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Radium - Geiger Counter Measurements

  1. TNTwatch Feb 4, 2019

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    Your method to distinguish alpha from gamma seems fine, but the 3 tools at the beginning of the thread below are not equipped to detect alpha, yet people were able to measure about 17-18 µSv/h with them. What do you think was detected there?

    https://omegaforums.net/threads/radium-emissions-on-early-2998.78228/

    PS: I was just trying to determine if an alpha particle detector could be additionally helpful to our hobby, or just a beta and gamma counter is good enough.
     
    Edited Feb 4, 2019
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  2. jshaw083 Feb 4, 2019

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    To be honest, I'm not sure I can explain this. I've read reports that the cheap handheld radiation detectors are fairly inaccurate and not congruent with commercial radiation detectors. Could be that it's just detecting gamma but not measuring it accurately. Or that the 2998 models have a lot of radium in that lume. Which would be surprising for any watch made post-1940s (since even at that point watch companies were drastically cutting back the amount of radium they used on dials). Would be interesting to see how the levels measured by these portable detectors compare to those used by professionals (e.g. Thermo-Fischer).

    I think we mainly care about gamma radiation from a health perspective. As far as anyone has ever been able to tell, alpha radiation is harmless, unless emitted from inside the body (which is what happens when you inhale/ingest radium chips, like the radium girls).
     
  3. Mspohn Feb 27, 2019

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    Annnnnd now I still don't know if I want to buy that Seamaster with Radium...but amazing information here - thanks guys!
     
  4. bardamu Feb 27, 2019

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    Great contributions here, thanks for sharing guys!
     
  5. TNTwatch Mar 10, 2019

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    Haven't been able to look much further into this and just got a few quick thoughts, so correct me if I'm wrong:

    1. The RadEye PRD you used is capable of gamma detection only. It's the RadEye SX that is capable of detecting Alpha and Beta additionally, and I think it's also able to tell what kind of radiation detected.

    2. A tool that is able to detect both benign and dangerous radiations but unable to tell them apart is potentially more dangerous than a more limited device that focus on one or the other type. When there's just a benign one, a false alarm may be raised unnecessarily. When the more dangerous gamma exists, the situation could be dismissed as a benign one instead.

    3. Radiation normally disperses omnidirectionally so it's strength relates to distance by the inverse squared law. Double the distance - a quarter of the strength. I looked back your first post and at the end where you checked the watch box, the measurements appear to be close to this inverse squared rule.

    4. As many measurements shown in this and the other thread, as well as many places elsewhere, gamma only tools are useful enough for radium watches. A beta capable device could be useful if it's of high quality and sensitive enough to detect minute amount of beta particles that may still remain on tritium watches.
     
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  6. jshaw083 Mar 10, 2019

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    Hi TNT,

    Interesting observations, and I had thought of the same thing recently (the way radiation rays disperse occurs and decreasing intensity with increasing distance). This likely accounts for a lot of the difference I observed with pulling the radiation detector away from the watch....That being said, i'm still curious. When I measured radiation levels just above the case (with the watches just underneath, practically just below the detector), the value was still much lower (0.53 uSv/h) compared to at the watch crystal surface.

    Although the RadEye PRD states on its website it is used to detect gamma radiation, nowhere does it say whether it can discriminate between alpha/beta/gamma or rule out contamination from other types of radiation. It uses a sodium-iodide detector. Was just trying to see online if it mentions anywhere that NaI detectors only detect gamma, and I couldn't really definitely rule it in or out. I emailed ThermoFischer, will try to get some extra information. I agree that measurement of gamma radiation is the most useful for our hobby (this is what we should care about). I suppose I was just hopeful that the measurements we are getting are mainly alpha, with only a small contribution from gamma (given gamma is the dangerous radiation, not alpha). I'll also email the person who helped me out with the detector to see what he thinks!

    Regardless, even if this is gamma, seems like the most protective thing to do is to keep your distance from your watch when you're not wearing it. Even a foot away, the radiation levels seems to be extremely low (near background). Radiation emitted from a single isolated source is different than being "immersed" in a full blown radiation field where your whole body is exposed to the same level of gamma radiation. Even when wearing it, it would be your wrist getting the brunt of the radiation. And presuming you don't wear it every minute of every single day, you'd have to multiple those total annual doses we calculated by whatever fraction of the time you're wearing it (e.g. 1 day/week -> 1/7 x 21 mSV = 3 mSV/year).

