if there's any water left in that water heater after a couple hours and it didnt explode from vapor overpressure, you'll painfully die of acute radiation sickness.
that's the best case scenario.
that's the best case scenario.
[1] https://en.m.wikipedia.org/wiki/Fukushima_Daiichi_units_4,_5...
One disposal plan called for mixing the fuel with silica to create glass bricks. By spreading the fuel mixture to a density that was low enough to allow the ambient air to cool it, the bricks are shelf stable for thousands of years and not a radiation hazard (less of a risk than even natural uranium deposits you might come across).
Many disposal plans were like this, encapsulate the spent fuel into a container that withstands (and blocks) the radiation while conducting enough heat to avoid changing the properties of the material over the lifetime of its storage. Glass and austenitic stainless are both good candidates for that material.
The fact that spent nuclear fuel must be kept in water at all until it is sufficiently decayed to be put into dry storage still safely away from humans means it is by definition not fail safe. Water evaporates and if you lose the ability to dissipate heat or absorb ionizing radiation, "you're in deep shit" would be a colossal understatement. How comfortable would you be that something on your property or in your home is one water outage or tank failure away from irradiating your family and probably a bunch of your neighbors. I imagine the hazmat team won't be happy to be invited to your housewarming either.
If it requires cooling or radiation-blocking-immersion to be safe, it absolutely has to be monitored by trained personnel 24x7 who can also immediately and reliably take necessary measures when something goes wrong. Anything less than this is a non-starter. Nuclear reactors work because they centralize risk to where it can be managed by a team of knowledgeable people; A 1GW reactor does not have the same risk profile as 1000 dispersed 1MW reactors.
If you lay a spent rod out on the ground in the air, it may glow (would depend on the amount of material in a single rod) and you wouldn't want to approach it without protection (again more material more radiation) but it would be fine.
The reason people put these things in water is two fold, one is that water is a great transporter of heat and you can generate almost an arbitrary amount of heat in a small space if you have enough water flow to carry it away (ask any highend gamer PC aficionado :-)) and water absorbs neutrons, which if they were not caught and hit another fissile atom nearby slowly enough might spit it, or a non-fissile atom might become an unstable nucleotide (which is going to eventually emit an alpha or beta particle)
If the material is clad in a neutron opaque material and can transfer the latent heat to the surrounding atmosphere or fluid at a rate that keeps the system temperature under the breakdown temperature of the containment, then it will be stable "forever".
Yes, it takes a year or two for the short lived nucleotides in a fuel rod pulled from a reactor to decay, but once it has, you can safely store this stuff.
In terms of why we haven't, most of the issues around storing high level nuclear waste arise because third parties do not want to encapsulate permanently this material, because doing so would make it uneconomical to recover. And in that calculus they know its "easier" to reprocess spent fuel for bomb grade uranium and plutonium than it is to build a breeder reactor to make it.
if it can boil water, can't it be used to generate electricity? What makes it "spent"?
I would also hope it would be dimensioned for radiation cooling when over 100°C.
Still wouldn't want people to have those at home anywhere near me. But it's mostly because of misuse, not because of operational dangers.
I bet that made it some much more secure! /s
From "Freaked" (1993)
Ugh