Jim
if you do a back of the envelope estimate you can find out when you
should be worried about this effect.
If 4 Volt discharge per two day deployment ("open" position) occurs at 13
microRad/hr exposure (this happens to be the value at the altitude where I
live)
than it decreases the electret at a rate of 2 Volt per day.
The gammas generate ions in the air volume of the device, whcih ions are
attracted to the electret bordering that air volume. Thus the air volume is
the actual detector volume.
Let's now compare the air volumes inthe two situations:
The volume of a short term chamber E-perm is 200 ml of air stated by
manufaturer.
When it is in closed conditon the air volume the electret is exposed to is
a cylindrical volume of approximately 1.5 mm high and 34 mm diameter (I
took a micro-meter next to it, because I did not want to touch the surface
and loose the charge of my electret), this is a volume of 1.36 ml
thus the volume reduction from "open" ("on", or deployed) to "closed"
("off") position is approximately a factor 150.
That means to generate a 2V discharge per day (which is
a reasonable criterium from a point of precision)
you need to place it next to a bag of cat litter that gives it an
exposure of 150x13 = 1950 uRad/hr. This is approx 2 mRad/hr. This is a pretty
big number!
So at levels of 2000 micro-Rad/hr I would believe I would see an
effect and get worried for e-perms that are sent via 1 day overnight mail.
My question is, do we know what the source strength of the cat litter
was, or the level they measured the truck exposed the detectors at that went
off?
It is also interesting that Michael Kitto brings up Bentonite clay as the
ingredient of cat litter that caused the problem. Bentonite is "expansive
soil" and in many areas where I live houses are built on it. Yet I have not
suspected it gives E-perms a larger reading. On the other hand I have
found a gradual increase of gamma exposure when I go from a third to
second level to the basement when I use the gamma meter, but these
are in the 14-10 uRad/hr level.
It is good not to place the detectors on the floor, or in crawlspaces
as a home inspector did a few weeks ago, despite being told at that moment
by a knowledgable realtor that placing the test in the crawlspace was
not following the EPA guidelines. [Accuracy of testing devices was not
the problem here...]
This crawlspace test was done with a charcoal tester, not e-perm.
Leo Moorman
In a message dated 5/11/2009 7:28:39 PM Mountain Daylight Time,
mcneesj@YAHOO.COM writes:
Paul,
When stored or transported in its holder, what is the sensitivity
of the electret to gamma radiation? With little air volume for the
gammas to cause ionization in, what level of gamma exposure would effect
it?
Thanks in advance,
JimJames L.
McNees, CHPAssistant DirectorOffice of Radiation
ControlAlabama Department of Public HealthOffice-334-206-5368
Fax-334-206-5387Cell- 334-850-5293--- On Mon,
5/11/09, pkotrappa@AOL.COM
wrote:
From:
pkotrappa@AOL.COM Subject: Re: [RNPROF]
Could this cause false positive radon readingsTo:
RADONPROFESSIONALS@LIST.UIOWA.EDUDate: Monday, May 11, 2009, 8:06
PM
I would like to confirm the observation from
Dr.Jenkins that the the response of SST or SLT E-PERM in
off position, is negligible.While using L chamber E-PERM
(LST OR LLT) the standard procedure requires that the electret be
shipped separately in electret holder, and screwed to L chamber at the
measuremnet location. The response of electret in its holder is
similar to that of SST or SLT E-PERM in off position.Paul
Kotrappa Ph.D.PresidentRad Elec Inc.
If the Eperm was short-term with the plunger down, in other
words in the "off" position, it would not be affected very much, as
the volume of the ion chamber is extremely small in that
configuration. However, if the Eperm was long-term; i.e. an
"L" chamber, then it would be
affected. PhilPhillip H. Jenkins, PhD,
CHPSenior Health PhysicistBowser-Morner, Inc.Mail: P.O.
Box 51 - Dayton, OH 45401Delivery: 4514 Taylorsville Road -
Dayton, OH 45424Voice: (937) 236-8805 x248Fax: (937)
233-2024E-mail: pjenkins@bowser-morner.comWeb:
www.bowser-morner.com
From: James McNees [mailto:mcneesj@YAHOO.COM]To:
RADONPROFESSIONALS@LIST.UIOWA.EDUSent:
Mon, 11 May 2009 10:51:35 -0400Subject: Re: [RNPROF]
Could this cause false positive radon readings
An error in the story is that cat liter does not
emit radioactive traces of uranium, thorium and other
natural elements.
