Friday, 14 March 2025
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Transient tests on a high-burnup metallic fuel that was archived from historic irradiation testing at Idaho National Laboratory (INL)’s EBR-II reactor were carried out at the lab’s Transient Reactor Test (TREAT) facility, using a new, specially designed test capsule with a variety of sensors to monitor fuel behaviour during testing.
The tests are part of a collaboration between the US Department of Energy (DOE) and the Japan Atomic Energy Agency (JAEA) to develop and qualify fuels for fast reactors through a five-year cost-shared facility sharing initiative under the . The researchers are testing a mixed oxide fuel used by current Japanese fast reactor designs and a metallic alloy fuel that is being developed in the USA and is “of interest to Japan”.
Transient tests study the safety limits of nuclear fuel under more extreme conditions than typically encountered in normal reactor operations. TREAT – which restarted in 2017 after 23 years on standby – is one of only a few reactors in the world that can produce the bursts of energy needed for such tests: short duration power cycles that may be more than ten times higher than in a commercial power plant.
The DOE and JAEA have performed similar tests on high-burnup fast reactor fuel before, but these came to an end in 1994 when the EBR-II – a 62.5 MWth, 20 MWe liquid-sodium cooled, fast breeder reactor used to test fuels and materials as well as being a demonstration fast reactor – was shut down after 30 years of operations. EBR-II has since been decommissioned, although its iconic containment structure is being repurposed to house the National Reactor Innovation Center’s DOME test bed facility.
INL Technical Lead for Transient Testing Colby Jensen said the main ambition of the initiative is to test fast reactor fuels in their weakest state to better understand their limits and inform the development of improved designs. “Fast reactor fuel designs in the United States have not made a major leap forward since the era when the EBR-II programme was shut down, and so the data from these tests of legacy fuel is highly valuable for advanced fuel designers today,” Jensen said.
Post-irradiation examination work will be performed at INL’s Hot Fuel Examination Facility and Irradiated Materials Characterization Laboratory. The initial project experiments are expected to be completed later this year, and DOE and JAEA plan to perform several additional safety tests “over the course of the next few years”.
