Cycling of 55Fe and 65Zn in Columbia River carp following reactor shutdown

The decline of 55Fe and 65Zn has been observed in the tissues of Columbia River carp following shutdown of the plutonium production reactors at Hanford, Washington. A model for the decrease in specific activity (activity per gram total element) is tested for carp flesh. The predictions of the model are slightly higher than the specific activities observed, probably because of stable element dilution. Rate of loss of 65Zn appears to follow the order skin>flesh>liver, eggs>heart, while the rate of loss of 55Fe follows the order heart>eggs>flesh>liver, underscoring the fact that each tissue may treat each element in a characteristic manner. Therefore the ability of an organism to free itself of radionuclide contamination will depend on what portion of the organism and what radionuclide is involved. (author)