IMO, the long term solution will be to simply launch the waste into space. With low enough launch costs the extra mass needed to armor the waste against accidents becomes tolerable.
I don't think that's the case, if launch costs are low enough. The options you describe there are quite expensive. Reprocessing costs somewhere in the neighborhood of $1000/kg. Even fast reactor have trouble disposing of the seven very long lived fission products. A fully reusable launcher might get costs down to $10/kg to LEO. Even if one had to wrap the waste in 10x its mass in launch armor this could be much cheaper than reprocessing.
That's true, but the cost of reprocessing is also very high, per kg. And aren't the nuclear bros always telling us how little nuclear waste is actually produced? There's about 30 tons of spent fuel per GW(e)-year from today's burner reactors. At $10/kg to space that would be just $300,000 (yes, ignoring lots of costs there, at $10/kg is aggressive, but this is for comparison), a pittance compared to the value of energy produced from the power plant: at $0.05/kWh it produces > $300 M in electrical energy, three orders of magnitude higher.
Why would launch costs be low? $10/kg is fantasy land. UPS won’t ship a kilogram across the country for $10.
And who wants spent nuclear fuel in low earth orbit? This is a far worse location for spent fuel than buried in a bunker. This is a worse location than Times Square.
Why wouldn't they be low? In the limit, if launch becomes operationally similar to air travel, costs will be a few times propellant cost. And propellant is very cheap. LOX is almost free (the second cheapest industrial liquid after water) and liquid methane isn't very expensive either.
Low earth orbit would just be where it's transferred to something to carry it farther out, for example using solar-electric engines.
For all this, remember it isn't done immediately, it's done in (say) 300 years when the short lived fission products are mostly gone.
I think the onus is on you to explain why costs would drop by >3 orders of magnitude (>4 accounting for the 10x launch armor). It’s something like $1500/lb on a fully loaded Falcon Heavy and all indications are that SpaceX isn’t making money at that price.
Plus even if this were free, “shoot 180k tons of nuclear waste into space” seems like a terrible idea in general. It’s one of those ideas that make sense only until you think about the ramifications. What happens when inevitably one of the 3 thousand Falcon heavy rockets explodes and the armor fails and we spread nuclear waste over 3 states?
Falcon Heavy is more expensive per kg than F9, because it throws away more things. SpaceX flies it for certain military missions but you will note they launch their own stuff on F9.
A full launch on F9 (with recovered S1) is estimated to cost $15M and can put up to 17,600 kg into LEO, or $850/kg.
> (>4 accounting for the 10x launch armor).
You're double counting there. 3x would be just fine even with 10x launch armor.
> seems like a terrible idea in general
And here's the problem: you started from an emotional reaction and are trying to rationalize that.
Depends. If we get explosive inertial confinement fusion to work you could build a pure fusion version of a nuclear pulse rocket. Look up Project Orion.
Orion (in its fission bomb form) is impractical and would be insane to launch from Earth, but it holds the title of being the only “torch ship” drive we know how to build. We could technically build it.
Probably not worthwhile. If you just leave it in orbit you're going to have to track it and worry about debris/micrometeoroid strikes. The ideal would be to stick it in some permanently shadowed crater on the Moon, it'd be a stable environment without wild temperature swings and much lower risk of somehow ending up where people are. But that's a long way to go and a lot more risk to take for now.
Once it's in orbit the cost of moving it farther out needed be very high. Just evaporating it with solar energy in very high orbit will allow the solar wind to carry it out of the solar system.
A much better, safer, and cheaper idea is dropping suitably packaged waste on the subducting side of the Mid Pacific Subduction Zone. It’d be inert long before seeing daylight again…
The only downside is the “waste” is quite valuable. MSRs can also use it, and their waste is only dangerous for ~300 years.
That's a bad idea. Subduction zones move very slowly, and material would come back up in "mud volcanoes", especially with the added heat input of the waste.
Nonsense. The sea floor in those areas is soft muck, 20,000 ft or more deep.
The waste, likely packaged in torpedo shaped structures made of corrosion proof, high density, high strength materials, would arrive at somewhere around 150 MPH. Being extremely dense and heavy, they would penetrate deeply into the sea bottom, estimated at 35-55 meters deep. There’s no chance they’d somehow be forced back to the surface. Even if they were, being sealed they would be harmless.
Even if by some miracle one broke open at the sea floor, the nuclear material is dense and wouldn’t disperse. There’s very little life to affect down there regardless.
Unless you live in Sci Fi future where space travel is magically free, this is a pretty bad deal since sending a pound of spent nuclear fuel out of earth orbit takes 50+ pounds of fuel. Sending all the spent nuclear waste into space would be something like 10 million tons of fuel.
It doesn't have to be free, it just has to have a low cost. And remember, we're talking not about the cost now, but the cost up to centuries in the future. The ultimate time limit is set by when spent fuel stops being self-protecting against amateur diversion of the plutonium, which is 300-500 years.
> 50+ pounds of fuel
Just out of curiosity, how much do you think LOX/LNG propellant costs?