Gamma Spectrometry Forum

Hi yawl

I'm a newbie just checking in to say hi. I have a GammaSpectacular detector set up and running but limited shielding so far. I see there's a lot of info about shielding online already (thank you all for that). How about dehydration? Do samples of food stuffs need to be dehydrated and if so to what extent and what procedures are recommended? Any thoughts greatly appreciated?

Actually, I bought the detector from Steven (thank you, Steven) two years ago and got slammed with other projects and have just cleared time to focus on learning this. My goal is to monitor food stuffs in the northwest US since we are downwind and downstream from Fukushima, have Hanford (the US military nuclear weapons facility) in the state, and Port Townsend is directly across a small bay from Indian Island naval weapons base and not far from a naval sub base. Just because I'm paranoid doesn't mean they aren't out to get us :-)

Thanks all

Stanford,

Welcome to the forum.

So you want to measure Cs-137 in food samples, well the amount you are hoping to detect will hopefully be very low, so your first task will be to build a good shield for your detector. Check out the shielding forum for ideas, and remember this is probably the most important thing you are going to do. It doesn't need to be pretty as long as it's pretty heavy.

Once you have reduced the background counts right down, it's time to put something in front of the detector, and since the space available in your shield may be limited maybe some dehydration is one way to concentrate the sample.

Hopefully in the end of it, you will be wishing for your food to be just that little but more contaminated, so you can get a decent spectrum.

Steven

Steven thank you
This is exciting and much learning already.

Is Cs-137 the only candidate? I thought that it doesn't bioaccumulate... not true? And no Strontium, Tritium, or Iodine?

So, dehydration isn't necessary.... water molecules don't block anything? Dehydration for concentration makes it easier than having to worry about precise levels of dryness.

Reducing the background counts down far enough to do this means lead shielding isn't enough? Copper and tin are also required?

Thank you!!!!

Stanford,

Although the media report radiation and throw in all these isotopes, it doesn't mean they are all easy to detect. You need to look at each isotope and decide if it's worth looking for. First of all, check if it is an alpha, beta or gamma emitter, then what is it's half life, and what other isotopes does it decay into.

After a nuclear accident there is iodine 131 in the immediate aftermath, but the half life is only 8 hours, so although it is quite toxic, it decays away quickly, it is also a beta emitter which makes it hard to detect directly.

https://en.wikipedia.org/wiki/Iodine-131

Cs134 is detectable for some time after an accident, but it also decays away, leaving Cs137 as the most long living (30 year half life) isotope.

https://en.wikipedia.org/wiki/Isotopes_ ... aesium-133

Detecting alpha and beta emitters is difficult unless they also emit gamma, the best way to learn about this is to look up the isotope in a table and see what they emit.

http://nucleardata.nuclear.lu.se/toi/nucSearch.asp

http://nucleardata.nuclear.lu.se/toi/nu ... iZA=550137

in the case of Cs137 it decays to Ba137(m) with a beta emission and then almost immediately to Ba137 emitting a gamma which is the one we actually see.

Steven