People are probably going to answer “safety”.

But it’s also hideously expensive. Plutonium is, apparently, one of the safer ways to build these things, because it is easy to shield, and the power density is good. But plutonium, as it’s not naturally occurring, is stratospherically expensive.

https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...

Additionally, the decay product of Pu-238 is U-234. Though a relatively 'safe' alpha emitter, it's half-life is ~200,000 years.

Note: With alpha emitters, it's 'safe' if it's outside your body, your skin can absorb it. But once you eat or inhale it, you get the full blast right into the quickest dividing cells in your body.

The first nuclear bombs cost billions of dollars each.

I wish I could say that’s a good thing. But no, after the first of them, nuclear weapons seem to have justified their own existence, no matter the cost.

I would rather see remaining weapons material repurposed as deep-space power sources. If that were to solve problems.

Anyhow, Perseverance makes me happy.

> I would rather see remaining weapons material repurposed as deep-space power sources. If that were to solve problems.

Unfortunately this is not possible, nuclear weapons make use of pu-239, which has properties that does not make it a useable RTG fuel.

> The first nuclear bombs cost billions of dollars each.

No, at least union's ones were priced at around $100000-$120000 a pop in materials.

Giant amount of money back in seventies union for an individual, enough to live on for a lifetime.

There's a lot of waste heat put out by RTG. The one powering Perseverance has an output of about 110W but thermocouples have about 5% efficiency so there's ~1900W of heat you have to deal with. For a fridge the running power can be almost double that it's just completely silly on Earth except for odd places like the lighthouses along Russia's northern coast where there was no way to get a grid connection, not enough sun for solar, and suppling diesel constantly was impractical.

Risk?

That is my basic opposition. Happy to be flexible on energy in almost every way. Cost, type, uptime...

But error with nuclear tech tends to endure for a very long time. Fukushima will be raising ocean radiation for a long time, just one example.

These are many lifetime events. Some minor, or recoverable, some profound.

Given we can reasonably run the fridge on solar, and other tech, that risk does not seem to make sense to a lot of people.

Doesn't to me.

Now, that said I am not ideologically opposed. Other tech could very seriously improve risk profile. Maybe it becomes worth it.

Then again, the fridge in my RV can run on a small flame, or a very low current source. And no moving parts!

So, we could make fridges differently too. Make tradeoffs.

> Fukushima will be raising ocean radiation for a long time, just one example.

Will it? The ocean is very, very big. Contaminated water from Fukushima is a literal drop in a bucket.

Already is. Drops over say, 10 to 100k year timelines add right up.

The solution to pollution is dilution.

I say that in jest, because dilution involving radioactivity works on much longer timelines than many things do.

There's a TON of power generation alternatives that look much better both from the "trying to not give you a lot of cancer" standpoint and the "efficiency is something we care about" standpoint. Most RTGs make about 3 to 6% efficiency, while a random Amazon 100w solar panel will give you 15/22% without most of the risks.

The main reason this are used vs (or sometimes along!) other technologies is that they function rather happily in super crappy conditions we don't -unless some world-ending event happens soonish- usually have on Earth.

Nuclear reactors are better and have economies of scale, it doesn't make much sense to everyone have their own.

To add to the other posts: nuclear weapons proliferation