Originally posted by grunt2
1)the U238 turns very fast in PU239, actually in that way it works the modern nuclear bombs, ahh i see it take years to detonate the U238 fase
from the neutrons bombardments , seriously the regenerators reactors actually must be more slower in the U238-Pu239 process, becouse the risk of
a nuclear reaction, also the U238 turns radiactive with alpha radiation, now just imagine a neutron bomb (obviously not a direct impact) over a M1
company.....maybe it could end in a .....BOOOOM!!, nice radioactive protection...
This concern seems somewhat penny-wise to me. It's been a while since I had to worry about any of this stuff, so I'm rusty, but here's what my take
is off the top of my head.
Alpha particles are essentially helium atoms stripped of electrons. They don't penetrate very far into solids, and a thin casing of steel is good
enough to shield people -- or depleted uranium -- from them, especially since they carry a strong positive charge which leads to them bonding with
The kind of neutron flux it would take to begin any sort of supercritical reaction in U-238 is high enough that the people inside the tank would be
fried long before the armor “touched off” -- assuming that it did at all, which is questionable, because the geometry of tank armor is not optimal
for sustaining fast fission reactions.
More significantly, neutrons interact with the atmosphere, with a tenth-thickness of about 500 meters, meaning, if we ignore the very real geometric
effect of the “expanding neutron sphere”, if you're 500m away from ground zero, the neutron flux will be 1/10th of what it is at ground zero. At
1000m, it's 1/100th, at 1500m, 1/1000th, etc.
Even if you're that close to a “little” tactical nuke, you're screwed anyway. The shock wave alone would throw the heaviest tank around like a
feather in the wind -- and the occupants would be spread thinly over the interior like pink goo simply from the multi-digit G forces.
That said, U-238 does have issues -- both radiological and chemical.
In the scenario you describe, the main thing a tank crew has to worry about is not neutrons which, like alpha particles, strongly interact with solids
(to a lesser extent), but rather electromagnetic radiation -- high-energy photons.
And all nuclear weapons -- including neutron bombs, which are extremely rare -- give off massive amounts of electromagnetic radiation.
Long before neutrons become a problem for a tank crew, the gamma and x-ray flux they are exposed to will decide their fate. Ironically, U-238 can help
by serving as a rather good shield from such radiation.
You can use boronated plastics (boron is a neutron sponge of sorts) or motor fuel as shielding, or water for that matter, but those come with their
own issues, including the not-so-unimportant issue that they offer little defense against incoming rounds.
In light of the fact that that's what tank armor is supposed to do, that's not a trivial detail.
The bottom line is that there are trade-offs in everything, and people can worry about stuff like this if they want to.
But some very smart people who designed this tank didn't seem too concerned about this scenario, and, based on what I know, there are good reasons
As things stand, no one has died in an Abrams from being too close to a nuclear blast, and in pretty much every reasonable scenario I can envision, if
anyone does die this way in the future, it won't be the tank's fault.
If you're looking for reasons to bag on the Abrams, I guess you can add this to the list, but when I see it, I call “bullflux”, and it calls the
other complaints into question.
Meanwhile, all the guys I've known who drive around in these things have seemed quite happy with them.
To date, none of them have expressed to me a desire to switch to something else, and considering how important those tanks are to their occupational
well-being, a high customer satisfaction rating should count for something.