Calibration of radiometers for mass-scale monitoring of incorporated nuclides of 131I, 134Cs and 137Cs conducted with involvement of volunteers

The paper describes the study in which six volunteers of different built took perorally 370 kBq (10 µCi) of 134Cs and 137Cs mix each. Results are presented of in vivo measurements performed with portable scintillation radiometers during more than 20 days with the detector arranged differently with respect to the body. The content of cesium radionuclides in each volunteer within 1 to 7 days was determined as a difference between the amounts of the radionu-clides taken in and excreted. Urine and feces was collected during 7 days and studied by gamma spectrometry. The cesium has been shown to be uniformly distributed in human organism 20 days after introduction. Non-uniformity in its distribution in the first several days can lead to considerable errors in vivo measurements using ordinary radiometers. The calibration of radiometers by thyroid 131I was performed with patients administered 131I for diagnostic purposes. The paper present the methodology for 131I determination in thyroid in the presence of interfering irradiation of cesium radionuclides uniformly distributed in human organism. The completed study has made it possible to develop a methodology for prompt determination of 134Cs and 137Cs in human body. This methodology has been used for more than 300 thousand measurements in the Chernobyl contaminated areas of Bryansk, Tula and Orel regions.