In situ determination of ¹³⁷Cs inventory in soil using a field-portable scintillation gamma spectrometer-dosimeter

A new empirical method for in situ determination of the inventory of ¹³⁷Cs in soil (A_Cs, kBq m^-2) at grasslands and forests using a field-portable NaI(Tl) scintillation spectrometer-dosimeter was developed. The method is based on evaluation of the ambient dose equivalent build-up factor. The practical implementation of the new method with the spectrometer-dosimeter does not require a priori knowledge of the vertical distribution of ¹³⁷Cs in soil. Moreover, the method allows assessing a value of the mean migration depth of ¹³⁷Cs in soil (Z) in terms of g cm^-2. The 95% confidence interval for the mean value of the conversion coefficients from the ambient dose equivalent build-up factor to A_Cs and to Z is less than 10%. The new method has been developed and verified using published data that where obtained at territories in Russia and Belarus heavily contaminated with ¹³⁷Cs (A_Cs > 37 kBq m^-2) due to the Chernobyl accident. Therefore, the survey of less contaminated areas requires additional validation of this method.