[en] The annual statistical summaries of occupational exposure at each nuclear power plant in Japan were compiled by reactor types, and the trend of occupational exposure at nuclear power plants was investigated for the years 1970-78. The individual exposure level has been well controlled below the occupational dose limit (5 rem/yr). However, the collective dose (man-rem) has been increasing with plant age, especially in BWRs. Most occupational exposure at nuclear power plants is incurred during maintenance rather than routine operation, so the annual collective dose is in reverse proportion to the plant annual availability. (author)