Result shows reactors could be built ‘without risk of meltdown’
The first full-scale demonstration of a nuclear power reactor designed to passively cool itself in an emergency was a success, showing that it should be possible to build nuclear plants without the risk of dangerous meltdown, researchers at China’s Tsinghua University have said.
The team of researchers working at China’s high-temperature reactor with pebble-bed modules (HTR-PM) nuclear plant in Shandong province, northeastern China, said the plant has passed a critical cooling test.
In a study published in Joule the researchers said they turned off external power to the plant Shidao Bay-1, also known as Shidaowan, to test its cooling abilities over two days.
To demonstrate that it could cool itself down without an external source, the researchers shut down the two reactor modules that make up the Shidao Bay plant when it was running at full power and tracked temperature movements inside the reactors.
Two safety tests were conducted, each at a power level of 200 MWt. The research team said the tests sought to prove that the plant is “incapable of melting down”.
During the tests, the power supply was totally switched off to see if the decay heat can be removed passively.
The researchers then monitored the plant in case of a meltdown, which did not occur. Instead, they said, stable temperatures were reached within 36 hours.
“The responses of nuclear power and temperatures within different reactor structures show that the reactors can be cooled down naturally without active intervention,” the researchers said.
“The results of the tests manifest the existence of commercial-scale inherent safety for the first time.”
Shidao Bay-1, the world’s first demonstration HTR-PM plant, began commercial operation in December 2023.
Background: China’s HTR-PM
The HTR-PM is a Generation IV high-temperature gas-cooled (HTGR) pebble-bed reactor, the world’s first commercial size power plant of this kind. It began commercial operation in December 2023.
China said at the time it was the first Generation IV plant in the world to go online. No precise definition of a Generation IV reactor exists, but the term is used to refer to nuclear reactor technologies under development including gas-cooled fast reactors, lead-cooled fast reactors, molten salt reactors, sodium-cooled fast reactors, supercritical-water-cooled reactors and very high-temperature reactors.
An international task force, the Generation IV International Forum (GIF), is sharing R&D to develop six Generation IV nuclear reactor technologies.
GIF said goals of Generation IV reactor design include lower cost and financial risk, minimising nuclear waste and high levels of safety and reliability.
In the HTR-PM, two reactors are connected to a single steam turbine to generate 210 MW of electricity. Each reactor unit has a thermal capacity of 250 MW.
The HTR-PM uses a helium coolant and a graphite moderator. Each reactor is loaded with more than 400,000 “pebbles”.
The pebbles used at the Shidao Bay HTR-PM are graphite-coated balls six centimetres in diameter, made up of about 12,000 four-layer particles dispersed in a graphite powder matrix.
The technology is intended to help replace coal-fired power plants in line with China’s plan to reach carbon neutrality by 2060.
