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Scintillation Detection

Posted by Tom Henderson  
Scintillation Detection
June 30, 2011 03:20PM
Hi all! I have been interested in radioactive minerals for some time. I am looking for a hand held visual scintillation detector. The type you hold up to your eye in the dark and view flashes on a phosphor screen. Basically a science-nerd toy. I saw one of these in an online catalog and now cant find it again. It was ~$30USD. Any idea where I can find (buy) one? Thanks, -Tom
avatar Re: Scintillation Detection
June 30, 2011 04:05PM
    
Here is a link to a kit that is available on eBay.

[cgi.ebay.com]

Also, do a Google search for spinthariscope for more info.

Only use an alpha emitter for a source, as alpha particles will be absorbed by the lens before reaching the eye. Using other materials that emit gamma could be hazardous, depending upon the length of exposure. WWII tank periscopes had lens coatings that were made with radioactive rare earth materials and eventually let to increased cancer rates for operators of that equipment.

Gene
avatar Re: Scintillation Detection
June 30, 2011 04:34PM
    
Tom,

I do not mean to advertise, but that catalog link is unitednuclear-dot-com

I wonder if you could make your own scintillating microscope cover-slide by coating a piece of mica with zinc sulfide.

This reminds me that I have been meaning to build a home-made cloud chamber based on dry ice and isopropyl alcohol. Has anyone attempted to do this?

-Dean Allum
avatar Re: Scintillation Detection
June 30, 2011 09:02PM
    
There's a page on my website where I describe observing scintillations using a smoke detector & phosphor. A much safer way to observe alpha particles is to use the bare CCD chip in a webcam, illustrated by this video

Regards,
Rog
avatar Re: Scintillation Detection
June 30, 2011 09:26PM
    
Warning! I'd bookmarked the video linked in my previous post some time ago. After having now watched it again, I realise that the young lady demonstrating the CCD radiation imager swears a couple of times when the alpha particles are hitting the silicon. Sorry for posting it if anyone is offended.

She has an excellent video of a large diffusion cloud chamber into which radon gas is introduced - fascinating! And she doesn't swear this time! Also this video, where the radioactivity from uranium minerals is shown to be rather alarming at Berlin Museum.



Edited 1 time(s). Last edit at 06/30/2011 10:09PM by Roger Curry.
avatar Re: Scintillation Detection
June 30, 2011 11:00PM
    
Samuel,

I would have to respectfully disagree with the statement that "owning radioactive minerals and the bottom line is not a problem or a peril". Obviously, the writer has no concept of the quantities of naturally occurring radioactive material (NORM) that exist in some amateur collections or what care they take in curating it. My own rather small NORM collection measures around 1mr/hr @ 4'. If I were to store that under my bed, I would receive a dose of approximately 3r/year. That is almost the DOE regulatory dose rate of 5 rem/year. Of course I don't store it under my bed, but that gives a notion of the fact that some care is required in curating such a collection. And, that does not address the issue of Radon, which the HPS has addressed and has even facilitated forced ventilation for a museum case of NORM specimens. Ingestion of dust from NORM is another area of potential danger. I would rather caution amateurs that may not be aware of the potential hazards than make statements which may cause them to be careless with such material. That said, I would recommend to anyone that owns, or is contemplating owning, NORM to read safety guidelines that are available on the internet, for owning such material. Properly curated, a small collection of radioactive materials should pose no health hazard. All of that said, please forgive my obsessive thoughts on the matter. Having been a DOE radiation worker for 38 years has permanently imbedded safe practices into my brain. Always err on the side of safety.

73
Gene K6ELC
avatar Re: Scintillation Detection
July 01, 2011 03:55AM
    
Nice reads there!
avatar Re: Scintillation Detection
July 03, 2011 09:30PM
    
Hello Samuel and all,

Thank you, Samuel, for your informative links to the HPS articles. I believe that these selected articles may impart the notion that naturally occurring radioactive minerals pose no health risk. At the end of my response, I have included a few more excerpts, also from the HPS, in hopes of presenting a broader and more accurate view regarding the health risk from naturally occurring radioactive minerals.

I have not claimed that owning and/or handling such material is necessarily dangerous, nor do I wish to scare anyone who may have such material or wish to own or collect some. My intent is to warn of possible health hazards and how to mitigate them by proper handling and storage of this material. Remember, all of the health physics community is in agreement that keeping dose rates “As Low As Reasonably Achievable” (ALARA) should be practiced when dealing with any kind of source material.

