Distribution of radionuclides in Dardanelle Reservoir sediments

Natural and reactor-discharged gamma-ray emitting radionuclides were measured in Dardanelle Reservoir surface sediments taken near the Arkansas Nuclear One Power Plant site. Samples represented several water depths and particle sizes, at 33 locations, in a field survey conducted in early September 1980. Radionuclide contents of dry sediments ranged as follows: natural radioactivity (40K as well as uranium and thorium decay products) 661-1210 Bq/kg; and reactor discharged radioactivity (137Cs, 134Cs, 60Co,, 58Co, 54Mn), no detectable activity to 237 Bq/kg. In general, radionuclide contents were positively correlated with decreasing sediment particle size. The average external whole-body and skin doses from all measurable reactor-discharged radionuclides were calculated according to the mathematical formula for determining external dose from sediment given by the U.S. Nuclear Regulatory Commission (NRC). Inside the discharge embayment near the reactor discharge canal, the doses were 1.7 X 10(-3) mSv/yr to the whole body and 2.0 X 10(-3) mSv/yr to the skin. Outside this area, the doses were 0.15 X 10(-3) and 0.18 X 10(-3) mSv/yr to the whole body and skin, respectively.