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(Another question )RE: Smear Collection Efficiency
Greetings,
The question:
Is a loose contamination, is a smearable?
1.1 I had an impression that smear refers to
"smearable"
contamination i.e. what can get onto smear.
So it is irrelevant if all of it gets onto smear or
only 10% of it.
2. It is of course under certain conditions that
properties of the surface will not change and to use
"moderate"??? pressure, while smearing.
2.1 If the surface conditions are expected to be
changed, use your judgment!
3. In the end, the NRC (10CFR20) does not go into the
definition of what contamination is, it rather
regulates licensee controls of radioactive material as
a potential dose contributor.
3.1 So it is up to you how to insure what IS, IS means
or how to keep it ALARA and within the applicable
limits.
Regards,
Emil.
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From: "Stokes, James" <StokesJ@TTNUS.COM>
Subject: RE: Smear Collection Efficiency
I ain't no expert, but let's take off our shoes for a
minute and consider
this:
Can anyone estimate the amount of water in the ocean
by smearing the
shoreline? I don't think so. Collection efficiency
factors are based on
assumptions, as ALL other estimes are. There will
always be a point at
which any survey technique is not appropriate for the
circumstances. Each
type of surface, contaminate, quantity and collection
media, will have their
own "rules of thumb". The US Navy adopted a system
that worked well for
them, under the "normal" conditions of surface
contamination. There were
certain jobs that I performed, where it was identified
that those
established techniques, did not accurately represent
what was actually
there. Other techniques were used in those
circumstances.
In example. Smears of porous materials will unders
estimate the CURRENT
level of loose surface contamination. But more
importantly, if this surface
is subject to mechanical vibration, what was fixed at
the time of survey,
will become, and contribute to the loose component
later.
Food for the gray matter to consider.
- -----Original Message-----
From: tom_dixie
To: Redmond, Randy R. (RXQ) ;
radsafe@list.vanderbilt.edu
Cc: 'William R Horne/HRW/CC01/INEEL/US'; 'Scott
Davidson'; 'Lavera, Ron'
Sent: 3/30/01 5:26 PM
Subject: Re: Smear Collection Efficiency
Randy,
Nice work, now that you have a basis (or perceived
basis) for collection
efficiency for activity on smears maybe something will
be done with
that.
The 'rule of thumb' that you have identified is an
unused rule.
For example, if it was used, a smear that collected an
activity of say
20,000 dpm would indicate a surface activity of
20,000/.1 or 200,000 dpm
over the area that the smear was rubbed. However, it
is recorded as
20,000
dpm over that area (usually 100 square cm).
10% is also what the Navy used when I first qualified
as a rad tech.
However, the 'loose surface activity' was never
determined using this
factor. It is real and should be used, any idea why
it isn't?
There was also some indication (back in the early
70's) that for larger
areas the smear would be less effective in collection
and for some
surfaces,
like concrete, the smear (paper) would disintegrate.
Or in some cases
would
become a medium for transfer of activity to clean
areas from
contaminated.
There are many caveats to the use of this collection
efficiency. The
smear
must remain whole, the pressure over the smear surface
must be uniform,
the
surface activity must be reasonably homogenious, etc.
It is obvious that smears do not collect 100% of the
activity on a
surface
(otherwise the surface would be clean) but the current
method of surface
activity determination simply leads people to believe
that surfaces are
cleaner than they are.
Tom O'Dou, CHP, RRPT
tom_dixie@msn.com
- ----- Original Message -----
From: "Redmond, Randy R. (RXQ) " <RXQ@Y12.doe.gov>
To: <radsafe@list.vanderbilt.edu>
Cc: "'William R Horne/HRW/CC01/INEEL/US'"
<HRW@INEL.GOV>; "'Scott
Davidson'"
<bsdrp@YAHOO.COM>; "'Lavera, Ron'"
<RLavera@ENTERGY.COM>
Sent: Friday, March 30, 2001 12:19 PM
Subject: Smear Collection Efficiency
> Many thanks to those who responded to my inquiry.
10% for the smear
> collection efficiency appears to be the
"rule-of-thumb". Found a
report
> (RADSAFE Archives) with some actual
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