RE: "Hot Particle"

[CHASE John -NUCLEAR <john.chase@ontariopowergeneration.com>]

I gave a presentation at the 2000 American Radiation Safety Conference and
Exposition on some anomalies that we have found with VARSKIN. We are working
with Jim Durham, VARSKIN Mod 2's author, and hope to have a beta version of
a modified program out for testing in a few weeks, along with information on
what we have found. Right now my advice to anyone using VARSKIN  for point
or small 2 and 3 dimension disk sources is to use a minimum source diameter
of 20 microns. VARSKIN Mod 2 underestimates the skin dose by 7% for the
point source geometry. Also, be very suspect of doses calculated for very
shallow skin depths with no air gap or protective clothing.

John Chase
Sr. Specialist, Dosimetry
Ontario Power Generation Nuclear
john.chase@ontariopwergeneration.com
<mailto:john.chase@ontariopwergeneration.com> 


	----------
	From:  Glen.Vickers@ucm.com [SMTP:Glen.Vickers@ucm.com]
	Sent:  Friday, July 28, 2000 12:52 PM
	To:  Multiple recipients of list
	Subject:  RE: "Hot Particle"

	NRC IE 90-48 provides a definition of a hot particle based upon the
musings
	in NCRP 106.  Both reports say the critical factor is the potential
for
	localized exposure, but IE 90-48 went ahead and defined a hot
particle.  A
	hot particle is a "discrete radioactive fragment that is insoluble
in water
	and is less than 1 mm in any dimension."  Also take a look at INPO
89-006
	which has some exposure-related rules of thumb.

	It is critical that anyone involved in this area get copies of IE
90-48 and
	NCRP 106.  The IE 90-48 document tells you how the NRC will judge
the
	exposure consequence of a hot particle exposure and relate it to the
annual
	50 rem SDE limit for the purposes of enforcement.  

	The most important points are to set up point/plane source action
levels for
	different attenuating materials (i.e. dpm-hr) and to understand the
	difference between hot particle dose and SDE.  Action levels help
you screen
	for the one required dose calculation for every 100 exposures to hot
	particles or planar sources.  The code of choice seems to be
Varskin.

	Glen Vickers
	glen.vickers@ucm.com

	
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