Plutonium Behavior Plutonium in debris from nuclear devices is the result of neutron capture by 238y, is derived from plutonium present in the fuel, or is derived from both. In the first case, the dependence of the plutonium concentration on the particle size is determined by the behavior of uranium (233y has a half-life of about 23 minutes). Therefore, we must discuss both uranium and plutonium behavior in order to enlighten ourselves with regard to the particulate properties of the contamination at NTS. We refer to the statements made and conclusions reached by Russell (1966) on the basis of work by himself (Russell, 1965) and others, such as Freiling (196la, 1961b, 1963), Freiling and Rainey (1963), Freiling et al. (1964a), Stevenson (1957), Lane (1964), and Miskel and Bonner (1964). The data used had been obtained almost exclusively by the radiochemical analysis of cloud and fallout samples without detailed size separation. The order of increasing refractivity (or decreasing volatility) has been established to be approximately as follows: 137¢5, 89cr, 136¢g, 14 Opa, L4lce, diy, 156Ey, 1617p, I57r, 115¢q, 93Mo, 3727r, 2371), 147nq, 1llag, 239py, 90sr, L43py, 131y, 144 Ce, 132Te, 237y, 153sm, 2374 Differences in the rankings between airbursts, tower bursts, and surface bursts are small. The behavior of %!y and the following nuclides is essentially refractory. Thus, 239pu (when present ab initio) behaves refractorily in about the same manner as l4/Nq or the latter's daughter, 147pm. The behavior of 239, the 233Pu precursor, is, of course, the same as that of *37U (formed by an (n,2n) reaction of 238y). This nuclide, 237y, is listed more than once in the volatility rankings, because its behavior appears to be dependent on the substrate over which or in which the shot is fired. The data and correlations examined by Russell (1966) have indicated that uranium behaves like a refractory element in coral surface and water surface bursts. For bursts on silicate, for which at the time of Russell's analysis, only data from lowyield (< 1.7 kt) shots were available, uranium behaves more volatile than ?°Zr. In Jangle S and Jangle U, the behavior was less volatile than !4%Ra, lllag, 115cq, and 89Sr. In Johnie Boy (Clark et al., 1963) and in Small Boy (Freiling et al., 1964b), uranium is similar to that of !4%Ba. the volatile character of From these observations, it would appear, then, that at the Nevada Test Site, the plutonium behavior as a function of the particles can be expected to be like a nuclide of intermediate volatility such as 140Ra, when the plutonium is exclusively present as an induced activity; like a refractory nuclide such as 147Nd@ (or 147Pm) when the plutonium was 562