ZettaJoule is developing high-temperature gas reactors for heat and power applications, modernising Japan's High-Temperature Engineering Test Reactor technology for oil and gas, steelmaking, aviation, data centre, and e-fuel applications. The company opened an office in Houston, Texas at the Ion innovation hub at Rice University in May 2026. ZettaJoule targets the hard-to-decarbonise industrial heat market — the same segment as X-energy and Jimmy Energy but with a different technology approach based on proven Japanese HTGR operational experience.