I would suggest to anyone with radioactive minerals in their collections to practice the following simple methods of reducing the possibility of health hazards associated with any source material.

1. Practice ALARA by using the simple rule of Time, Distance and Shielding.
2. Avoid ingestion or inhalation of source material
3. Wash hands after handling source material

Until such time that there is a consensus among the scientific community regarding the validity of the linear no-threshold model (LNT), I will continue to accept it and to act in accordance with its worst case scenario and to err on the side of safety.

Also, thanks for questioning my measurements and calculations regarding the radiation levels associated with my small collection of radioactive minerals. For that reason, I have repeated the measurements in a more rigorous way, in an attempt to better validate them. I have used all three of the following survey instruments in my measurements.

1. Monitor 4EC calibrated in the past 3 months at the factory and certified to +/- 20% (Ce137 reference).
2. TBM-3S calibrated from Monitor 4EC using several sources in the past year.
3. CDV-700 calibrated with provided calibration source in the past year.

When tested on several sources, all three instruments agree to +/- 25%. The level of discrepancy is not too surprising considering calibration accuracy, the geometry of the detectors, pancake vs. long tube, and placement repeatability.
Several measurements were made at a distance of 4’ with each instrument and the results averaged for each instrument. The averaged measurements between instruments agreed to within +/-30%. Because the Monitor 4EC was the most recently calibrated instrument, I have used only its averaged measurements in my calculation. That average measurement at 4’, with the Monitor 4EC, was ~1 mR/hr. My claim that I would receive close to the DOE regulatory dose rate of 5 rem/year is based on the following simple assumptions and calculation: I assume that if my collection were stored under my bed the average distance would be 4’ or less for whole body exposure, extremities being less important. Using the measurement at 4’ of 1 mR/hr dose rate gives: .001 R/hr X (8X365)hr = 2.92 rem (assuming a quality factor of 1). By the way, this dose is a little less than the DOE regulatory limit of 5 rem/year, but higher than the administrative limit of 2 rem/year.

What effect would that dose have on me? The National Academy of Sciences, National Council on Radiation Protection and Measurement, and the International Commission on Radiation Protection estimate the risk value (to an adult) for an occupational radiation dose (above natural background) of 1 rem (1,000 mrem) represents a risk of 0.0004 or 4 in 10,000 of developing a fatal cancer. The average estimated days of life lost/person from receiving 100 mrem/year from age 18-65 is 5 days. This is, of course, based upon the linear no-threshold model and would therefore exempt those of you who reject this model from being one of the four fatalities. :) This also addresses your facetious question as to why we are not all riddled with cancer by the time we are adults. The answer is that 100 mrem/year will not cause us all to be riddled with cancer by age 65, but will on the average take 5 days from our lives. Being equally facetious, I could extend this to say that if we live long enough, we will all be riddled with cancer.

I should mention that it is not uncommon for collectors to have sizable collections of radioactive minerals and this is evidenced by one personal friend who has a collection that is perhaps a factor of 10 larger than mine. The collecting of radioactive materials has a certain amount of mystique about it, as well as scientific interest to many mineral collectors. It is therefore understandable why this specialization of the mineral collecting hobby is growing so rapidly and why many collections are sizable.

Quotes from the HPS, including references:

1. “Lots of folks collect geological specimens containing uranium (I even have couple of uranium ore-bearing rocks on display in my hallway at home) and so long as you do not have large numbers of samples, or samples quite rich in uranium, they should pose no problem but need to be handled with care. Natural uranium is only weakly radioactive and its chemical toxicity is actually of greater concern. Thus, the mineral samples should not be handled frequently, or for very long periods, and the hands should be washed after handling. Obviously one should not carry the specimens in one's pocket or keep them around food. Children should not be allowed to play with them. They should generally be kept away from folks as much as practicable, and it would be well to shield the specimens containing more than a few tens of grams of uranium when they are stored or displayed. Shielding against the beta radiation can be accomplished by a sheet of LuciteTM or other clear plastic at least 1/4-inch thick. This will allow the specimen to be viewed but will greatly reduce the radiation field associated with it.” [hps.org]

