Fukushima Soil

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Go-Figure
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Re: Fukushima Soil

Post by Go-Figure » 19 May 2019, 00:08

luuk wrote:
18 May 2019, 00:25
Almost forgot but here is a link to the location were the soil was harvest.

https://www.google.com/maps/place/37%C2 ... 140.750785

Luuk
Thank you!
I was hoping that you could tell us where exactly the sample came from.
I checked it out on Japan Radiation map
https://jciv.iidj.net/map/.
It should be the spot where the arrow points (attachment). The current reading is 1.801 µSv/h.

I am doing a second test on the sample. I took a longer background to start with (10 hours) and the actual measurement will be of the same duration. I will post the results.
I am keeping a close eye on the region around 600 keV. I see something, but it's always clearer at the beginning, then it tends to get "buried" below Cs137's slope.

Thanks again.

Massimo
Attachments
Fukushima - Arrow.png

luuk
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Re: Fukushima Soil

Post by luuk » 19 May 2019, 00:39

Hi Massimo,

please look at the following link:

viewtopic.php?f=5&t=27&sid=2e7ed2902ce1 ... 133d80e496

I did in 2015 some tests with different resolution crystals with a Fukushima sample to show what you can see and also expect with a certain resolution crystal you might find it interesting.
Luuk

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Go-Figure
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Re: Fukushima Soil

Post by Go-Figure » 19 May 2019, 01:15

luuk wrote:
19 May 2019, 00:39
Hi Massimo,

please look at the following link:

viewtopic.php?f=5&t=27&sid=2e7ed2902ce1 ... 133d80e496

I did in 2015 some tests with different resolution crystals with a Fukushima sample to show what you can see and also expect with a certain resolution crystal you might find it interesting.
Luuk
Thanks Luuk!
"Something to dream about" is the right expression. I don't even want to know how much the last two can cost!
You really have access to pretty amazing material.
It looks like my current 6.1% res at 662 keV would have allowed me to spot Cs134's peak at 604.721 keV quite comfortably back in 2014-2015, unfortunately I am two half life times late, and maybe just one would have been enough (why didn't I came across Steven's kits a bit earlier?) but I am still happy I made it in time to "catch" the one at 795.864 keV.
Always better to see the glass half full.

Massimo

cicastol
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Re: Fukushima Soil

Post by cicastol » 19 May 2019, 06:09

Go-Figure wrote:
19 May 2019, 01:15
It looks like my current 6.1% res at 662 keV would have allowed me to spot Cs134's peak at 604.721 keV quite comfortably back in 2014-2015, unfortunately I am two half life times late, and maybe just one would have been enough (why didn't I came across Steven's kits a bit earlier?) but I am still happy I made it in time to "catch" the one at 795.864 keV.
Always better to see the glass half full.

Massimo


Ciao Massimo,

yes,unfortunatly now is a little bit too late to see the lower 134Cs peak with a NaI(Tl) scintillator, your's current estimated resolution of 6,1% is a little optimistic, i noted that is common a compression of the spectra that tend to show higher than real resolution, you need to do energy calibration across multiple peak,well suited is Th232 for this purpose.
This was my last year spectrum of Fukushima soil
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ProvaFuku.jpg
ProvaFuku.jpg (54.1 KiB) Viewed 206 times
Ciro

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Go-Figure
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Re: Fukushima Soil

Post by Go-Figure » 19 May 2019, 19:09

cicastol wrote:
19 May 2019, 06:09
Ciao Massimo,
yes,unfortunatly now is a little bit too late to see the lower 134Cs peak with a NaI(Tl) scintillator, your's current estimated resolution of 6,1% is a little optimistic, i noted that is common a compression of the spectra that tend to show higher than real resolution, you need to do energy calibration across multiple peak,well suited is Th232 for this purpose.
Hi there.
Right now I am in no position to tell if the resolution I am reading is optimistic so I can't really answer that, I will leave it to Steven, or Luuk.
I have a Th232 source (two lantern mantles, a classic) and yes, they are great for multiple points calibration. I would say for this particular spectrum a calibration with a Cs137 check source is still pretty good, since basically that's what you are mainly detecting in the sample and peaks looks right on the money, off by no more than 1-1.5 keV.
In my experience Cs137-based calibration starts to go off at higher energy for obvious reasons, and in my case it's typically 15-25 keV off at 1460 keV (K40).

Anyway, I repeated the test on the soil sample. I more than doubled the duration for both the background measurement and the soil measurement.
The soil measuremenet alone lasted 18 hours, by far the longest I did so far. This is still unshielded with background subtraction.

I think that's a good improvement on the last one as far as "smoothness" is concerned.
Also the very weak K40 peak I got the first time around disappeared, so maybe that was coming from the background (or maybe it was just noise incidentally located in K40 region?). This time you can spot something, even weaker, centered a little bit south than 1400 keV. It's a bit more evident in the energy per bin view, but still so weak I didn't call it this time, even because I wouldn't know how to identify that.

As expected Cs134 peak at 604 keV again didn't show up. In the early stages of each measurement I saw something there (although PRA showed no gaussian correlation at all), but then the slope of Cs137 buried it completely. In the log scale view there's maybe a hint that something is there (actually not a peak, only a change of slope) but this is probably me wanting to see something where there isn't. So I reminded myself the words of Richard Feynman "the first principle is that you must not fool yourself and you are the easiest person to fool" and finally I left it alone.

I post both counts per bin and energy per bin spectra.
I also post both spectra without background subtraction, so the magnitude of Cs137 and Cs134 peaks at a few mm distance are comparable with the usual background peaks. You can see something around 600 keV there, but it's Bi214 peak at 609 keV+ Tl208 at 583 at keV, both from the background.

