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  While looking for something else I found this report from the National
Bureau of Standards about radioactive illumination.

gl


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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