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slightly OT WHERE and WHAT to buy for a good radiation meter?

Discussion in 'Electronic Design' started by Robert Macy, May 4, 2013.

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  1. Robert Macy

    Robert Macy Guest

    I did a google search and way too many of the listings either produced
    dead websites [of items I really wanted!], or Amazon, or eBay -
    neither of which I want to use. Amazingly, google's own ads came up
    with nonexistant websites?!

    There must be some industrial/commercial manufacturer, or some
    bonafide outlet that sells a nice portable meter.

    Anybody have one, or know what to watch out for, or where to buy one?

    PS: I'm not afraid of assembling a kit, but kits I've seen either
    don't exist (?) or have NO housing and I can't believe somebody
    offshore hasn't done an effective meter all for less than this fussing
    around.
     
  2. Robert Baer

    Robert Baer Guest

    RAD meters were the rage when everyone was hyper over the a-bomb.
    Dosimeters, and RAD meters are available via surplus markets,and you
    have snubbed the two major sources.
    Hell, even GM tubes are rare as the helium used is a government
    controlled substance.
    Even the big boys in the oil patch have problems in that area.
     
  3. miso

    miso Guest

    I have a Ludlum model 3 with a 44-6 tube. Does the job for me. I got it
    on ebay sans cable for about $100. Ludlum sold me the cable for about
    $20 and included a manual. The cable used C connectors. Not BNC, but C.
    I figure it was worth $20 rather than trying to make one. I was at a DOE
    facility a few years ago and compared it to their calibrated meter on a
    test source. Accurate enough for me.

    The deal is you will need way better sensitivity than the old civil
    defense meters you find at swap meets. The model 3 can sense background
    radiation, typically 5 to 15 uR/hr. That won't show up on an old civil
    defense meter, though you should probably hear the clicks.

    The sensors are used in two manners. That is it has a gamma shield you
    can open or close. Just look it up on the Ludlum webiste: I notice there are a lot of model 3 on ebay without tubes. The meters
    themselves are pretty simple. I suspect the tubes are what fails, which
    is why they are sold without tubes. It might pay to see what Ludlum
    charges for a new 44-6 or whatever you want. I doubt the meters
    themselves are defective.

    I have never found any place hotter than 100uR/hr. That was out in the
    Mojave around Kelbaker, where they have a few uranium mines.

    You are free to pay the full retail price if you don't want to use Ebay.

    The nice thing about Ludlum unlike more of the civil defense
    manufactured gear, Ludlum is still in business and they support the old
    products.

    If you are looking for hot rocks, you probably want to get a UV flashlight.
     
  4. Jon Kirwan

    Jon Kirwan Guest

    Have you tried it up in a commercial airplane at 37,000'
    inside the spallating aluminum tube you ride in? I did, some
    years ago. Quite a difference from ground level.

    Jon
     
  5. Get the one called the 'Inspector' comes in different variations. They
    can be calibrated and traceable.
    If you looking for measuring specific kinds of radiation get one with
    the changeable filters.


    Cheers
     
  6. miso

    miso Guest

    Well, actually no. I'm trying to think of a scenario where I can whip
    out a geiger counter in a commercial airplane without the passengers
    thinking I'm a jihadist.

    "We have now reached cruising altitude. You may now use electronic
    devices, but beat the shit out of anyone with a geiger counter."
     
  7. Jon Kirwan

    Jon Kirwan Guest

    I got some very serious stares. And I was asked to turn it
    off, as well. Which I did. However, the silly reason I was
    given as their "justification" was that they didn't want
    anything that might interfere with their communications
    system (radios have IF oscillators.) I informed them that
    there was no oscillator here and no means by which it could
    interfere (I'd built this geiger counter myself.) But I also
    turned it off.

    See if you can sneak it aboard. hehe. It's fun.
    hehe.

