[en] As a prelude to in-situ measurements of gamma exposure rates from reactor plumes, baseline terrestrial gamma-ray surveys have been run at five preoperational nuclear power stations: Fort St. Vrain, California; Fort Calhoun, Nebraska; Cooper Nuclear Station, Nebraska; Rancho Seco, California, and Diablo Canyon, Colorado. A pressurized ion chamber was used to measure the total exposure from cosmic rays and terrestrial radionuclides. A portable Ge(Li) spectrometer was used to make in-situ measurements of the radionuclide soil concentrations and of the individual external gamma exposure rates at the TLD sites. Subsequent measurements after start-up will enable accurate determinations of deposition and buildup of reactor produced fission products to be made. The application of the in-situ Ge(Li) spectrometer for real-time plume dose measurements is being investigated. (U.S.)