Geiger counters detect X-rays but may not be precise in measuring the dose rate. This is because an x-ray is usually a short concentrated burst of radiation. A geiger counter measurement is done by detecting individual ionizing events in its Geiger tube. The events during the X-ray usually take place so fast that the instrument cannot detect all of them, giving a reading that does not reflect the full amount of radiation. For a true dose rate, an ionization chamber would be needed.
Dental and medical X-ray machines have leakage or scatter sometimes in directions other than the target. Inappropriate shielding may result in this scatter reaching personnel causing unnecessary exposure. In order to screen for scatter, the Radalert 100 can be placed in the location where testing has to be done during activation of the X-ray machine. In case the instrument is in Audio mode, a rapid burst of clicking or chirps will be heard and it will produce a reading higher-than-normal. It is important to note that though the reading is a reliable measure of scatter, it is not an accurate measurement.
Measurement of Radiation in Food
Geiger counters can measure ionizing, or nuclear, radiation. Radiation from cellular phones, microwave ovens, cellular phones, power lines, and electric appliances is non-ionizing electromagnetic radiation, which cannot be detected using these instruments.
In order to precisely measure food radiation, a multi-channel analyzer is needed and a special oven is also required to ash the food for concentrating the radioactivity. Geiger counters have been used for educational, experimental and screening purposes for checking food.
It is quite tricky to measure radiation in food. Naturally-occurring radiation in potassium-rich food like bananas when dried into salt substitutes and banana chips can be identified easily using the Radalert 100 and the Inspector Alert. While checking during nuclear testing or accidents, one would look for Cesium 137, Strontium 90 and Plutonium 239. Due to its sensitivity, the Inspector is the most suitable for this application.
The Inspector Alert efficiency for Sr-90 and Cs-137 beta is good, and it does detect the Cs-137 gamma. It does detect Pu-239, but Pu-239 can have health impacts at very low concentrations, which can be difficult to detect with any instrument.
Before screening for radiation in food, a baseline measurement must be established in the same location where food testing is planned. The baseline counts need to be accumulated for 12 h as explained below.
Tips for Measuring Radiation in Food
Certain tips to be followed while measuring radiation in food are:
- During measurement, place the mica window of the instrument directly over the measured food.
- In case of liquids or milk, the container must be filled very close to the top without glass in the way. In case all the milk is from the same source one can concentrate it by boiling sufficiently.
- The display needs to be set to Total and the counts accumulated for 12 h in each location
- The total count for the period is divided by the exact number of minutes to get the Average CPM.
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This information has been sourced, reviewed and adapted from materials provided by International Medcom.
For more information on this source, please visit International Medcom.