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  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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