Comment by pfdietz
7 days ago
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.
7 days ago
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.
Economically absurd, much more expensive than reprocessing or fast waste burning reactors.
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.
The problem with launching anything into orbit using current rocket motor technologies is that heavier stuff costs more to put into orbit.
The elements that are used in nuclear reactors (particularly Uranium and Plutonium) are pretty dense, and thus heavy.
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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.
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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.
For a thorough analysis (which shows how useful the frontier models are getting at this kind of thing), see https://x.com/i/grok/share/276607c72b5e4f639527935cbc614fa0
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?
Can't wait for one of those launch rockets to explode in the atmosphere!
And the armored waste carriers to fall back to Earth and be recovered for relaunch.
The requirements for a rocket to be allowed to fly nuclear material tend to be even more stringent than those for flying humans.
Haven't you seen https://en.wikipedia.org/wiki/Space:_1999 ?
Yes, it's a horrible pile of pseudoscientific TV crap. Why did you imagine it was relevant?
It isn't even pseudoscientific, just fiction, though their 'Eagles' don't need much suspension of disbelief ;->
Metaphor. Allegory. Analogy. Parable.
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