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Friday, May 17, 2024

I Wanted a Gamma Ray Source to Test my Survey Meter...

So when I went in for my nuclear stress test today, using technetium-99 metastable isomer.   I thought I knew nuclear physics pretty well but metastable and isomer (at least for nuclei) were both brand new.  This produces gamma rays and beta particles.  The tech confirmed that my radiation survey meter should get excited in my presence.  

It appears to be true.  I zeroed the meter.  I tried the X1 setting on my abdomen (maximum tissue with blood in it) which gave between .01 and .02 roentgens/hour, and barely off the 0 on the floor, which is about what I would expect for whatever quantity they injected me with about 5 hours ago. (i think she said it was about 10 microcuries of Technetium-99.)

At first guess .01 r/hr seems plausible.  Unfortunately, roentgens are from a Civil Defense and public safety standpoint, obsolete.  REMs, or roentgens equivalent mammal are a bit smaller than roentgens. 

"The dose of radiation expected to cause death to 50 percent of an exposed population within 30 days (LD 50/30). Typically, the LD 50/30 is in the range from 400 to 450 rem (4 to 5 sieverts) received over a very short period."


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5 comments:

  1. B May 17, 2024 at 8:14 PM

    You gotta be pretty "Hot" to tickle the survey meter. A CDV 700 is a lot more sensitive, the 700 uses a Geiger tube

    A CDV 715 or 720 survey meter is for a much more high energy environment...it uses an Ion Chamber that will work where an Geiger tube would become saturated. . Not sure your dose would do more that maybe make the meter move. Much less sensitive and takes more energy to trigger.


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    Replies
    1. Clayton CramerMay 18, 2024 at 10:34 AM

      CDV-710.

      Delete
    2. B May 22, 2024 at 8:25 PM

      Same thing, essentially. Just a different model.... It is a Survey meter rather than a low level geiger counter. Still an Ion chamber...less sensitive.

      If you are getting a reading on a Civil Defense survey meter you need to think hard about finding somewhere else to be.....

      Delete
  2. Windy WilsonMay 17, 2024 at 8:50 PM

    And I do wish I had thought of this when I had MY nuclear stress test last month. We do know that my heart's good and strong and in the right place. ;)

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  3. FidelMay 19, 2024 at 1:53 PM

    Had that meter calibrated lately?

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