Title: BRAWM Air Filter Alpha Spectrometry Report
Source: University of California, Berkeley Department of Nuclear Engineering
Date: July 31, 2011
BRAWM took an air filter sample in mid-April and performed alpha spectrometry on the air filter. We did not detect any Uranium, Plutonium, or Americium-241, and our calculated detection limits indicate safe levels. Our limits are much higher than the limits set by the EPA in their testing for Uranium and Plutonium.
Comparison with EPA results
While our limits are comparable to the limits we have set for fission product isotopes from Japan, the EPA reached much lower limits. The EPA performed several tests for Pu and U in the first few weeks after the Fukushima disaster. They issued a report on their findings [LINK BROKEN]. In San Francisco, there was a detection of U-238, but no detections of U-234, U-235, Pu-238, or Pu-239. Here are the data, accessed via the EPA query search. MDA was estimated by taking twice the uncertainty (CSU):
So our limits are about 200–300 times higher than the EPA limits. Even though we spent a longer time collecting data, the signal-to-noise is just too poor for us to reach similar limits.
Because of the difficulties inherent in measuring alpha particles from an air filter, the standard procedure is to perform some chemistry on the filter to extract and concentrate the actinides (Uranium, Plutonium, Americium, and others). These elements are then electroplated onto a metal film and placed in front of a detector. Because there is no intervening filter material, these samples have much sharper lines and greater sensitivity (i.e., lower limits) can be achieved.
Since uranium and plutonium have long half-lives, we may consider performing other analyses on our filter sample that could be more sensitive. [...]
Read the report here
Published: April 8th, 2012 at 7:44 am ET