[donw]

Nuclear batteries, powered by thermocouples that transform the heat of decay into a small amount of electricity. For long-running batteries, they've got pretty good energy density, although even the most advanced designs struggle to hit 15% efficiency.

The nice thing about these is that there's only a few kg of radioactive material, and an accident high enough to generate fallout will also burn up both the fuel and the shielding.

[ars]

It will still be radioactive even if you burn it.

Instead they are actually designed NOT to burn up, but rather fall to the ground in one piece.

[tocomment]

I'd love to get one of those for a laptop. Does the power, size, weight work out? Imagine running your laptop for 20 years without ever plugging it in!