Im my proposal, as much of the HEU as possible would be downblended as possible by a hypothetical multinational fuel-cycle center. Some of the PU could be used in a MOX fuel, but much of it cannot.
That doesn’t actually matter since the waste would later be buried by more lava. As an alternative, you could drop a container packed full of waste but with flotation tanks into the sea off Hawaii (or wherever) and place it with a submarine near a lava outflow, so the waste will simply be safely buried by the lava. Or just drop the container off the side of the ship. The container would have to be lava-resistant to some degree, of course, but a few hundred metres of solid lava’s a pretty good safety barrier.
You seem to be laboring under several misapprehensions here:
- That there are enough locations erupting continuously with enough volume of lava that they could be reliably planned on as radioactive waste disposal sites (because, realistically, it’s unlikely that one nation is going to agree to have its volcano become the key dumping ground for the world’s high-level radioactive waste). The vast majority of volcanoes a) erupt only episodically, b) are unpredictable in terms of timing, and c) even if they erupt “continuously,” it’s only for a few years, and we have no way of knowing right now how to predict the length of eruption. You might well plunk your waste down in one spot only to find that the eruption ends two days after you’ve left. That would hardly be useful for covering dumped waste.
By way of illustration - Mauna Loa in Hawai’i is one of the most active volcanoes in the world, yet it only erupted 15 times between 1900 and 2003, the last time in 1984. Kilauea has been erupting now continuously for 23 years, setting a local record for length of eruption and volume of material, but not in a predictable fashion and a maximum burial depth of 35 m after all this time. If it were your responsibility to dispose of the waste, how confident would you be in your selection of such locations, really?
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That any one location would normally be covered by several hundred meters of lava in a short time. Well, they aren’t - a few meters (depending on local topographic features controlling flow) is a lot more typical. If you happened to have an eruption that was rapidly producing a lot more (or a combination of lava and ash), there may also be the not-so-tiny safety issue of trying to maneuver waste/equipment/people close in to an active eruption.
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That lava flows extending into the ocean would remain molten long enough for a flotation device/whatever to maneuver into position and drop waste into the lava flow. But lava doesn’t do that - the surface soldifies within seconds of being exposed to the (relatively much colder) sea water, just like quenching helps solidify hand-blown glass. That’s exactly what obsidian is: volcanic glass that formed at the contact between the lava flow and the sea water.
National Geographic has a well-used bit of stock footage showing the lava extending across previous flows in little spurts that produce pillow-like forms. That is what lava flowing under water looks like. It’s useless for burying anything to any significant depth.
Apart from these points… as with ice, rock can crack and frequently does, and those cracks become conduits for fluid flow. If there is any damage to the containers at all, the waste might no longer be contained before it ceases being dangerously radioactive.
I’m sorry, Quartz, but this is just a really bad idea.