0012933 value in fallout must be measured. Then: y= [n99%Cx] g - RPCpp [R99(zy 5 - [299(x) po This formula can be derived by algebraic operations from the definitions of the R-values (see Appendix E). If, despite the fact that it is incorrect, the R value for Y in fallout is assumed to be zero, the above equation reduces to the expressior for a gas and y becomes the upper limiting value for the fraction of Mo?? (or refractory debris) left in the region sampled. Fission products such as Sr89 and Cs137 (to a somewhat lesser extent sr?) appear to behave very much like Kr88 in Koa, Walnut, and Oak events and may be used to estimate fractional fallout of refractory debris or upper limits to the fraction remaining aloft. The disadvantage of using sr®9 or ¢s13? for this purpose is that R valves must be measured in fallout and are not necessarily constant. The chief advantage is that the analyses may be extended to longer times since the half-lives are long and a sufficient sample may be obtained by simply filtering more air. Values heave been calculated in the above manner and are given in Table 3.7-