Objective: The purpose of this research is to make analysis, revision and estimation both reliability and accuracy of all measurements of radioiodine in the thyroid for residents of Ukraine, which were performed in 1986, and to justify the calibration factors to be applied for interpretation of measurements performed by non-calibrated devices.
Materials and methods: The radioiodine activity in the thyroid for residents of the most contaminated oblasts of Ukraine has been calculated on the base of 150 thousands direct measurements of the content of 131I in thyroid obtained in the frames of the thyroid monitoring in 1986. A method for the calculation of measurement errors has been developed and the accuracy of the errors has been determined assuming that the density of errors' distribution for main parameters of the measurements is close to Gaussian. Using the results of laboratory measurements, the calibration factors have been determined for integrated radiometers SRP-68-01 - devices which were often used to perform the thyroid dosimetric monitoring.
Results: The distribution of estimates on the content of radioiodine in thyroid is close to the lognormal one with geometric mean being equal to 4.8 kBq and geometric standard deviation being equal to 3.8. Most of these estimates (90 %) are in the range of 0.58-47 kBq, and the main set of their relative errors (90 %) are between 0.1 and 0.6. Thus, the model of thyroid activity observation with classical additive error has been obtained.
Meta. Analiz, reviziia, otsinka nadiinosti i tochnosti rezul'tativ usikh vymiriuvan' radioiodu u shchytopodibnii zalozi meshkantsiv Ukrainy, shcho buly zdiisneni u 1986 rotsi, ta obґruntuvannia koefitsiientiv kalibruvannia, iaki maiut' buty zastosovani pry interpretatsii vymiriuvan', vykonanykh nekalibrovanymy pryladamy.Materialy ta metody. Na osnovi danykh 150 tys. priamykh vymiriuvan' vmistu 131I u shchytopodibnii zalozi, otrymanykh v ramkakh tyreodozymetrychnogo monitoryngu 1986 roku, rozrakhovano aktyvnist' radioiodu u shchytopodibnii zalozi meshkantsiv naibil'sh zabrudnenykh regioniv Ukrainy. Rozrobleno metodyku rozrakhunku pokhybok vymiriuvan' ta vyznacheno ikh tochnist' u prypushchenni, shcho shchil'nist' rozpodilu pokhybok osnovnykh parametriv vymiriuvannia blyz'ka do gausivs'koi. Za rezul'tatamy laboratornykh vymiriuvan' vyznacheno kalibruval'ni koefitsiienty integral'nykh radiometriv SRP-68-01 – pryladiv, shcho naichastishe vykorystovuvalys' pry provedeni tyreodozymetrychnogo monitoryngu.Rezul'taty. Rozpodil otsinok vmistu radioiodu v shchytopodibnii zalozi ie blyz'kym do lognormal'nogo z serednim geometrychnym – 4,8 kBk ta geometrychnym standartnym vidkhylenniam – 3,8. Bil'shist' tsykh otsinok (90 %) lezhyt' v intervali 0,58–47 kBk, a osnovnyi masyv znachen' ikh vidnosnykh pokhybok (90 %) lezhyt' v mezhakh 0,1–0,6. Takym chynom, oderzhano model' sposterezhennia radioaktyvnosti ShchZ z klasychnoiu adytyvnoiu pokhybkoiu.
Keywords: Chornobyl disaster; calibration factor; errors of a measurement; radioactive irradiation; thyroid; thyroid dosimetric monitoring.
I. A. Likhtarov, L. M. Kovgan, M. I. Chepurny, S. V. Masiuk.