A fast algorithm for real-time monitoring of artificial radioisotopes in presence of variable natural radioactivity

We present an agile, hardware independent analysis methodology based on the spectral windows technique to detect and quantify the environmental activity concentration of artificial isotopes of interest. The method removes counts from Compton scattering, peak overlapping, intrinsic background and other unconsidered contributions to the spectral region where photopeaks from artificial elements are expected. Taking into account the varying concentration of 214Bi, 214Pb, and 212Pb, we compute the activity concentration of the artificial isotopes (when detectable), or a variable Minimum Detectable Activity Concentration (MDAC). This allows to set statistically robust early-warning levels. In the scenario with the lowest concentration of natural occurring isotopes, and for 10-min integration time, we achieve a MDAC of 5.4/4.1/3.9 (Bq/m³) for 131I/137Cs/60Co using a LaBr3(Ce) detector; and 4.2/2.8/2.7 (Bq/m³) for 131I/137Cs/60Co with a SrI2(Eu) detector.