Book Description

The ORNL Whole Body Counter is one of the few in the country that is capable of assessment of body burdens of low-energy photon and x-ray emitters. This requires detectors and electronics specific for the task. Isotope identification and quantification capabilities are crucial at the facilities which deal with quantities of many radionuclides. The standard procedure for whole counting done at ORNL employs a 13.34 cm-dia. phoswich, a hyperpure germanium (HPGe) array consisting of six detectors totaling 80 cm/sup 2/, and a 23 cm by 23 cm NaI detector positioned under the subject's back. Isotope identification and quantification capabilities for detection of the actinides using the HPGe array are greatly improved over the phoswich system, making the HPGe detector an integral part of lung counting operations at ORNL. The HPGe array has been fully operational since May 1980. Since that time, calibrations have been performed with various sources, a calibration curve derived, and minimum significant measured activity (MSMA) and minimum detectable true activity (MDTA) for various radionuclides have been determined. The current analysis techniques are discussed, examples of MSMA and MDTA for various isotopes are given, and the derivation of a universal calibration curve for preliminary estimation of body burden is discussed using data acquired by the HPGe array.