[api]

Is anyone working in the US on a waste solution that isn’t a big hole with a straight out of cyberpunk sci-fi warning plaque?

The French reprocess and recycle fissile material but that’s kind of a gnarly industrial process. Still they do it and it works.

The long term solution is to create a second kind of reactor that has a higher burn fraction which means a more fuel efficient fast reactor. Those would be, ideally, the big base load plants if we did this rationally.

[yabones]

I don't see the issue with dry cask storage medium term, and deep geological storage long term. Spent fuel isn't really that dangerous once it's been cooled down and for a couple decades before putting it in the ground, to the point that there are far more dangerous natural things you can dig up.

What concerns me is that 250 years of fossil fuel energy continues to store its waste products in my lungs and the water I drink. That's the issue we need to solve with urgency.

[quirkot]

Europe has about 60,000 tons of nuclear waste storage[1], so lets say the global nuclear waste quantity is 2-3x or 120,000 to 180,000 tons. That sounds like a lot, however it's less than 2 weeks of coal deliveries to a coal plant (at 1 train of 115 cars each with 116 tons of coal = 13,340 tons delivered per day[2]). To take another approach, the average landfill size is 600 acres[3].

The "eh, just bury it" approach is really not a bad one. Its not even that much stuff to bury

[1] https://worldnuclearwastereport.org/

[2] https://www.eia.gov/todayinenergy/detail.php?id=16651

[3] https://www.colorado.edu/ecenter/2021/04/15/hidden-damage-la...

[fc417fc802]

I thought something like 30 tons per Gwatt capacity per year was the ballpark for high level waste without reprocessing? How are you arriving at a 120,000 ton estimate?

[quirkot]

Footnote has the backup. 2-3x is guesstimate, but it doesn't really matter. The answer is there's just not much waste to store

[fc417fc802]

Sure there isn't a prohibitive quantity either way but regardless I think the 120k number might be off by one or two orders of magnitude even before reprocessing reduces the amount by ~95%.

[quirkot]

you'll have to take that up with the folks from worldnuclearwastereport.org

[bigbadfeline]

Fast neutron reactors can also "burn" waste from other reactors, the "ashes" are radioactive for only 300 years, there is no need for special storage after that. Untreated waste has to be kept in storage for around 100K years before it reaches safe levels of radioactivity.

Other than marketing propaganda, there isn't much real information about Mark-0. I'm assuming it's a sodium cooled, slow and hot pebble bed reactor. Hot pebble beds are well known but one with sodium cooling appears to be a first.

Why slow sodium? You get all the risks associated with sodium with none of the benefits of fast neutrons. There are operational, electricity producing, fast sodium reactors which do make some sense. I can't say the same for Mark-0.

[pfdietz]

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.

[api]

Economically absurd, much more expensive than reprocessing or fast waste burning reactors.

[pfdietz]

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.

[lenerdenator]

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.

[pfdietz]

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.

[dpark]

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.

[fc417fc802]

> UPS won’t ship a kilogram across the country for $10.

I can purchase produce grown on a different continent for less than that at the grocery store so something isn't right here.

[dpark]

It was a metaphor for how absurd the statement was. But if you try to ship a 1kg package across the country it will likely cost way more than $10.

Freight cost is certainly way lower.

[pfdietz]

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.

[dpark]

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?

[api]

$10/kg isn’t fantasy land if we have fusion rockets, but then we don’t need fission power anymore. :)

[pfdietz]

Fusion would be useless for launch to orbit. Even fission sucks for that. It's really hard to beat the cost and power density of chemical rockets.

[hgoel]

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.

[pfdietz]

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.

[pfdietz]

needn't

[Recurecur]

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.

[pfdietz]

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.

[Recurecur]

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

[pfdietz]

If you're going to put it 20,000 feet deep in the sea floor, do it somewhere far away from subduction zones.

[dpark]

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.

[pfdietz]

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?

[jampekka]

Can't wait for one of those launch rockets to explode in the atmosphere!

[pfdietz]

And the armored waste carriers to fall back to Earth and be recovered for relaunch.

[hgoel]

The requirements for a rocket to be allowed to fly nuclear material tend to be even more stringent than those for flying humans.

[LargoLasskhyfv]

Haven't you seen https://en.wikipedia.org/wiki/Space:_1999 ?

[pfdietz]

Yes, it's a horrible pile of pseudoscientific TV crap. Why did you imagine it was relevant?

[LargoLasskhyfv]

It isn't even pseudoscientific, just fiction, though their 'Eagles' don't need much suspension of disbelief ;->

Metaphor. Allegory. Analogy. Parable.

[pfdietz]

It was intelligence-insulting crap.

[LargoLasskhyfv]

It was https://en.wikipedia.org/wiki/Rudi_Gernreich !