[roenxi]

If it can generate enough energy to be dangerous then it probably has an economic use if enough of it can be gathered in one place Like the sun - as I recall per-m3 it isn't all that energetic but there is enough sun that it provided the energy for ~99% of all life on earth. Lots of not-quite-enough energy is enough energy.

That is part of why this "no human should set foot for 100,000 years" is silly. We only have recorded history going back a few thousand years, and all of civilisation was invented in that time. If humans are exist in 100,000 years we'll be using that century-long half life material for something important.

[pjc50]

> If it can generate enough energy to be dangerous then it probably has an economic use if enough of it can be gathered in one place

This is the basis of the radiothermal generator (RTG); but generally, the spent fuel is deemed spent in the first place because it's no longer emitting enough heat/neutrons to be worth keeping in the reactor. It's already got to the point of "it's no longer worth the hassle of handling this and dealing with all those neutrons/gamma radiation in exchange for a mediocre amount of warmth".

[AnthonyMouse]

> spent fuel is deemed spent in the first place because it's no longer emitting enough heat/neutrons to be worth keeping in the reactor.

It's in a fission reactor and those isotopes aren't fissile, and aren't a huge proportion of the "spent fuel" to begin with. To be useful it has to be separated.

Short-lived highly radioactive substances are commercially valuable as radiation sources. Medium-lived radioactive substances are useful in RTGs (not fission reactors). Long-lived radioactive substances are often fissile and therefore useful as reactor fuel.

But none of them are useful when they're all mixed together, because what they're each useful for is a different thing. So separate them.

[ben_w]

> If it can generate enough energy to be dangerous then it probably has an economic use if enough of it can be gathered in one place Like the sun - as I recall per-m3 it isn't all that energetic but there is enough sun that it provided the energy for ~99% of all life on earth.

The sun is also a third of a million times the mass of the entire planet, or about 1.4 billion times the mass of all our oceans.

And the power output being in the form of ionising radiation is really bad: the power density of the core of the sun is 276.5 W/m^3, but in a form which will, if you leant against it for a minute and given reasonable guesses as to your body mass and shape, give you a remaining conscious lifetime of vomiting, diarrhoea, seizures, bleeding everywhere inside and out, relieved only by being followed with a coma after about an hour then death within a day or two.

(That's ignoring the fact that it's also hot and dense and would immediately explode, it's just the effect of the radiation coming from it).

> If humans are exist in 100,000 years we'll be using that century-long half life material for something important.

There are three possible futures: business as usual, collapse, transcendence/singularity.

With business as usual, there's a fairly good chance that everything from our era will be forgotten and dismissed as myth and legend.

With collapse, all of society might of forgotten how the abstract concepts of "money" and "writing" work, reinvented them, gotten up to our level, and then collapsed again 50 times over.

With the singularity: the planet itself and every star visible to the naked eye (and many which aren't) may have been physically disassembled in that time frame.

I think we should be the kind of civilisation that plans for how to minimise the damage of bad outcomes, even if only to make sure we don't mess up the "singularity" option.