tQ.measure the postshot wind conditions to aid in construction of a fallout mod@by Project 34.8. Both objectives were completed satisfactorily. 2.5 PROGRAM 40, RADIOBIOLOGICAL SURVEY _The objectives of Program 40 were to determine the amounts and distributio#of radioisotopes in the sea water, soil, and biological material at the test site, in the northern Marshalls, eastern Carolines, and other islands westward to the Palais. Pretest surveys were conducted at Eniwetok and Rongelap Atolls to determine the isotope content and the amounts of residual radioactivity from the previous test programs. During the operation, soil, plants, and animals were collected from the islands of Eniwetok and Bikini Atolls and from the reefs and lagoons for measurement of radioactivity. Emphasis was placed on samples of food, water, plankton, and soil. Selected samples were analyzed for isotopic content. Observations on the rat population at Janet Island, Eniwetok, were continued to evaluate the soil-plant-rat relationship. Tungsten-185, an isotope not previously detected at Eniwetok Atoll, was found on plant leaves (7.9 x 10° d/m/g dry weight) and soil (13 x 10° d/m/in.?) samples from Belle Island, and lower levels were detected at Janet, Vera, Keith, and Henry. The isotope was also present on samples from Bikini, Ujelang, and Rongelap Atolls and on plankton collected nearby (Report UWFL57, 1959). The levels of the other radioisotopes in the same samples were also determined. The U.S. Hydrographic Office, Office of Naval Research, Naval Medical Research Institute, and the Laboratory of Radiation Biology, University of Washington, undertook a cooperative program on shot Wahoo aboard the USS Rehoboth (AGS-50) to measure the amount, kinds, and movement of radio- active materials. The methods used included survey readings, automatic monitoring gear installed on the ship's water systems, a deep water scintillation probe, and radiochemical separations on samples of water, plankton, and fish. The initial survey showed that the major radioactivity in the water extended one mile southeast from target zero 80 min post shot (500 mr/hr) and about 3 miles west within 2 hr. In this area the radioactivity was mostly above the thermocline (100 m). At 48 hr post detonation, the major part of the radioactivity at target zero was below the thermocline. After 34 days the detectable boundaries of the radioactive water mass extended west from target zero at least 50 miles and to a depth of 300 meters. The plankton contained principally Np**, Mo"-Tc®™, Te!-y!%, and u?"_ Present in lesser amounts were Ce!4!-pri4!, Ry3-RAts pal0.p20 ang Zr-Nb®, Fish had essentially the same radioisotope content as the plankton. Shrimp and squid contained Np*™ and Te4*?-1'* but no detectable Mo”-Tc™ (UWFL58, 1959). In order to evaluate the distribution of fallout outside the area of the EPG, measurements were made and samples collected at the weather stations on Ponape, Kusaie, Tarawa, Ujelang, Utirik, Kapingamarangi, and Wotho Atolis. The highest levels of activity were found in samples from Ujelang, Utirtk, Wotho, and Rongelap Atolls. not appreciably above background. The radioactivity at the other sites was 57