[ RadSafe ] Air samples on west coast

Jim Hardeman Jim.Hardeman at dnr.state.ga.us
Thu Jun 23 15:15:23 CDT 2011

Folks --
How about some real data?
UC Berkeley (I refuse to call it "California") has been operating an interesting air sampling setup (Air Filtration Experiment B) involving a HEPA-filter from a commercial HEPA vacuum system. Turns out the filter fits conveniently over one of their high-purity germanium (HpGe) gamma spectrometers. Looks to me like they're sampling for 24 hours (sample volume ~3,500,000 liters in ~24 hours) and then counting for 24 hours. It's not clear how long the filter is allowed to decay (to allow radon / thoron daughters to decay away) before analysis, but as you can see by looking at the individual spectra, radon / thoron daughters and K-40 account for the bulk of the activity on these filters, even in late March -- when the concentration of Fukushima-related radioactive materials was at its peak.
I would note that many of these radon daughters are alpha-emitters as well, and would be expected to light up an autoradiograph -- particularly in a "fresh" automobile air filter.
See http://www.nuc.berkeley.edu/AirSamplingResults 
Jim Hardeman, Manager
Environmental Radiation Program
Environmental Protection Division
Georgia Department of Natural Resources
4220 International Parkway, Suite 100
Atlanta, GA 30354
(404) 362-2675
Fax: (404) 362-2653
Personal fax: (404) 521-4485
E-mail: Jim.Hardeman at dnr.state.ga.us

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