    One of the flights, after the above event, I was sitting next
    to a United Airlines pilot. After some conversation I asked
    him if they'd ever checked out the radiation levels during
    flight. He told me, "Yeah. Actually, they had us wearing
    badges for a while." I asked, "What were the readings? Did
    you ask?" He said, "Yeah. And they wouldn't tell me, except
    that it was 'safe'." We talked a little longer and I could
    tell he wasn't particularly happy about not being told, too.
    Apparently, they never did disclose the readings to him.

    Made me even more curious, especially after seeing my GM unit
    counter go wild up there. (By the way, I used a series string
    of NE-2s as the HV regulator for that unit.)

    Jon
     
  8. Fred Abse

    Fred Abse Guest

    Only very bad radios ;-)
     
  9. Jon Kirwan

    Jon Kirwan Guest

    Thinking of 455kHz.

    Jon
     
  10. Jon Kirwan

    Jon Kirwan Guest

    Crap. I'll probably get shot without warning for wearing my
    tritium dial watch, then. ;)

    Jon
     
  11. Fred Abse

    Fred Abse Guest


    I think you meant local oscillators. Any oscillation at IF is called
    instability.
     
  12. Jon Kirwan

    Jon Kirwan Guest

    Yes. That's what I meant. It was me conflating "IF frequency"
    with "local oscillator" into a mush. Cross-purposes between
    us at an end now. Lesson learned.

    I was merely pointing out that a receiver's local oscillator
    can act like a weak CW xtr, because that was a reason given
    to me to stop me from using any personal receiver at some
    point in my frequent flying career.

    This all goes back quite some years when this was an issue
    for me.

    I used to listen to tower traffic when it was offered by the
    flight services I used. I learn better technique for when I
    pilot a small plane in controlled airspace. (And yes, I got
    some nice laughs from time to time.) Then I had that option
    removed by those same services. So I began bringing my own
    receivers on board. Then perhaps a year or two later they
    told me I couldn't use those receivers inside the plane --
    even when sitting at the gate and not moving. I had a nice
    discussion with appropriate "officials" and got pretty much
    the same boilerplate -- the radios may "interfere" with their
    communication. This coupe de grâce against my listening
    pleasure all happened BEFORE 9/11.

    To bring this full circle, the GM unit I brought on board did
    not have any "intentional" local oscillators in it. But I'm
    sure I'd get the same boilerplate about local oscillators
    causing interference if I bought one on board. When I did
    bring mine, it was BEFORE bringing a personal receiver had
    become an issue. Still, I eventually was asked to shut it off
    as I was explaining readings to interested nearby passengers
    who were quite curious. ;)

    Jon
     
  13. Robert Macy

    Robert Macy Guest

    So, how much MORE is it at the space station? Or, even outside the van
    Allen Belts?
     
  14. Jon Kirwan

    Jon Kirwan Guest

    I believe the details within and where within the Van Allen
    belts (I think they discovered something new about them
    recently, by the way) have no bright line definitions. It's
    constantly changing and some places are better than others,
    given that. The trailing dark-side edge pulses in bursts as
    the lines develop and then cross each other and release
    energy. I'm not sure there is any specific place to be
    positioned with security in mind. The Van Allen belts
    themselves pose their own radiation hazards.

    I have very little real knowledge about current details. I
    remember the Forbush effect (I think first noticed as a
    reduction in cosmic ray events due to coronal mass ejections
    from the sun and later, I think, applied to the effects of
    the solar wind on arriving cosmic rays -- which cuts them in
    about half, memory serving, but depending on where in the
    solar cycle the sun is at.) I'm not sure how much effect the
    Van Allen belts have on cosmic rays, though the atmosphere
    certainly has a huge impact as they arrive. But probably the
    radius of gyration deflects most of them.

    I think galactic cosmic rays and solar proton events from the
    sun are the biggest concerns.

    But I generally hear it's horrible -- not something to do for
    extended times. One of the guys I worked with for years had
    spend years himself as part of a team designing satellite
    systems. He talked about how they start out neutral, but are
    impacted by energetic particles, which split charges with
    some going to the satellite and the rest going to ions that
    are dislodged for a distance then re-attracted back but
    somewhere you don't want them to stick as "brown crud" that
    accumulates in bad places. Charge and heat accumulation are
    serious problems, I gathered. As far as astronauts go, the
    ISS (I read) experiences 150mSv/yr for astronauts inside. But
    the Skylab astronauts experienced over 500mSv/yr rates. The
    new Mars rover is taking data there, not sure what the
    results are (or if any are published yet.)

