EXPOSURE INHOMOGENEITY FROM 241AM AND 90SR/90Y SOURCES IN TERMS OF THE EYE LENS MONITORING IN THE NUCLEAR FACILITIES

This article highlights the issues of exposure inhomogeneity that are relative to eye lens monitoring for low-energy photons from 241Am and beta-rays from 90Sr/90Y including a personal protective equipment because eye lens exposure has been concerned more than before due to the proposed reduction of relevant dose limit. These nuclides are common and concerned sources in the nuclear industry. Our previous study presented a quantitative estimation of exposure inhomogeneity, which was applied to simple but typical exposure situations. For the present study, exposure inhomogeneity of 241Am was approximately within a factor of 1.6, implying a more homogeneous situation than expected. Regarding 90Sr/90Y exposure, estimation from both Hp(10) and Hp(0.07) on trunk would lead to an over- or underestimation by a factor of more than 10. In contrast, Hp(3) measurement on trunk will improve by up to a factor of 2. With respect to the personal protective equipment, lead apron and protective glasses are effective for the 60-keV photons for both anterior-posterior and rotational irradiations, while a full-face respirator can reduce the eye lens dose by approximately 17% for 90Sr/90Y betas. As a whole, this study demonstrated that the effect of protective equipment could be effectively incorporated into the homogeneity evaluation.