General Question

XOIIO's avatar

Have I got this radiation calculation correct?

Asked by XOIIO (18283points) February 5th, 2016

So, I finally got something radioactive, an old bullfinch mantle, complete with thorium and asbestos string.

Now, assuming my Geiger counter is reasonably accurate (last calibrated in 84 I believe, yes it is a bit out of date), this puts of at most around 4 milliroentgen per hour peak (when the meter is right against the thickest quantity of the mantle).

So, that converts to 34.78 microsieverts, and according to the xkcd chart, a flight from NY to LA is 40 microsieverts, so in effect, holding the mantle in my hand for 1 hour would expose said hand to just under the amount of radiation my whole body would experience in one flight.

Also, based on that, I think that I would need to hold the mantle in my hand for 1,437 hours to reach the safe annual radiation dosage for radiation workers, or 966 hours for civilians (at least in that hand)

Just wondering if someone can confirm I have got that all straight, or perhaps I made a mistake somewhere.

Observing members: 0 Composing members: 0

8 Answers

LuckyGuy's avatar

Ha! We’re on the same page! I just measured a 3 pack of old Bright Brand Gas lamp Mantles Extra heavy duty. I measured mine at 4.82 microsieverts/hr or 0.48 milli rem/hr . Your mantle is about 10X mine. Nice! My package is still sealed so Alpha particles are trapped. My reading is about 2 times the exposure rate I measured flying in a commercial airplane at 30000 ft.
Your math is right!

I measure ambient here at 0.1 uSv/hr. ~10 uRem/hr (Rem are old units)

XOIIO's avatar

Lol, talk about a coincidence.

My pack is open, but it’s just thin plastic, and it’s only one mantle. Couple pics of it here.

I’ve got a CDV 700-b, what type of counter have you got?

SquirrelEStuff's avatar


It’s pretty awesome that you guys are experimenting with these.
Would it be at all possible for you to experiment with a cigarette?
When I went to work at a nuclear power plant, we had extensive training in radiation safety and the instructor said that a person who smokes a pack a day far exceeds the annual allowable exposure to radiation as a worker.

XOIIO's avatar

Don’t know anyone that smokes, but maybe luckyguy does.

Maybe those ashtrays sitting outside of malls are a massive hazard :p

LuckyGuy's avatar

Mine is a modified solid state unit. Incredibly sensitive (and small). The mantle package is near the max authority of the unit. I can measure exposure rate from the radioactive potassium in a banana 0.01 uSv/hr. A human contains potassium and will expose a nearby person to about 0.05 uSv/hr. If I am walking in a crowd I can set the detection tresold such that it will vibrate when 3 people are within my radius. It is neat.

I don’t smoke and have no cigarettes.
Here’s a fun thing to try. Go to a flea market and look for old Fiestaware. The orange and yellow ones are pretty hot. They max out my unit 10 uSv/hr. (1 millirem/hr)
Yours goes much higher.

Similar to Radex RD1503+

XOIIO's avatar

Yeah, I’ve been looking for fiestaware and uranium glass without much luck. There was a guy with what I thought was a bottle of radium paint, which would have been the best fucking score ever, but it wasn’t old enough, I guess it was the tritium style paint which has a pretty short lifespan :(

CWOTUS's avatar

Your calculations seem reasonably accurate, assuming the accuracy of the observations. However, since you can’t observe or perceive radiation directly, the quality and calibration of your instrumentation is paramount. Not that I’d be overly concerned with a commercially available gas lantern mantle, but still … the principles are important.

I’m also not up to speed on the types of radiation emitted from a product like this, so I would heed @LuckyGuy‘s allusion to alpha particle emission. Those are potentially the most damaging (to living tissue) particles, even though they have the lowest energy. So it’s important to maintain the integrity of the packaging … and of your skin. I wouldn’t want to hold that in my hand without a membrane of some kind between my skin and the packaging. So, gloves, please.

One final note: Assuming the small size of the item you’re measuring and its relatively low emission level and the supposition that you’d be holding it in your hand for all of those hours (as if!), the generally accepted radiation limits for extremities (US NRC § 20.1201 Occupational dose limits for adults) are considerably higher than the whole-body limits.

But I wouldn’t go testing those without equipment that I trusted, essentially, with my life.

Again, you’re not running an extreme risk with these mantles, but if you’re going to fool with radiation much beyond this I would urge you to acquire up-to-date and reliable equipment, and to maintain its calibration.

Spoken as ‘the safety guy at work’.

It is pretty cool that you’re interested in this, though. I wish that more were.

XOIIO's avatar

Somewhat related, just made a little amp to build an external speaker for this thing instead of shelling out $30 or so for one.

Answer this question




to answer.

This question is in the General Section. Responses must be helpful and on-topic.

Your answer will be saved while you login or join.

Have a question? Ask Fluther!

What do you know more about?
Knowledge Networking @ Fluther