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> the FAS report I linked above is from 1993 and states that "There is almost 1000 MT of reactor Pu (R-Pu) in existence now, with the amount growing by about 100 MT per year."

Why couldn't we find a few kg for NASA missions? IIRC for Juno mission the DoE said "plutonium is out of stock for now, come later", so they had to use these oversized solar panels.



Those deep space missions use plutonium 238 to power radioisotope thermoelectric generators: https://en.wikipedia.org/wiki/Plutonium-238#Use_in_radioisot...

Surplus weapons plutonium is plutonium 239: https://en.wikipedia.org/wiki/Plutonium-239

Since plutonium 239 decays 275 times slower than plutonium 238, it also generates 275 times less decay heat and is therefore not useful in RTGs.


> Why couldn't we find a few kg for NASA missions?

It's not a technical problem, but a bureaucratic dispute. NASA has been getting the Pu essentially for free, but the DoD/AEC made it as a byproduct.

Now they don't anymore, and would like NASA's budget to pay for its manufacturing.

NASA has decided it's not worth the money, and as a result is only using Pu power for missions that really need it, such as the large Mars rovers.


Didn't know it, thanks!




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