08-20-2025, 11:14 PM
(08-08-2025, 12:52 AM)IdeomotorPrisoner Wrote: Well... There you go.. All my basic criticism withdrawn.
Go reactor on the moon with liquid metal cooling. I forget it's not a three mile island technology-wise anymore. And possibly want to find a way to criticize this retarded dick measuring contest with China to bring nuclear power to the moon and be first to depleted its resources too.
But that looks like a nice and compact unit for module living.
There are a number of considerations in the design of a nuclear reactor for the moon or Mars that would differentiate it from terrestrial use.
Physical size is one issue. First, it has to be able to fit within the mass and volume constraints of a feasible lunar delivery vehicle. There are two main factors that drive reactor size. The first one is the enrichment level of the Uranium (assuming Uranium is the fuel). The higher the level of enrichment in U235, the smaller the core can be and still go critical. For weapons grade Uranium, a sphere about 7 inches in diameter can go critical. Canadian CANDU reactors use natural Uranium (0% enrichment) and require a reactor core about 6 meters in diameter. Pressurized Water
Reactors like Three Mile Island have an enrichment level of around 5% and a core size of about 4 meters. The new generation of Small Modular Reactors (SMRs) are designed to use fuel enriched to about 20%. Above that level, and it starts to get easy to enrich up to weapons grade, so there is a regulatory limit at about 20%. This fuel is called High Assay Low Enriched Uranium (HALEU). It is basically as enriched as the Uranium can be without starting down the road to weapons. Use of HALEU can get the reactor core diameter down to less than one meter, everything else being equal.
The other factor that affects core size is whether it uses fast neutrons or slow neutrons for the fission process. In order to slow down the neutrons for a slow neutron reactor, a bigger core is needed because the neutrons need to bounce around inside the core for a while in order to lose energy. A fast spectrum reactor doesn't need that, so the core can be smaller. A fast spectrum reactor with HALEU fuel results in the smallest practical size and the most efficient use of the fuel. Fast spectrum reactors typically use a Liquid Metal coolant, like Lead or Sodium. Because they don't contain any coolant like a gas or that can turn into a gas (like water) they can't overpressurize and explode. They are inherently safer than Boiling Water Reactors or Pressurized Water Reactors.
A fast spectrum SMR using HALEU fuel is also much more efficient at burning up its fuel. That's important for moon or Mars use, because any time you have to refuel the reactor, you would have to bring that fuel from Earth and go through a complex refueling process on the Moon. Some of the fast spectrum SMRs being developed have a time between refueling of 10 to 20 years, depending on how much power you pull out. Some of the slow spectrum reactors need to be refueled every few years. That makes a huge difference in the transportation and maintenance costs.
There are currently a handful of fast-spectrum SMRs being developed that are approximately in the right power range. Of those, only a couple are US made and well on their way to being certified and licensed. If they are serious about making the 2030 launch date, a clean sheet design is out of the question. They are going to have to select a candidate that is already designed and going through the test and certification process. My personal favorite is the OKLO microreactor, but there may be 1 or 2 other feasible choices. OKLO is already under contract to deliver a SMR to the Air Force to provide power to Eielson AFB in Alaska in the 2030 timeframe, so a few extra bucks might speed that up for NASA.
The other factor is that there is also only one feasible lunar delivery vehicle being developed that could be ready in time, and that is the SpaceX lunar cargo Starship.
I think that when former reality TV star, log-rolling competitor, and current acting NASA Administrator from Central Casting, Sean Duffy gets around to figuring all this out, he's going to realize that there is only one path to meeting the 2030 deadline, and that's SpaceX delivering a SMR fast spectrum reactor. And unless he figures this out quickly, he's going to miss the deadline anyway.
