> Giant radiators?

Yup, that's the thing on top [1].

[1] https://www.nasa.gov/tdm/fission-surface-power/

Thanks, I have seen a lot of pages on nasa.gov, but not that one. Neato!

On the Moon you could also use the Moon itself as a heat sink. But yeah, any near-term solutions would use giant radiators.

Solids don't conduct too much heat. I think most of the cooling in a nuclear plant is generated by evaporation of water.

Yes, what I mean is that theoretically you could do something like have a very very wide base to passively dump heat into the ground (since we're still only looking at kW scale reactors in space), or actively cycle large amounts of regolith through the cooling loop (say, via a heat exchanger from a closed water loop) and dump it out. Depending on how much heat the system can handle, you could maybe even extract stuff boiling off from the regolith.

The nuclear plant nearest to me uses sea water, which is put back into the ocean.

Interesting. I had to look for more details. I found this link https://nuclear.duke-energy.com/2013/11/13/why-don-t-all-nuc...

Oversimplifiying: All new plnats have cooling towers, so the water they return to the environment is not too hot.

It would likely be a thermal reactor, I guess? So no waste heat, since the little heat it gives is used to generate electricity.

Thermal power plants don't use up the heat. They make energy through its transfer (like a dam with water).

Most nuclear reactors are thermal power plants and they all need to dump waste heat. Thermal power plants convert heat into electricity with turbines and are limited by dumping the waste heat.

Are you thinking of radioisotope generators? Those aren't reactors. They use thermocouples and need to get rid of the waste heat. The Voyager RTGs have radiator fins.

Yeah, that's what I meant, sorry about the incorrect naming.

Perhaps? Any reason that sounds silly to you?

No, and this is not some attack on nuclear power. I am just curious. On earth, nuclear power plants use lots of water and cooling towers. How does that work in a place with no spare water?

I also meant to write fission in my original question, not fusion.

Mostly cooling towers are not likely to work in a place with no atmosphere.

Radiators though, are constantly used in spacecraft, and seem to work well. Low gravity, no motion might let the thing be mostly the radiator, with not much support structure. Except it might need to be in shade, in the shadow of a building? hill? solar panels?

> How does that work in a place with no spare water?

I wonder if recycling human liquid waste through evaporation could be of some use for that purpose.

Heat is what you use to make steam and drive the turbines with. I don't understand your question.

maybe not so hot indeed due to the scarce air that's why it's so cold at night on the moon. Only turn on the reactor at night to generation and use capacitors at day?

You can't really turn fission reactors on and off, they're always producing decay heat even if not being used for power generation. But why not radiate the excess heat into the crust of the moon with a subsurface loop, kind of like a ground source heat pump.

The day is 28 times longer than on Earth. You'd need very big capacitors.