[NewCandle] influence of aluminum geometry on Geiger counter rates

[Nick Reiter]

Hi all,

Been a while since I had been able to finish off some "effect-screening" tests I wanted to do, one of which was suggested by Keith a few weeks ago.  All of course in regards to the phenomenon of the jump in Geiger counter readings when a solution of uranyl acetate in water wicks into the inter-turn spaces of an aluminum foil roll...

There essentially were four tests I made to check the influence of geometry on the effect.

In the first, I replicated the observation made on two occasions previously, with the foil roll, added to a column of .1M uranyl acetate in H2O.  The set up was simple, Geiger counter head strapped to a plastic 500ml graduated cylinder.  Baseline readings were made with water, then with uranyl acetate solution.  Then we poured the solution back out, inserted a 75 foot roll of Al foil, and poured 250ml of solution back in, enough to cover the roll top. (no D2O added)

The jump upward in count rate was noticed within 3 to 5 minutes.  This was reported here about 3 weeks ago.

I then tried three other geometries of Al introduced into the column of 250ml of solution.

1.  A 1.25" x 8" round solid bar of aluminum, inserted into the liquid.  A slight drop in counter reading (about 40%) was noted immediately, and did not change until the bar was removed.  We might be safe to presume that this drop in count was due to thinning of the annular volume of emitting solution, and shielding by the solid Al mass.

2.  Next, a duplicate of the original foil roll was modified by sealing the inside seam and the outside seam with plastic tape, and sealing both ends of the roll with silicone rubber.  Thus we produce an aluminum foil cylinder, with all internal turns and voids, however it is sealed against any immediate ingress of solution into the turns.  When this piece was inserted, a slight drop in count rate - similar to test 1 - was observed immediately.

3.  Finally, a test suggested by Keith.  About 50ml of 3 to 5 micron diameter spherical Al powder was added to the uranyl acetate column while the Geiger counter was operating.  The powder made a grey dispersion, though no immediate hydrolysis reaction or bubbling was noted.  I periodically swirled the dispersion a bit and kept it afloat for 5 minutes.  From a starting count rate of 250cpm average, there was no discernible change.

Thus these three geometric tests to me seem to support the general idea that the act of infiltration of the uranyl acetate solution into foil roll inter-turn cavities is related to a rise in count rate noted by a Geiger Mueller counter nearby.

Of course, one then asks "why".

Maybe some kindly seasonal avatar will gimme that epiphany for Christmas!

Best regards and seasonal cheer to all.

nr