Cat liter contains trace quantities of uranium,
thorium and other natural elements. No uranium,
thorium, or other natural elements are emitted
from the cat liter. The radioactive elements
stay in the cat liter and emit radiation, some of which will
penetrate from beyond the container to the outside of the
truck.
If one shipped the electret from an E-perm or an E-perm
containing an electret in close proximity to the radiation
source it could discharge it some and thus
invalidate the future reading. No real
concern for charcoal or alpha track detectors, unless one
actually contaminated the alpha track with an alpha emitter.
JimJames L.
McNees, CHPAssistant DirectorOffice of
Radiation ControlAlabama Department of Public
HealthOffice-334-206-5368 Fax-334-206-5387Cell-
334-850-5293--- On Mon, 5/11/09, Khudgi
wrote:
From:
Khudgi Subject:
[RNPROF] Could this cause false positive radon
readingsTo: RADONPROFESSIONALS@LIST.UIOWA.EDUDate:
Monday, May 11, 2009, 9:17 AM
On a recent afternoon, an 18-wheeler with
Canadian plates set off a radiation alarm as soon as
it crossed the Peace Bridge to Buffalo, the northern
border's busiest crossing.
The driver was ordered to pass another monitor
and park in an inspection bay. A metal arm swept the
truck's top and sides and produced a gamma ray image
of the cargo. A guard used a hand-held device to
identify the offending isotope. Another grabbed bolt
cutters and snapped the truck's rear lock.
He quickly found the problem in boxes stacked
inside: scented kitty litter. Clay in cat litter
emits harmless radioactive traces of uranium,
thorium and other natural elements.
"We see this all the time," said Brad Kovach, a
U.S. Customs and Border Protection
http://www.azcentral.com/news/articles/2009/05/09/20090509canadianborder-ON.html?&wired
Kurt Hudgins,
Protech Environmental Services
Inc.RN PROF
(Subscription changes - archives) - http://list.uiowa.edu/archives/radonprofessionals.html
***** RN LEADERS - http://www.radonleaders.org/ **** RN
Linked In: http://www.linkedin.com (Search radon)
RN PROF
(Subscription changes - archives) - http://list.uiowa.edu/archives/radonprofessionals.html
***** RN LEADERS - http://www.radonleaders.org/ **** RN Linked In:
http://www.linkedin.com (Search
radon)
NOTICE: This transmission is sent on behalf of Bowser-Morner, Inc. and it maybe privileged, proprietary or confidential. It is intended only for the intendedrecipient. If you are not the intended recipient or a person responsible fordelivering this transmission to the intended recipient, you may not disclose,copy or distribute this transmission or take any action in reliance on it. If youreceived this transmission in error, please notify us immediately by telephone at937-236-8805 ext 228 or by e-mail at postmaster@bowser-morner.com or byfacsimile transmission at 937-233-2016, and please destroy all copies of thistransmission. Thank you.RN
PROF (Subscription changes - archives) - http://list.uiowa.edu/archives/radonprofessionals.html
***** RN LEADERS - http://www.radonleaders.org/ **** RN Linked In: http://www.linkedin.com (Search
radon) -----Original Message-----From:
Phillip H. Jenkins To:
RADONPROFESSIONALS@LIST.UIOWA.EDUSent: Mon, 11 May 2009 11:09
amSubject: Re: [RNPROF] Could this cause false positive radon
readings
#yiv308079576 #AOLMsgPart_2_6ed20134-1d8a-47d3-aa27-a87930a12fb3 BODY{font:10pt Tahoma, Verdana, sans-serif;}
If the Eperm was short-term with the plunger down, in other words
in the "off" position, it would not be affected very much, as the
volume of the ion chamber is extremely small in that
configuration. However, if the Eperm was long-term; i.e. an "L"
chamber, then it would be affected. PhilPhillip H.
Jenkins, PhD, CHPSenior Health PhysicistBowser-Morner,
Inc.Mail: P.O. Box 51 - Dayton, OH 45401Delivery: 4514
Taylorsville Road - Dayton, OH 45424Voice: (937) 236-8805
x248Fax: (937) 233-2024E-mail: pjenkins@bowser-morner.comWeb:
www.bowser-morner.com
From: James McNees [mailto:mcneesj@YAHOO.COM]To:
RADONPROFESSIONALS@LIST.UIOWA.EDUSent:
Mon, 11 May 2009 10:51:35 -0400Subject: Re: [RNPROF]
Could this cause false positive radon readings
An error in the story is that cat liter does not
emit radioactive traces of uranium, thorium and other
natural elements.