2. “Having said all this, the guiding philosophy in the radiation safety community is that we should keep exposures to radiation as low as reasonably achievable. This is what we refer to as the ALARA principle.
The simple ways for you to achieve this would be to reduce the amount of time you handle the ore, keep the ore stored at some distance from occupied areas, and store the ore in a shielded container or room (e.g., a room with brick walls). These actions are really "overkill" for the small sample you have described however. Their main benefit might be to provide "peace of mind."” [hps.org]

3. “I have not measured radon emission from uraninite, but have had experience with several uranium ore samples in a variety of sizes. The only case I found in which radon in the air was a problem was in a geology department that had a large number of specimens. In that case, we placed the specimens in a display case with its own exhaust system to prevent radon from entering the room.” [hps.org]

Kind regards,
Gene
avatar Re: Scintillation Detection
July 04, 2011 03:50PM
    
At the risk of seeming self-serving, here's my ha'penneth ...
Care and feeding of radioactive minerals

It's a practical guide, so ... Enjoy!

When you invited me to see your etchings, I didn't expect to see so much degraded quartz. Really.
avatar Re: Scintillation Detection
July 04, 2011 11:56PM
    
Alysson,

Thanks so much for your comprehensive article on radiological safety, as it pertains to NORM specimens and the collecting and curating of them. Your work will serve to better inform collectors of such minerals as to the possible risks of collecting them, as well as how to mitigate those risks. This is a project that I have had in mind for quite a long while now, but had no time to devote to. I do hope that your link to the article will remain active, as I will certainly be pointing my collector friends and clients to it. Again, nice work!

Gene
avatar Re: Scintillation Detection
July 05, 2011 10:33AM
    
Gene,

I'm glad that you found it useful.

The artcle is currently a work in progress, and I hope to eventually have a comprehensive list of radioactive minerals and their calculated specific activities and dose-rates, as well as instrument design and construction tips. Updates will be irregular at best, as the data compilation is extrmely slow.

Since that is on my own web space, the link will remain active indefinitely, though once completed, I will be asking Jolyon to host a copy on Mindat.



I would remind everyone that the presence of a hazard is only dangerous when it goes unaknowledged and unprotected.

This is why most fluoroscope operators and early radiation researchers generally died of radiation-mediated cancers, and why modern radiographers are so carefully monitored and highly trained. Recognising and aknowledging the hazard goes most of the way toward preventing one's exposure to danger.



I have had the rare opportunity to measure radon buildup from dispersed radium (Ra226) under a range of conditions, and to experience the radon-daughter activities. By inference, this will suggest the same for Uraninite, though at a rate approximately 1000 times lower.

Even a small amount of Radium (in the micro-curie range - say ten grammes of uraninite) will raise the Radon levels in a small, closed room detectably in a few hours, and will reach a good approximation of equilibrium inside 3 days.

Even an open cieling (i.e. open to the air) will make no significant difference as Radon is a dense gas. The only ventilation that works well is a floor-level ventilator or forced extraction at floor-level. An open door is perfect. Cellars and basements are just traps for Radon.

Long-term exposure of porous materials (paper, brickwork etc) to trapped Radon will lead to those materials becoming heavily contaminated with Radon daughter products, and may raise them to the level of being classifiable as radioacive hazards in themselves. Removal of the Radon source will allow the contamination to decay to background levels over a period of several weeks.

Radon emission rates are increased by large surface area of source (metamict Autunite, crusts of finely crystallised minerals etc).

Surfaces exposed to radon will, over a period of years, eventually react positively for lead when subjected to even basic chemical testing.

Hope this helps,
Alysson

When you invited me to see your etchings, I didn't expect to see so much degraded quartz. Really.
avatar Re: Scintillation Detection
July 08, 2011 07:56PM
    
If my previous posts seem a bit out of context, the person's posts that I was responding to have been removed for reasons unknown to me.

Gene
Anonymous User
Re: Scintillation Detection
August 12, 2011 09:59AM
Hi Gene:

My posts were removed for reasons unknown to me too. The debate was about low level radiation and collections containing a few radioactive specimens. I am not talking about very large collections as might appear in a University Geology Department or the basement of an old Museum. Nor am I talking about people exposed to X-Rays or Gamma Rays on a daily basis, or those working at Nuclear Power Plants.

