[grey_whiskers]

Moreover, heavy metals like uranium and plutonium are among the most brittle materials known to man, and the slightest bit of humidity turns them into uranium oxide or plutonium oxide (i.e. worthless rust).

Interesting point, the uranium in uranium oxide would still be fissionable, as fission is a nuclear reaction.

My questions would be twofold:

1) Would the presence of oxygen change the energy dependence of the neutron capture cross section, affecting the yield?

1a) Or the difference from that is too small?

2) Would the plutonium "rust" change important factors like density, shape, etc. so that the "implosion" of a "Fat man" would not achieve the desired density, or not achieve it quickly enough, resulting in a lowered yield?

Cheers!

[Southack]

"Interesting point, the uranium in uranium oxide would still be fissionable, as fission is a nuclear reaction."

Only in the sense that all matter is fissionable to some degree...just not within our technical reach for most of it to go boom.

[Southack]

"1) Would the presence of oxygen change the energy dependence of the neutron capture cross section, affecting the yield? 1a) Or the difference from that is too small? 2) Would the plutonium "rust" change important factors like density, shape, etc. so that the "implosion" of a "Fat man" would not achieve the desired density, or not achieve it quickly enough, resulting in a lowered yield?"

Uranium Oxide (i.e. rust, commonly seen in nature or after rudimentary refining as yellowcake) is typically a neutron absorber...certainly the critical chain reaction speed is changed going from Uranium to Uranium Oxide...not a good thing for a precisely calculated boom.