[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Radiation lesson

Wright wrote:

> Electromagnetic radiation comes in lots of useful forms.

According to the AP article in the morning paper, they're talking about
using an electron beam on mail in the DC area only.

> Particle bombardment with neutrons and electrons (alpha and beta "rays") may
> penetrate some materials and can cause residual radioactivity if they actually
> split atoms into unstable isotopes. The kind used for killing salmonella in
> ground beef is most unlikely to ever do that. It takes a pretty big
> accelerator.

Alpha rays are essentially helium nuclei.  They aren't neutrons, and
they aren't very penetrating.  Beta rays are electrons, and that's what
they're talking about using.  I recall that these are mildly
penetrating, but I don't know if the electron guns they're talking about
using produce electrons with energies anything like a beta ray.

Neutrons are fairly penetrating and depending on the energy of the
particle they can get involved in a number of different kinds of
reactions; typically they are captured by an atom, which creates an
unstable nuclear configuration. Various forms of radiation can be
produced as the unstable atom returns to a stable configuration. 
Fission reactions leading to radioactive isotopes basically won't happen
because they require a) fissionable material, which is hard to come by
and b) a neutron of the correct energy. 

You don't need a particle accelerator to generate a neutron beam, just a
neutron source.  I think that an Americium source is commonly used in
well-logging tools that use neutron reactions to determine rock
properties.  I don't know if a neutron source like that would produce
enough energy to be sterilizing, but it isn't a particularly important
point anyway.

> None of them can be used on packages of widely different thickness and
> contents to reliably kill microorganisms, so quit worrying about shipping
> stuff in boxes. OK? They ain't gonna do it any time soon. Letters, maybe.
> Boxes, no.

I think an electron beam can penetrate paper, and maybe cardboard, but
it would be attenuated by either.  Just the same, I think they're most
interested in sterilizing the outside of packages and envelopes.  That
would hopefully prevent many of the secondary exposures that we seem to
be getting now.

> The morons we elect to office, and the dimwit bureaucrats they like to hire
> don't usually know very much physics. They do know they can get away with
> extracting more money from you and hiring more underlings if they can scare
> the pants off of you.

The Post Office is depending on doctors and researchers to help them
save the lives of their own employees and maybe to limit the scope of
any similar attack.  Your polarizing politics needs to be taken
somewhere else.

Roger Miller