“The NSTF was carefully designed to ensure the physics observed inside the facility represents the physics involved with a real, full-scale reactor,” said Matthew Jasica, a nuclear engineer in Argonne’s Reactor Safety Testing and Analysis group. “We receive requests for data from industry stakeholders and the Nuclear Regulatory Commission to ensure that the output from their models reflects the real world.”
Hot water: The NSTF is currently testing a water-based reactor cavity cooling system with support from the DOE’s Office of Advanced Reactor Technologies. The system boasts a 4,260-liter storage tank and piping with a 389-liter capacity. It can operate in three different modes: natural or forced circulation, single-phase with active cooling, and two-phase with steam boil-off.
A large steel plate, electrically heated on one side, is used to simulate the reactor core. On the other side of the steel plate pipes filled with filtered water run through an insulated cavity. The water begins to circulate through a large, vertical closed loop of pipes and tanks as it is heated. Then the water boils.
Argonne states: “Boiling can cause challenges including pressure waves and fluid loss. It is also a complex and chaotic process to model. Small deviations in the thermal conditions and system configuration can cause dramatically different performance outcomes.”
NSTF researchers can run tests with blockages in different areas of the pipes or with different water levels in the tanks. The team has also worked with industry stakeholders to simulate an extended, real-world scenario where active cooling is suddenly lost.
“We are generating large, high-quality datasets under different conditions, from normal operation to accident scenarios, to make sure the nuclear industry has the best possible understanding of how small changes affect decay heat removal,” said Jasica.
More on the NSTF: The 18-meter-tall natural circulation boiling water thermal hydraulic test facility was originally built at Argonne in the 1980s to provide data for the development of General Electric’s PRISM reactor and Reactor Vessel Auxiliary Cooling System. Since then, it has been adapted to test a series of reactor technologies and configurations.
In 2005, the program began exploring air-based passive safety systems. That work led to a patent by Darius Lisowski, NSTF’s group manager of reactor safety testing and analysis, for a weather cap device that protects sensitive exhaust systems from wind-induced downdrafts. The program shifted to its water-based configuration in 2018.
“Our facility is always responding to the evolving needs of the nuclear industry,” said Jasica. “This type of open science is critical for the advancement and long-term operation of the next generation of nuclear power plants.”
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