RUG Vault (RUG - Radioactive Under Ground)

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Paul McK
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RUG Vault (RUG - Radioactive Under Ground)

Post by Paul McK » 20 Jan 2016, 21:33

I recently came up with a simple idea for a low cost underground store for small quantities of low level samples. It uses plumbing pipe and fittings to give a 150mm diameter waterproof underground storage vault. This seems to do the job, have a look at the attached pictures to make sense of the following.

I have a small amount of low level mineral & other samples the most energetic being one Radium watch that measures 0.3mSv/hr (milli) on the counter. The vault described stores these out of the way for little outlay on shielding.

The vault comprises a 150mm diameter PVC pipe which has an end cap glued to one end and a screw adapter to the other, I made it about an arms length long. A suitable hole is dug into the ground in a shed with the tube then cemented in place - so that the screw cap is flush to ground level. Leave about 5mm clear to the sides for the cap to turn freely. The earth to the sides provides shielding and all that is left is to make a lead filled plug for the top of the tube. This was made by cutting a 65mm length of the same pipe and reducing its diameter by removing a a small piece so it is a loose fit into the screw adapter section - this screw adapter section has a locating ring that the pipe buts up to and this ring makes a convenient stop for the plug to sit on.

To complete the plug assembly, cut another small piece of 150mm pipe say 25mm and again reduce its diameter so it can be glued inside the 65mm long pipe you have just modified, glue it towards the top to give rigidity until the top/ bottom discs are glued into place. This inner strip is positioned so that the top disc surface sits a few mm down to allow a bead of silicon to be applied to both sides. Further the placement of this piece towards the top maximises the lead diameter at the base. Now carefully cut out 2 circles of PVC from 2 end caps, fit these inside the plug tube and glue these with beads of silastic on both sides having first fitted a rope handle to the top disc. To located the base disc into place I sat it on washers and then glued it in place with silastic to the inside of the tube. When dry turn it over and there is now an indent to run another bead of silastic to the outside. Also on the base I put a thin disc of Aluminium as an additional beta shield (probably un-necessary). This completed plug is then filled with lead shot, I tried about 25mm of shot first but had to increase this to 40mm to reduce the radiation level to close to background. This is approx equivalent to 25mm of solid lead.

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Paul McKelliff
Adelaide/ South Australia

Homebrew 2"x 2" NaI(Tl) & smaller CsI(Tl) NaI(Tl) Scintillation detectors
GS1100 PRO & Asus U7 sound card
Homebrew 30kg 4 module lead castle

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Steven Sesselmann
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Re: RUG Vault (RUG - Radioactive Under Ground)

Post by Steven Sesselmann » 21 Jan 2016, 19:09

Paul,

It's a nice idea, but I would be a bit concerned about radon build up in a sunken air tight container like this. If you were to keep samples of Uranium in this vault, the heavy radon gas would gradually displace the air in the vault.

You would have to have some pretty hot samples to justify this kind of storage, most of us don't have high level nuclear waste, and the gamma at least is rarely a health concern.

Anyway, consider a system of venting the vault to the outside air.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

Paul McK
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Re: RUG Vault (RUG - Radioactive Under Ground)

Post by Paul McK » 21 Jan 2016, 20:36

Steven

Yes I was concerned about the radon build up and couldn't find a simple method to vent to outside. As an alternative I have put samples in old plastic pill containers with tight fitting lids that I retrieve and open outside when I want a sample. Do you think this is OK?

Initially I tested some Uraninite in a plastic bag with a Radon detector and the reading went up quite high (900+ Bq/m3) in a matter or an hour or so. I measured it with with a Corentium Canary solid state radon detector. After thinking about it I am going to try it in the vault by removing the contents so they don't interfere with the detector and see if there is any radon sitting in there, ditto with the plastic containers.
Paul McKelliff
Adelaide/ South Australia

Homebrew 2"x 2" NaI(Tl) & smaller CsI(Tl) NaI(Tl) Scintillation detectors
GS1100 PRO & Asus U7 sound card
Homebrew 30kg 4 module lead castle

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brehwens
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Re: RUG Vault (RUG - Radioactive Under Ground)

Post by brehwens » 23 Jan 2016, 05:21

Hi Paul

I am not sure what problem you are trying to solve; are your samples so hot you have to store them outside?
I would be more concerned that someone finds the storage and removes the contents.

I have my sources in quite alot of lead, maybe 3 cm thicknes on average. It is in a locked box, in my workshop. I maybe have 0.8 µSv/h directly outside the storage box. Where I never spend more than 5 seconds at a time. When I am in an airplane, I might be exposed to 3 µSv/h cosmic radiation for hours at a time, so I don't really think it is an issue.

Just my 5 cents.

Otherwise it looks like a nice and waterproof way of storing stuff; I am thinking to prevent burglary or the likes...
Karl Brehwens
Eskilstuna, Sweden.

Setup: 5 cm lead castle, 2mm copper lining. Gamma Spectacular Pro 2002, Sound Blaster Live! 5.1,
Primary detector: Scionix refurbished 2x2" NaI(Tl) well detector, 7.5% @ 662 keV

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Steven Sesselmann
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Re: RUG Vault (RUG - Radioactive Under Ground)

Post by Steven Sesselmann » 23 Jan 2016, 08:58

When it comes to storing sources I think the main objective is to find a well ventilated place out of children's reach and preferably a few meters from where someone might spend a lot of time, i.e. not right next to where you sit and work. It can be a little tricky if you live in a small apartment, but even a few meters separation is better than right on your desk.

Another suggestion I have is to maintain an inventory list if you have many sources, and check it when you put away your sources, this will prevent you from accidentally leaving a source on your desk and exposing yourself or others more than necessary. Something like a fishing tackle box might be a good way to maintain inventory at a glance.

I used to have a Cs137 source on my desk all the time which I used to calibrate my drivers, but now I have replaced it with an electronic pulse generator which simulates a Cs137 detector.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

Boris
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Re: RUG Vault (RUG - Radioactive Under Ground)

Post by Boris » 24 Mar 2016, 08:40

Hi all, long time no posts...

Keep in mind that for minerals & ore´s (alpha and beta emitters) it is better to store the source in plastic (perspex) to prevent the generation of gamma rays due to rem radiation.(they are harder to shield)
The plastic itself should be shielded on the outside with dense materials like lead for the gamma´s, the lead should be painted or you should use gloves to handle it.

I use a steal box, the inside is lead lined, and all the sources are extra sealed in plastic, i´m not able to detect any radiation outside the box.
it is locked with a lock, and only I have the key.

that is in the box?, only the legal things like a watch, smoke detector, etc- so yes the lock on the box is the safest add-on. and lead is not needed.
anyway it looks cool...

Cheers Boris

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