An attempt for generalized evaluation of the minimal detectable activity in routine beta-radioactivity measurements

A methodological description of errors in routine beta detection measurements in radiometric laboratories is presented in order to explain the sources of errors and estimate quantitatively the thresholds of detectability of beta radiation activity in the air, in sediments and in water solution samples. Three types of errors are considered in connection with the sample quantity variations, the measurement conditions and the statistical limitations of the sampling. The ultimate detection limits are derived. The sensitivity values of the adopted measurement algorithms provided for the detection and analysis of radioactive contamination are determined. For a single sample 120 hours after the sampling and for average monthly contamination (30 samples) they are 1 and 0.2 mBq/m3 for air, 0.5 and 0.1 Bq/m2 for sediments and 0.6 and 0.1 - 0.5 Bq/l for water samples. The conclusion is that the adopted measurement practice assures sufficient level of accuracy in the detection of technogeneous radioactive contamination of the environment. (R.Ts.)