    Interesting discussion...I'm sure we'll eventually get to the bottom of things (and hopefully re-assure ourselves!)

    - J
     
  7. jshaw083 Mar 10, 2019

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    Addendum - Just found on wikipedia that NaI detectors mainly detect gamma radiation @TNTwatch so seems like what I was detecting was in fact gamma. I suppose the distance factor is still re-assuring with respect to overall body doses.

    https://en.wikipedia.org/wiki/Scintillation_counter

    "The scintillator consists of a transparent crystal, usually a phosphor, plastic (usually containing anthracene) or organic liquid (see liquid scintillation counting) that fluoresces when struck by ionizing radiation.
    Cesium iodide (CsI) in crystalline form is used as the scintillator for the detection of protons and alpha particles. Sodium iodide (NaI) containing a small amount of thallium is used as a scintillator for the detection of gamma waves and zinc sulfide (ZnS) is widely used as a detector of alpha particles. Zinc sulfide is the material Rutherford used to perform his scattering experiment. Lithium iodide (LiI) is used in neutron detectors."
     
  8. Rasputin The Mad Monk of OF Mar 10, 2019

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    Radium based watches have been worn for decades before they were discontinued in the 1960s. Has there been any significant clinical evidence over the years supporting a higher incidence of cancer in the normal wearing of an intact radium based watch? I've only seen a study from Kingston University and University of Northampton supporting a theoretical risk due to radon emission from WW2 era watches. This is not to say that no risk exists but how clinically significant is it?
     
    Edited Mar 11, 2019
  9. M'Bob Mar 11, 2019

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    Good point. Sometimes the answers to these questions cannot be definitively answered due to a lack of well-controlled research, so the the question really boils down to figuring out your own level of risk aversion.
     
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  10. Tony C. Ωf Jury member Mar 11, 2019

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    Given the risks that we human guinea pigs are being exposed to with GMOs and electromagnetic fields, I feel confident in asserting that wearing vintage watches is a relatively healthy thing to do! :D
     
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  11. Leica May 9, 2019

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    i bought a watch online and border custom had it opened as they claimed it detected radioactive signal thru their scan. I did not know anything about radium prior my purchase so I was pretty much surprised and shocked by it. I took the watch to a local Nuclear Medical Facility and they did a quick scan and said it is very active, but i didnt think it is economical to pay for a full report.

    I found a local dealer which carries geiger counter and I spent $400 on their top of the line model. I quickly did a scan in my car and the reading was 150-157uSv/hr . It was a sunny day and I did it right under the sun with the watch on my wrist, I figured it might not be accurate. I tried again and run a 5mins reading several time it average at 135uSv/hr . I sent the video to manufacturer and they said everything looks correct.

    The tech at the lab suggest me not to wear it , if i would have known i wouldnt buy it.
     
  12. jshaw083 May 9, 2019

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    That's an extremely high reading (as far as radium watches go). What model/brand is it and from what year?

    To give you some perspective, my radium watches range from 0.50 uSv/hour to 2.20 uSv/hour measured at the crystal surface.
     
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  13. 77deluxe May 9, 2019

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    What kind of watch?
     
  14. Leica May 9, 2019

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    after my research on the serial , I believe its a 1957 watch . Rolex Precision had dots lune and on both hands. I am not a vintage watch collector, bought it solely thought it looks good.
     
  15. 77deluxe May 9, 2019

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    Pic?
     
  16. jshaw083 May 9, 2019

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    ...I don't think a Rolex from 1957 should have a reading that's that high, regardless of the model... Most watch manufacturers began reducing radium content in the 1930-40s and by 1957 most watches only had a small fraction of the radium contained in watches from the earlier 1900s. Are you sure your counter is accurate?
     
  17. Leica May 9, 2019

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    i placed in 2cm above the crystal
     
    5953CF89-B5A6-4F1C-911D-5AE968AD2CB7.jpeg
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  18. Leica May 9, 2019

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    i verified with the manufacturer they say it looks accurate, and while i was at the lab their geiger counter needle went off the scale for a a 30s reading.
     
  19. jshaw083 May 9, 2019

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    Are you using a Radex detector?
     
  20. AdInfinitum May 9, 2019

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    Can you place it 2cm above a banana so we can see the negative control?
    Can you place a lead sheet between the detector and the watch for additional verification?