A 1 MWe high-temperature gas-cooled microreactor using TRISO fuel and helium cooling with passive emergency shutdown.
Shipped to INL's DOME in Aug 2026 for a five-phase test ending in a 150-hour full-power run; first commercial unit due 2028.
Updated 17 Dec 2025Checked 11 Oct0 updates this week
TRISO particles survive above 1000°C without melting, enabling higher operating temperatures than water-cooled reactors.
Helium flows through the graphite core, absorbing heat and driving a turbine. On power loss, natural convection cools passively.
Gravity and density differences keep helium flowing. The reactor cools itself without pumps or operator action.
| Spec | Kaleidos |
|---|---|
| Electrical output | 1 MWeR (reported) |
| Thermal output | 3 MWthR (reported) |
| Fuel type | TRISO in graphiteR (reported) |
| Coolant | Helium gasR (reported) |
| Emergency shutdown time | 300 msR (reported) |
| R-50 factory long-term capacity | Up to 50 units/yearR (reported) |
R reported by the company
| Spec | Kaleidos | Kairos Power Hermes 2 |
|---|---|---|
| Fuel type | TRISO in graphiteR (reported) | TRISO coated particle fuelR (reported) |
| Coolant | Helium gasR (reported) | Flibe molten fluoride saltR (reported) |
R reported by the company
Radiant Industries
Kaleidos microreactor, HTGR, portable nuclear
Radiant develops Kaleidos, a 1 MWe high-temperature gas-cooled microreactor for remote sites. Founded by former SpaceX engineers, it manufactures in El Segundo, California.
radiantnuclear.com (opens radiantnuclear.com)Company profile →
