During 1997 environmental external radiation exposure rates were measured along the Columbia River shoreline and at numerous perimeter locations to assess the rate of exposure from Hanford Site operations.
External radiation is defined as radiation originating from a source external to the body.
It is predominately measured by thermoluminescent dosimeters. A dosimeter is a device that is constructed of material that can be analyzed to determine the exposure the material has to ionizing radiation. In 1998, dosimeter results ranged from 71 millirem, average in distant communities, to 93 millirem, average of all shoreline dosimeters. Additional information on external radiation surveillance is available in the Hanford Site 1999 Environmental Report, Section 4.7 .