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    Re: Radium illumination
    From: Gary LaPook
    Date: 2010 Sep 16, 22:53 -0700

      While looking for something else I found this report from the National
    Bureau of Standards about radioactive illumination.
    On 9/8/2010 10:18 PM, Gary LaPook wrote:
    >  O.K. maybe I was overreacting. I had been considering putting lead on
    > the other side of the sextant box to protect my neighbors. But now,
    > giving it some more thought, since the radiation rate inside the
    > sextant box and one inch from the radiation source was 51 rems per
    > year, which is ten times the OSHA allowable rate of 5 rems per year, I
    > only needed to reduce the rate by a factor of 10 to bring it down to
    > the OSHA safe exposure limits. Since the inverse square rule is at
    > work, I only need to stay 3.16 inches (the square root of 10) away
    > from the bubble chamber to reduce the rate to 5 rems per year.
    > Considering the size of the box, I only need to stay outside the box.
    > In fact, I could duct tape the box to my chest and wear it 24 hours a
    > day, 365 days a year and not receive a dose greater than the OSHA
    > limit so sitting on my couch 15 feet away poses no danger to me and I
    > don't have to worry about my neighbors.
    > Whew!
    > gl
    > On 9/7/2010 7:35 PM, Gary LaPook wrote:
    >>  Thanks for all the suggestions. I have decided to just leave the A-7
    >> alone since I have other sextants to use at night and the A-7 works
    >> really well and I don't want to disassemble it and possibly screw up
    >> a good thing.
    >> But since you guys have scared me about the radiation exposure I
    >> decided to cover the sextant with lead scuba diving weights and lead
    >> shot. The lead is a little more than 4 inches thick which equals two,
    >> one-tenth thicknesses. This will attenuate the radiation by a factor
    >> of one hundred so instead of the 1.6 millirems exposure per year
    >> without the lead it should only be 16 microrems which is well below
    >> the 200 millirems normal background exposure and only about
    >> 1/300,000th of the 5 rems per year exposure allowed under OSHA regs.
    >> On 9/7/2010 12:49 AM, Frank Reed wrote:
    >>> Gary, you wrote:
    >>> " Twelve hours later the most sensitive dosimeter registered 70
    >>> milliroentgens which was confirmed by the second dosimeter showing
    >>> something less than a tenth of a roentgen and the least sensitive
    >>> dosimeter registered no change.This means that the rate is about 6
    >>> milliroentgens per hour which would result in an exposure of about
    >>> 50 roentgens per year, about 250 times the normal background
    >>> exposure! Any exposure below 25 rems (approximately the same as a
    >>> roentgen) produces no detectable clinical effects on humans so one
    >>> could spend six months inside the sextant box without harm."
    >>> That's very close to my experience with a nice old mechanical alarm
    >>> clock that I've been carrying around since I was about ten. The
    >>> clock was nearly new when I found it, and I would guess by the style
    >>> that it was probably manufactured in the 1960s. It's a common
    >>> Westclox "Baby Ben". I discovered, when I was about twelve, one dark
    >>> night with a telescope eyepiece used backwards that the hands looked
    >>> like a swarm of thousands of fireflies when magnified. The
    >>> scintillation was, and is, just beautiful. I just checked, and it's
    >>> still sparkling away... Way back then, I was somewhat surprised to
    >>> discover that other "glow-in-the-dark" clocks and toys were much
    >>> less interesting when magnified --no fireflies. Years later,
    >>> sometime around 1990, I acquired a little radiation monitor that
    >>> connects to a PC serial port (it's very entertaining and I still
    >>> experiment with it now and then. If anyone wants one, the
    >>> home-business selling this particular item is still around. It's
    >>> Aware Electronics, and the model of radiation monitor that I have is
    >>> the "RM-60". If you don't have a computer with a serial port, you'll
    >>> need an adapter. See his web site). When exposed to the old alarm
    >>> clock, the radiation monitor's software spikes right through the
    >>> roof, and it's software geiger counter, normally clicking quietly,
    >>> becomes a continuous buzzing sound. It's amazing to see and hear.
    >>> Various rocks and other objects also show higher than normal
    >>> radiation levels. It's also interesting to see the radiation levels
    >>> climb during airline flights --at 30,000 feet you're above most of
    >>> the atmosphere so radiation exposure is about 20-30 times higher
    >>> than normal sea level background radiation. In fact, the correlation
    >>> is so good that the radiation count makes a decent altimeter.
    >>> Again, the paint on the hands of my alarm clock is scintillating
    >>> RIGHT NOW. I presume that these "hot" clocks turn up on ebay
    >>> regularly. Buy a few. Scrape the paint off the clock's hands and
    >>> grind it up (being VERY CAREFUL not to inhale the dust) and mix with
    >>> fresh paint. Apply to sextant. Would that work?
    >>> -FER
    >>> PS: I also used to assemble nuclear weapons... but only as a
    >>> hobbyist. :o
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