Spectrum of Rain Collected in Anchorage, Alaska

[Geoff]

How strange that Peter shared the results of his water filtering the same day that I had setup vacuum filtration on my rain gutters to detect Be-7.

While my spectrum is still collecting data, I figured I 'd share the early results showing a prominent Pb-212 peak from thorium decay. This spectrum is from filtering 10 gallons of rain through medium speed 125 mm filter paper.

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[luuk]

Hi Geoff,
Nice set up you got there, maybe I should try something like that, great!
Luuk

[Geoff]

Thank you Luuk! I only collected about 2.5 mm worth of rain, which worked out to 10 gallons. Even with that small collection it required constant attention to empty the 1L flask every 2-3 minutes. I think next time I will use Jonathan's idea of initially collecting in a large bucket or barrel.

It's been two half lives for Pb-212 and I'm still not seeing any Be-7. I reserved 5 gallons of the filtered rain water and am now running it through a small fish tank filter with an activated carbon filter. It's not analytical grade by any means, but I figured it wouldn't hurt anything to try it.

[Peter (vital1)]

I have tried a few different rain water filter designs. I found that activated charcoal often can be contaminated with natural Thorium and other isotopes, if made from wood.

For my purposes I found running down pipe roof water through polyester wool, or paper towel roll cut in half worked better. Cheap and cost effective, plus testing showed both these materials where cleaner than charcoal.

I tried a combination of polyester wool and charcoal at first, but ended up just using the half paper towel or the polyester wool most of the time. I dry these filters in the sun before testing.



I created the page below, to provide information on the different roof rain water filter designs I have used.

http://sccc.org.au/down-pipe-filter-design

[sgt_bear]

Hi Geoff,

Happy to see you made results! Nice to see that isotopes can be found easely in the water. Did you use shielding or not?

[Geoff]

I like that design Peter! I tested the charcoal lest night after filtering for several hours and saw the same isotopes as with the filter paper. It seems that the carbon isn't contaminated initially, but I will do a spectrum of a new filter soon. I will definitely try filtering with polyester cloth next time. Looks like we've a few days before we can expect another rain.

Jonathan, yes, my setup is shielded. I have a shield consisting of ~18kg of lead, tungsten, tin, and copper. It does an excellent job of cutting background down to a minimum, around 0.5 cps compared to an unshielded background of over 16 cps.

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