China has developed the first large-scale nuclear power plant that appears to be resistant to catastrophic failures.
This new design, not applicable to existing nuclear reactors, represents an innovative model for future constructions.
Current nuclear reactors require cooling systems powered to function.
These systems vary depending on the type of reactor – many use water, while others employ coolants such as CO2, helium, molten metals, or molten salts – but all share the common purpose of dissipating excess heat from the reactor core.
Water cooling systems are known for their high power density, which translates into greater thermal efficiency.
However, they pose risks, such as the possibility of explosion in the event of core meltdown, due to the loss of power to the water pumps which can lead to the splitting of water into explosive hydrogen and oxygen gases.
Gas-cooled reactors, although less prone to explosions compared to water-cooled ones, tend to have lower thermal efficiency.
In an emergency, regardless of the type of cooling system used, human intervention is necessary to shut down the reactor and prevent disasters, as the cooling systems depend on external power sources.
The new reactor design, known as the pebble bed reactor (PBR), could offer solutions to the problems of older designs.
These reactors are “passively safe,” as they can shut themselves down in the event of cooling system issues.
Unlike other reactors that rely on high-energy-density fuel rods, PBRs use low-energy-density fuel spheres in greater quantities.
Although they contain less uranium compared to traditional fuel rods, their number is greater and they are surrounded by graphite, which moderates the activity of neutrons in the core, slowing down nuclear reactions and generating less heat.
Recently, China has built a high-temperature gas-cooled modular pebble bed reactor (HTR-PM) in Shandong, which became operational in December 2023.
To verify its effectiveness, engineers deactivated both modules of the HTR-PM while they were fully active.
During the tests, the reactor modules naturally cooled without emergency core cooling systems or powered cooling systems, reaching a stable temperature within 35 hours of the power outage.
The ability to test a nuclear reactor in operation by removing its cooling is extremely unusual.
Although further tests will be necessary to ensure the system’s proper functioning, it is hoped that this can serve as a model for future reactors in other parts of the world.
the loss of cooling tests confirm the intrinsic safety feature of the world’s first demonstration plant of an HTR-PM.
To contribute to the goal of mitigating climate change, new projects have been initiated to provide high-temperature steam up to 500°C and electrical energy to the petrochemical industry in China.
The study is published in Joule.
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