4 ms·

I work at a nuclear reactor, and for the type of dosimeters we wear on the job (thermoluminescent dosimeters), there's no chance of a false-positive, as far as

I work at a nuclear reactor, and for the type of dosimeters we wear on the job (thermoluminescent dosimeters), there's no chance of a false-positive, as far as I'm aware. The only thing that can cause the crystal to lose electrons is ionizing radiation in a certain energy range. As long as there were procedures to ensure that the badges are only worn on the job, false positives shouldn't be an issue.

jballanc 16y ago
You'll get false positives if anyone goes for a cardiac stress test...
- aperiodic 16y ago
  That's why you only wear your dosimetry when you're at work.
  - Vivtek 16y ago
    From all this uproar lately, sounds like work is a cardiac stress test for the TSA.
    - shpxnvz 16y ago
      Not nearly as much as it is for the passengers. For all the uproar, as of the last time I went through TSA security (about a week before the new "sexual assault" procedures started), the screeners seemed to be perfectly happy in their roles.
  - jballanc 16y ago
    Wouldn't matter. Cardiac stress tests usually use technetium or some other radioactive tracer which remains in the body for a day or two after the test. That means that, for the next day or so, you are a "radiation hazard" (not really, but the dosimeters don't know the difference, or at least that's what I was told by the radiation control officer).
AngryParsley 16y ago
Yes, with standardized work-issued dosimeters, training, and strict obedience to policies, you will reduce false positives. They'll still happen, though. Some types of dosimeters will read positive if exposed to heat or sunlight. Some are sensitive to oils or dirt. One nuclear waste disposal facility had false positive rates around 5% per quarter (http://www.osti.gov/bridge/product.biblio.jsp?osti_id=515496 http://www.osti.gov/bridge/product.biblio.jsp?osti_id=515496). They eventually found the lights in their building to be a major cause. Now take that information and extrapolate it to using dosimeters in every airport in the nation. Even if the TSA deployed dosimeters as competently as a nuclear waste disposal facility, they would still get so many false positives that the dosimeters would be useless.
rmc 16y ago
As long as there were procedures to ensure that the badges are only worn on the job, false positives shouldn't be an issue. And that's how your false positives happen. How many people would have to wear dosimetres? Would they be mandatory? How many people per year will leave them at home and borrow their workmate's dosimeter so the boss doesn't give out? How many will drive home in their uniforms? Go to the shops in their uniforms? There are loads of ways for errors to happen. Nuclear reactors are (I'm guessing) very strict on their policys, it's foolish to extrapolate that to airport workers.
- amanfredi 16y ago
  After all this, you don't think the TSA is strict on their policies?
- aperiodic 16y ago
  It's not very hard to solve this problem. At work, we just have a bunch of small cubbies where everyone keeps their dosimeters. When you come in, you take it out and put it on; when you leave, you take it off and put it in. Occasionally people forget to take their dosimetry off, but it's not a big deal–it's extremely unlikely you're going to receive a significant dose outside of the facility (although you are constantly receiving a low-level radiation dose from cosmic rays, and, if you're below ground, from radon gas). I should mention that I work at a test reactor where the typical dosage is so low that the Federal Government doesn't even require us to track employee dose. I get more dose from flying cross-country several times a year[1] than I do working at the reactor. So, I don't know how dosimetry policy differs at power reactors. Regardless, I think it would be particularly illuminating if there <i>were</i> false positives. Why not have employees who are concerned wear dosimeters constantly, and at the same time stick reference dosimeters near where they usually stand while a scanner is in operation. If their dose is roughly the same as that of the reference dosimetry, there's not much room to complain about the scanners. The fact is we are being constantly bombarded by low-level radiation from cosmic rays and radon gas simply by virtue of standing on the surface of the earth. The level of radiation these scanners output is much smaller than that. Wikipedia[2] cites an article in the European Journal of Radiology that gives a dose range for backscatter machines of between 0.07 and 6 micro-Sieverts. For reference, the National Council on Radiation Protection and Measurements reports that the annual radiation dose from naturally occurring radiation is on the order of several hundred micro-Sieverts [3]. TSA employees have a right to be concerned, because they are involuntarily being exposed to it as a course of their job, without this being made clear to them when they were hired. If you're a traveler, you should be much more concerned about the radiation dose you receive on the plane than the one you receive from the scanner. [1] Health Physics Society page on radiation exposure on commercial airflights: http://hps.org/publicinformation/ate/faqs/commercialflights.html http://hps.org/publicinformation/ate/faqs/commercialflights..... [2] https://secure.wikimedia.org/wikipedia/en/wiki/Backscatter_X-ray#cite_note-37 https://secure.wikimedia.org/wikipedia/en/wiki/Backscatter_X... [3] http://hps.org/documents/environmental_radiation_fact_sheet.pdf http://hps.org/documents/environmental_radiation_fact_sheet....

