Monthly Archives: February 2012

Radioactive Banana! Peeling Away the Mystery

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Radioactive Banana! Peeling Away the Mystery

All bananas contain potassium (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.

My calculations for the typical radioactivity of a banana:

The number of Potassium (K) atoms per gram of potassium:
(Avogadro’s Number / Atomic Weight of K40) = 6.022 x10^23 / 39 = 1.544 × 10^22 K Atoms/gram

The amount of Potassium in a Banana (approx):
grams of Potassium in a banana = 0.442 grams

Natural abundance of K40 per normal Potassium (A): 0.000117

Half life of Potassium: 3.9357×10^16 seconds (T 1/2).

Calculation:
((Avogadro’s Number) / (Atomic weight)) x (0.442 g) x (A) x (ln 2) / (T1/2)
(((6.022*10^23 / 39)*0.442) x 0.000117) x ln2 / (3.9357×10^16)
=14.0633 decays per second per banana
= 14.0633 Bq Banana^-1
=lol

Practical Gamma Spectroscopy Links

For $350 USD – $500 USD
http://beeresearch.com.au/ – Quality and inexpensive MCA
http://www.physics.usyd.edu.au/~marek/pra/index.html – PRA software for viewing peaks.

You can often find a good scintillation probe on eBay for a few hundred dollars (USD), but you have to shop for it.

$4,000-$5,000 USD
http://spectrumtechniques.com/ucs30_system.htm — Entry lab-grade setup.

Some potassium and banana sites!!!
http://www.orau.org/ptp/collection/consumer%20products/potassiumgeneralinfo.htm
http://en.wikipedia.org/wiki/Banana_equivalent_dose
http://www.chiquitabananas.com/Worlds-Favorite-Fruit/bananas-and-potassium.aspx
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0000089/

Radioactive Food: Brazil Nuts

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Are Brazil Nuts radioactive? You bet!

I tested a bag of them using gamma spectroscopy and found clear peaks for Radium 226 and Lead 214, as well as probable peaks for Bismuth 214. In the end, the radioactivity of Brazil nuts isn’t something to worry about. In an entire 24 hour period I only few a few hundred gamma rays from each peak. The radioactivity was just too low to be of worry.

Like most nuts, Brazil nuts are quite good for you and typically get a “glowing” review from health care professionals. =)

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

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.

Gamma Spectroscopy: Americium 241 Smoke Alarm Tested

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0.9 uCi 241 Am Smoke alarm tested using gamma spectroscopy.