> Gentlemen, gentlemen, gentlemen. Come on now, Mining Plutonium!?!?
> D. M. Gall
Several people wrote about Pu. Yes, plutonium is a valuable energy resource
and it is used in Europe and in Japan to fabricate reactor fuel (the technical
name is MOX, mixture of oxides). The US has a self-impossed moratorium (since
J. Carter's presidency) on processing of spent civilian reactor fuel. Yes, the
term "burning" is not appropriate for the fission process but it is often used
metophorically in that way. In the same spirit a hybrid machine able to
destroy spent fuel is often referred to as a "nuclear incinerator".
The energy content of Pu is enormous and it would be wasteful to put it
into a geological depository. One variant of the the LANL hybrid system is
designed to get energy from Pu while incinerating it. Yes, underground
depositories of the unprocessed spent fuel (U.S. favored option) may become
mines of military-grade plutonium in 10000 years or so. Here is a problem
on mining of plutonium (for students familiar with the law of exponential
decay and reactors).
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About 150 kg of plutonium is produced each year in a civilian power plant
(in a typical reactor generating electricity at the rate of 1000MW). The
isotopic composition is 60% Pu-239 and 40% of Pu-240 (I simplified, other
isotopes are also present). The half-life of Pu-239 is 24100 years while the
half-life of Pu-240 is 6500 years. Suppose that a mixture which has less
than 20% of Pu-240 (I am guessing here) can be considered a bomb-grade
material. How long would it take to turn a geological depository of Pu into
a mine of ready-to-use bomb-grade material? What precautions must be taken
to prevent a spontaneous nuclear explosion underground?
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The bottom line: technologies for getting energy from plutonium exists and
burrying the unprocessed spent fuel underground is no longer the best option.
That is my opinion based on what I hear from experts. Did you know that the
are about 500 metric tons of bomb-grade plutonium in the world now. Only
about 20 kilograms (an educated guess again) is needed for a bomb.