XE-38 as a typical sample, a straight dotted line is fitted by inspection to that part of the curve to the right of the break (see Figure 3). The slope of this line is such that the c/m decrease by one-half in approximately 275 days, the halflife of cel#4 a fission product that would be expected to be present. For the absorption curves, the samples were placed on the first shelf of a sample holder mounted in a lead shield and were counted with a 1.7 mg/cm? RCL end window GM tube and Victoreen scaling circuit. It was necessary to place the sample on the first shelf rather than the second or lower shelves because of the low activities of the samples, The aluminum absorbers were placed directly on top of the plate, i.e., about 0.2 cm. from the sample and less than 1 cm. from the counter, Absorption curves add further evidence that the energy of one of the isotopes present is approximately that of Pr'#4 the daughter of cel44, ent nemaenfin mab bles cote Ph -- Sopece * . . ines g ; iting ine aI + seein ag or ie ee 3SMallet Seal ahd eeTE SY ee i 5 gC: 20 ee a at mee EE Seay”ON : ole Fa 4 ewe mop Be Et RNR o 1 ovine i. absorption curves are plotted for a Bikini bottom sample from the Target Area, = : for a sample of Eniwetok coral sand, and for the most active sample used for r the decay curves - XE 51, a gut sample from a parrotfish collected at Eniwetok : in May, 1948. eH In Figure 4 eer Using sample en is such that the c/m decrease by onehalf in approximately 15 days. “ped Fitting a straight line by inspection to the curves prior to the break, the slope i 1949, followed by a more gradual but regular slope from early 1949 to the present, “ of the curves during the first few months, then a break from late 1948 to early : The general pattern is that of a high slope aay tion regardless of species or tissue. ae PEPree Age Po A By visual inspection, the curves appear similar when comparedsection by sec- © sample collected in August, 1948, 250 yards from the crater on Engebi Island, ay counts of the most highly active samples are shown plus the count of a coral sang ‘ie In Figure 3 the “oe: intermittently since that time up to the present, June, 1950. ne From samples collected near Runit Island in May, 1948, counts have been made sae same Victoreen GM and window tube and Victoreen scaling circuit for all counts, a The samples used for plotting the decay curves were counted with the “ we OFi Adin, Senne ee wo, EE E ee neonate ee pe -26- AECD-3446 The general pattern of the three curves is similar. To the left the steep slope at the very beginning of the curve suggests a weak energy isotope but there are too few points to accurately define its projection upon the abscissa. Since it is possible that some gammais present, the range of the beta particles was determined by a Feather analysis using pe? a pure beta emitter, as a stand- - é ¥ * -