[daveslash]

I don't know why you're downvoted. I think it's a legitimate question. When I was in high school I asked "Why don't we just shoot our nuclear waste into the sun?".

As an adult, Kerbal Space Program has taught me that it's incredibly difficult to lose the orbital velocity and get things into the Sun!

But the answer my teachers told me was "Well, even if rockets have a 99.5% success rate and a 0.5% failure rate, and only 1 out of every 200 rockets explodes during launch... then eventually a rocket carrying nuclear waste is going to explode and spread it everywhere"

As others have pointed out: Nuclear rockets don't have the thrust ratio necessary for take off, so presumably they'd be assembled and used in space. My question is: What level of risk does launching nuclear rocket parts/fuel into space pose?

[mcpackieh]

A rocket explosion is unlikely to pulverize solid nuclear fuel or vitrified nuclear waste. It would most likely fall, intact or in large pieces, into the ocean which is a pretty good place for it anyway. If it blows up over Florida that's worse, but the worst case scenario is that it reenters earth's atmosphere at near-orbital speeds over a populated area and burns/breaks up. Then you have a situation like Kosmos 954, where the radioactive material is spread over a large area and is consequently much harder to clean up.

The biggest issue for the nuclear waste disposal idea is that it doesn't make any economic sense. It's better to dump it into the ocean, or down a mineshaft, or even just to let it sit in storage near the power plant for decades. But with nuclear fuel for rovers, satellites or rockets the rewards could outweigh the risks, and so this is sometimes done.

Here's a NASA doc that goes over the risks of launching plutonium into space for their Mars rovers. To summarize, it's not really a big deal: https://rps.nasa.gov/resources/81/mars-2020-launch-nuclear-s...

> The General Purpose Heat Sources (GPHS) inside the MMRTG is designed specifically to prevent such an occurrence. The fuel inside each GPHS is surrounded by several layers of protective materials, including the type of tough material used in the nose cones of missiles designed to survive fiery conditions during re-entry into Earth’s atmosphere. In addition, the radioisotope fuel is manufactured in a ceramic form (similar to the mate- rial in a coffee mug) that resists being broken into fine pieces, reducing the chance that hazardous material could become airborne or ingested.

[nickik]

> The biggest issue for the nuclear waste disposal idea is that it doesn't make any economic sense.

No the biggest issue is that its a stupid idea in the first place. Nuclear waste is fine and perfectly reasonable to handle here on earth with close to zero chance of actual danger.

[Symmetry]

Yes, but nuclear reactors carried up to space for rockets or electricity can still make sense. Before you turn on your reactor it's not very radioactive, to survive to the present day uranium has to have a very long half-life which means low radioactivity. But as soon as you turn it on you start transmuting the uranium into all sorts of things with much shorter half-lives and so much higher radioactivity.

So its safe to fly a new reactor into a stable orbit, if something bad happens you'll scatter some uranium but that's just toxic heavy metal bad, not radiation hazard bad. Just make sure the orbit is high enough to be stable, not like Kosmos 1402.

https://en.wikipedia.org/wiki/Kosmos_1402

[agent327]

Why would you dispose of such a useful material by attempting to shoot it into the sun? Sure, there is some danger associated with storing it, but it's not as if nuclear material is the only hazardous substance on the planet, and with the rest of it we seem perfectly ok with just sticking it in a hole somewhere. Nor does nuclear material, by itself, represent a danger of civilisation-ending proportions (only if you build a bomb out of it, and that is quite a significant operation that can only be conducted by people that know what they are doing. In other words, it won't explode if left by itself.).

[rsynnott]

> Nuclear rockets don't have the thrust ratio necessary for take off, so presumably they'd be assembled and used in space.

Or just used as an upper stage! See https://en.wikipedia.org/wiki/Saturn_C-5N, for instance, and a bunch of even more ridiculous Soviet designs.

Amazingly, this project (nuclear third stage for Saturn V) was actually under serious development. This to be used on a rocket stack which had had two major incidents in 13 launches; it really was a very different safety culture back then.

[_yb2s]

This article addresses that. They claim that, like you said, they are only used at very high altitude or in space, and the raw materials, before ignition are not dangerous. They say that the low enrichment uranium is even safe to touch with your bare hands.

[starbase]

We can store the fuel pellets in a crash can during transit. That way if the rocket blows up nothing hot gets dispersed.

But even without a crash can, it's of less concern to public health than the radioisotopes in coal.