- ~~ UNCLASSIFIED of the fall-out comes from the stem, ‘The information available fram the fall-out of T/S tower shots is not sufficiently detailed for this type ef analysis, but it appears that for lesser KT tower shots (10 ET) the soil in the stem remains relatively inactiv;, and most of the fall-ent comes from the sand mixed in with the mustreom of the cleud. ‘Therefore dein for T/S Test Operation the Py/Ps rat’. may be 2 or 3. If the ratio of Py/P, continues to decrease with decreasing scaled height then fer a we i surface shot a large percentage of the activity will be in the soil within the stem rather than the seil in the mushreom. Attention is invited to the relative constancy of the P,/P, ratio for 0/K towr shota, This type of constancy tends to increase ene's confidence in the fall-out picture indicated in this report and in the air readings utilized to delineate the centaminated area, During T/3 tower shots approximately 15% of the total residual activity of the bemb fell out within six hours over an area ef 5000 te 10,000 square miles, 5% coming from the stem and 10% from the mushroom. During the tower shots of 0/K the average percentage fall-sut appears to be 20%, 15% coming from the stem, 5% from the mashroem, According to Reference #9, 50% of the total activity of Trinity was deposited immediately dowmwind (23 XT, shot from a 200 ft tewer). However, it is not clear how complete the study ef fall-out was during the Trinity explosion. There is sexe evidence that altheugh an attempt was made to delineate the fall-~ent quite accurately some years after the Trinity explosion, the fall-out pattern was not studied in teo great a detail on the day of the shot is Ad C3 ae fu UNCL ASSI FIED 27