Cat liter contains trace quantities of uranium,
thorium and other natural elements. No uranium,
thorium, or other natural elements are emitted from
the cat liter. The radioactive elements stay in
the cat liter and emit radiation, some of which will penetrate
from beyond the container to the outside of the truck.
If one shipped the electret from an E-perm or an E-perm
containing an electret in close proximity to the radiation
source it could discharge it some and thus invalidate the
future reading. No real concern for charcoal or
alpha track detectors, unless one actually contaminated the
alpha track with an alpha emitter.
JimJames L.
McNees, CHPAssistant DirectorOffice of
Radiation ControlAlabama Department of Public
HealthOffice-334-206-5368 Fax-334-206-5387Cell-
334-850-5293--- On Mon, 5/11/09, Khudgi
wrote:
From:
Khudgi Subject:
[RNPROF] Could this cause false positive radon
readingsTo: RADONPROFESSIONALS@LIST.UIOWA.EDUDate:
Monday, May 11, 2009, 9:17 AM
On a recent afternoon, an 18-wheeler with
Canadian plates set off a radiation alarm as soon as
it crossed the Peace Bridge to Buffalo, the northern
border's busiest crossing.
The driver was ordered to pass another monitor
and park in an inspection bay. A metal arm swept the
truck's top and sides and produced a gamma ray image
of the cargo. A guard used a hand-held device to
identify the offending isotope. Another grabbed bolt
cutters and snapped the truck's rear lock.
He quickly found the problem in boxes stacked
inside: scented kitty litter. Clay in cat litter emits
harmless radioactive traces of uranium, thorium and
other natural elements.
"We see this all the time," said Brad Kovach, a
U.S. Customs and Border Protection
http://www.azcentral.com/news/articles/2009/05/09/20090509canadianborder-ON.html?&wired
Kurt Hudgins,
Protech Environmental Services
Inc.RN PROF
(Subscription changes - archives) - http://list.uiowa.edu/archives/radonprofessionals.html
***** RN LEADERS - http://www.radonleaders.org/ **** RN Linked
In: http://www.linkedin.com (Search radon)
RN PROF
(Subscription changes - archives) - http://list.uiowa.edu/archives/radonprofessionals.html
***** RN LEADERS - http://www.radonleaders.org/ **** RN Linked In: http://www.linkedin.com (Search
radon)
NOTICE: This transmission is sent on behalf of Bowser-Morner, Inc. and it maybe privileged, proprietary or confidential. It is intended only for the intendedrecipient. If you are not the intended recipient or a person responsible fordelivering this transmission to the intended recipient, you may not disclose,copy or distribute this transmission or take any action in reliance on it. If youreceived this transmission in error, please notify us immediately by telephone at937-236-8805 ext 228 or by e-mail at postmaster@bowser-morner.com or byfacsimile transmission at 937-233-2016, and please destroy all copies of thistransmission. Thank you.RN
PROF (Subscription changes - archives) - http://list.uiowa.edu/archives/radonprofessionals.html
***** RN LEADERS - http://www.radonleaders.org/ **** RN Linked In: http://www.linkedin.com (Search radon)
We found the real 'Hotel California' and the 'Seinfeld' diner. What
will you find? Explore WhereItsAt.com. RN PROF
(Subscription changes - archives) -
http://list.uiowa.edu/archives/radonprofessionals.html ***** RN
LEADERS - http://www.radonleaders.org/ **** RN Linked In:
http://www.linkedin.com (Search radon)
RN PROF (Subscription changes
- archives) - http://list.uiowa.edu/archives/radonprofessionals.html ***** RN
LEADERS - http://www.radonleaders.org/ **** RN Linked In:
http://www.linkedin.com (Search radon)
Recession-proof vacation ideas. Find free things to do in the U.S.
RN PROF (Subscription changes - archives) - http://list.uiowa.edu/archives/radonprofessionals.html ***** RN LEADERS - http://www.radonleaders.org/ **** RN Linked In: http://www.linkedin.com (Search radon)