Test Site (Area 15) Both phases of the experiment were conducted at the Nevada Adult cows l system. disposa ed waste y install recentl the of use made Farm and ion of collect total the d for designe ism stalls metabol d were confine to metal urine and feces. The cows were catheterized with an indwelling inflatable urinary catheter. Urine was collected in 20-liter plastic bottles placed at the rear of the stall and connected to the catheter by polyethylene tubing, while a grid-covered pan lined with polyethylene sheeting was used to collect A Hobart mixer was used to mix the fecal collections prior to the feces. sampling. Milk was collected with individual bucket milkers. Blood samples, collected by jugular venipuncture, were taken periodically from Blood collections were centrifuged and the plasma and the adult animals. Packed cells were washed with cells separated using a disposable pipette. physiological saline solution during the preparation process. Calves were kept in.small metabolism stalls located in the same room as the Urine and feces were collected to prevent floor contamination adult cows. Milk but, in the case of the calves, were not analyzed for plutonium content. collected from the plutonium-treated cows was placed in suitable buckets and fed to the calves. During Phase II, milk collected during the period of peak plutonium concentration was refrigerated and saved for subsequent calf feedings. The refrigerated milk was warmed in a modified water bath prior to feeding. In both phases, each calf had an individual plastic feeding bucket to reduce the possibility of cross contamination. DOSE ADMINISTRATION AND SAMPLE ANALYSIS Plutonium-238 was obtained as a dioxide from the Oak Ridge National Laboratory. It was dissolved in concentrated HNO, with a trace of HF before being converted to the citrate form. The doses were calibrated by liquid scintillation counting of the plutonium-238 alpha particles. Radionuclide solutions, approximately 5 ml by volume and 5 to 6 in pH, were administered to the adult cows by jugular venipuncture. The in vitro plutonium- labeled milk, given to the Phase II calves, was prepared by the addition of approximately 5 ml of a plutonium citrate solution per gallon of uncontaminated milk. This tn vitro labeled milk was thoroughly shaken and samples were removed for direct counting to ensure homogeneity and known dosing concentrations. Samples collected throughout the study were analyzed for plutonium-238, based on the 17 keV X ray from the plutonium isotope. All samples were counted in 200-ml aluminum cans using a phoswich detector, containing a thin Nal scintillator, backed by a thick CsI scintillator. Overall measurement error was assessed by considering potential uncertainties in each step of the sampling and analytical scheme. The phoswich detector was energy-calibrated with appropriate plutonium-238 solutions. Checks were also made for gain shifts and changes in efficiency after every 10 samples with an aliquot of the dosing solution. Backgrounds were taken before, during, and after a series of counts to confirm that contamination of the counting chamber had not occurred. To establish differences in counting variability between sample types (milk, 185 \ ao