- Japan Health Physics Society
- 保健物理 (ISSN:03676110)
- vol.25, no.2, pp.121-128, 1990 (Released:2010-02-25)
A practical conversion factor to estimate the value of effective dose equivalent rate in Sv unit from absorbed dose rate in air in Gy unit was examined for natural gamma radiations. The experimental examination was carried out by two methods; one measures the effective dose equivalent rate directly by using a measuring instrument having effective dose equivalent response for isotropic gamma radiations and the other obtaines it from calculation applying the gamma flux-to-effective dose equivalent factor to actual gamma energy spectrum measured in various indoor and outdoor places.From these investigations the value of the quotient of effective dose equivalent to absorbed dose in air was found do be 0.748±0.007 Sv per Gy for natural radiation exposures in various environments. The value of the quotient 0.7, which is adopted to applied to environmental gamma radiations in the UNSCEAR 1982 and 1988 Reports, was clarified to be about 7% lower than the one obtained experimentally for natural gamma radiations.