PREFACE At the conclusion of a conference on the long-term effects of atomic weapons, held at The RAND Corporation, Santa Monica, California, in 1953, a classified report, R-251-AEC, was prepared. Along thelines sug- gested by this conference a concerted effort, under the name of Project SUNSHINE, developed to evaluate the long-term effects. Since R-251-AEC has formed the basis of many subsequent studies, it was felt desirable to issue an unclassified version of this report. As presented here, the report has some deletions and changes, but differs little from the original 1953 version. This report should be read in the context of the state of knowledge of the SUNSHINE problem asit existed in 1953. It is presented as anhistorical document. The changes in some of the physical constants should be particularly noted. When the calculations in Chapter 5 and othersections of the report were made, it was believed that the half-life of strontium 90 (Sr°°) was 19.9 years. A more recent and better value seems to be 27.7 years.” This value combined with a new value for the fission yield of Sr°° gives the basic result that approximately ¢wo megatons of fission will produce 1 millicurie (mc) of Sr°’/mi’, if the fission products are uniformly distributed over the earth's surface.* This should be contrasted with the early (1953) correspondence of one megaton resulting in 1 mc of S1°°/mi’. To preserve the perspective of this report, the original data stand un- regarding half-life and fission yield should heso desire. It should be noted that the effect of a greater half-life and a smaller fission yteld will be to *D. M. Wiles and R. H. Tomlinson, “Half-Life of Strontium 90," Can. J. Phys., Vol. 33, 1955, pp. 133-137. TW. F. Libby, “Radioactive Strontium Fallout,” Proc. Nat. Acad. Sci., Vol, 42, June, 1956, pp. 365-390. iti