World’s 1st meltdown-proof nuclear reactor

 Chinese nuclear reactor is completely meltdown-proof with 105 MW capacity in clean energy breakthrough

The first ever full-scale demonstration of a nuclear 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. The High-Temperature Gas-Cooled Reactor Pebble-Bed Module (HTR-PM) is in Shandong, China. A large-scale nuclear power station in China is the first in the world to be completely impervious to dangerous meltdowns, even during a full loss of external power. The design can’t be adapted to existing nuclear reactors around the world, but could be a blueprint for future ones. Materials used in reactor can withstand very high temperatures without melting

Nuclear fission, which fires nuclear plants, generates extreme heat that poses substantial risks if not properly managed. The plant, developed by researchers at Tsinghua University, represents a major leap forward in nuclear energy safety, which has been under scrutiny since the catastrophic meltdown at the Fukushima nuclear plant in Japan over a decade ago. Traditional nuclear plants face the risk of meltdown for this reason. All modern nuclear power plants rely on powered cooling mechanisms to take excess heat away from reactors or, in the event of an emergency, human intervention to shut the plant down. Water or liquid carbon dioxide are often used. If cooling systems in these plants fail, the reactors can overheat, potentially leading to explosions and the release of dangerous radiation. The new Chinese plant uses an innovative design called a "pebble-bed reactor” to mitigate the risk of meltdown.

The nuclear reactor has been in the works since 2016 and was only began operations in December 2023. In a global first, researchers at Tsinghua University in China have successfully demonstrated a meltdown-proof nuclear fission reactor. The twin reactor design can generate 105 MW of power each. The technology is a welcome step for the nuclear energy industry after the meltdown at Fukushima in Japan more than a decade ago. During nuclear fission, large amounts of heat energy are generated, which is useful in generating electricity but is also a risk for the reaction. Nuclear reactors are designed with in-built cooling mechanisms that take the heat away from the reaction, failing which the reactor can overheat or even explode. And instead of large fuel rods, it uses small, billiard-ball-sized graphite spheres filled with tiny uranium fuel particles. These spheres are provided by the German company SGL Group and are highly resistant to heat. The materials used in this reactor can withstand very high temperatures, up to 950C, without melting.

Typically, the cooling mechanisms use water or carbon as cooling agents and are backed by external power supplies to ensure that the reactor temperature stays within control. In 2011, the Fukushima nuclear reactor experienced a rare event in which the standard and emergency power supply to the cooling mechanism failed, leading to a meltdown. Researchers have since pushed to build a nuclear reactor that is passively cooled and uses natural cooling methods. One such design is a high-temperature reactor with a pebble-bed module (HTR—PM). Conventional nuclear reactors use fuel rods that are energy-dense, containing large amounts of uranium with smaller amounts of graphite. In the HTR-PM reactor design, the fuel rod is inverted, and a large amount of graphite is used within which uranium is encased. This makes the energy density of the fuel much lower, almost like pebbles in a larger body of water. The approach has two major advantages. The first is that the nuclear fission reaction occurs much slower than a conventional reactor and can withstand a higher temperature for much longer. The second advantage is that the excess heat generated through the process is dispersed over a larger fuel area and can be cooled using passive or non-energy-consuming methods such as conduction and convection. The approach has previously been demonstrated in prototype reactors built in Germany and China but a full-scale HTR-PM reactor had yet to be attempted. 

The design of the Chinese reactor ensures that it won’t overheat to a dangerous level even if the cooling system fails. The helium gas and graphite spheres naturally dissipate heat. If the reactor gets too hot, it automatically slows down the nuclear reaction, preventing any chance of a meltdown. In 2011, the Fukushima nuclear reactor faced a rare problem where both regular and backup power supplies to its cooling system stopped working, causing a meltdown. While pebble-bed reactors do not completely solve the problem of nuclear waste, the fuel’s form allows for multiple options for waste disposal. China’s eventual goal is to eliminate or greatly reduce waste by recycling the spent nuclear fuel.

Nuclear power offers a large and reliable source of low-carbon energy, helping reduce greenhouse gas emissions and combat the climate crisis. But safety has always remained a major concern. The development of the innovative nuclear plant is part of China’s broader push to increase the supply of nuclear power and cut the reliance on coal, which is still the country’s main source of energy. It was previously reported China’s ambitious push for nuclear power to reduce its dependence on fossil fuels. The Asian country has been building nuclear reactors at an unprecedented scale, but attempting a commercial-scale nuclear reactor for a new technology is a first for China, too. Success did not come easily either. The Institute of Nuclear and New Energy Technology began constructing the commercial-scale HTR-PM at a facility in Shandong in 2016, with expectations that the site would be ready for testing a year later. 

The reactor began commercial operation only in December 2023. To demonstrate that it could cool itself down without an external source, the team shut down both modules when it was running at full power and began tracking temperature movements inside the reactor. As expected, the reactors cooled down naturally and reached a stable temperature 35 hours after they were shut down. The technology’s drawback is that it cannot be retrofitted onto existing nuclear reactors. To build a future where nuclear reactors are meltdown-proof, the nuclear energy industry will have to build HTR-PM reactors first.