Incorrect shielding

How to build the perfect shield for your measurements? Discuss it here!
Post Reply
User avatar
Peter-1
Posts: 108
Joined: 07 Oct 2016, 01:45
Location: Germany
Contact:

Incorrect shielding

Post by Peter-1 » 02 Feb 2018, 00:59

In addition to my previous shielding with lead and copper , i still add blocks made of tungsten. But the shielding became worse ! Now I have the blocks made of tungsten measured and investigated and found that they self-rays. The blocks come from an old betatron with 6MeV and were in 1960 - 1970 in use. What has happened ? Who has a solution to this?
I add the spec with background (grey) and the tungsten (green) as a probe.
2018_02_01-Wolfram-3.jpg
Peter

User avatar
sgt_bear
Posts: 75
Joined: 16 Jan 2017, 07:06
Contact:

Re: Incorrect shielding

Post by sgt_bear » 02 Feb 2018, 04:32

I guess since the Betatron had nothing to do with spectrometry, there wasn't a real need to use a super pure material. Maybe there is just a inpurity in the tungsten?
Tungsten Ore is found along with granite, and there is also the possibility of inpurity from melting / handling. Also, the tungsten could be reprocessed - you never know what it was before.

Does the tungsten has painting or something on it? Maybe there is something you can clean off


In general, there are to definitions of shielding. One would be shield from something dangerous, and the other would be to get a better reading. For example, if you look for "shielding lead", you mostly will find lead made for the shielding of sources or devices, so the content/purity doesn't matter at all. The commercial shields for spectroscopy are made from special low background lead..

Its kinda like the story from sunken boats. If you take a piece of steel from a sunken boat before the 1900's, you will see a different spectrum then when using a piece of todays steel. Todays steel has inpurites from nuclear test, chernobyl and fukushima in them.
- Jonathan from Switzerland

User avatar
Peter-1
Posts: 108
Joined: 07 Oct 2016, 01:45
Location: Germany
Contact:

Re: Incorrect shielding

Post by Peter-1 » 02 Feb 2018, 21:05

Thank you for the explanation.
The tungsten blocks are not painted with a color. Unfortunately I cannot check the purity but I think its thorium.

Peter

Alain
Posts: 22
Joined: 05 Jul 2018, 06:57
Location: Slovenia, EU
Contact:

Re: Incorrect shielding

Post by Alain » 09 Jul 2018, 02:34

On the first view it looks that this tungsten is realy badly contaminated with Th-232, maybe during production, maybe during some experiment... But when some metal part coming from high-energy devices, you may always consider the posibility that it is being activated. Betatron is a kind of particle accelerator (one of the earliest), capable of high energies, and it was commonly use also to produce neutrons with right combination of ions and target. So 6 MeV itself, even just electrons and gamma rays, is certainly high enough energy to make a metal radioactive (mostly only temporarily), not to mention real activation with neutrons. Regarding your spectra, that is very unlikely, if the only isotope which appeared to be on the spectra is realy Th-232 (although a bit unusual spectra for Th-232, if you ask me), so probably is only contaminated. But be careful with metalic parts, which comes from high-energy devices, they may be artificially radioactive, even to such degree, which could pose health hazard!
You probably know, that some welding rods (electrodes) for TIG (WIG) welding are made from "alloy" (sintered matrix) W-ThO2. ThO2 is added from 0,5 to 4% in mass. And of course that electrodes are radioactive (they are mostly out of the sale now, being replaced wit non-radioactive alloyng compounds). Maybe that blocks were made from one such alloy or the production line (furnace, melting pot...) where they made those blocks, was contaminated with Th from previous batch, if they were making also welding rods. There are plenty of possibilities.
Regards,
Alain

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests