Your discovery prompts many simple home experiments;

1. Looking for alphas with an PDR-56 alpha scintillator counter on the OUTSIDE
of the plastic bag to see if Radon or Radon daughters have diffused thru the
plastic...

2. Repeat the above alpha scintillator check on an unopened bag-encased deck
marker. I;d expect that alphas would not make it thru plastic, but I'm not sure
about Radon atoms...

3. Repeat the above alpha check on both sides of the bag, see the relative alpha
count on either side of the plastic.

How long did you have the deck marker sealed inside the bag? I can see all
kinds of experimental fun here. Of course, if you have only 1 marker, there'll
be lots of reseals and waiting for equilibrium again.

I have a PDR-56 and a plastic-wand-encased Ra-226 check source. The -56 ONLY
counts alphas, counts like a bansee on a WWII aircraft gauge if the glass is
removed, hardly nothing if glass is in place or if a piece of paper is between
-56 and the source. Hmmm, may have to investigate myself for creeping Rn
daughters,,,

Jay Boggess

Steve wrote;


I am selling a deck marker on Ebay:

Item 190630224674

I keep them in heat sealed plastic bags. Well I cut open the bag that this disk
was in to test it. It measures ~16 mR/HR with a calibrated CDV700 standard
configuration with beta shield closed.

Then I tested the bag.

HOLY COW !

I could hardly believe my eyes. With the beta shield open on the X1 scale it
pegged.

On the X10 scale it registered ~1500-2000 CPM

With the beta shield closed just barely on X1.

I held it up to the light to see if there was any evidence of contamination. It
was clear as ever.

The most likely culprit is Radon (Ra-222) that saturated the plastic.

So leaving the bag open for a while, the readings over the next couple of days
decreased, at a rate that is consistent with Radon.

I think that Radon had actually permeated the plastic poly bag to saturation,
and an equilibrium was established over the months that I had the disk heat
sealed in that bag.

So, polyethene bags can serve as well if one whats to snag Ra-222 from a radium
cow.

And what remains as the Ra-222 decays are the daughters.

Steve




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