0018933 contain 1-5% of the weapon for megaton-range detoenations (References 16 46, 47). Determinations of this quantity by 2 world-wide retwork of -stations for shots Mike and King of Operation IVY gave 2 figure cf 2% {Reference 47). Some data on sr?? concertrations in the stratozphere bas been obtained from filter samples collected cn flights of the General Mills high-altitude balloons, This work was part of a continuing program for sampling the stratosphere along the 0th meridizm. (Reference 48), 1.2.7 Fractionation Effects (J}: Observations at Other Tests. The occurrence of fractionztion is manifested by differences in radiochemical compesitien, decay rate cr energy spectra zmong various samples of fallont taken at different times or lecations in the contaminated region, Otsexrvations of some degree of fractHiorzticn have been made at miny different detonztions, Ps As expected, fiszion j roduct nuclides such as sr®?, - Sr we “3ter walt which hzve razv2-gzs ancestors with half-lives of & fraction of a minute or lenger, are frequently found emeng the products which are most severely fractionated with respect to the bulk matrix material, which is always a refractory materiale impertant fector, The location of the burst is also an Separation of the nuclides frem one another appears to be most prenounced in underground or surface shots (References 49%, 50), generally less for a water surface (Reference 51) and still smzller for bzlicon, hiyh tower and air detonations (References 51, 52). Relatively