October 15, 2006

Details: Using Thorium reactors for power without proliferation of nuclear weapons

from the thorium energy blog, using thorium as the fertile material and U-233 as the fissile material has a secret advantage in the "proliferation" department--the inevitable formation of uranium-232. The "4n" decay chain, of which U-232 and Th-232 both follow has a decay product (thallium-208) that emits a strong and penetrating gamma ray during its decay that makes it very unattractive in weapons use. Weapons, especially those that want to be launched on ICBMs, can't afford thick heavy gamma shielding around their fissile cores to protect the sensitive electronics that trigger detonation.

In a two-fluid thorium reactor, thorium nuclei in the blanket will intercept neutrons and breed--first to protactinium-233, then to uranium-233. If the protactinium is isolated chemically after it is formed, then the U-233 in the protactinium decay tank will have little U-232 contamination.

The real question I've had is: how can we generate U-232 contaminated material, even in the Pa decay tank? Ionium is thorium-230, which is part of the natural decay chain of uranium-238, which is rather abundant. If the thorium in the blanket was "spiked" with ionium, it would be impossible to chemically separate the two forms of thorium (since they are chemically identical) but the ionium would preferentially absorb neutrons and form Pa-231.


mackay said...

For this general argument to work, gamma shielding would have to stay cost-prohibitive for more than another 5 years (unlikely, given the development of CNT polymers with gamma sink properties: ) Even if that were the case, thorium and its byproducts would still be decent material for all sorts of high-yield IED's, no?

coonass said...

In addition, one can imagine places like North Korea or even India (where instead of having adequate shielding and remotely actuated fluid loop valves in some nuclear reactors, laborers are paid to run over and turn valves manually and replaced when they max out on absorbed radiation dose) where life is cheap and processing highly radioactive material is a plausible "human wave" activity.