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Adam Munich

Thu Apr 28 2011, 04:23PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Well it's not complete, but it is capable of producing x-rays. If it's nice outside later I'll try the lead nitrate/acetate thing and the iron filings thing, but I have no lead or galena powder.

klugesmith

Thu Apr 28 2011, 07:30PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1715

cedric wrote ...

what's about sand-bag?it's not expensive ,non toxic and it does protect against x-ray...
by the way ,I use lead shielding for x-ray as well but I don't like to use lead directly after the tube because lead reflect also a lot of x-ray .I think an absorbing material like dense wood before the shield can help to reduce secondary emission...

I agree regarding shielding, but have doubts about scattering. Don't x-ray cassettes or tabletops have lead backing, to avoid getting a backscattered image of structures on the far side of the film?

If you look up material prices and attenuation coefficients, figuring dollars per half-thickness per unit area, then for a dental-tube x-ray spectrum steel costs less than lead. Earth materials such as ordinary concrete and sand cost even less.

As the spectrum gets harder, the balance tilts toward favoring higher-Z materials.
For radioisotope gamma source enclosures that can be hand-carried, uranium metal becomes an economical choice. (The price of U3O8 took a plunge after Fukushima but is back above $60/pound.) Let's not talk about proper disposal of U waste.

James

Thu Apr 28 2011, 07:40PM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

Lead sheet is not terribly expensive, McMaster Carr has it in a variety of thicknesses and you don't need very much of it to shield a dental tube. It's a small price to pay when it comes to protecting yourself from radiation.

Those on a really tight budget I suppose could harvest the lead plates from an old car battery and cast it into the shapes required. I've cast lead in an old saucepan over a propane camp stove but personally I would just buy a sheet of the stuff.

magnet18

Thu Apr 28 2011, 08:14PM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

Grenadier wrote ...

Well it's not complete, but it is capable of producing x-rays. If it's nice outside later I'll try the lead nitrate/acetate thing and the iron filings thing, but I have no lead or galena powder.

Please post pictures... I love pictures... especially of x-rays...

Adam Munich

Fri Apr 29 2011, 12:59AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Well It's raining... so no testing tonight.

I had an idea, just take lead shot and sew up little "beanbags". That seems like the most cost effective option, especially if you make your own shot (since all you need to do is drop some lead down a long tube into water). A 99 foot tube isn't needed since the shot doesn't need to be perfectly round. Hmm... I think I may have just found a use for the 100lbs of lead I still have left.

magnet18

Fri Apr 29 2011, 01:08AM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

Grenadier wrote ...

Well It's raining... so no testing tonight.

I had an idea, just take lead shot and sew up little "beanbags". That seems like the most cost effective option, especially if you make your own shot (since all you need to do is drop some lead down a long tube into water). A 99 foot tube isn't needed since the shot doesn't need to be perfectly round. Hmm... I think I may have just found a use for the 100lbs of lead I still have left.

old socks?

Sulaiman

Sat Apr 30 2011, 05:21AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Just curious;

why lead ?

wouldn't other (less toxic) materials work?
steel, concrete, aluminium etc.?

Adam Munich

Sat Apr 30 2011, 05:36AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

They would, but because they are less dense more of it is needed. I haven't tested anything yet, mainly because I got caught up in writing this.

It's one of my many unpublished guides...

Bored Chemist

Sat Apr 30 2011, 12:53PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Aargh!
Why is it that people think
1 lead is particularly dense?
2 The density is the reason why it's a good Xray shield?

An atom of lead weighs roughly twice as much as an atom of silver yet the two metals have about the same density.
That means that the lead atoms are not actually densely packed at all.
Another way to look at it is that gold has atoms that are a little lighter than lead, but it's nearly twice as dense.

The big advantage to using lead is that it has a large nuclear charge and so it scatters Xrays well. The scattering cross section varies as the square of the atomic number. That's what makes lead a good choice in spite of its low density. (It's also relatively cheap and easy to work with).

Other materials are sometimes used.
Concrete and steel because they are cheap.
Tungsten ( because it actually is dense, so a thinner layer can sometimes be used than if lead were chosen)
And, rather oddly, depleted uranium.
Uranium is very dense and has an even higher scattering potential than lead. It's a bit radioactive but the alpha radiation from lead can be stopped with a sheet of aluminium foil (or a couple of sheets of paint).

Adam Munich

Sat Apr 30 2011, 12:55PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

We think that because we have never been told otherwise!

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