simulating loss of coolant in a light water reactor environment.

Lost capability: According to the Department of Energy’s October 4 announcement, the test is the first of its kind to be run in the United States in more than 35 years.

The United States lost the ability to perform LOCA tests when INL’s Power Burst Facility shut down in the mid-1980s. In need of testing, U.S. researchers worked with Norway to conduct fuel safety tests at the Halden Boiling Water Reactor. And when that reactor shut down in 2018, LOCA testing was available only in Russia.

INL made modifications to TREAT to accommodate a larger experiment rig that can hold TWIST and other future experiments. The larger rig could support upcoming sodium loop tests for TerraPower’s Natrium reactor.

Purpose and use: Fuel inside a TWIST capsule is irradiated by TREAT’s transient pulses—five times more powerful than a commercial reactor—to simulate LOCA conditions in a controlled environment. Data collected from the experiment will help assess fuel performance and provide data that regulators will need to assess accident tolerant fuels for light water reactors. Those fuels could extend operating cycles and reduce the volume of fuel needed to operate commercial reactors—leading to less waste and a reduction in fuel costs over the lifetime of the plant.

“Loss of coolant accident testing is essential to developing new fuels that will boost the performance of our nuclear power plants and help them run more efficiently,” said Bill McCaughey, director of advanced fuel technologies for the DOE’s Office of Nuclear Energy. “Bringing this testing capability back to the U.S. ensures the timely deployment of accident tolerant fuels that our industry has worked so hard to develop.”

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