China hot-tests first MW-class helium turbine for reactors

China has completed the first hot power-generation test of a megawatt-class helium turbine, a machine that could give high-temperature gas-cooled reactors a higher-efficiency way to turn heat into electricity. The test bench, built by China National Nuclear Corporation subsidiary CNNC Huaxing, is China's first at this scale.

Key facts

• CNNC Huaxing completed the hot power-generation test of China's first megawatt-class helium turbine facility.
• The rig is a closed-loop Brayton-cycle heat-to-work system using helium as the working medium.
• CNNC called it a step "from theoretical verification to engineering demonstration" for gas-cooled microreactor core power equipment.
• China's HTR-PM demonstration reactor at Shidao Bay entered commercial operation in December 2023.
• HTR-PM uses two pebble-bed reactors driving a single 210 MWe steam turbine.

What happened

According to World Nuclear News, CNNC Huaxing's helium turbine comprehensive performance test bench passed its hot power-generation test — the stage where the rig actually produces electricity under temperature, not just spins cold. The system is a closed-loop Brayton-cycle machine: it compresses helium, adds heat, expands the hot gas through a turbine to extract work, then rejects heat and recirculates the same helium.

CNNC framed the milestone as moving "from theoretical verification to engineering demonstration" in core power equipment for gas-cooled microreactors, crediting the project team with completing installation of the entire test-bench system and carrying it through cold, hot, and power-generation testing.

The distinction that matters is direct versus indirect power conversion. Today's gas-cooled reactors, including China's operating HTR-PM, transfer reactor heat to water and drive a conventional steam turbine. A helium Brayton turbine instead lets the reactor's hot gas do the work directly, cutting a conversion step.

Why it matters

High-temperature gas-cooled reactors are prized because they run hot — hot enough to open efficiency and process-heat options that water-cooled reactors cannot reach. But most HTGR designs, including the pebble-bed line China has commercialised, still bolt on a steam cycle. That leaves efficiency on the table.

A working megawatt-class helium turbine is the piece that would let a gas-cooled reactor use a direct Brayton cycle, which at high turbine-inlet temperatures can convert heat to electricity more efficiently than steam. For the microreactor market NNN tracks in its SMR explainer and DOME microreactor test-bed coverage, compact direct-cycle machines are attractive because they shrink the balance of plant — no large steam generators, condensers, or water circuit.

Efficiency is the whole point. A steam (Rankine) cycle bolted onto a high-temperature reactor typically converts heat to electricity in the low-40% range; a direct helium Brayton cycle running at high turbine-inlet temperature can, in principle, do better while dispensing with the water circuit entirely. That combination — higher efficiency plus a simpler, drier balance of plant — is what makes gas-cooled microreactors attractive for remote sites, industrial heat, and places where water is scarce. It is also why helium turbomachinery has been a decades-long research target in the US, Japan, and Europe, and why a working megawatt-class rig is a genuine milestone rather than a lab curiosity.

It is also a competitive signal. China already has the world's only commercially operating HTGR; pairing that reactor experience with domestic helium-turbine hardware would deepen a lead in a reactor class the US, Japan, and others are also chasing.

Background

China's HTR-PM at Shidao Bay (Shidaowan) reached commercial operation in December 2023, using two small pebble-bed reactors feeding a single 210 MWe steam turbine — the first modular HTGR of its kind to run commercially. That plant proved the reactor side of high-temperature pebble-bed technology at demonstration scale. The power-conversion side has lagged: steam remains the default because helium turbomachinery at reactor-relevant scale is hard, with demanding seals, bearings, and materials in a high-temperature helium environment.

CNNC's test bench is aimed squarely at that gap. A comprehensive performance rig lets engineers characterise the turbine, compressor, recuperator, and controls of a closed helium loop before committing the design to a reactor. Hot power generation is a meaningful checkpoint: it shows the loop can make electricity, not merely circulate gas.

What's next

Watch for CNNC to report performance numbers — efficiency, turbine-inlet temperature, and endurance — that would show how close the helium turbine is to reactor-grade duty. The strategic question is whether a future Chinese HTGR or gas-cooled microreactor is designed around a direct helium Brayton loop rather than a steam cycle. If the test-bench results hold up, direct-cycle gas-cooled power conversion moves from textbook advantage toward a buildable option.