Tag Archives: gamma spectroscopy

Cesium 137 Detected in my Rain! (Radioactive Rain Detected)

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As you all know, I have always maintained that there is Fukushima fallout in the rain… but that the levels (even if they are unsafe) are too low for a Geiger counter to detect.

My sensitive Gamma Spectrometer has now (I believe) detected Cs137 in a rain water collection bucket which concentrates, or so it seems, the Cs137.

Most of the radiation detected by Geiger counters from rain is from Radon Washout, a processes whereby radon in the air (decays from natural uranium around the world) is “washed” out and falls to the ground in the rain. The decay chain is sudden and very quick, providing a few hours of potent readings before falling to background.

Inspector (regular or EXP) Sensitivity to Iodine 125:

0.02 µCi = 740Bq = 44,400Bq/60seconds
(At contact for I-125)


Iodine -125 Electron Capture
Gamma – 35.49 keV 6.60 %
X-Ray – 27.47 keV 75.7 %


Best energy range for detection by LND7317 probe:
10 keV = 100 keV (max)

The range where detector efficency falls rapidly (Cs137 is also in this range):
100 keV = 1000 keV (declining)


A great place to find data on isotopes:

*** Update! ****

I have calculated the activity:

My original calibrated Cs137 source (cal. vs. NIST tracible source, source ID SRS:80899-854, at 95% accuracy) was 3737 Bq.

I accounted for decay of the source:
3737*e^-((ln(2)/10979)*173) = 3696.4059560683608390980241545539265887454856828520474 Bq
=3696 Bq

For an ROI of the same size for both calibrated sample and rain water sample, I ran tests and determined counts per second:

Calibrated Source 91.2633 c/s
Rain Water Sample: 0.01439814814814814814814814814815 c/s

Now, I divided the detected calibrated sample c/s into the expected c/s to determine ratio of emission vs detection for the energies around 661.66 keV. (3696Bq * 0.851 [intensity for gamma from Ba137m])/2 = 1572.648. The division by two is because I entirely detected one side of the thin sample disk. so… 91.2633 / 1572.648 = 0.05803161292291727074335769987944

My detector is only about 5.8% efficient for such energies. (lower than my 12% “ball park by half”)

Now, merely divide the counted detection from rain by the efficiency and you have about the correct result.
(311counts/21600) /0.05803142216185694446564011781403 =

=0.01439814814814814814814814814815 / 0.05803142216185694446564011781403 = 0.24810951742643665986093914169915

Or 0.248 Bq/liter

(that is zero point two four eight Becquerels per liter)


Waterford Crystal – Radioactive!

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Waterford Crystal – A beautiful addition to any home! It shines, looks lovely, and it is radioactive!

I recently tested a piece of Waterford crystal to see why it was radioactive. For a long time I have wondered by my Geiger counter went crazy when near it. The truth was quickly revealed by Gamma Spectroscopy! The little Angel statue contained potassium 40, (element K). All potassium contains 93+ % Potassium 39, stable potassium, and a little bit of the isotope Potassium 41, perhaps 6+ %. But, all potassium also contains a tiny fraction of the radioactive isotope of potassium, Potassium 40 (K40). Potassium 40 undergoes three forms of decay, beta -, rarely beta+, and electron capture. The last step emits a gamma ray with an energy of 1461 keV. It is this gamma ray that I detected.


Waterford Crystal Angel

Waterford Crystal Angel

Waterford Crystal - Gamma spectrum

Waterford Crystal - Gamma spectrum

Nuclear Alchemy: The Transmutation of one Element into Another

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Nuclear Alchemy: The Transmutation of one Element into Another

I bombard aluminum 27 (13 protons and 14 neutrons), the stable type we have all come to know and love, with energetic alpha particles (two protons and two neutrons) at an energy of 5.3042 MeV! (MeV means Millions of Electron Volts). Most of the alpha particles would have bounced off of the aluminum without joining… but some would. Those lucky alpha particles bonded with the nucleus of the aluminum 27 to produce a new element: phosphorus 30! (15 protons and 15 neutrons). The reaction emits one spare neutron with way too much energy! =(

The phosphorus 30 has a short half-life of a mere 2.49 minutes, decaying into stable silicon 30 (14 protons and 16 neutrons) via beta+ decay (a positron). The position emitted is an Anti-Electon! That’s right, anti-matter. The quick little positron has an average energy of about 1438 keV (a max of 3203.3!!!). The position lasts only a short time before slamming into a normal electron and annihilating with an energy of 1022 keV, expressed as two gamma rays, each with 511 keV of energy. It is these emissions which I detect, using gamma spectroscopy. A Geiger counter would never be able to give me these results.

Al-27 + He-4 → P-30 + N
(e+) + e → y

I had calculated the energy of the reaction many times, but each calculation was a little wrong. I asked a very smart physicist for some help and he gave me a formula for figuring it out, but my math and his still didn’t add up…

Here is what I used for my determination:
I took the mass of an atom of P-30
(4.97802×10^-26 kg), call it M, and the mass of a single Neutron (1.67493×10^-27 kg), call it N, and the energy of the alpha particle which slammed into the aluminum (which was not at rest, but probably not doing too much whilst in its lattice, 5304.2 keV = 8.498×10^-13 joules, call it E. Also, let Em = momentum of P-30 atom after ejection of neutron, En momentum of neutron after being ejected: Em = (N/(M+N))E =(1.67493×10^-27 kg / (4.97802×10^-26 kg+1.67493×10^-27 kg)) 8.498×10^-13 j = 2.76620721*10^-14 joules = 172.6531 keV En = (M/(M+N))E = (4.97802×10^-26 kg /(4.97802×10^-26 kg+1.67493×10^-27 kg)^-1) 8.498×10^-13 j =8.22137928×10^-13 joules = 5.131382 meV

But… his numbers didn’t match (he thought the neutron would be 2.574 MeV and the phosphorus 30 would be 0.086 Mev.

Either way… OMG! That’s too much neutron flux for me in my tiny home lab. =)

WWI Radium Compass Spectrum!

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WWI Compass

WWI Compass

Here is a spectrum for a 7,000+ CPM – 1917 Dennison Birmingham Mk VI radium compass! Enjoy!

P.S. Check out my radioactive materials section to see the actual compass.

Autunite Uranium Spectrum!

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Autunite - Uranium

Autunite is a very beautiful, many might say the most beautiful, uranium-bearing mineral. Autunite contains many amazing isotopes, including a few transuranic elements! I received a sample of the beautiful and deadly mineral from a friend at the cost of an analysis using my gamma spectrometer.

I have finally completed a calibration analysis of my spectrometer, to include a 17 KeV to 2MeV window with a +/- 3KeV tolerance. These are favorable conditions for analysis of uranium and uranium daughters.

Today, I tested my new Autunite sample in my gamma spectrometer to see what I might find within it’s calcium-encrusted innards. The primary natural uranium products are there, as expect: Lead 214 and Bismuth 214 being heavy gamma emitters, lead the way with large spikes at 351.92 KeV, 295 KeV, and 609.31KeV, 1764.49 KeV, respectively. I detected a tiny bit of Radium 226, Uranium 235, and Uranium 238.