The effect of quantity of intake Cesium-137 on its tissue absorption

Some dangerous radionuclides can be distributed in the environment because of human activities. Nuclear weapon tests and big nuclear catastrophic events such as Chernobyl and Fokushima accidents are among such activities. Cs-137 is one of the most important released radionuclides during the accidents. Due to its long half-life (around 30 years), it can exist in the environment after the nuclear contamination. Huge amount of Cs-137 have been released into the environment after Chernobyl and Fokushima accidents. Cs-137 can be dangerous both internally and externally. In this research, internal exposure and dose have been considered. Caesium-137 can easily enter to body through food, drink and breathing of contaminated air. Generally, duration and extent of the internal radiation depends on the kind of radionuclide and the amount of contamination. In this study, the multi-compartmental model was implemented to study of Cesium intake. The first compartment is the blood and the second one is other tissues. The Cesium activity in blood and other tissues was obtained by using analytical and numerical methods by considering food activity as input of equations. Transfer coefficients of the different tissues were obtained for assessment of model by solving the differential equations and ICRP-54 data. The transfer coefficients are in a very good consistency to the COMKAT software code results with the absolute difference in an order of 5.5×10-6. For study the input radiation to the tissue, different input conditions as the continuous, acute, periodic and random inputs were considered in differential equations system and the activity curves were obtained in urine and excretion in these conditions. The results indicates that although the human intake activity was assumed to be equal in all conditions but the excretion and the urine activity curves were different for different shape of input functions. Moreover, the results show the percentage difference between recommended ICRP input (impulse function) and the different inputs were significant and it must be considered for internal dosimetry after the nuclear accidents.