Radioactive Mineral Sample Prospecting Equipment - Advice Sought / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Radioactive Mineral Sample Prospecting Equipment - Advice Sought

1 2 3 4 next last

Move Thread

LAN_403

IntraWinding

Fri Mar 26 2010, 07:21PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

I'm hoping to visit some old closed mines in Cornwall this summer to find good radioactive mineral samples at ground level or very near the surface.

Can anyone advise on the best detector to take?

I've been focussing on two possibilities so far:

The Gamma Scout Geiger Counter

The Polimaster PM1703M CsI(Tl) Scintillator

Ideally the detector would be sensitive enough that I can zero in of a good hot sample from some distance. If I can use it for Alpha and Beta too, that's a bonus, and I'll be relying on finding a second hand and preferably faulty/repairable example to keep costs in my range!

Proud Mary

Fri Mar 26 2010, 10:00PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I'm sure you are aware that radon levels in some of the failed Cornish tin mines are such that you can expect to be exposed in one hour to the maximum personal 'safe' dose for an entire year. It is the radon daughters that do the damage, nanoparticulates which can lodge in the lung where they form centres of necrosis and abnormal cell division.

See Two abandoned metalliferous mines in Devon and Cornwall, UK: radon hazards and geology here:

As for a GM counter, I would not recommend either of the instruments you have asked about for prospecting. The capture area of the detectors inside them is simply too small for them to be of much use until you are very close to the source. The Gamma Scout uses an LND712 tube, which has an effective length less than 40mm, and an effective diameter of about 9mm. (LND712 is LND's version of the better known Centronic ZP1401)

The bigger the tube the better, since there is more of it for gamma rays to hit.

You don't need to be able to detect beta and alpha particles when prospecting for uranium minerals. The emission from radium and the other gamma-emitting U-238 decay products in the ore is such that you can easily detect a chunk of pitchblende the size of a small egg from a distance of a few metres with a tube of suitable size.

The best Cornish pitchblende is of a very dark chocolate colour, and conspicuously heavy. A piece the size of a double sugar cube will produce about 100uGy/hr gamma at 10mm.

The World and His Dog have all visited South Terras looking for pitchblende - even organized clicking tours - so don't place too much hope in finding anything very active lying around in the remains of the old radium works.

IntraWinding

Sat Mar 27 2010, 12:18PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

Thanks for that. I get your point about that larger the Geiger chamber the better. What sort of tube size would detect 'pitchblende the size of a small egg from a distance of a few metres'?

I'm very sad to hear you don't hold out much hope for me finding any good samples though.

Thanks for the Radon warning. I think my inbuilt cautiousness would probably have kept me out of any caves, but that will help.

Proud Mary

Sat Mar 27 2010, 02:12PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

IntraWinding wrote ...

I'm very sad to hear you don't hold out much hope for me finding any good samples though.

I think you have every chance of finding some lively chunks of ore, but not just lying around on the surface at South Terras, where hundreds of people with GM counters - enthusiasts, geology students, mineral dealers, and officials of the National Radiological Protection board - even members of an organization called Dangerous Lavatories - have all been before you. The site was much overgrown last time I was there, so you have a chance of finding something if
you look in some of the thickets and brambles, for example.

But you will surely find it interesting to visit the ruins of Britain's only ever uranium mine and concentrate works, where it is said Marie Curie obtained the pitchblende used in her discovery of radium. The ambient dose rate around the works is significantly above background in a diffuse kind of way consistent with industrial contamination.

You may well find some active samples there, so I did not mean to discourage you, with the proviso that the liveliest specimens attract the most attention to themselves gamma-wise, and may have been taken away.

Having found what you can at the works, I would suggest you have a look in the River Fal, starting slightly uphill of the mine, and following it downstream of the works.

Here you have two probable sources of pitchblende - placer deposits resulting from erosion of uraniferous veins, and material sluiced away by the mine and the ore concentration plant, for which the River Fal was the sole source of water. See if you can find any overgrown ditches and sluices connecting the mine with the river.

