RE: Data on Porous Surfaces

["Redmond, Randy R. (RXQ) " <RXQ@ornl.gov>]

Eric and others,

Thank you for the information.  It will save myself and our researcher
many hours.


Randy Redmond
Lockheed Martin Energy Systems
P.O. Box 2009
Bldg.  9769,  MS 8081
Oak Ridge, TN  37831-8081
Email:  rxq@cosmail3.ctd.ornl.gov
Phone:  423-574-5640
Fax:  423-576-6047


	-----Original Message-----
	From:	Abelquist, Eric [SMTP:ABELQUIE@ORAU.GOV]
	Sent:	Wednesday, November 04, 1998 10:12 AM
	To:	Multiple recipients of list
	Subject:	RE: Data on Porous Surfaces

	Randy-

	ISO-7503 (1988) presents an excellent approach to the problem
you
	mention.  This standard allows the overall (or total) efficiency
to be
	divided into two components: instrument efficiency and surface
	efficiency.  The instrument efficiency is a 2 pi efficiency and
accounts
	for such factors as the calibration geometry and detector window
	thickness.  The surface efficiency is the fraction of the
radiation from
	the total surface activity that is emitted from the surface (in
the
	direction of the detector), and is nominally 0.5.  Backscatter
increases
	surface efficiency, while self-absorption decreases the value
	(particularly for alpha radiation).  In fact, ISO-7503
recommends a
	nominal value for alpha surface efficiency of 0.25.  [This
approach has
	been adopted in the recently finalized MARSSIM manual.]

	We performed experiments for the NRC in support of their
decommissioning
	rulemaking that evaluated the effects of various surface
conditions on
	detectability of commercially available instrumentation, with
emphasis
	on surface efficiencies.  Results have been published in
NUREG-1507,
	which is available on the NRC web page.  Overall, our research
indicates
	that the surface efficiency used for alpha radiation (0.25) is
not a bad
	starting point, but that under some situations encountered in
	decommissioning projects, even an alpha surface efficiency of
0.1 may be
	overly optimistic.   

	Finally, one question that usually comes up in this discussion
is: at
	what point does your surface contamination become a volume
contamination
	problem?

	Sincerely,
	Eric Abelquist
	ORISE
	abelquie@orau.gov
	423 576 3740

	-----Original Message-----
	From: Redmond, Randy R. (RXQ) [mailto:RXQ@ornl.gov]
	Sent: Wednesday, November 04, 1998 6:38 AM
	To: Multiple recipients of list
	Subject: Data on Porous Surfaces


	I am trying to find some data or, preferably, reports or
articles, which
	deal with the expected quantity of rad contamination which could
be
	trapped in the pores of a porous surface and remain undetected
while an
	alpha scan shows the surface to be at or below some release
criteria.
	Surely, someone has done an experimental or theoretical study of
this -
	I am just after a very rough estimate of what we might have
hidden in
	the pores of a closed cell foam rubber.  Data for large cell
porous
	ceramics or weathered wood would probably be quite relevant.


	Randy Redmond
	Lockheed Martin Energy Systems
	P.O. Box 2009
	Bldg.  9769,  MS 8081
	Oak Ridge, TN  37831-8081
	Email:  rxq@cosmail3.ctd.ornl.gov
	Phone:  423-574-5640
	Fax:  423-576-6047

	
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