How do you determine the MDA (minimum detectable activity) of beta radiation in a contaminated sample?
You need to know the efficiency of the detector for the particular radionuclide, then you need to determine the sampling time to obtain the (statistical) level of confidence that you want (for example, 2 sigma). You must also consider the detector geometry in relationship to the source; for example, if you are measuring on a flat surface, you detect only the radiation that decays in the direction of the detector; so, using a 1000 DPM point source with 100% detection efficiency, you would detect approximately 500 DPM. Using the Radalert 50 or the Inspector in the Total mode (accumulated counts) greatly enhances the sensitivity by providing a longer sampling period.
You need to know the efficiency of the detector for the particular radionuclide, then you need to determine the sampling time to obtain the (statistical) level of confidence that you want (for example, 2 sigma). You must also consider the detector geometry in relationship to the source; for example, if you are measuring on a flat surface, you detect only the radiation that decays in the direction of the detector; so, using a 1000 DPM point source with 100% detection efficiency, you would detect approximately 0 DPM. Using the PalmRAD 907 in the Total mode (accumulated counts) greatly enhances the sensitivity by providing a longer sampling period.
