russia_1.html

[Paul Pomes]

Even a fizzle with a yield in the hundreds of tons equivalent is respectable.
Plutonium decay products have a high neutron cross-section and steal the
fast neutrons necessary for the chain reaction to build.  Sufficient amounts
can kill off the last three or more re-doublings which is where most of the
explosive power comes from.  On the other hand finely dispersed Pu and
other fission products plus the irradiated material that becomes radioactive
will make a few square miles dangerous to inhabit for several years.

/pbp