Microreactor companies
13 companies build reactors of 20 MWe or less. They range from Radiant’s 1 MWe Kaleidos↗ to Last Energy’s 20 MWe PWR-20↗, and three of them, Antares, Valar Atomics and Aalo Atomics, have already taken test reactors critical↗↗+↗.
| First site | |||||||
|---|---|---|---|---|---|---|---|
| Last Energy | PWR-20; PWR-5 pilot | LWR | 201 | DOE test authorization | Texas A&M RELLIS campus, Bryan, Texas (PWR-5 pilot); Haskell County, Texas (30 PWR-20s, ERCOT connection requested) | — | 2026-11-11 |
| Deep Fission | Deep Fission Gravity reactor (borehole PWR) | LWR | 152 | Pre-licensing | Great Plains Industrial Park, Parsons, Kansas | Endeavour (Edged) | 2026-11-11 |
| NANO Nuclear Energy | KRONOS MMR | HTGR | 154 | Construction under review | University of Illinois Urbana-Champaign campus | Tillman Digital Gateway; Supermicro | 2026-11-11 |
| Aalo Atomics | Aalo-X; Aalo-1; Aalo Pod | Sodium-cooled | 103 | DOE test authorization | Idaho National Laboratory (Aalo-X, with a co-located experimental data center planned) | — | 2026-11-11 |
| Hadron Energy | Halo MMR | — | 101 | — | Smartland Energy MOU for up to five units; first deployment in the early 2030s | — | 2026-11-11 |
| Valar Atomics | Ward 250 | HTGR | 51 | DOE test authorization | Utah San Rafael Energy Lab, near Orangeville, Utah | — | 2026-11-11 |
| BWX Technologies | Project Pele; BANR | HTGR | 1.51 | — | Project Pele: built in Lynchburg, Virginia, tested at Idaho National Laboratory | — | 2026-11-11 |
| Radiant Industries | Kaleidos | HTGR | 14 | DOE test authorization | DOME test bed, Idaho National Laboratory | Equinix | 2026-11-11 |
| Terra Innovatum | SOLO | HTGR | 11 | Pre-licensing | — | — | 2026-11-11 |
| Antares Nuclear | Mark-0 (test); R1 | Heat pipe | — | DOE test authorization | Idaho National Laboratory (Mark-0); military installations from 2028 | — | 2026-11-11 |
| Calogena | CAL30 | LWR | — | Design review | Pierrelatte, France (first commercial reactor) | — | 2026-11-11 |
| Jimmy Energy | Jimmy high-temperature heat generator (INB Fermi) | HTGR | — | Construction under review | Bazancourt (Marne), supplying heat to Cristal Union’s industrial facility | — | 2026-11-11 |
| Steady Energy | LDR-50 | LWR | — | Pre-licensing | Helsinki: non-nuclear pilot at the former Salmisaari B coal plant; agreements with Helsinki, Kuopio and Kerava | — | 2026-11-11 |
Where microreactors fit
How the data is sourcedGas, sodium, heat pipe or water
6 designs here are helium-cooled gas reactors, among them Radiant, Valar, NANO Nuclear’s 15 MWe KRONOS↗ and BWXT’s 1.5 MWe Project Pele↗. Antares uses sodium heat pipes↗, Aalo cools its 10 MWe units with sodium↗, and Last Energy and Deep Fission scale down pressurized-water technology.
Heat-only reactors
Steady Energy (50 MWt LDR-50)↗, Calogena (30 MWt)↗ and Jimmy Energy (20 MWt)↗ make heat for district heating and industry, not electricity. They sit here on one third of their thermal output.
For grid-scale modules, sort the full SMR table by MWe.