Geiger counter readings
On March 31 EPA's RadNet reported precipitation measured in Jacksonville, Florida at 150pCi/l for Iodine-131.
If a common hand-held geiger counter was used to measure the radioactive level of 1 liter of that precipitation:
1.) Would one get a reading of 330 CPM plus the radiation from other radioisotopes plus whatever background radiation level was occurring at that time?
2.) Would one get a reading not significantly different than that of the background level of radiation (in CPM)?
3.) Would one get some other reading? If so what reading would be expected?
Thank you for all the time you've been putting in to help us all. You help is very much appreciated.
Just a little bit of information that may help
The Jacksonville EPA air monitor is of little use as far as beta
gross count. It shows only a handfull of spikes of up to 450+ CPM
between 3/20 and 3/23. There is literally nothing else shown in
the graph.
The Tallahassee EPA air monitor looks a little better. At least
it has a normal graph. But, only up to 4/1. The highest spike
during that time was just over 250 CPM.
Miami, Orlando and Tampa have no data (except for gamma reporting).
Augusta Ga. had a spike up to 225 or so.
Atlanta Ga. trends much lower (<50 CPM). But, had a spike of about
140 CPM.
So, your 330 CPM is flirting with background levels. At least as
far as spikes in Fl. go.
Jacksonvill:
http://www.epa.gov/radiation/rert/radnet-jacksonville-bg.html
Tallahassee:
http://www.epa.gov/radiation/rert/radnet-tallahassee-bg.html
Augusta, Ga:
http://www.epa.gov/radiation/rert/radnet-augusta-bg.html
spike
Would an average of 330 CPM (average over 2 hours of continuous readings) considered a spike?
answer found
Thanks, I think I just found the answer below.
CPM can't be predicted
CPM can't be predicted because it depends on too many unknown variables, like local fallout, local natural sources, weather patterns, amount of rain, radon concentrations in the air at the time, etc.
There are a number of natural sources that will be elevated in rain, at least initially before accumulated isotopes are scrubbed from the atmosphere. These include: Rd-222, Be-7, K-40, Po-212, Pb-210-212, Bi-210-211, Ra-226, and many others.
As well, you might find small concentrations of man-made isotopes from medical or laboratory uses that are legally disposed of in the waste stream.
As this subject has come up before, it bears repeating:
A Geiger counter can only tell you "how much" radiation us in a sample. It can not help you easily* determine "what is radioactive"
* (you can make some guesses based on type of radiation detected and plotting decay curves, but it's not that reliable)
Is it possible to rule out
Is it possible to rule out radon by boiling? (or will it affect Iodine too?)
Is there any way to use TDS meter (for example) while heating rainwater sample to determine what it is?
what geiger counter reading is dangerous.
How high a reading on my geiger counter is safe?
Some particles may be able
Some particles may be able to be distiller from rain water, while isotope that are gaseous will not be able to be removed.
I-131 is gaseous in water, so boiling or distilling will not help. Activated carbon filtration in addition to RO and Ion exchange will remove most of the nuclides.
A reading of more than 2x background is considered to be an alert level. If counts remain above background or significantly elevated (more than 100 CPM) for more than a few minutes, it is safer to leave the area where the radiation exists.
That is not an accurate criteria
We've had many cases where background radiation has been above 2x or
100 CPM for hours. Such examples have been posted many times on this
forum.
It is accurate critera. The
It is accurate critera. The EPA monitors are incorrect and uncalibrated.