Spectrum of Fukushima soil

[lodovico]

Thanks to Luuk I could take the gamma spectrum of a small soil sample from Fukushima area.
Here below you can see the results with a shielded 63x63mm NaI(Tl) crystal, 3600 seconds :

the Cs137 and even the Cs134 are clearly visible !
In the next days I will try to estimate the activity of the sample with beqmoni software.

Lodovico

[luuk]

Hi Lodovico,

Thanks for posting the spectrum, one question what is the resolution of the detector you used to make this spectrum?
Luuk

[cicastol]

Great !!
Theremino imho should not be trusted too much for resolution calculations, even switching off weirds filters, given resolution percent is far from real ....
Hope to get a Fukushima soil sample me too to get some spectra :-)

[lodovico]

Hi everybody,
the resolution is around 7-8%. A question : the small peak around 150 KeV could be due to Plutonium 241 ? It has a strong emission line at that energy and I read that at Fukushima there was a strong plutonium leakage ...
Lodovico

[MartinM]

"strong plutonium leakage" is a relative term ;)
I doubt the leakage had such a significant Pu release, otherwise this would be a huge problem.
You'd see also a significant amount of U-237 (and Am-241) peaks as the decay products of Pu-241 there.
https://fas.org/sgp/othergov/doe/lanl/l ... 326403.pdf

[lodovico]

yes, the peak is not so evident and there is no evidence of Am-241.
L

[luuk]

I have never seen this peak before and have tested many different Fukushima soil samples, maybe it is a software/mca errror?
Luuk

[ZeeCaptain]

I can confirm the peak in the 150ish area. I got it at 125 keV, FWHM is 8.97% in one, and at 142 keV HWHM 7.7% in another spectrum of fukushima-soil so this could be a real peak. But in my spectrum it is so small, only the peak finding algorithm detected it and i would most likely have overlooked it. Maybe its just noise, but how likely is it, that there is noise in 3 spectra from 2 different setups?

I did 2 (calibrated) spectra from a soil sample i got from luuk (thanks a lot again!).
The first, i calibrated with Cs-137 only when i remember correctly. It was in a shielding with only steel plated lead with a thickness of about 2-2,5 cm. I got about 5 cps background in the shielding and 110 cps without.

The second one i calibrated using Am-241, Th-232/Pb-212 (the 238,63 keV peak) and Cs-137. The shielding got bigger to about 5 cm of steel plated lead (160 kg total). Background in the castle is 2,2 cps now.

At the moment i am calibrating with Am-241, Cs-137 and K-40 to take a look at the 1-1,8 MeV peaks. I will look at the 150ish peak too.

So is there a problem with my or lodovico's calibration/setup?

Here are the images:

1. The first Fukushima spectra (calibrated with Cs-137 only)



2. Overview over the second Fukushima spectra (calibrated with Am-241, Cs-137 and Th-232):



3. A closer look at the little peak from the second spectra:

[luuk]

Hi all,
I did a test at work from my soil sample interested please read the pdf.

Luuk

[Peter (vital1)]

I was sent this resin encapsulated sample of black fungus like material. It has reportedly come from somewhere in the Minamisoma area Japan. A contact in Japan sent a friend this sample. This is my test chart of it. This fungus started growing on the concrete, and rock surfaces in Japan after the Fukushima Nuclear disaster. It appearers to be bio-accumulating Cesium.

Here is a pen tip placed next to the sample, to give you and idea how small the sample is.The black centre is the sample. Also, the sample does not fill up the small sample container, that is in the centre of the resin encasement. The sample container is only around two thirds full.

Update on the possible weight of the Black Fungus sample from Japan. This comment was posted on a forum discussing this test.

“I’m an expert on weighing objects (sell scales, use different ones daily, some precise to .01g). Fungus in that form does not appear to hold too much water weight and would likely weigh less than a gram given the scale. If it is thin and flakey type fungus, it may be under .25-.5g. Is it thick like a mushroom cap or more like lichen? I’ve only observed extremely thin fungi growing on concrete, and I would err on the very low side. My best guess is .3g.”

My reply

That means the black fungus sample from Japan is very, very, hot.

Test results 117 Bg Cs-137 and 58 Bq Cs-134

117 + 58 = 175 Bq x (1000 grams/0.3 grams) = 583,333 Bq/Kg of Cesium

Even if it was 10 times greater in weight 3 grams, it would still be 58,333 Bq/Kg of Cesium.