The debate on the real hazards of low level radiation will go on for decades. I am inclined to agree with the philosophy, findings and reasoning of Bernard Cohen and others, and reject the Linear No Threshold Hypothesis outright. The model is flawed and is really an administrative tool than a scientific one. There is overwhelming evidence to show the model is flawed, but not just flawed, very seriously flawed. But like religion belief in the hazards of low level radiation is a personal one, perhaps based on fear and misunderstanding, perhaps part of a hidden environmental/greenie agenda. So I am not here to convince you. All I can say is read the HPS responses and if you have any doubts or misunderstandings please put them to the HPS. Also put the questions regarding the Radon issue back to the HPS, but do not expect them to change their opinion or their findings. On matters of radiation I gave a good reference, chapters 4 and 5 of the book by Richard A. Mueller "Science and Technology for Future Presidents. It contains a wealth of practical information some of which even surprises Physics graduates. Allysson’s PDF was good but if you really want to see how the experts perform their calculations with lots of details given for the underlying assumptions please look at "Introduction to Health Physics" 4th edition by Cember and Johnson. I encourage Alysson to read this book also. So where does this leave us? For me I categorically reject the Linear No Threshold Hypothesis. I will gain great joy in handling and viewing my radioactive mineral specimens and I will continue to maintain my regular exercise program involving walking and serious weight training. According to the WHO obesity will rival tobacco smoking and low level radiation as the number 1 taker of life in the 21st century. To those people who collect radioactive specimens I congratulate and encourage them in their endeavours, and tell them they have more to worry about the size of their girth than the size of their collections.
avatar Re: Scintillation Detection
August 12, 2011 10:25AM
Samuel. You know you why your previous posts were removed, and it wasn't to do with your dangerous comment that "owning radioactive minerals and the bottom line is not a problem or a peril" - as others have shown this is simply untrue. It was to do with your comments elsewhere on the site, and basically not being a "good internet citizen".

I agree that natural radioactivity in most minerals is statistically irrelevant compared to background radiation levels. And some minerals which are samples of "radioactive minerals" actually have a lower natural radioactivity than some samples of minerals we would think of as harmless which happen to have small % of radioactive impurities, or are associated with a radioactive matrix.

A few small radioactive minerals in your collection won't be that harmful if you ensure you are not exposed to their dust. Having lots of large radioactive specimens in your home, or worse still breaking them up with a rock cracker (for example), is certainly NOT safe.

Jolyon
Anonymous User
Re: Scintillation Detection
August 12, 2011 01:34PM
Dear Joylon:

Please do not take me out of context, and please do not call my comment about owning radioactive minerals dangerous. The real danger lays in maintaining beliefs that have no basis in fact which is the main problem with the linear no threshold hypothesis. If an esteemed body such as the Health Physics Society in the United States and the Academy of Sciences in France also feels owning a small collection of radioactive minerals is not a problem or a peril, well I will agree with them. The real danger lies not in the low level of radioactivity these minerals possess but the way the knowledge is misunderstood and misused by those not so well informed or misused by the informed with hidden agendas. You might recall the serpentine scare that hit the Californian legislature a year or so ago. We know lead is a cumulative poison yet what about Galena, we know Mercury is toxic so what about Cinnabar; we know Cadmium is toxic so what about Greenockite, we know Antimony is toxic so what about Stibnite or Native Antimony. And no sane collector would eat them, but I know a lot of people who have no interest in minerals who firmly believe that these dangerous rocks should be banned also. The Health Physics Society in the United States has already given clear direction about owning radioactive minerals, exposure to radioactive mineral dust and radon emission and it is not a bad as Gene and others would have you believe.

I build Geiger counters and scintillator counters as well as Ham Radio gear and a lot of digital electronics and I can tell you it is easy to make things look worse than they are. Place an Americium 241 smoke detector source right next to a GM tube and watch the count rate rise rapidly, yet 4 inches away and you are struggling to get a reading much above background. If I put my large Uraninite right next to the GM tube the counts go very, very high but from 5 feet away you are again struggling to get a reading much above background. My 9x8x7cm Torbernite specimen from Rum Jungle does not even cause any increased clicks even when two feet away. Things only start to “heat up’ when it is about 1 foot away, but not too hot. If you want precise readings I can give them. The best defense against any form of radiation is distance.

And please Joylon do not be so demeaning of me. You are not God and anyway the position is already filled.
Re: Scintillation Detection
August 12, 2011 01:48PM
In the 50's we were advised not to store our radio-actives under the bed if we wanted to have children

LOL
avatar Re: Scintillation Detection
August 12, 2011 03:57PM
> If an esteemed body such as the Health Physics Society in the United States and the Academy of Sciences
> in France also feels owning a small collection of radioactive minerals is not a problem or a peril, well I
> will agree with them.

