[pfdietz]

You need to think more clearly about this.

Reprocessing is very expensive; $1000/kg and up. Launch to space will likely become much cheaper than this as fully reusable launch vehicles become available. Even if the spent fuel must be armored against accident the cost of launching it to LEO, and then to the moon, is likely to become much cheaper than the cost of reprocessing it here on Earth.

Space disposal has the positive advantage that the seven very long lived fission products are removed from the biosphere, along with the very long lived actinides like Np-237.

[hex4def6]

That $1000/kg figure is reprocessing something like 10kg of material to get 1kg of enriched material.

Current costs to launch a kg to orbit are something like $2,000-$6,000.

If we're comparing it to you enriched amount, you'd have to launch 10kg, which means you'd have to hit $100/kg launch costs to break even. I'm not convinced that will ever be possible; that's on the order of a first class arline ticket for a 50kg person.

This also doesn't consider what you're getting for launching it into orbit. If the 100 year risk of a casket leaking is (say) x mrads into the environment, you're going to have to consider what the equivalent of vaporizing all of it into the atmosphere in the event of a failed launch is. the fallout (hah) from a failed launch of nuclear waste seems magnitudes more catastrophic than having the same stuff slowly leaking in the middle of a desert cave.

[pfdietz]

> Current costs to launch a kg to orbit are something like $2,000-$6,000.

This is false. Launch on Falcon 9 is under $1K/kg.

Moreover, current launch costs are just a milestone toward future launch costs, which promise to me much lower. Ultimately launch will be a few times the cost of propellant (just like air travel), so $10/kg is a reasonable expectation.

> vaporizing in the atmosphere

How does this happen? Launch explosion? That doesn't vaporize an armored container. Entry from near-orbital speed? Also survivable passively.

The result of an accident will be tracking down the armored canister(s), cleaning up any local impact fragments, and prepared the stuff for another launch.

The armored canister doesn't have to be sent beyond LEO, so it could be reused, and doesn't impose a mass penalty on that beyond-LEO transport system.

[hex4def6]

> This is false. Launch on Falcon 9 is under $1K/kg.

Every number I find is ~$2,700 or so per kg. I'd be interested to see your data.

>$10/kg is a reasonable expectation.

Citation needed. The tyranny of the rocket equation means you need about 95kg of propellant for every kg of payload. To be clear, assuming it costs $0 to build a rocket, you're going to need to find propellant for under 10c/kg.

Or flip it around. Falcon 9 can lift 18,400kg. You're suggesting therefore that the gross income for spacex will be $184K per launch at $10/kg. It currently costs them about $15-20M per launch. They have to reduce their cost 100x to make a profit with your numbers. From $15,000,000 to ~$150,000. That seems... unlikely.

> Entry from near-orbital speed? Also survivable passively.

... To be clear, you're suggesting that a rocket in a bad state (engine failure / tumbling) is able to survive a re-entry at 17,500mph? Also -- your "armored canister". How many kg of armor per kg of payload? 50:50?

[gavinsyancey]

Currently, the most reliable rockets are maybe 99% reliable but certainly not 99.9%. If you are trying to send nuclear material to space, you have to account for the possibility that

* The rocket blows up on the launchpad

* The rocket gets you part way up, then blows up during ascent

* The rocket fails before orbital insertion, and your nuclear payload re-enters the atmosphere at near-orbital velocity

In all of those cases, you need to have enough shielding to avoid spreading nuclear waste over a very large area -- that adds a lot of mass. And everyone whose jurisdiction you're launching over needs to trust you have enough shielding. And in the case where it fails during orbit insertion and re-enters the atmosphere, you don't have a lot of control on where the nuclear materials end up, which has proliferation issues.

[pfdietz]

> In all of those cases, you need to have enough shielding to avoid spreading nuclear waste over a very large area -- that adds a lot of mass.

Conservatively it might add an order of magnitude, and likely less. This still renders future reusable launchers much cheaper per kg of spent fuel than reprocessing would be, unless you are projecting very large improvements in the cost of reprocessing.

You might object current launchers aren't cheap enough, but I wasn't proposing doing this right now with current launchers, so that would be a strawman objection.