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Greenpeace and their Mini Monitor

Dear Reader,

I have noticed the output of Greenpeace, they like to write stuff about issues such as nuclear power which oftein has silly mistakes, errors and half truths. I have noticed that they like to show a scary looking picture of two people holding what looks like a NaI gamma contamination meter while wearing gas masks and plastic suits.

They have made several major errors.

If I was about descend into a radiological version of hell where I needed to don respiratory protection due to the contamination level then in common with these Greenpeace people I would tape up the point where my glove meets the sleeve of my clothing. But they have made a few basic errors.

1. A 900 series Minimoniter is a super sensitive detector which is not very suitable for the measurement of dose rates in a location unless you know exactly what isotope you are dealing with. I suspect that if the Greenpeace people are trying to measure the radiation from “waste” then it is unlikely that they will be dealing with a single isotope. While some wastes contain a single gamma emitter which emits monochromatic gamma rays (such as Cs-137 or Co-60) many wastes contain a mixture of different isotopes. Unless the Greenpeace people are trying to determine the background level (in terms of counts per second) where they are standing then I think that they are barking up the wrong tree.

2. If you are about to enter a strongly contaminated area then unless you place your gamma contamination meter in a plastic bag, then you can soon have a magic contamination meter which indicates that everything is contaminated. What you are meant to do is to put the probe in a plastic bag and the other half of the machine in another bag. This way you avoid getting splashes of water on it, and also you prevent the contamination meter getting contaminated.


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