China has achieved significant breakthroughs in nuclear safety, developing and testing two distinct types of advanced nuclear reactors designed to inherently prevent meltdowns. These innovations, encompassing both High-Temperature Gas-Cooled Reactors (HTGRs) and Thorium Molten Salt Reactors (TMSRs), represent a major step forward in addressing the critical safety concerns that have historically challenged nuclear energy adoption globally.
The High-Temperature Gas-Cooled Reactor (HTR-PM): Passive Cooling in Action
One of China’s leading achievements in meltdown prevention is the High-Temperature Gas-Cooled Reactor Pebble-Bed Module (HTR-PM) at Shidao Bay. This reactor, which began operations, has successfully demonstrated a passive heat removal system that eliminates the need for external power or human intervention to prevent overheating.
The HTR-PM employs a unique “pebble-bed” design. Instead of traditional fuel rods, it utilizes thousands of billiard-ball-sized graphite spheres, each encasing tiny TRISO (TRi-structural ISOtropic) fuel particles of uranium. These TRISO fuel cells are highly resistant to extreme temperatures and radiation, ensuring that radioactive materials remain contained even under severe conditions.
The heat removal method in the HTR-PM is inherently passive. The reactor uses inert helium gas as a coolant, which can operate at much higher temperatures than water. In the event of a power outage or cooling system failure, the reactor’s low power density and the high heat resistance of its components allow heat to dissipate naturally through conduction, convection, and radiation. Researchers from Tsinghua University successfully conducted tests in August and September 2023, where they intentionally shut off the active power supply to the cooling systems of two commercial-scale 100 MW reactors. The reactors subsequently cooled down to stable temperatures within 36 to 50 hours, demonstrating their inherent safety and “meltdown-proof” capability. This design, according to researchers, would have prevented the catastrophic events of the Fukushima Daiichi accident in 2011, where a tsunami caused a power outage that crippled active cooling systems.
Thorium Molten Salt Reactors (TMSRs): Draining Away Disaster
Parallel to the HTR-PM’s success, China is also making significant strides with Thorium Molten Salt Reactors (TMSRs), primarily with an experimental prototype located in the Gobi Desert. This technology offers a fundamentally different approach to nuclear safety and fuel.
The TMSR utilizes liquid thorium fuel dissolved in molten fluoride salts, which act as both the fuel carrier and the coolant. Unlike conventional reactors that rely on solid fuel rods and high-pressure water cooling, the molten salt design operates at high temperatures but low pressure, significantly reducing the risk of explosive pressure failures.
The key “meltdown-proof” mechanism in TMSRs is a passive safety feature known as a “frozen salt plug.” During normal operation, this plug, located at the bottom of the reactor vessel, is actively cooled. However, if the reactor experiences an emergency, such as overheating or a power failure, the plug automatically melts. This allows the liquid radioactive molten salt fuel to drain by gravity into a subcritical cooling chamber below, where it cools down and solidifies, effectively halting the nuclear reaction without any active control or external intervention.
Chinese scientists achieved a significant milestone in October 2024 (announced in April 2025) by successfully refueling an experimental thorium-fueled molten salt reactor continuously without shutting it down – a world first. A 2MW prototype achieved criticality in October 2023. China plans to begin construction of a larger 10MW facility in 2025, aiming for full operation by 2030, with a roadmap to scale up to 100MW TMSRs from 2030 onwards.
Why Meltdown-Proof Matters: Enhancing Nuclear Safety
The development of these meltdown-proof reactor technologies directly addresses the historical anxieties surrounding nuclear power, stemming from incidents like Three Mile Island, Chernobyl, and Fukushima. These past disasters were characterized by a loss of cooling, leading to severe core damage and the release of radioactive materials.
The passive safety systems in China’s new reactors fundamentally change this paradigm. By relying on natural physical principles (like natural circulation, conduction, and gravity drainage) rather than active, power-dependent systems, the risk of a catastrophic meltdown is virtually eliminated, even in the event of a complete loss of power. This enhanced safety is crucial for public acceptance and broader global adoption of nuclear energy as a clean, reliable power source.
China’s Ambition in Advanced Nuclear Technology
These advancements underscore China’s aggressive push to become a leader in advanced nuclear technology. The nation views nuclear power as a critical component of its strategy to reduce carbon emissions and achieve carbon neutrality by 2060.
Beyond safety, thorium reactors offer additional advantages, including the use of a more abundant fuel source than uranium, and the generation of significantly less long-lived radioactive waste. While challenges remain, such as the high initial construction costs and the corrosive nature of molten salts, China’s continuous research and development aim to overcome these hurdles. With plans to deploy numerous advanced reactors in the coming decades, China is not only reshaping its own energy landscape but also positioning itself to influence the future of nuclear power globally.