    From:

    http://www.nap.edu/openbook.php?record_id=1224&page=384

    You can see that the global average background radiation is
    on the order of 1mSv/yr. Elsewhere, I read figures of
    1.5mSv/yr and slightly higher. And it depends on where you
    are, of course. But that gives an idea for comparison

    A Mars mission is estimated to result in a 1 Sv dose, which
    seems consistent with the Skylab rate.

    There are no known effective measures. Even lead is mostly
    vaccuum. Liquid hydrogen isn't bad, nor water -- both are
    needed anyway. But best would be a nice big asteroid with the
    astronauts nicely in the center of it. Active shielding
    (magnetics and electrostatics mixed) may help, but no one has
    fielded any serious testing of the idea.

    In interstellar space the problem is even more acute.

    By the way, I just found this link:

    http://www.ncbi.nlm.nih.gov/pubmed/2818404

    Which is germane to my point about measuring radiation in an
    airplane at 37,000' altitude.

    "The dose equivalent to air carrier crewmembers from galactic
    cosmic radiation was estimated for each of 32 nonstop flights
    on a variety of routes to and from, or within, the contiguous
    United States. Flying times were from 0.4 to 13 hours. The
    annual dose equivalents received on the flights ranged from
    0.2 to 9.1 mSv (20 to 910 mrem), or 0.4 to 18% of the
    recommended annual limit for occupational exposure of an
    adult."

    This is entirely consistent with the measurements I took on
    that flight I mentioned. I found that in a 2hr flight you
    receive about 1 year's ground level dose. My estimate,
    because I didn't calibrate things beforehand, is approximate.
    I would say that you get about 0.5mSv to 1mSv per hour of
    flight at altitude, given my readings.

    In short, every two hours of altitude flying gives one year's
    sea level dosage. Nice.

    The really FUN thing to do is to take your geiger counter and
    show it to a few passengers BEFORE boarding and then show it
    to them AFTER reaching altitude. They will FREAK! The level
    is about 4000 times higher. And if you teach them about the
    switch that selects the range before they board, they will
    see that you switch ranges a few times when at altitude and
    it scares them. hehe. It's a "must do" when you get a chance.

    Jon
     
  15. Jon Kirwan

    Jon Kirwan Guest

    I just checked my notes from 20 years ago (when I did this.)
    Had to go look for the notebook. My memory is exaggerated. I
    got a little over two orders of magnitude increase, not over
    three orders as I just stated. It was several hundred times
    greater than what I measured at sea level before taking off.

    Still impressive, though!!

    Jon
     
  16. Bill Martin

    Bill Martin Guest

    Not to mention the water hazard! :)
     
  17. Guest

    If you don't own a Geiger counter, you may be able to get a reading
    cheaply from those who do. Just spend a couple of bucks on a ticket for
    your local public transit system:

    http://chicago.cbslocal.com/2013/03...-on-metra-train-after-detecting-nuclear-risk/

    Although I must admit that the above is only one data point. It would be
    interesting if more people who have had similar medical procedures made a
    point of taking the subway (or equal) home, to see if that happens every
    time.

    Somewhat related: This chart http://xkcd.com/radiation/ attempts to give
    some scale to the amount of radiation produced from various sources, from
    "eating one banana" to "chest CT scan" to "ten minutes next to the
    Chernobyl reactor core". There is some discussion of it at
    http://blog.xkcd.com/2011/04/26/radiation-chart-update/ . The chart was
    first published after the Fukushima Dai-ichi power plant meltdown.

    Matt Roberds
     
  18. Bill Martin

    Bill Martin Guest

    Yikes, it looks crowded out there!
     
  19. Does no one get SDR yet?
     
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