the world-wide fallout of Sr-90 croduced in U. 5S. nuclear detonations. 3. In compiling the data in table 1 of the attached report (Appendix A) consideration was given to the amounts of fission occuring in the various components of the weapon and to the variation of Sr~90 fission yield with weapon type. Thus, the total Sr-90 produced for a specific operations, where yields of all the devices detonated may be released, as unclassified, nanely, Trinity, Japanese bombincss, Crossroads, and Sandstone would show that the Sr~90 production per kiloton of fission yield varied for these tests: From ARC:CLL From Table 1 Average Sr-90/kt curles 27 kt 1.7 63 3.5 85 Fission Yield Trinity Japanese Sr-90 production kilocuries «LL kta Crossroads | O kt 3.3 67 Sandstone 106 kt 12.9 122 Prom data released (18 and 23 kt) From this variation in average rate of Sr-90 production, it would be ‘4 possible to conclude that the devices in these tests were composed of The type of fissionable material used in Trinity, Japanese and Crossroads devices is unclassified. The hy sm different types of fissionable material. higher average rate of Sr-90 production per kiloton yield for the Sandstone St A tests and the known data on Sr-90 production in the fission of U-235 and Pu~239 would indicate that a large part of the yield of the Sandstone devices resulted from fission of U-235. However, it would be impossible on the basis of this information alone to establish the actual proportion of the fissionable material which was Ue235. It is concluded, therefore, that this information does not reveal any classified weapon design information. he oo . a ee an 5, Sel comer . wre . ToeoeSparrirerrs EN, se os . & es i phat + pee RTS Vey ae tee * BETTSme | \ ‘Fe