OFFICIAL USE ONLY The procedure outlined in NYO-l,617 was followed for the radiochemical analysis of Sr90. The Cs137 analyses were performed by S. Tarras using a method which to date has not been documented. It involves the coprecipitation of cesium with ammonium alum to eliminate mixed fission products as well as potassium, then a final precipitation as the chloroplatinate. ric yields of 95% are attainable. Radiochemical and gravimet- The samples were analyzed for calcium by C. Baxter employing the oxalate-permanganate titration method ‘4) , &s a check on radiochemical purity, beta absorption analyses were carried out by N. Haliden‘>) on the Csl37 fractions of two pooled urine samples (specimens collected at Utirik and Likiep), one water sample (HASL #3457), and one soil (HASL #3462). In each case Csl37 was positively identified and there was no evidence of other interfering isotopés. The radioactive decay of the YO frac- tions of the urine samles was followed over a period of one hundred hours. Within statistical limits concurrence with the theoretical half-life was observed. Analytical results are shown in Tables 2 through 6. The error term accompanying each absolute result represents one standard deviation due to the error in counting. The only available interlaboratory cross—check data are given in Table 7. These