Gamma Spectrometry Forum

Here is another possible Tritium detection, this time in an April 2015 rain water filter test. The test results show that Be-7 and Pb-210 were also present. The polyester filter which also had significant amounts of organic matter in it, was placed in a thin sealed plastic bag for testing. Attached is the test chart.
I have also attached a previous January 2015 rain water test for comparison. As you can see in the January chart, the previous combined Pb-210 X-ray peak, was much thinner.

Anyone have any other suggestions for the wide peak, I have marked in April test chart in yellow?

I aim suggesting it is Tritium, which can generate Bremsstrahlung Radiation from Beta decay, from 3 to 20 keV. In this test chart it is in a combined peak with Pb-210 X-rays. These have been detected in previous rain water filter tests, when Pb-210 is present.

There were a lot of solar storms recently.

Hi Peter

Always interesting to see these charts, always makes me want to build some similar filtering device myself. But as I understand it, you use the runoff collected from an entire roof, and I guess this greatly adds to the sensitivity of the method (as opposed to simply putting a tube with a funnel in the garden)

The very low energy peak at 13-20 keV, are you sure that this is not "noise" from the PMT or something like that? What source do you use for calibration (if a peak is outside the range of the calibration points used, the keV values become shaky). Can you confirm you can see such low energies ?

did you try to filter water from any other source using your contraption?

Peter,

There is no doubt trace amounts of tritium in rain water, from what I have read it could be in the order of 10-50 Bq/litre, but this is usually measured with a liquid scintillation counter, as tritium is primarily a beta emitter. It is possible that you might be seeing something, but the energy range you are looking at is at the fringe of your detectors capability. Looking for trace amounts of anything at the fringe of detection is ambitious.

That said, do you have any means of quantifying it?

"the energy range you are looking at is at the fringe of your detectors capability."

Agreed, it is pushing the limits of what the equipment can detect.

I have been using Theremino 6.7 for rain water testing for a few months now. The Pb-210 lead X-ray combination peak at ~ 12 keV has shown up as a well defined peak for each test.

Is it the Pb-210 X-rays?

A small peak ~12keV does show up in the background test with no sample present. This test chart is minus background.

I have a PB-210 contaminated lead solder sample I can use for low level energy calibration. It produces a combined X-ray peak in the same keV region.

From Nuclide data http://ie.lbl.gov , PB-210 has significant X-rays from around 11 to 13 keV.

X-ray - %
10.731 - 0.97 6
10.839 - 8.6 5
11.712 - 0.083 5
12.480 - 0.137 9
12.691 - 2.2 3
12.967 - 2.15 14
13.023 - 3.53 23
13.211 - 2.6 4
13.393 - 0.299 19

I haven't found any NaI Pb-210 test charts on the Internet showing these X-ray peaks. I have found Ge charts that show these Pb-210 X-rays.

http://www4vip.inl.gov/gammaray/catalog ... /pb210.pdf

http://www4vip.inl.gov/gammaray/catalog ... 10_new.pdf

If a NaI crystal and software was capable of detecting these X-rays, it would show up as combined peak, because the NaI crystal is not as sensitive.

By the time I post a test chart here, I have tested the sample a few times, to make sure it not a calibration or testing error.

"are you sure that this is not "noise"?"

A small peak ~12keV does show up in the background tests.

The chart is minus background.

I use a Thorium gas mantle in a seal container for multiple peak calibration, plus smoke detector Americium and the Pb-210 contaminated lead solder for low level keV peak calibration.

Attached is a calibration test chart of the Thorium gas mantle spectrum using Theremino 6.7.

The broad peak at ~12keV in the April rain water test, suggests another isotope has been detected.

Tom (Anti-Proton), has a Youtube video showing Tritium Bremsstrahlung Radiation detection from Beta decay, here.

https://www.youtube.com/watch?v=4Y3Hu6hEwow