NATO Advanced Research Workshop on Radiation Safety Problems in the Caspian Region, Baku, Azerbaycan, 11 - 14 Eylül 2003, cilt.41, ss.197-204
Phosphatic fertilizers are manufactured from phosphate ores which contain naturally occurring radionuclides such as U-238 and its daughter products. Large amounts of phosphogypsum. is obtained and has Ra-226. The natural radioactivity was measured by a gamma ray spectrometer. The activity concentration Ra-226 was 465 Bq/kg as a mean value. The natural external gamma radiation dose rate is estimated to be 205 nGy/h at 1 m above ground level when 1-1.5 kg of phosphogypsum is applied in 1 m(2) surface area of field.