METHODOLOGY OF RECONSTRUCTION OF INTERNAL DOSES FROM 137Cs AND 134Cs OF RESIDENTS OF RADIOACTIVELY CONTAMINATED SETTLEMENTS IN UKRAINE NOT COVERED BY WBC MONITORING.

Objective: Scientific justification of the methodology for calculating radiation internal doses from 137Cs and 134Cs intake for residents of Ukrainian settlements radioactively contaminated as a result of the Chornobyl (Chernobyl) accident in which measurements of incorporated radiocesium isotopes in humans using whole-body counters (WBC) were not carried out.

Materials and methods: The paper presents a new methodology for reconstructing doses due to internal irradiation from Chornobyl fallout for both surface (in 1986) and root (in 1987-2023) contamination of vegetation with 137Cs and 134Cs and their transfer into the human body. The methodology for calculating the dose due to surface contamination of vegetation was based on the theoretical model of the transfer of radiocesium isotopes through the food chain with further adjustment of this model to the results of WBC measurements carried out between 15 July and 31 December 1986. For root intake, an ecological dosimetric model is used with the parameters determined by the types, quality and completeness of cow's milk and WBC monitoring carried out in radioactively contaminated territories in 1987-2013. In the absence of WBC measurements, the doses were estimated considering the properties and specifics of radioactive contamination of environmental objects in each region: soil type, levels of soil and milk contamination, and milk equivalent.

Results: A new methodology for reconstruction of internal doses from radionuclides 137Cs and 134Cs to residents of the territories of Ukraine radioactively contaminated due to the Chernobyl disaster is substantiated. The methodology is based on the analysis of all data obtained as the result of radioecological and dosimetric monitoring carried out in Ukraine after the accident.

Conclusions: According to the methodology developed in the work, the calculation of annual internal doses to residents of settlements that were not covered by WBC monitoring is based on the measurements of the 137Cs activity in the milk of private farms, which were carried out in these settlements. In the absence of such measurements, a linear regression model which connect the incorporated in human body 137Cs with four groups of soils in the vicinity of the settlement is used for doses calculation. The doses calculated according to the new methodology agree with the dosesderived directly from the results of WBC measurements.