[ RadSafe ] Fwd: hand held meters

Sat Jan 18 12:28:03 CST 2014

I would think a Ludlum Model 19 would be sufficient! Depends on what you
mean by hotter, and your proximity to the rock!

Dan ii

Dan W McCarn, Geologist
108 Sherwood Blvd
Los Alamos, NM 87544-3425
+1-505-672-2014 (Home – New Mexico)
+1-505-670-8123 (Mobile - New Mexico)
HotGreenChile at gmail.com (Private email) HotGreenChile at gmail dot com

On Wed, Jan 15, 2014 at 10:10 AM, Tianna Gross <Tianna.Gross at uregina.ca>wrote:

> Hello All,
>
> I would like to ask a follow up question regarding this topic. I am up in
> Canada, so some regulations may differ but I would like to hear your
> opinions and expertise. I have a academic geologist going into the field to
> "find" and "bring home" uranium and other rock samples for study. He goes
> with other Government Geologists, which seem to be unaware of radiation and
> do not reliably monitor the samples to bring home. He would like to
> purchase and bring a survey meter into the field for future studies, to
> eliminate the "hotter" rocks from coming back on campus. What survey meter
> do you recommend? I was thinking a GM pancake would be sufficient for these
> basic proposed activities. Thoughts?
>
> Thank you so much!
>
> Tianna
>
>
>
>
> -----------------------------------
> Tianna Gross, M.Sc.
> Radiation & Biological Safety Consultant
> Health, Safety & Environment | Human Resources
> University of Regina
> Office: (306) 585.5198/ Cell: (306) 527.4320
>
> http://www.uregina.ca/hr/hse/
>
>
>
> This email and any attachments may contain information that is
> confidential, legally privileged, or exempt from disclosure under
> applicable law and is intended only for the user of the addressee(s). Any
> use, disclosure or copying of this email by anyone other than an
> addressee(s) is strictly prohibited. If you have received this email in
> error, please delete or destroy it immediately without making a copy and
> notify the sender by telephone or return email.
>
> >>>
>
> Hi John:
>
> Hand-held devices are very sensitive to the geometry of the sampling
> conditions. For instance, if you are in a swale or depression, the meter
> will sense a higher level than if the ground is flat. This gave rise to
> many misunderstood measurements related to e.g. craters made by artillery.
> If a reading is made inside the crater, it will be always be higher than
> the soil surrounding the crater.
>
> In my experience, it takes a full "field-season" for a newby geologist to
> understand what he is actually measuring, and to take into account the
> geometry of the measurement conditions.  I recommend that your people leave
> the meter on all the time so that they can get a basis for understanding
> what they are measuring,
>
> Measurements will also differ according to the height above the soil that
> an instrument "sees" the surrounding gamma values.  Difference will also be
> present in soils that have been used for agriculture from the radium &
> radium progeny from the phosphate fertilizers spread on the soil.  SInce I
> was "looking" for uranium ores, my measurements included background as well
> as elevated rates for rocks that had elevated levels of natural
> radionuclides (K-U-Th Series).
>
> My ears can still hear the 1000s of hours that my scintillation counter was
> active during field work. I'd average about 140 days each year in the
> field, so I became very accustomed to hearing artifacts. Temporal spikes
> are not uncommon, so set the time constant on a longer integration time to
> smooth these features out.
>
> Also, measurements with meters will vary slightly according to the ambient
> temperature of the meter; but please guard against thermal shocks since it
> is possible to crack the NaI crystal that way.
>
> Best!
>
> Dan ii
>
> Dan W McCarn, Geologist
> 108 Sherwood Blvd
> Los Alamos, NM 87544-3425
> +1-505-672-2014 (Home – New Mexico)
> +1-505-670-8123 (Mobile - New Mexico)
> HotGreenChile at gmail.com (Private email) HotGreenChile at gmail dot com
>
>
> On Tue, Jan 14, 2014 at 3:51 PM, Chris Alston <achris1999 at gmail.com>
> wrote:
>
> > Hi John
> >
> > I think that we need to ask you to be a little more specific as to
> > your application.  So, for instance, what would you be looking for?
> > E.g., interesting variations in background, deposits of uranium ore,
> > subject of your choosing here_____________________.
> >
> > Generally speaking, NaI scintillometers are much more sensitive and
> > faster than GM meters; but the time to "return to background" from a
> > random spike is essentially immediate, if you are listening to an
> > audio output.  Of course, you cannot tell that until you perceive the
> > longer interval between clicks, or the lower frequency of a tone.
> > Then, on many meters, one can select the response time constant of the
> > visual indicator of dose rate or event count rate, on others it is
> > preset for each range of the instrument.  A "short" time constant
> > might be 0.5 - 2 seconds, a "long" one might be 5 - 22 seconds.  In
> > this context, "response time" usually means something along the lines
> > of how long it takes for a meter's needle to go from 10% to 90% of a
> > final reading.
> >
> > Hope this helps a little.  It sounds to me like you might want to demo
> > a couple of instruments, to see what works for you.
> >
> > Cheers
> > cja
> > ---------- Forwarded message ----------
> > From:  <JOHN.RICH at sargentlundy.com>
> > Date: Tue, Jan 14, 2014 at 3:18 PM
> > Subject: [ RadSafe ] hand held meters
> > To: radsafe at health.phys.iit.edu
> > Cc: EDWARD.L.MARTIN at sargentlundy.com
> >
> > radsafers
> >
> > We're looking for practical experience on using hand held monitors in an
> > outdoor setting.
> >
> > The background gamma dose rates in the area are about 0.02 mR/hr.
> > The expected change that we want to see is from about 0.02 mR/hr to 0.04
> > mR/hr.
> > So the dose rate goes from about 0.02 mR/hr to 0.04 - 0.06 mR/hr. (two x
> > background to 3 x background)
> >
> > The questions are:
> > (1) what kind of hand held monitor would be good to see this change
> (e.g.,
> > PIC, GM tube, scintillation detector, etc.)?
> > (2) since this is outdoors, how long should the surveyor wait for the
> > readings to stabilize after a random spike?.
> >
> > I asked a similar question earlier,  and the consensus seemed to be that
> > making these measurements with a hand held monitor was problematic. My
> > personal experience in this area is very limited, but it seems like the
> > spikes could reach about 0.01 mR/hr and lasted several seconds.
> >
> > thanx in advance  - -jmr
> >
> > John Rich
> > 312-269-3768
> > _______________________________________________
> > _______________________________________________
> > You are currently subscribed to the RadSafe mailing list
> >
> > Before posting a message to RadSafe be sure to have read and understood
> > the RadSafe rules. These can be found at:
> > http://health.phys.iit.edu/radsaferules.html
> >
> > For information on how to subscribe or unsubscribe and other settings
> > visit: http://health.phys.iit.edu
> >
> _______________________________________________
> You are currently subscribed to the RadSafe mailing list
>
> Before posting a message to RadSafe be sure to have read and understood
> the RadSafe rules. These can be found at:
> http://health.phys.iit.edu/radsaferules.html
>
> For information on how to subscribe or unsubscribe and other settings
> visit: http://health.phys.iit.edu
> _______________________________________________
> You are currently subscribed to the RadSafe mailing list
>
> Before posting a message to RadSafe be sure to have read and understood
> the RadSafe rules. These can be found at:
> http://health.phys.iit.edu/radsaferules.html
>
> For information on how to subscribe or unsubscribe and other settings
> visit: http://health.phys.iit.edu
>