| T O P I C R E V I E W |
| jun192022 |
Posted - 12/17/2023 : 23:06:52
TL;DR: I'd like someone to run an experiment to prove that it is possible to induce a static electric charge on a plastic bubble mailer envelope (such as through rubbing with a plastic grocery bag or peeling packing tape off its surface) which is significant enough to attract radon decay products and induce an elevated reading on a GMC-600+. I currently no longer have the Geiger counter mentioned below in this post. Thanks guys!
After purchasing a GMC-600+ for a university lab, I have been confused about an elevated radiation reading from the USPS Priority Mail bubble mailer envelope the Geiger counter came in. When I put the Geiger counter up to the envelope, the reading went up to about 155 CPM (0.44 uSv/hr), compared to about 40 CPM (0.11 uSv/hr) for background and 110 CPM for a granite countertop. If I held up a piece of paper between the Geiger counter and envelope, the measured radiation went down to around 130 CPM. These readings were repeated 3 separate times 15-30 minutes apart, but I forgot to record the readings at the time. When I retested the envelope a day later, I was not able to detect elevated radiation levels.
I have been a bit confused and concerned about possible radioactive contamination on the envelope falling off and spreading elsewhere. However, I also read that static charges may temporarily induce false radiation readings for pancake Geiger counters, as noted with plastic sandwich bags: https://hps.org/publicinformation/ate/q10421.html. I am wondering whether there was a static charge on the envelope, given that 1) I had put the envelope inside a plastic grocery bag earlier that day and it could have rubbed against the plastic bag, and 2) the envelope had been taped together and I had peeled some packing tape off its surface before taking the Geiger counter out.
Questions:
1) Would anyone here be able to 1) induce a static charge (either through rubbing with a plastic bag or peeling off tape) on a plastic bubble mailer envelope (preferably a USPS Priority Mail bubble mailer envelope), wait awhile for radon decay products to settle on its surface, then replicate an elevated radiation reading using a GMC-600+, and 2) show that the elevated reading persists when a sheet of paper is inserted between the Geiger counter and envelope? I no longer have access to the original envelope or Geiger counter (it was purchased for a university lab but I am no longer working in that lab), so any help to confirm that I likely did not encounter radioactive contamination would give me some peace of mind and be much appreciated!
- This is the type of envelope: https://store.usps.com/store/product/shipping-supplies/priority-mail-flat-rate-padded-envelope-P_EP14PE
- Here's a similar experiment which was able to induce a static charge on a balloon, attract radon daughters to the balloon surface, and reproduce elevated radiation readings on a Geiger counter: https://www.youtube.com/watch?app=desktop&v=tl5oHojFzXc&ab_channel=Matthiasrandomstuff
2) Has anyone else had similar experiences with static electrical charges affecting GMC-600+ readings, and if so, with what kinds of items?
3) How concerned should I be about this measured radiation level if there were some kind of contamination? If my readings were accurate, I calculated the potential extra yearly radiation above background as: (0.44-0.11)*24*365/1000 = 2.89 mSv/yr.
- One one hand, this is below the 5 mSv/yr occupational limit for minors and pregnant women: https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/full-text.html#part020-1207
- On the other hand, it is above the 1 mSv/yr NRC exposure limit for members of the public: https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/full-text.html#part020-1301
- In the worst-case scenario of contamination leading to chronic radiation exposure, an online predictor of cancer risk from radiation exposure (https://www.xrayrisk.com/calculator/calculator-recurring-studies.php) calculated that a female chronically exposed to 2.63 mSv/yr above background every year of life from age 1 to 77 (expected lifetime in US) could have a 2.866293% (1 in 35) additional lifetime cancer risk. This seems a bit high when compared to the lifetime risk of dying in a car accident of 1 in 93 (https://injuryfacts.nsc.org/all-injuries/preventable-death-overview/odds-of-dying/data-details/)? |
|
|
