[ExI] cost of SBSP and thorium

[Charlie Stross]

On 20 Aug 2012, at 11:14, Eugen Leitl <eugen at leitl.org> wrote:

> 
> Compare the half life of Pu-239. Nuclear warheads do not have
> a shelf lifetime of more than a couple decades.

I'm informed (ahem) that it's more like low single-digit years for the weapons that go into ICBM warheads. Those particular warheads need to be as light and small as possible (so you can fit more of them atop the bus, or more penaids, or other extras) so they're manufactured with very high purity ("supergrade") Pu-239. Trouble is, any Pu-240 in the mix will decay via gamma emission and mess with the explosives in the surrounding implosion system (to say nothing of the spontaneous fission problem). So the chemical explosives around the pit need to be replaced regularly, and at somewhat longer intervals the pit itself may need to be remanufactured to get rid of fission products from Pu-240 decay, and then there's the 12.3 year half life of the tritium used as a neutron emitter and a booster in suspended-core warheads.

Obviously the components that need regular replacement/refurbishment are made as modular as possible, but I'd expect a complete tear-down-and-rebuild to be needed at least once a decade unless a nuke is *specifically* designed for long-term storability.


-- Charlie