THE IMPACT ON THE EYE LENS OF RADIATION EMITTED BY NATURAL RADIONUCLIDES (LEAD-210) PRESENT IN RADIATION PROTECTION GLASSES.

ABSTRACT

Most radiation protection items made from modern lead contain 210Pb. This study estimated the impact on eye lens of radiation derived from the 210Pb in three types of radiation protection glasses. The counts from the glasses were measured using a Geiger-Müeller survey meter. The net count rate was 92 ± 1 cpm at a distance of 0.5 cm for one type of glasses. Additionally, we conducted a qualitative γ-ray spectrum analysis using a high-purity germanium semiconductor detector. The absorbed dose in the eye lens was related to 210Pb and its daughter radionuclide, 210Bi; this dose was calculated by applying dose conversion coefficients provided by the International Commission on Radiological Protection. The absorbed dose rate in eye lens was conservatively calculated to be on the order of 10 nGy/h for the type of glasses containing the most 210Pb. The dose from ß-rays accounted for >99%. In addition, we investigated the dose-reduction effect using a thin acrylic plate. The count rate approximately decreased to background level by inserting a plate with a thickness of 1 mm. We conclude that the impact of 210Pb contained in radiation protection glasses is negligibly small, particularly considering the usefulness of the significant external exposure reduction.