Dangerous Radiation exposure at Saranac Mine?

Hi all. I recently came back from a trip to the Saranac Mine Ontario, Pegamtite Showing and i took a radiation reading on my Geiger counter in a crack in the pegmatite. The reading i was getting was 1.6 microsieverts an hour. Is this level of exposure dangerous? When i got home, & i scanned my specimens 2 samples came up giving of 10 and 15 microroentgens an hour. Should i be worried? I gotten worried to the radiation that they are giving off and put them in an aluminum box, which brought the radiation to 0.2 microsvierts an hour, my normal reading at home is 0.1 microsvierts an hour. Here is a picture of the reading i took an Saranac Mine. Should i be worried with the 2 samples i have now?

Federal rules say only atomic radiation workers should normally be in an area with more than 2.5 microSieverts per hour.

The aluminium box won't do much at all. To block out radiation you need
A- lead shielding
or
B- distance

The zircons from Saranac are slightly radioactive, but nothing to be worried about, I've been told.

Philippe.



Edited 1 time(s). Last edit at 05/03/2008 11:15PM by Philippe M. Belley.

You should not put radioactive materials in an aluminum box as aluminum (and more so beryllium) releases fast neutrons when bombarded with alpha particles. -Andrew

i suppose you are right about the aluminum box, but when i take a reading of the sample right up to the geiger counter the readings are very strong but a foot away they barely register a bit above normal background radiation. It is probably a thorite or an uranothorite in the smaple.

As long as you are not in extended contact with the samples I wouldn't worry at all.

In common practice, I think the most dangerous thing about keeping radioactive specimens is if they are stored on a closed container, cabinet, or drawer, which will allow radon gas to accumulate and be inhaled when the container/cabinet/drawer is occassionally opened. Otherwise, baring such things as powdering them and inhaling the dust, the risks from keeping a few warm specimens should be small.

I wouldn't worry about them. Just don't put them under your pillow or carry them in your pocket. And, wash your hands after handling them. BTW radon concentrations hit equilibrium very fast. The half-life is about three days; and if your specimens are not boulders, the quantity is going to be small.

I have had specimens of things like titanite give off a bit of radiation likely from thorium substitution or inclusions of something. I havent really got anything from bancroft that is too hot other than the betafites. everything else i can barely pick up radiation. Other than what is already said i dont keep them in my bedroom. They are for the most part in my back porch.

"A man is not finished when he is defeated. He is finished when he quits."

OK, let's apply some science. Not all radiation is equivalent in the danger it poses. If the radiation is alpha particles (likely if you're talking zircons, monazite...), a piece of paper is sufficient to stop them, and the same goes for your clothes. However, you should be fastidious about washing your hands after handling the specimens and about not breathing any rock dust (e.g. during lapidary processes, etc.).
On the other hand, if the radiation is gamma radiation, it is unlikely that a light material like Al will stop it. A lead lining on the inside of the box will stop the gammas and also absorb any straggling radiation left over. However, gammas are not as damaging to tissue as alphas.
Sort of intermediate between alphas and gammas are beta particles--essentially just high-energy electrons (or positrons). These are less damaging than alphas, but have somewhat longer range in matter.

So how do you tell what you have. Your geiger counter should have a window. If you get the same counts when the window is between the sample as when it is not, your radiation is predominantly gamma. Otherwise, probably alpha or beta. To separate alpha from beta, hold a piece of paper between the counter and the open windowed geiger.

To protect yourself you have 3 allies--
shielding--put material between yourself and the specimen
distance--radiation intensity decreases as the square of the distance from the source.
time--your dose increases linearly with the time you are exposed to the source.

For doses like you have cited, I suspect you are in no danger. You get more dose every time you fly cross country on a jet airplane.

I think you've got your units mixed up - 10-15 microRöntgen is not much - do you mean milliRöntgen?

I've got the same geiger counter, the units that it displays are in microrontgens and microsieverts.

fine - still believe there is a mixup somewhere - 15 microröntgen is only about normal background, so in that case your samples are not really radioactive.
I dont know with your meters but often there is a shift to go from 1x, 10x, 100x times the scale-reading.

Michal:

I wouldn't panic unless there was some reason to believe you inhaled or ingested a relatively significant quantity of radioactive dust. If you take the proper precautions as Ray and the others suggested you can collect radioactive specimens with a relative degree of saftey but keep in mind there are always risks.

You know, with all of the interest in radioactive minerals, someone should write an article explaining GM-counters, dosage, the different types of radiation, shielding, etc.

Andrew makes an important point. Aluminum is a poor shielding when used on alpha sources and so is lead. When particle radiation hits lead, it is stopped 'instantly' forming Bremsstrahlung = x-rays, necessitating even more lead to limit.

If you really want to shield specimens (I don't and I do collect uranium and thorium minerals), wrap them in a bit of paper first. The paper stops alpha particles 'slowly' without producing x-rays.

Claus

____________________________________________________________________________
Claus Hedegaard
[www.Hedegaard.com]
Strandvejen 2a, 8410 Rønde, Denmark



Edited 1 time(s). Last edit at 05/12/2008 08:38PM by Claus Hedegaard.

Michal, if you are really worried you can make a lead box for your specimens.

I don't know if those can be bought (probably yes but I didn't look), so just made my own: I got some lead sinkers at a fishing supplies store, melted them and poured the lead into a can after green peas I used a flat can after dog food to make the lid. The thicker the lead, the more shielding you get.

S.

Some folks have brought up the possible hazard of secondary particles that might result from interactions of alpha particles with lead or other shielding materials. While most alphas aren't all that energetic, you can significantly reduce the secondaries with a layered shielding--heavy metal like lead on the inside and lighter metal like Aluminum on the outside to stop the secondary radiation.

I think that melting and pouring lead might be more hazardous than the radiation.

True, if one's not careful when playing with hot lead the results can be painful. I armed myself with good heat protecting gloves, forceps and eye protection. The lead was melted very slowly and in a big evaporating dish (leftover stuff cleans off porcelain easily after it cools) over a hot plate, then poured into the pea can. The entire operation took a while, the sides had to be well covered...

S

Molten lead is baddddd! I was making a replica of the Shinn nugget. (The last big gold nugget found in NC) There was some residual water in the concrete mold. The liquid lead made the water flash to steam blowing the lead back up into my face and arm. I have many scars on my face and arm from the third degree burns and if I didn't wear glasses I would be blind.

So once again. Molten lead badddd!

Keith

OUCH!!!!! Sorry to hear you had such an awful experience!

Things must be absolutely dry, otherwise it will do that.

Just as with cooking - oil will boil "quietly", but add water (fruit/veggie juices) and things splatter all over. That's why I prefer to eat out, heh heh!

S