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Wednesday, January 23, 2008

TERRA-P with a check source

So have I found anything radioactive with the TERRA-P around me? No. Fortunately. I consider this to be a good thing. Except of course the natural background radiation, which is generally somewhere around 0.10 uSv (where u=micro). But that's not fun, and won't really show whether my shiny new and bright yellow radiometer works as it should...
What I did not know is that Danex's vintage Victoreen has a check source on its side. As the you might have concluded by now, a check source is a source which allows you to check if your device works correctly or not:) I had the privilege to abuse Danex's radiometer to test my own. The picture below shows the source, and the TERRA-P showing the normal background radiation:
The check source emits beta radiation. So to measure the beta (in addition to the gamma) radiation, one has to remove the little hinged door. The door has a thin lead lining, which is supposed to prevent beta radiation to enter the tube. Without the door, you can see the Geiger-Mueller tube exposed:
Just about a foot (~30cm) from the check source surface, the readings are not too terrifying - but still well over the admissible maximum. The values below indicate about 4 times the background reading. That's certainly a lot more than I would like to have in my house - at least for prolonged exposure:
Aaand this is where the fun begins. The TERRA-P has an user adjustable alarm limit. The maximal value what you can enter is 9.99uSv/h. If the radiation level is over the set value - the device will warn you with a loud beeping. (Instead of the standard clicking - chirping count sound.) As you can see, this is well over the alarms limit, and violates every possible health regulation. I don't even know how this went through the customs???:) Anyways, this picture shows the radiation 115 times over the normal levels. Even though this is a direct reading - I would not carry the check source in my pocket... ;)