In Situ Methods for Quantifying Specific Radionuclides

Field spectrometry methods utilizing high resolution detectors can be used to quantify the concentration of radionuclides in soil, and the resulting external exposure rate. Advantages of the method compared to soil sampling followed by laboratory analysis are greater speed of analysis, integration of inhomogeneities of radionuclide areal distribution, and the immediate availability of data to guide further field studies. A disadvantage is that the calculation of results depends upon some knowledge or assumption about the distribution of radionuclides with depth in soil. The procedures necessary to calibrate and use a field spectrometer are discussed, and a practical guide is developed. Examples of uses of field spectrometry are the quantitation of complex mixtures of radionuclides in soil, the calculation of the resulting external gamma exposure rate apportioned by radionuclide, geochemical studies, preoperational and continuing studies at nuclear reactor sites, and the identification of short-lived, noble gas radionuclides in reactor plumes.