In order to know what you are looking at just read the description in each image.

As soon as I can I will also post some quantitative data.

Massimo
Attachments
Fukushima Soil - ID - 18 Hours - Counts x Bin - No Shield - BG Subtraction - 0.045-Clean - 18_19-05-19.png
Fukushima Soil - ID - 18 Hours - Energy x Bin - No Shield - BG Subtraction - 0.045-Clean - 18_19-05-19.png
Fukushima Soil + BG - ID - 18 Hours - Counts x Bin - No Shield - 0.045-Clean - 18_19-05-19.png
Fukushima Soil + BG - ID - 18 Hours - Energy x Bin - No Shield - 0.045-Clean - 18_19-05-19.png

luuk
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Re: Fukushima Soil

Post by luuk » 21 May 2019, 03:18

Hi Massimo,
I did today a test to see if it is still possible to see the 605Kev peak separated from the 662Kev in the Fukushima soil with a simple NaI(Tl) detector.
I took a 2x2” NaI(Tl) with an excellent resolution of 6.0%@662KeV.
The first test I did without shielding you can see on the left edge of the Cs-137 peak just a little of the 605KeV.
test without shielding.png
test without shielding.png (7.53 KiB) Viewed 192 times
The second test is done with a simple and light “portable “ lead shield the 605 peak is just a little better visible but still not a clear peak.
test with a lightl shield.png
test with a lightl shield.png (7.73 KiB) Viewed 192 times
For the last test I took a 1.5x1.5 CeBr3 crystal with a resolution of 4.0%@662KeV no background shielding.
test with a CrBr3 4% detector no shield..png
test with a CrBr3 4% detector no shield..png (8.87 KiB) Viewed 192 times
Now it is finally possible to see the 605KeV peak separated from the 662KeV this result will be better when it is done in a lead shield but I ran out of time to do more tests with it.

So the simple conclusion is: that it will not be possible without the use of a special high resolution crystal to really separate these two peaks, so just a small bump on the edge is all you can detect.
Luuk
Last edited by luuk on 21 May 2019, 05:43, edited 1 time in total.

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Peter-1
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Re: Fukushima Soil

Post by Peter-1 » 21 May 2019, 03:54

It has left me no peace
and so I have measured again. The resolution is certainly not bad, but I can not see more with my 2 "x 2" NaI.
2019_05_19-Fukushima.png
2019_05_19-Fukushima.png (96.23 KiB) Viewed 189 times
Peter

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Go-Figure
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Re: Fukushima Soil

Post by Go-Figure » 21 May 2019, 07:26

luuk wrote:
21 May 2019, 03:18
So the simple conclusion is: that it will not be possible without the use of a special high resolution crystal to really separate these two peaks, so just a small bump on the edge is all you can detect.
Luuk
Yeah, after a 18 hours measurement + roughly as much for background I know by now that that peak is beyond my reach and Peter's result is a further confirmation of it.
Today was very busy but I will post some other data from this test shortly.

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Steven Sesselmann
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Re: Fukushima Soil

Post by Steven Sesselmann » 21 May 2019, 11:13

Hi Guys,

Whenever I hear the word impossible, I feel challenged, because nothing is impossible :D

I have a suggestion, how about taking a background recording in PRA with a pure Cs137 check source, then run a recording of the Fukushima soil with background subtraction.

Possibly the peaks Cs134 will stand out more clearly.

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

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Go-Figure
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Re: Fukushima Soil

Post by Go-Figure » 21 May 2019, 17:43

Steven Sesselmann wrote:
21 May 2019, 11:13
Hi Guys,

Whenever I hear the word impossible, I feel challenged, because nothing is impossible :D

I have a suggestion, how about taking a background recording in PRA with a pure Cs137 check source, then run a recording of the Fukushima soil with background subtraction.

Possibly the peaks Cs134 will stand out more clearly.

Steven
That's an interesting idea Steven, and I like the approach! :D
I guess what Luuk meant was you can't see that peak in a full spectrum of that soil sample, but I think you should be able to do it if you could subtract the Cs137 slope. I know the peak is there, I see something there at the beginning of each recording before the Cs137 slope shapes up fully and completely covers it. Besides, Luuk just showed us it's there, only "impossible" (sorry for dropping the "i" word) to resolve.

You guys can effectively shield the actual background so you can probably do that taking a straight recording of the Cs137 check source.
Help me out here but I think I have to do something different having no shield yet. Since I cannot get rid of the actual background I probably have to build a composite background spectrum with Cs137 and the actual background peaks in the right ratio, something like the one in the image below but without Cs134. That depends on how PRA operates Background subtraction but I suspect that's the case.
I know the background peaks are there even when I take an unshielded measure of Cs137 check source but they are dwarfed to insignificance by the activity of the source taken at a few mm distance and I don't think it would work that way.
I will try that just in order to be sure and if that's the case I will have to take advantage of the inverse square law and play with the distance between the source and the detector until I got the ratio right. I guess getting in the right ballpark will be relatively straightforward, fine-tuning will be another matter, and you can't really getting exactly right because the background is not always the same, I just made a quick check and in my two recordings of the soil sample (done in the same room at a few days distance) the counts-ratio between the central point of Cs137's peak at 662 keV and K40's peak at 1460 keV is 13.5 the first time around and 15 the second (I used the central point and not the total number of counts in each peak for this initial check because I am a bit out of time at the moment).
I will check if other peaks give me a more stable result, maybe the Pb214 peaks, and hopefully it will very less during the same day with roughly the same humidity, temperature, etc.
I know what I am going to do next weekend!

Massimo
Attachments
Fukushima Soil + BG - ID - 18 Hours - Counts x Bin - No Shield - 0.045-Clean - 18_19-05-19.png

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