Researchers at Idaho National Laboratory (INL) performed a new experiment that shows what happens to nuclear fuel when there is a loss of coolant accident.
The safety test is the first of its kind in the U.S. in more than 35 years and restores the nation’s ability to conduct similar experiments that are only available in Russia.
A New TWIST
INL developed a specialized experiment holder that can be loaded into its Transient Reactor Test (TREAT) Facility.
The lab’s new “TWIST” capsule is designed to hold a fuel sample that is surrounded by water, which can be rapidly drained during testing.
The TWIST experiment is paired with TREAT’s transient pulses, which are short, sudden bursts of energy that are five times more powerful than a commercial reactor, to simulate loss of coolant accident conditions in a controlled environment.
Data collected from the experiment will help industry assess fuel performance, answer regulatory questions, and develop new fuel technologies
“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 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.”
Restoring Loss of Coolant Accident Testing
All commercial reactors in the United States use water to cool their cores.
A loss of coolant accident (LOCA) could occur if water rushes out of the reactor faster than it can be added back in, causing significant damage to system.
LOCA testing is a key part of assessing the behavior of nuclear fuels and materials. It’s used to ensure that the equipment maintains its intended safety function under this scenario.
The TWIST experiment restores the nation’s ability to perform LOCA testing and supports the development of accident tolerant fuels that could extend operating cycles and reduce the amount fuel needed to operate commercial reactors — leading to less waste and a reduction in fuel costs over the lifetime of the plant.
The U.S. lost the ability to perform LOCA tests when its Power Burst Facility shut down at INL in the mid-1980s.
To bridge this testing gap, the U.S. worked with Norway to conduct fuel safety tests at the Halden Boiling Water Reactor.
When that reactor shut down in 2018, LOCA testing only existed at a Russian test reactor.
Expanding the TREAT Testing Capabilities
INL made modifications to TREAT to accommodate a larger experiment rig that can be used by TWIST and future experiments at the facility. The larger rig will also be used for upcoming sodium loop tests to support the development of TerraPower’s Natrium small modular reactor.
The TREAT facility will also house DOE’s MARVEL microreactor.
The sodium-potassium-cooled microreactor is expected to be operational in 2025 and will be used to advance small reactor technologies.
