Small Modular Nuclear Reactor Reaches Criticality in First Test
11th June 2026
Antares is one of a number of companies that is basing its design on a new fuel system called TRISO that takes some of the complexity and safety out of the reactor design and places them in the fuel design. The fuel design is based on tiny pellets with a uranium oxide core. The pellets are surrounded by several layers of carbon that can moderate the energy of both the neutrons and lighter nuclei that are released by fission reactions. All of that is encased in a hard ceramic shell that’s designed to withstand the highest temperatures that can be produced by the encased uranium.
As long as your reactor can keep the TRISO pellets contained, then there should be no risk of meltdown or even the release of the most dangerous isotopes produced from the reactions. There are still some safety concerns, as neutrons will still escape and can potentially convert some of the surrounding material into unstable isotopes. But the Antares design surrounds the TRISO with a graphite sheath, which should slow most of these neutrons down.
To mitigate non-radioactive risks, the Antares design uses sodium to take heat from the reactor to a heat exchanger. The heat is transferred to pressurized nitrogen, which then drives a turbine in a closed Brayton cycle setup.
This appears to be a form of the pebble-bed reactor, although it’s difficult to tell from the bare-bones description in the article.
Pebble-bed reactors strike me as the best and safest form of small reactor we can build.
June 12th, 2026 at 06:14
Yes, that’s exactly what it is. I live near Oak Ridge, TN, there’s quite a bit of talk about it in these parts, as you might imagine. A friend of mine works at XE here. The grand plan is actually pretty smart? There’s a couple companies working on it, US, foreign, and internationals. The action is happening in Oak Ridge, because of all the expertise, DOE, and existing uranium stuff at the national lab. They’re shipping all the used/old uranium ‘waste’ (medical, nuclear industry, and military) here, watering it down and making the pebbles, and shipping it back out to fuel the reactors (some of them are being made, or plans are in the works to make them here in Oak Ridge, and a few other locations around the country).
The concept is pretty slick, I’ll hand it to them. The entire reactor and generation equipment is designed to fit in a ‘tractor trailer sized container’. The fuel and design (allegedly) CANNOT go critical (at best terrorists could make a dirty-bomb). The concept is you ship one of these things to where you need power, and poof, 50Kwatts. Need more power, take 2. Or you want 4? LINE ‘EM UP! Make power-generation distributed instead of centralized like now, and just pump these containers out like Model-T’s. Each neighborhood gets its’ own, datacenter gets their own, university gets their own, research lab, military base, etc., everybody gets one! Need a whole lotta juice in the middle of nowhere? We got you! They can air-lift the thing in w/ a helicopter.