1990 Volume 39 Issue 8 Pages 357-359
Measurement was made to determine self-dose at Mihoro Dam Tunnel where cosmic-ray was fairly attenuated. The dosimeter with Pb and Sn filter had the same self-dose of 0.26 nCkg-1 h-1 as that without the filter. Our experiment shows that self-dose is due to any traces of natural radioactivity in the phosphor and the packaging. Cosmic-ray dose was evaluated 0.74 nC kg-1h-1 from our experiment at sea surface, and this value was somewhat smaller than the cosmic-ray intensity in Japan. The reason is considered to be low TL response for cosmic-ray hard component.