Exercise: Working With Radioactive Material

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In the first exercise you shall learn how to use a contamination detector to find contaminated equipment or areas. The monitor is a simple radioactive detector that uses a handheld gass filled probe (Geiger-müller detector) to find active areas. Your counsellor will show you hove to use the detector.

The student must write a short description of the things that are important to remember when using the detector:






Do the following measurements with the probe connected to the hand held detector:

The count rate (counts per second – cps ) on the following places:
The laboratory bench …................ cps
Inside of the fume hood …............... cps
outside of the laboratory …................ cps

was there any significant difference in the counting in the three places?



Remove the probe - be careful so that you don’t pull the cable ( ask the lab-assistant). The handheld detector is calibrated to measure dose rate. Dose rate is a measurement of how much “strain” the radiation gives the body. It is measured in sievert (Sv) per unit time. Sievert is a large unit and dose rate is therefore often given in [math]\mu[/math]Sv per hour. In comparision the natural background radiation will give you a yearly dose of about 4 mSv (0.46[math]\mu[/math]Sv per hour)
measure the dose the same places you measured the count rate. The laboratory bench …................ [math]\mu[/math]Sv/h
Inside of the fume hood …............... [math]\mu[/math]Sv/h
outside of the laboratory …................ [math]\mu[/math]Sv/h

Reconnect the probe. There is a source placed on one of the benches in the laboratory ( the place should be clearly marked). The source is well shielded, but you can insert the probe past it, so that you can see what happens when the probe finds activity.

Which source is placed out?.....................
What is the count rate of the source?......................cps

One of the laboratory benches shall be controlled for contamination. For this part of the exercise the contamination is covered and sealed. There is no need to worry that you will receive any contamination on yourself or your clothes. Therefore the exercise can be done outside of the fume hoods. You shall still take the same precautions you would as if it had been a unprotected contamination.

It is very important that you manage these exercises since in exercise Measurement of 99mTc gamma-spectrum and Yield of Tc in liquid-liquid extraction you will work with activety that is not sealed and then you must be able to identify eventual contaminations


Find the contamination(s) on the benches. Draw in the approximate position and give the count rate for each contaminated are on the drawing.