職業上の被ばくの現状と問題点

Abstract

The dose assessment of radiation workers from external exposure is principally carried out with the aid of personal monitoring device such as film badges or thermoluminescent dosimeters. This paper describes the present status of occupational exposures in Japan on the basis of the data concerning the individual annual cumulative dose equivalent by sex, age-group and type of radiation work which were obtained from a nationwide survey on the occupational exposure in 1978. According to the 1977 report of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the Recommendations of the International Commission on Radiological Protection (ICRP), the collective dose equivalent, the special factor of dose distribution, Ω, and the index of harm for radiation-induced somatic and genetic effects were calculated from the cumulative dose equivalents determined with the personal monitoring devices.In spite of increasing in the number of radiation workers who must be monitored for neutron exposure, the collective dose equivalent of neutrons was negligibly small compared with the X and gamma-ray dose equivalent. In Japan, the NTA film badges are commonly used as the personnel neutron dosimeters for radiation-protection purposes. The problem of personnel neutron monitoring is discussed in this paper, together with the determination of quality factor. Also, this paper reviews a few problems in the determination of the effective dose equivalent and dose equivalent index.