wee CRLIR - 115 - DECAY OF RADIOACTIVE MIXTURES. Hugh R. Lehman and Robert H. Iynch, 8 April 1952. UNCLASSIFIED (U) The fission of u23? by slow neutrons results in a fission- product rixture that exhibits a distinctive radioactive decay curve, which, short- - as derived by Way and Wigner, approximates a straight line when plotted on log-log graph paper. From curves derived by Hunter and Ballou, it appears that during the decay of such a mixture, the fractional activity of every participant nuclide passes through a maximum value of percentage activity. The purpose of this report was to derive a function predicting the time at which the various fission products "peak", and to explain the deviations from the wWay-Wigner theoretical curve. 1as ate It was demonstrated that a nuclide exhibits a "peak" at a time dependent only on its half-life and on the slope of the log-log relation- ng ship for a particular fission-product mixture. For the cited fission- product mixture, the slope constant is approximately -1.2. Thus, most nuclides will exhibit their fractional activity "peaks" at approximately 1.7 half-lives from the time of formation of the mixture. Whether or not 33 ited a particular nuclide or fission chain will become so prominent during its "peak" thet the mixture will temporarily appear to be a single species depends on several factors (1) possible reinforcement of the “peaking” nuclide by competitors of similar half-lives, (2) the original fission yield of that nuclide, and (3) parent-daughter doubling of the activity when the daughter's half-life is shorter than that of the parent. CRLIR - 126 and - STUDIES ON ARMORED VEHICLES AT OPERATION JANGLE. (WT-402 ) Elmer H. Engquist, 21 April 1952. a> SECRET-RESTRICTED DATA D Tre studies reported here pertain to the protection provided by various types of armored vehicles against airborne, radioactive, particulate material; to the shielding afforded by such vehicles in traversing contaminated areas; to the effectiveness of field decontamination of o these vehicles; and to the protective efficiency of the E26 tank collective protector. Test vehicles were located 2,000 ft from ground zero of the surface anc underground shots, variously positioned with respect to the blasts. To provide comparative data, hatches were closed or open, and the engines were operating or stopped. 54 an ee: GY A oe REST ATO 1S