cent or better, Results of analyses on cloud sanples are included to allow comparisons between fallout and cloud material. The cloud samples were portions of filter paper collections made for radiochemical deter~ minations of weapon yield by LASL and UCRL. 5.2.3 Fractionation 5.24 Fission Yield Curves 53 INDUCED ACTIVIT Analyses for Na@4, K42, Mg28, 0138, Np239, 0237, and 0240 were performed on cloud and fallout samples. However, because of the diffi- culty of obtaining early samples only Na@4, Np239, 0237, and U240 were detected. The fallout samples analyzed at the site were aliquoted as described in Section 3.1, The remainder of these samples and tie cloud sanaplss were analyzed at USNEDL. 5.3.1 Radiochemical Procedure Radiochemiceal dete tions were made according to either standard published procedure or those developed at USNRDL. outlined here and described more fully in Appendix A. cedure. They are Na*4 was separated from the gross activity by a two-step pro- First, the alkali metal fraction was separated from the gross activity by ion exchange. Then, Na®4 was isolated by a gravimetric procedure employing the specific precipitation of sodium zinc uranyl 123 4. SECRET — RESTRICTED DATA 142 delefed.