Alpha spectroscopy report (7/31)

Submitted by bandstra on Sun, 2011-07-31 21:16

7/31 (9:15pm): We have finished the analysis of the alpha particle spectrum from an air filter collected on April 16–19. 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. If you would like to skip directly to our limits, please click here.

Thanks for your patience with us as we ventured into alpha spectroscopy, which is very different from our main expertise in gamma-ray spectroscopy.

Mark [BRAWM Team Member]

‹ NRC Members Reject Quick Overhaul for Nuclear Plants BRAWM Team: What Are The Results Of The Plutonium Analysis ›

Thanks, Mark!!!

Submitted by VB (not verified) on Mon, 2011-08-01 14:36.

Thanks for keeping at this and finally getting the results out to us. It's something I've been eagerly waiting for. I guess it doesn't matter if you match the EPA minimums. Just as long as unsafe levels were not detected (not that even the natually occuring isotopes are safe).

Thanks again for the great work.

Thanks Mark. You guys had to

Submitted by BC (not verified) on Mon, 2011-08-01 06:35.

Thanks Mark.

You guys had to work at this one, didn't you? A whole different cup of tea from the gamma testing....

Hi BC, Yes, it was a stretch

Submitted by bandstra on Mon, 2011-08-01 14:17.

Hi BC,

Yes, it was a stretch :) We have done laboratory course-level experiments with alpha particles, but never such a "real world" application. And hence the time it took to understand and analyze the data.

To get very low limits requires special chemical preparation that our lab is not set up with (we don't usually do chemistry). Even so, I was pleasantly surprised that we could get within a factor of 1,000 of the EPA's limits in our crude manner. There is a great deal of uncertainty in our "efficiency" term, but I tried to estimate it as conservatively as possible.

Personally, I was fascinated by the amount and strength of the different alpha emitters that are in our natural background: Polonium-210, Polonium-212, Polonium-214, and Bismuth-212. Alpha particles are much more dangerous internally than beta and gamma rays, since they only travel about one cell distance and they deposit several MeV of energy (betas and gammas are measured in keV, where 1 MeV = 1,000 keV). The radon progeny are the source of about 50% of our total background dose, and that dose is primarily from these alpha emitters inside our lungs. And this is why is important to mitigate indoor radon levels through proper ventilation!

Mark [BRAWM Team Member]

Just learning whats a level you would consider unsafe?

Submitted by Tdm (not verified) on Mon, 2011-08-01 10:20.

Honest question what makes u an authority to claim a level is safe .since the EPA did detect these isotopes above there mda and your mda is higher almost seems that your test may have been a great learning tool for u all but far from a scientific all is s afe and clear .I really wonder what your statement would have been if u detected level-s above your higher than EPA detection limits.Thank you for being transparent with the data and posting it.

Hi Tdm, I used dose

Submitted by bandstra on Mon, 2011-08-01 15:10.

Hi Tdm,

I used dose conversion factors derived from the NRC isotope intake limits, as we have done for our other calculations. The dose conversion factors for these alpha-emitting isotopes are much larger than those for I-131, Cs-137, and the others since they are more dangerous. Still, the limits we find imply that breathing the air for one year would give a dose of at most several millirem. Given that a person's average background dose is about 200–300 millirem per year, a dose of several millirem is very small. These dose levels are safe in that they are much smaller than typical background dose fluctuations. I know there are folks who disagree with this, and so the raw data are there as well.

The EPA had some detections of U-238 and U-234 but had non-detects of the other isotopes. Using the EPA findings, the yearly dose for these isotopes is measured in microrem. That level is even farther below fluctuations in natural background and is considered very safe.

We may be able to test the air filter with other equipment, but that will take a while to do. No concrete plans there yet.

Mark [BRAWM Team Member]

That's a big difference

Submitted by Tdm (not verified) on Mon, 2011-08-01 10:27.

"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."

Mark any plans for the dept to improve testing equipment so u could come close to the epa's csu.