Comparisons of ISDMAP Estimates of Cs-137 Distributions With the Use of In Situ Data from Empirical and Generic Detector Characterizations

Levan Tkavadze

ISDMAP is a computer mapping program for the deconvolution of in situ gamma spectrometry measurements on a grid resulting in a map of radionuclide contamination in surface soil. The program can combine data from soil samples and in situ gamma-ray spectrometry. It was originally developed as a tool to qualitatively determine whether the data (in situ measurements on a grid) is consistent with small areas of elevated activity “hot spots” that might exceed some regulatory limit. The question we are trying to answer is how do ISDMAP results compare when run with generic versus empirically determined
detector characterizations. Tables for calibration factors for Ge detectors have been developed by I. K. Helfer and K. M. Miller. The accuracy of the results obtained from these tables is estimated to be 10-15%. The work has been performed to compare ISDMAP
estimates of Cs-137 distributions with the use of in situ data from empirical and generic detector characterizations. Two sets of data used in this work are: 1) Data obtained by another group from an area of known Cs-137 distribution and 2) experimentally created with a known “hot spot”.