Radioactive Banana! Peeling Away the Mystery

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

Geiger Counter Myths

Many myths are propogated on the internet concerning Geiger counters. This video seeks to disprove some of the more common myths.

I may have missed some, so if you think of any, please let me know.

Victoreen CDV-700 6A Geiger Counter -- Review

Victoreen CDV-700 6A Geiger Counter -- Review
Manufacturer: Victoreen Instrument Company

Purpose: Civil Defense Nuclear Fallout Survey Geiger-Muller Counter

Detectible Particles: Muon, Beta, Gamma, X-Ray
Tube: Victoreen 6993 Energy Compensated Geiger-Muller Tube
Sensitivity: Approximately 60 CPM / 1 mR/hr

Alert Features: None
Timer: None

Housing: Steel case with nickle plated brass probe
Power: Four standard D cell removable batteries
Endurance: 100 to 200 hours at background

Unit Ranges:
CPM
1x 0 to 300 CPM
10x 0 to 3,000 CPM
100x 0 to 30,000 CPM

mR/hr
1x 0 to 0.5 mR/hr
10x 0 to 5 mR/hr
100x 0 to 50 mR/hr

Anti-jamming: None

Pros
Rugged
Designed to survive nuclear war
Less susceptible to EMP than digital units
Very Easy to use
Can change calibration very quickly
Field serviceable (with required skill)
Probe has very long cable
Built-in nuclear check source
Very rapid response (30 seconds initially, 7 seconds after that)

Cons
Heavy
Exposure to check source may be of concern
Analogue scale can be harder to read than digital display
Check source can cause problems with transportation
No internal data logging. Requires external software (e.g. Geiger Graph)


(Details accurate per manufacturer's website as of July 22, 2012)

Three Geiger Counters Compared