3. Eu™, y*!, and Ce’ were measured-by a cation exchange procedure after preliminary separation of the rare-earth group by precipitation reactions and anion exchange (Reference 75). 4. Ca“ was separated by 2 procedure using precipitation reactions. Barium and strontium were removed by precipitation as the nitrates, using fuming HNO, under controlled conditions. The calcium was recovered from the nitric acid solution by precipitation as the sulfate. The sulfate was then dissolved, scavenged twice with zirconium, tellurium, tron and lanthanum hydroxidea, once with basic molybdenum and cadmium sulfides and once with acidic molybdenum and cadmium sulfides. Calcium was precipitated as the oxalate for mounting and counting. 5. Sr** and Sr™® were originally separated by precipitation procedures (References 76 and 77). For the determination of Sr, the Y” was allowed to grow into equilibrium, the SrCO, precipitate dissolved in HNO, containing Y carrier, Y (OH); precipitated with ammonia gas, and the Sr removed as the nitrate tn fuming nitric acid. The Y was precipitated as the oxalate from an acetic acid solution in the pH range 3 to 5 and ignited to the oxide for mounting and counting. 6. The cesium procedure used for the determination of Ca! and Cs" was a modification by the original author of a precipitation and ion exchange procedure (Reference 78). The modification consisted mainly of a cesium tetraphenyl boron precipitation in the presence of EDTA, the use of Dowex-50 in place of Duolite C-3 in the cation exchange step, and the addition of an anion exchange step. The radiochemical work reported as being done at LASL was performed in conjunction with diagnostic measurements on the events. The methods used were those reported in the LASL compilation of radiochemical procedures (Reference 79), The gas samples were analyzed for Kr", Kr**, Kr**™, and in some cases for Xe", The rare-gas radionuclides were separated from the constituents of the atmosphere and then counted in a gas counter. The separation procedure used was developed at UCRL, under the direction of Dr. Floyd Momyer. Carrier amounts of inactive krypton and xenon were added to the alr sample, and the mixture was pumped through a series of traps for purificaticn purposes. Water and carbon dioxide were condensed out in the first trap, which was filled with tnert packing and held at liquid nitrogen temperature. The krypton and xenon were absorbed on activated charcoal in a second trap, also immersed in liquid nitrogen, but the major part of the nitrogen molecules, oxygen molecules and argon passed through the trap and were removed. Residual air was desorbed at —80°C and the krypton desorbed by subsequent warming to 10°C. Further purification was effected by two more absorption-desorption cycles on charcoal. After determination of the pure krypton yield, it was transferred to the gaa counter. This was the procedure used when krypton alone was the desired product; additional purification steps were necessary when xenon was also determined. 2.6 DATA REDUCTION The analytical results were computed in the normal mannerfor the elemental analyses done for the project. However, the first and more time-consuming phases of the data reduction were carried out on the IBM 650 computer at UCRL. The radiochemical data was manually tran- scribed to [IBM cards in the proper form for use by the computer, which was coded to apply a least-squares fit to tlie decay data and to make corrections for chemical yield, radioactive decay, and the aliquot of the sample used. The output of the computer gave the counting rates for the individual radionuclides at zero time of the shots. Further computation was performed by hand to obtain the number of fissions, product-tofission ratios, or R-values. Determination of the R-values, defined in Section 1.2.1, required calibration values on fission products from the thermal neutron fission of U*"5, When these were not avallable, or only recently obtained, comparison analyses between LASL and NRDL provided the necessary factors. 28