[ RadSafe ] Skyshine

[JOHN.RICH at sargentlundy.com]

It's true that gamma radiation isn't reflected the same as light from a 
mirror, but it is scattered, and gammas that scatter back to the ground 
are the source of skyshine.  Skyshine is a common phenomenon with Boiling 
Water Reactors.  Basically, the gamma photons are "Compton Scattered" from 
the electrons in the air above the source.  For BWRs, the major source is 
N-16 in the steam (e.g., in the turbine, etc.)  N-16 has a ~6 MeV gamma, 
but what scatters back is at a much lower energy (from 6 Mev going up to 
about 1 to 2 MeV coming back down as a rough approximation).  Air has a 
low density but if the gamma goes high enough it's bound to interact with 
an electron and scatter.  A fraction of the scattered gammas head back 
down to the ground. As a rough approximation, the "skyshine" dose rate 
(from gammas scattered back to the ground) is a few percent of the dose 
rate directly above the source.

Pls feel free to correct  or amplify the explanation - - It was done from 
an old man's memory - -jmr


John Rich
312-269-3768



From:   Chris Alston <achris1999 at gmail.com>
To:     "The International Radiation Protection (Health Physics) Mailing 
List" <radsafe at health.phys.iit.edu>
Date:   04/16/2012 09:50 AM
Subject:        Re: [ RadSafe ] Encounter with Caldicott and Gundersen on 
KGO Radio
Sent by:        radsafe-bounces at health.phys.iit.edu



Roger

I cannot speak directly to whatever Gundersen is talking about, but
"skyshine" is just radiation which has been scattered back down, by
the atmosphere, which originated in a relatively intense source at or
near ground-level.  I think that there was a well-known instance of
this phenomenon at Brookhaven, many years ago, involving (I think) a
Cs source with which they were experimentally irradiating trees.
However, please do *not* quote me.  You might try Googling it.

Cheers
cja


---------- Forwarded message ----------
From: Roger Helbig <rwhelbig at gmail.com>
Date: Mon, Apr 16, 2012 at 4:49 AM
Subject: [ RadSafe ] Encounter with Dr Helen Caldicott and Arnie
Gundersen on KGO Radio
To: RADSAFE <radsafe at health.phys.iit.edu>


Kallie Metzger is the hero of the week.
http://nuclearliteracy.org/nuclear-all-stars/kallie/
Wouldn't it be good if more people went to these kinds of meetings and
questioned the dogma
preached by Caldicott and others?

I did not hear anyone question Gundersen, all of the callers to the
Pat Thurston program (5PM-6PM was the actual time that Gundersen was
on the program) were anti-nuclear power fanatics who seemed to have
worshipped the ground Gundersen walked on.

As I mentioned before, anyone can download and listen to the
interview.  I am very certain that Gundersen lied about his own
background along with making up science along the way.  His concept of
gamma radiation reflecting off the atmosphere as "deadly skyshine"
seemed quite far out.  I did not think that anything reflected gamma
radiation.

www.kgoradio.com, Listen, Hourly Archives, Sunday, 5-6PM (I will also
be able to send the audio file to anyone who e-mails me and asks for
it) - I will transcribe this to some degree; it is really hard to do
since I do not take dictation!
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