体内汚染管理に関する情報理論的考察

概要

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The authors emphasized in the former paper that the measured values in the field of radiological protection are inevitably concerned with the uncertain factors which can never be dissolved by mere improvement of measurement techniques. A concept of “Entropy”popularly used in information theory was introduced in this paper in order to give a quantitative estimation of the uncertainty which appears in the problem of internal contamination measurement. Body retention of the radioactive contaminant after a single intake changes with time according to the physical decay and biological elimination. Hence we have uncertainty in case of estimating the initial amount of contamination from a single value of one-point sampling and measurement. When the detected body burden is q (μCi), the probability with which the initial intake Qo (μCi) may have been over the predecided reference value qo (μCi) was given as follows, p (Qo≥qo) =1-Teff/τlog2qo/q where τ is the interval of measurement and Teff is the effective half life. Apparently, p (Qo<qo) =Teff/τlog2qo/q The authors also gave a graphical presentation of the entropy and discussed the effectiveness of internal contamination sampling program.