BEST AVAILABLE COPY BEST AVAILABLE COPY BEST AVAILABLE COPY BEST AVAILABLE COPY BEST AVAILABLE COPY BEST AVAILABLE COPY Page 2 will be subject to the thermal currents produced by the fires Some particularly the finest particles in the lower half of the spherical ball of fire will be drawn upward by the negative blast wave and follow in the up-draft of the rising cloud without ever reaching the ground Since less dust will be available in the cloud and its column of up-draft it seems reasonable to expect less chance for agglomeration and absorption of active material on dust and other particles large enough to fall out of the cloud rapidly Thus it is not unlikely that a high detonation level may result in a less active deposit in the devastated area per unit of area and likewise less along the path of the cloud than was the case in Test II It is probable that a greater proportion of the active material particularly if the majority of it is in very fine particles may stay up in the air and not settle out quickly or even for long periods of time If they come in contact with moisture and not as a focus for drop formation or rain passes through the cloud the active material may be brought down to the ground 8 The presence of a strong inversion at 20 000 ft or several inversions at and below 20 000 ft with humidities below 60 % are that sic by Dr Hirschfelder sufficient to stop the rise of the cloud at the strongest inversion level The high humidity over 80% and the lack of an inversion up to 40 000 ft are that to be the reasons favoring the height attained by Test II It is this office’s opinion that this subject needs more elaboration and study before any definite predictions as to elevation can be made This is particularly so if it is desired to find the proper conditions which might hold the cloud down to levels from which it can be precipitated with rain or to avoid its precipitation by rain 9 Preliminary analysis of active materials found on the ground after Test II indicates that about 25% are water soluble Thus a rain would dissolve some of the active material on the ground and mechanical washing would tend to carry it into the soil along with the water Actual experience with sandy soil has shown a reduction of 2 3 following a thunder shower 10 The wind tends to drift “active” dust into hollows and crevices 11 The intensity of the gamma radiation in a vehicle a sedan or carry-all is about ¾ that measured on the ground 12 Simple dust filter masks covering only the nose and mouth appear to furnish adequate protection for several hours against inhaling active dust raised by wind and passing vehicles 13 The doesy rate is apparently somewhat more rapid than anticipated is less than K T so that delays for safety from exposure to high intensity will be less than those formerly considered 14 Oiled or dirt roads suffered little damage from the blast until they neared the crater area in Test II Page 3 15 Certain conditions may be suitable for the use of gadget as an assault weapon a A strong steady wind essentially perpendicular to the line and in the direction of the assault The wind should be in the same or the higher the velocity the better to dilute any activity which might fall out near the devastated area and carry it into the back country particularly if that part of the back country were of no tactical value b A rain to wash the active material into the natural drainage unless this would handicap maneuvers or put out fires which might have other advantages c Immediate advance of armored vehicles through the right and left margins of the devastated area These vehicles could be in readiness about 10 miles away The drivers should be protected by welder’s goggles against the flash and all personnel should be equipped with the simple masks The front vehicles would be accompanied by monitors who would try to find the best path through the one or two miles of marginal safety through the edge of the devasted area This would probably be through the burning zone also This zone might have intensities as low as 10 to 50 r hr by the time it was being used The terrain wind vegetation etc would influence the local intensities The presence of roads or lack of roads would be a large factor in the time spent and thus the dose received in passing through the critical area 16 The gadget would produce a large tidal wave in a restricted harbor This would be very effective on a low coral island harbor The intense wave action might prevent or wash off the deposit of two active materials on the land portions so that occupancy might be possible shortly thereafter 17 Recently dug deep slit trenches would offer a great deal of protection to the occupant 18 The following is an over-simplified table of probabilities for normal active troops Limit of Safety Acute exposure within 1-24 hrs Prolonged exposure 1 week Prolonged Exposure 2 week Some blood changes 30 r 60 r 60 r 25% weak in 2 days till recover 50 r 75 r 100 r 50% weak 75 r 100 r 150 r 75% weak 100 r 150 r 200 r 200 r 250 r 300 r 25% permanent damage 50% permanent damage 100% weak Stafford L Warren Colonel Chief of Medical Section