Measurements of individual external exposure doses by electronic pocket dosimeter

For the aim to obtain error factors in the estimation of external dose measured with the electronic pocket dosimeter carried by an individual, the variation of daily doses was examined in an office worker. The voluntary person, living and working in Saitama Prefecture, carried the dosimeter for one month each in May, August, November 2003, and February 2004. One dosimeter each was placed in his bedroom, dinning room of the wooden house and in working place in a ferro-concrete building for 1 week to measure the ambient dose. External doses of other 5 persons, working in the same office as above, were also measured similarly for 1 week as references: two living in wooden houses and three, in the ferro-concrete building. The dosimeter was Aloka PDM-111 (1 cm dose equivalent, 0.01-99.99 μSv) and was read at 9:00 and 21:00 for the daytime, nighttime and daily doses. Mean daily external dose in a month (around 1.4 μSv) was found independent on the season but the daily variation, 50% at maximum. Housing structures were found to change the dose possibly. Measurement for 1 week or more and consideration for the house structure were suggested necessary. (S.I.)