External radiation

External radiation levels were measured using thermoluminescent dosimeters at all air sampling locations in the Hanford environs. Dosimeters were also used to measure the dose rates along the Columbia River islands and shoreline near the Hanford Site and the immersion dose in Columbia River water upstream and downstream of Hanford liquid effluent discharge points. Measurements during 1980 at the air sampling stations could not distinguish any difference in external dose rates between the perimeter and distant stations. The number of Columbia River Island and Shoreline dose measurement locations was increased during 1980 to include areas with the highest dose rates measured during an extensive radiological survey of the river in 1979. Based on measurements at these locations, the maximum potential increase in radiation dose to recreational users of the river was 3 mrem/yr. The radioactivity causing these dose rates is from pre-1971 operation of production reactors at Hanford