A RE-EVALUATION OF RADIATION DOSE-RATE CONVERSION FACTORS

Abstract

It has been about forty years since the dose-rate conversion factors commenced to appear in tabular forms and, ever since, periodical updates have been published. The present work contributes to this continuous updating, using the latest evaluated nuclear data for the 238U-, 235U- and 232 Thseries, as well as for 40K and 87Rb, obtained from the Evaluated Nuclear Structure Data File (ENSDF) database and the Nuclear Wallet Cards. An estimate of the accuracy of the dose-rate conversion factors is further attempted for the first time, by taking into account individual uncertainties in all quantities involved in the calculations.

A literature comparison between all previously published dose-rate conversion factors is presented and their Historical Mean (HM) values are calculated. The standard deviation from the HM is introduced as a measure of the fluctuation in individual updates. A selected example is given to show that the use of the HM instead of the present dose-rate conversion factors has a minimal impact on dating calculations performed by the thermoluminescence, the optically stimulated luminescence and the electron spin resonance methods. It is concluded that there is no justification in periodically reviewing the dose-rate conversion factors and thus, the present values can be considered as a revised overview that future dating applications should safely rely upon.