jballanc 16y ago

You'll get false positives if anyone goes for a cardiac stress test...

aperiodic 16y ago
That's why you only wear your dosimetry when you're at work.
- Vivtek 16y ago
  From all this uproar lately, sounds like work is a cardiac stress test for the TSA.
  - shpxnvz 16y ago
    Not nearly as much as it is for the passengers. For all the uproar, as of the last time I went through TSA security (about a week before the new "sexual assault" procedures started), the screeners seemed to be perfectly happy in their roles.
- jballanc 16y ago
  Wouldn't matter. Cardiac stress tests usually use technetium or some other radioactive tracer which remains in the body for a day or two after the test. That means that, for the next day or so, you are a "radiation hazard" (not really, but the dosimeters don't know the difference, or at least that's what I was told by the radiation control officer).

AngryParsley 16y ago

Yes, with standardized work-issued dosimeters, training, and strict obedience to policies, you will reduce false positives. They'll still happen, though. Some types of dosimeters will read positive if exposed to heat or sunlight. Some are sensitive to oils or dirt. One nuclear waste disposal facility had false positive rates around 5% per quarter (http://www.osti.gov/bridge/product.biblio.jsp?osti_id=515496 http://www.osti.gov/bridge/product.biblio.jsp?osti_id=515496). They eventually found the lights in their building to be a major cause. Now take that information and extrapolate it to using dosimeters in every airport in the nation. Even if the TSA deployed dosimeters as competently as a nuclear waste disposal facility, they would still get so many false positives that the dosimeters would be useless.

rmc 16y ago

As long as there were procedures to ensure that the badges are only worn on the job, false positives shouldn't be an issue. And that's how your false positives happen. How many people would have to wear dosimetres? Would they be mandatory? How many people per year will leave them at home and borrow their workmate's dosimeter so the boss doesn't give out? How many will drive home in their uniforms? Go to the shops in their uniforms? There are loads of ways for errors to happen. Nuclear reactors are (I'm guessing) very strict on their policys, it's foolish to extrapolate that to airport workers.

amanfredi 16y ago
After all this, you don't think the TSA is strict on their policies?
aperiodic 16y ago
It's not very hard to solve this problem. At work, we just have a bunch of small cubbies where everyone keeps their dosimeters. When you come in, you take it out and put it on; when you leave, you take it off and put it in. Occasionally people forget to take their dosimetry off, but it's not a big deal–it's extremely unlikely you're going to receive a significant dose outside of the facility (although you are constantly receiving a low-level radiation dose from cosmic rays, and, if you're below ground, from radon gas). I should mention that I work at a test reactor where the typical dosage is so low that the Federal Government doesn't even require us to track employee dose. I get more dose from flying cross-country several times a year[1] than I do working at the reactor. So, I don't know how dosimetry policy differs at power reactors. Regardless, I think it would be particularly illuminating if there <i>were</i> false positives. Why not have employees who are concerned wear dosimeters constantly, and at the same time stick reference dosimeters near where they usually stand while a scanner is in operation. If their dose is roughly the same as that of the reference dosimetry, there's not much room to complain about the scanners. The fact is we are being constantly bombarded by low-level radiation from cosmic rays and radon gas simply by virtue of standing on the surface of the earth. The level of radiation these scanners output is much smaller than that. Wikipedia[2] cites an article in the European Journal of Radiology that gives a dose range for backscatter machines of between 0.07 and 6 micro-Sieverts. For reference, the National Council on Radiation Protection and Measurements reports that the annual radiation dose from naturally occurring radiation is on the order of several hundred micro-Sieverts [3]. TSA employees have a right to be concerned, because they are involuntarily being exposed to it as a course of their job, without this being made clear to them when they were hired. If you're a traveler, you should be much more concerned about the radiation dose you receive on the plane than the one you receive from the scanner. [1] Health Physics Society page on radiation exposure on commercial airflights: http://hps.org/publicinformation/ate/faqs/commercialflights.html http://hps.org/publicinformation/ate/faqs/commercialflights..... [2] https://secure.wikimedia.org/wikipedia/en/wiki/Backscatter_X-ray#cite_note-37 https://secure.wikimedia.org/wikipedia/en/wiki/Backscatter_X... [3] http://hps.org/documents/environmental_radiation_fact_sheet.pdf http://hps.org/documents/environmental_radiation_fact_sheet....