And did I not agree with this myself?

> A few small radioactive minerals in your collection won't be that harmful if you ensure you are not exposed to their dust.

What you have singularly failed to realise is that the main danger from keeping radioactive minerals is not the mineral itself (although I agree, keeping them under your bed is a bad idea), but radioactive particles (and to a lesser extent radon gas). Distance is critical as you have mentioned, and when particles are inhaled and in your lungs, the distance is zero, which is when even the tiniest particles can be of serious danger.

Many radioactive minerals are safe as long as you treat them with respect. But it's an extraordinarily bad idea to let people think they have no risk.

Jolyon

ps. Cinnabar is relatively non-toxic.
Anonymous User
Re: Scintillation Detection
August 13, 2011 12:55AM
Joylon:

I have not failed to realise that radioactive dust and radon in high concentrations might be a problem. In my earlier posts I addressed this problem by telling mindaters not to eat or inhale their radioactive minerals, but you deleted these remarks. I still have copies of this advice on my computer.

No one denies that accidental inhalation of particles of radioactive minerals “might” be a problem. It is still an area of considerable research and debate, and there are many factors involved apart from the inhalation of a single radioactive dust particle itself. I suggest a review of the literature on the use of depleted uranium as armour piercing bullets, which deals largely with the problems of uranium dust particles that defense force personnel might be exposed to. What we do not need is ill informed paranoia suggesting that an accidental sniff of one’s Autunite will cause lung cancer without doubt. You might recall the HPS dealt with the accidental sniffing of Autunite by a Geology undergraduate.

What you have singularly failed to realise is that the supposed “risks” from keeping radioactive minerals are not a simple one alpha particle kills all scenario. If treated with the same caution one uses with other minerals such as Native Arsenic, Orpiment, Realgar, Stibnite, Native Antimony, Galena and many others the dangers will be minimal at worst.

All my minerals are given the “shake and bake” treatment on arrival, and by that I mean I soak them in water followed by a thorough cleaning with liquid soap and a brush. Some are even cleaned in an Ultrasonic bath. Any particles of loose material and dust are thoroughly removed before the mineral is displayed.

And please Joylon do not be so demeaning of me. You are not God and anyway the position is already filled.
avatar Re: Scintillation Detection
August 13, 2011 04:52AM
Sam, I am not sure what God has to do with it, regardless of what God is to you, all sectors of society from the churches to Government to Anarchy Society to bike gangs have codes of conduct and people designated to uphold rules and remove offenders. The rules of this group is we welcome your knowledge and experience with minerals, but reject personal attacks on anyone. Unfortunately your posts to Jolyon and others have a tendency to sound abusive, and detract from your messages.

Regards,
Ralph
Anonymous User
Re: Scintillation Detection
August 13, 2011 06:41AM
OK Ralph B I will tell you what irritates me, when people try to simplify a topic as broad and as complex as ionizing radiation and all the connected fields. No one denies that high doses of radiation are bad for personal health. No one denies that if you got a lung full of radioactive dust you would become very ill. But the verdict on lethality of low levels of radiation and accidental inhalation of a small particle of radioactive rock is an entirely different story. I can direct you to a Website run by a friend of mine in Staten Island, NY. He makes Geiger counters and loads of neat electronic stuff. He has an experiment that one can perform at home using an old CRT television, which electrostatically attracts radioactive dust, and you can measure the radioactivity of this dust with a Geiger counter. This simple experiment shows that radioactive dust is all around us whether you have radioactive minerals or not, but is this dust lethal, who knows. Calculating death rates and exposure rates from airborne radioactive dust is very, very complex and not my area of expertise and that is why I called upon the experts at the Health Physics Society in the USA and the Academy of Sciences in France. I have given references to learned texts that should help people make their own conclusions.

But let us accept what Gene and Joylon are saying is true, that the risks of ionization radiation are too great and so owning radioactive minerals is a real peril. Why is Mindat accepting advertising dollars from vendors who sell such material and why is Gene’s company selling that material? I know Gene’s company requires a waiver but that is for the protection of the seller. The bottom line is this – if the risks are too great even if there is a tiny, tiny chance that a radioactive mineral might cause someone harm Joylon should not be sponsoring those vendors which sell such minerals and Gene should surrender all his stock to the NRC for disposal. You can't have your yellow cake and eat it, too."
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