Re: PAC 3 a hit! woo hoooo!

From: John Clark (
Date: Thu Jul 27 2000 - 11:20:57 MDT

Michael S. Lorrey <> Wrote:

> I imagine he means that you can sniff out odd isotopes of helium,

There are only 2, common He4 and very rare He3 and I don't see why
a bomb would make a lot of He3, at least not until it went off.

>Proper shielding for that much plutonium is at least 6 inches of solid metal,

The plutonium in every fission weapon is surrounded by several inches of lead,
or more usually, something even denser like tungsten. The reason for this is not
shielding, although it has that effect, it's because it acts as a tamper, the added
mass slows the expansion of the plutonium core allowing the nuclear chain reaction
to proceed for a few extra nanoseconds. Also, the plutonium usually has a thin layer
of beryllium around it because that element has more atoms per volume than any
other and so is good at reflecting precious neutrons back into the core. The 5 or 6
inches of chemical high explosive around it all also acts as a radiation shield.

>which would weigh at least a half ton.

All that does add weight of course, the tamper weighs more than any other part
of a fission weapon, but not half a ton. After all, the plutonium core is smaller than a
orange. Besides, it you're delivering the warhead by truck not ICBM then weight is
not a issue.

               John K Clark

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