China just ran a megawatt helium turbine inside a nuclear reactor loop
China's nuclear industry has pulled off something engineers elsewhere have only studied on paper: a working megawatt-class turbine powered entirely by helium, running inside a sealed loop with no steam involved. CNNC Huaxing — part of the state-owned China National Nuclear Corporation (CNNC) — confirmed the successful hot power generation test, using a closed Brayton cycle in which helium circulates continuously without ever leaving the system. The test feeds directly into China's push to commercialize high-temperature gas-cooled reactors, or HTGRs — a reactor type widely regarded as one of the safest ever designed.
The loop
Conventional power plants boil water to spin a turbine. This system cuts water out entirely. Helium — chemically inert and stable at extreme temperatures — cycles through a sealed circuit, spinning the turbine and returning to the heat source. Because helium doesn't corrode metal the way steam can, the system can run hotter, which means higher efficiency and a more compact plant footprint.
CNNC Huaxing engineers at the helium turbine test facility. Illustration: CNNC
The hard part
Helium atoms are among the smallest in existence. They seep through microscopic metal defects and the tiniest imperfections in seals — the same properties that make helium escape party balloons so quickly become a serious engineering liability in a pressurized power system. CNNC's engineers had to achieve micron-level precision during turbine assembly; any misalignment causes pressure loss and the whole system fails. The completed test confirms China has solved that containment problem at megawatt scale.
Why it matters now
China's HTR-PM — the world's first commercial modular HTGR — connected to the grid in December 2023, per World Nuclear News. It currently uses a conventional steam turbine driven by two 250 MWth reactors. The helium turbine work is the next phase: replacing steam with a direct gas cycle for even greater efficiency and flexibility. HTGRs can operate in water-scarce regions where traditional nuclear plants can't be built, and their passive safety design means they cool themselves even if power is completely lost.
The Western response is still early-stage. UK startup Nuclear Turbines — a BAE Systems spinoff that raised £15 million in July 2026 — is developing a competing compact reactor concept using a compressed-air turbine rather than helium, reports World Nuclear News. The UK Atomic Energy Authority has scoped closed-loop helium coolant research but has no operational test rig. Nine countries are active in HTGR development through the Generation IV International Forum; none has yet matched China's combination of a commercially operating reactor and a proven turbine test at this scale.