A second excellent place to look is in pebble banks formed at the back of the beaches around St Austell. I found five very lively pitchblende pebbles, well rounded and smoothed by the sea, in about ten minutes, the last time I went there. I would divide these pebbles into two classes: very active, very dense, very dark chocolate brown specimens, and a second type, coffee coloured and less dense, with only about half the activity of the dark chocolate kind.

As for the type of detector, you need nothing more for a minimalist design than a small HV source suited to the GM tube, and an audio amplifier so you can hear the clicks. A good piece of ore will produce 100 cps and more with the tube right up to the specimen, so there is no need for a meter or any software gimmicks. At a 100 cps, individual clicks are no longer discernible as the counts become a continuous rushing sound.

PS added later. I forgot to mention the uranium-vanadium nodules in the Permo-Triassic red Littleham Mudstone at Littleham Cove, near Exmouth. The Mudstone
erodes rapidly so there are radioactive nodules in among the pebbles on the beach, as well as in the freshly exposed red Mudstone in the cliffs themselves.
Some of the nodules are of coffinite, uranium silicate, which makes a change to the usual variable oxides.

IntraWinding

Sat Mar 27 2010, 11:37PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

Thanks! I'm brimming with enthusiasm again!

So what size Geiger-Muller tube do you think I need?

There are plenty of small Russian ones on eBay and some pancake types, but I don't see anything I'd call 'large'.

I'm tempted to try making my own, but that's a project for another day, I think.

Patrick

Sun Mar 28 2010, 01:54AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

yeah intrawinding a second proud marys thoughts,when i got the chance to snag some GOOD cobalt-60 calibration targets for the old vacuum cloud radiation monitors for thermo nuclear fallout at near ground-zero level like in the 60's, (totally obsaolete now, too insensitive. which is whay they were used for nuclear fallout a few hous after the event lol yikes!) anyway my professors and i had to get them so close to the modern gieger (super sensiteve) window, just to get a good count rate. i immeadiatley gave up my plans to search for natural sources, but good luck with your search in the wilderness!

and remember the bigger thw window the better for your purposese, and a real mica window too, not some crummie knock off.

EDIT: you might consider ultra long exposures with those new plastic flexible scintillator sheets, to ease your searching time.

As, always guard your brain and huevos from unwanted exposusre, and other target organs you value

Though i guess in your case it would be bioaccumulation in your body that would be infinatley greater as a hazard. purple nitrile gloves might be good enough as precaution, then wash your hands before eyes, ears, nose, mouth, contact

Hey Dr. Strangelove, i need to snag some Thorium-G please!

whooo hoooo! have fun, good luck, try not to die.

-Patrick

Proud Mary

Sun Mar 28 2010, 02:17AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

At Littleham Cove, you can actually see the uraniferous nodules in the red mudstone cliff.

Have a careful look through the website below to get a feel for the kind of geology to expect at Littleham Cove.

Make sure you have a current tide table, so you can go at low tide when more of the beach will be exposed. Clear off well before high tide until you have seen for yourself what gets cut off and what does not.

Patrick

Sun Mar 28 2010, 03:19AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Proud Mary, are ther any places in northern California for rdio active minerals/rocks, in case i decide to collect some samples myself?

Proud Mary

Sun Mar 28 2010, 11:05AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Patrick wrote ...

Proud Mary, are ther any places in northern California for rdio active minerals/rocks, in case i decide to collect some samples myself?

Here's a map of mines and claims for you, but don't hijack the other guy's thread.

1269774290 543 FT86405 U Mines And Claims California

plazmatron

Sun Mar 28 2010, 12:47PM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

The best piece of prospecting equipment I have ever used, was a surplus CDV-700 geiger counter, will a Scintillator probe.

The modification to the CDV-700 is easy, and there are several variations around the net like:

here

Les

1 2 3 4 next last

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob