Gamma Spectrometry Forum

Hello all,

Luuk sent me one of his Fukushima soil samples. It is very useful for me because before I didn't have a Cs-137 sample. I can use this to better specify the resolution of my detector-DAQ combination.

The following spectrum is from my new detector (also from Luuk): The resolution is below 6.1% ... and my calibration is a little bit wrong (the 661keV peak appears ~20keV too high)

Since the sample is not pure Cs-137, and Cs-137 has no coincident gammas, It is interesting to make coincidence measurements to better see what other isotopes are in the sample. I had a second detector in the setup, face-to-face with the first one, and the soil sample sandwiched in between. The coincident matrix looks like this: I added the tables with known coincidences from Cs-134 (from here http://www.nndc.bnl.gov/chart/decaysear ... CS&unc=nds) and marked them in the picture (I might have forgotten some... there are lots of overlaps).

In the matrix, I can see two more coincidences that I couldn't find in the table for Cs-134. I have marked them in the following picture of the same matrix (with half the bin size to better see the weak spots). Does anybody know what other isotopes are typically in Fukushima soil sample that could cause these lines? kind regards,
Michael

Hi Michael,

Nice spectrum you made really good!
But you have to remember that the soil is ofcourse not just Cs_134/137 in the stones and sand there is also some natural Th228? and K40 in it.
I have different soil samples and all are a little different in natural background, your sample is a mix of 2 other samples so i is hard to tell how much of the natural energies are in it.
Luuk

Hi Michael,

Unfortunately I cannot see pictures anymore. Is it possible to re-post them or maybe send them via PM?

Thanks,
Alain

Hi Alain,

I don't know what happened to the pictures, I'll try to re-post them. And I was affected by the forum login issue and couldn't do it earlier.

Michael

Ah! I can post again :)
Michael