Will the Era of Airlifting Nuclear Power Plants Arrive?... The Revival of 'Gas-Cooled' Reactors [Tech Talk]

Gaining Attention as Fourth-Generation Advanced Nuclear Technology
Cooled by Gases like Helium Instead of Water
Power Supply Possible Even in Remote Regions Worldwide

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On February 18, 2026 (local time), a U.S. Air Force transport plane flew with a micro nuclear reactor loaded in its cargo hold. The reactor, called 'WARD 250', was manufactured by a startup named Valar Atomics. With a power output of 5 megawatts (MW), the reactor is small enough to fit inside an airplane's cargo bay, yet it can stably supply electricity to about 5,000 households.

WARD 250 is somewhat different from conventional nuclear power reactors. While most reactors use water (light water) for cooling and heat transfer, WARD 250 is a 'gas-cooled reactor' that uses gas to cool the reactor. The U.S. government expects that small reactors utilizing gas-cooling technology will become game changers in the future, providing power to military bases, remote areas, and disaster zones.

Pressurized Water Reactor vs. Gas-Cooled Reactor

U.S. soldiers transporting the Ward 250 micro reactor in the cargo hold of a military transport aircraft. U.S. Department of War

The majority of nuclear power plants use pressurized water reactors (PWRs). The ARP1400 developed by Korea Hydro & Nuclear Power is a representative example of a PWR. In a PWR, water contained in a high-pressure vessel absorbs the intense heat from the reactor, and the thermal energy is sent to a steam generator to drive turbines and generate electricity.

In contrast, gas-cooled reactors use gases such as helium or carbon dioxide (CO2) to cool the reactor. A key characteristic of gas-cooled reactors is that the reactor temperature rises more slowly than in a PWR. This means the risk of meltdown (damage to nuclear power plant structures caused by overheating of nuclear fuel) is lower. However, since the heat transfer efficiency of gas is lower than that of water, gas-cooled reactors historically had to be much larger than PWRs, which was a significant drawback.

However, advances in nuclear fuel fabrication technology and the sophistication of pumps and valves used for transferring thermal energy have paved the way for the miniaturization of gas-cooled reactors. High-temperature gas-cooled reactors using these downsizing technologies are defined as 'fourth-generation advanced modular reactors (AMR)' under the leadership of the U.S. Department of Energy, and countries around the world are currently engaged in intense research on this technology.

Nuclear Power Plants That Don’t Need Water

Busan Gijang-gun Shin Kori Nuclear Power Plant. Pressurized Water Reactor (PWR) plants are established in locations where securing water is easy. Korea Hydro & Nuclear Power

The appeal of fourth-generation AMRs, compared to PWRs, lies in the fact that they do not require water. PWRs must be equipped with backup cooling water to respond to emergencies. This is why most nuclear power plants are built near coastlines—so that water can be secured easily in case of an emergency.

This limitation also applies to small modular reactors (SMRs), which are nuclear plants that have been dramatically downsized; all SMR plants must include backup water tanks or pools. In other words, it is difficult to install SMR plants in locations where water is hard to obtain, and this exacerbates issues for data centers, which consume as much water as power plants. This is precisely why AMR is attracting attention as the next generation of nuclear power technology.

Because AMRs can be installed relatively freely even in places where water is unavailable, they can provide vital energy immediately to military units operating in remote areas or to disaster zones where water and electricity supplies have been cut off due to natural disasters.

Overshadowed by PWRs During the Cold War... Now Gaining Attention

The fourth-generation advanced modular gas-cooled reactor (AMR) power plant unveiled by Rolls-Royce, the leading heavy industry company in the United Kingdom. Rolls-Royce website

In fact, gas-cooled reactors are a longstanding technology that has been under development since the 1950s, primarily led by the nuclear authorities in the United Kingdom and France. However, as mentioned earlier, the need for a much larger reactor due to lower heat transfer efficiency led to their gradual displacement by PWRs over time. In particular, during the Cold War, PWRs were far more suitable for nuclear-powered submarines aggressively built by NATO and the Soviet Union.

AMR technology is being actively researched not only in the United States, but also in traditional nuclear powerhouses such as Japan and the United Kingdom. In Japan, research into gas-cooled reactors intensified after the 2011 Fukushima Daiichi Nuclear Power Plant accident, and the country unveiled its own GTHTR300 design. As the birthplace of gas-cooled reactors, the United Kingdom—through its major heavy industry company Rolls-Royce—is developing a 100-megawatt (MW) class AMR, and next-generation nuclear fuel suitable for AMR is being manufactured by the state-run URENCO.

This content was produced with the assistance of AI translation services.