In situ estimation of the air volumetric activity

The proposed method allows to quickly estimate in-situ the air volumetric activity with acceptable uncertainty. The new method eliminates the need for sampling and personnel exitting the vehicle. It becomes possible to quickly double-check the measurement results and study in more detail the area of the territory where a high gradient has been detected. The volumetric activity of the atmospheric surface layer is estimated based on the «clean» areas of the photopeaks of total absorption and using the original calibration of spectrometer. The minimum detectable activity depends on the composition of the radionuclides in the emergency release, the duration of the spectrum acquisition, and does not exceed 1 Bq·m -3 , which is significantly lower than the established intervention levels. The uncertainty of the proposed in situ assessment method is estimated at 30 % with a 95 % confidence interval.