Liquid fluoride thorium reactor

[randomly]

The main benefit above is not so much the energy difference but the much smaller quantity required to reach critical mass, aka you can make an efficient core at a smaller size.

Not much weight benefit to be had there. You need less than 8Kg of HEU to achieve critical mass in a reactor.

[Rei]

The main benefit above is not so much the energy difference but the much smaller quantity required to reach critical mass, aka you can make an efficient core at a smaller size.

Not much weight benefit to be had there. You need less than 8Kg of HEU to achieve critical mass in a reactor.

I believe you're thinking of bombs, including reflectors, compression and the like. My reading says that the bare sphere critical mass of 100% 235U is ~50kg, vs. ~10kg for 100% 239Pu.  Practical reactor geometries lead you to significantly worse than the bare sphere minimum before neutron reflection comes into play.  Neutron reflector effectiveness is proportional to thickness, wherein mass for a constant thickness reflector grows proportional to the core radius squared.  Hence my comments about scaledown.

[DLK]

My two cents...

The choice of a reactor cycle could be important in the long run, particularly if intentions of becoming a space-fairing civilization are being seriously considered. This would include a supply of unlimited fissile material that doesn't require a lot of effort.

Thorium has a number of advantages:
1. There's apparently lots of it distributed around the solar system. It has such a long half-life (~13Gy) that not much decay has occurred yet.
2. It gives you a way to replenish your fissile inventory. The only natural fissile isotope, U-235, takes a bunch of resources to separate it from U-238.
3. It's the only fertile material that can breed fissile material (U-233) in a thermal neutron spectrum, which limits the amount of fissile inventory you have to maintain and makes smaller reactors possible.

The molten salt reactor concept is a good fit for breeding thorium into U-233. The liquid fuel allows relatively easy recovery of potentially-useful fission products. High temperatures at low pressures reduce loss-of-containment risks.

[randomly]

I believe you're thinking of bombs, including reflectors, compression and the like. My reading says that the bare sphere critical mass of 100% 235U is ~50kg, vs. ~10kg for 100% 239Pu.  Practical reactor geometries lead you to significantly worse than the bare sphere minimum before neutron reflection comes into play.  Neutron reflector effectiveness is proportional to thickness, wherein mass for a constant thickness reflector grows proportional to the core radius squared.  Hence my comments about scaledown.

No, not thinking of bombs. You are thinking of bombs, prompt neutrons, and fast reactors.

 Fully functional HEU reactors with around 8kg core material. The SNAP-10A reactor launched into orbit had a core load in that range.

You are missing the large increase in fission cross section from thermal neutrons. A moderated reactor requires about 1/10 the fuel load of a fast reactor.

In any case weight of the fissile material only accounts for a few percent of the total weight of the reactor and power system. The tiny weight advantage can easily be 'outweighed' by safety, handling, and design impacts from accommodating a highly radioactive core. Given the current state of the art, and economics, I think it highly likely that an HEU reactor would be the most cost effective, by far.

[JulesVerneATV]

A new memorandum has firmed up China and Russia's intent to lead the construction of a new lunar base to be completed by 2036, as NASA talks about scaling back its own lunar ambitions.
https://www.livescience.com/space/the-moon/china-signs-deal-with-russia-to-build-a-power-plant-on-the-moon-potentially-leaving-the-us-in-the-dust
Russia has signed a deal with China to build a nuclear power plant on the moon.

[JulesVerneATV]

UPSC Key: Operation Rising Lion, India-France relationship, and Nuclear reactors
https://indianexpress.com/article/upsc-current-affairs/upsc-key-operation-rising-lion-india-france-nuclear-reactors-10066709/


they closed the discussion?

Most users ever online was 7940 on Mar, 2025
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[Asteroza]

UPSC Key: Operation Rising Lion, India-France relationship, and Nuclear reactors
https://indianexpress.com/article/upsc-current-affairs/upsc-key-operation-rising-lion-india-france-nuclear-reactors-10066709/


they closed the discussion?

Most users ever online was 7940 on Mar, 2025
https://energyfromthorium.com/forum/index.php

The Energy from Thorium forum was getting assaulted by bots, so Kirk was forced to implement draconian blocks via Cloudflare, but it appears he wholesale blocked asia, maybe europe too. If he was better able to use the more nuanced blocking Cloudflare provides he wouldn't have to exclude the world outside the USA, but he's paying for the forum, not us, so it's his call.