INTER-Of f ICE MEMORANDUM _ DATE Kr •• E Br u rJ' TO w 17 December 1945 r ··· FINAL' DETERl INA TIOH - - _• I •• -I I NCttASm lEO i ·i i svF'i'sS R a FROM H Dl J' SUBJECT Possible Difficulties in Naval 'feats- llew11on __ L M RedmoD UEC 211982 V 0120851 Radiation Slick Sinoe we now know very little about the probable distribution of t'ission products in aea- water - we must e8't1 mafi ·th'e·ir· dis Let us assume that all the fission tri ution_pessimisticall7 pro6LJ cts are capt ed b R water warmed 1 the b mb explosion under water and are- carried to the surface and spread uni t'orml 7 It' no self absorption occurs we will have a situation similar to the Trinity crater basis of the plutonium captured l Rough calculatlons made on the re overy the e ot the fission products indicate that the crates To maintain our pessi• mistic outlook let us consider the aeriousl7 contaminated area increased by a t'actor of ten This gives us a region about a half mile in radius which would irradiate a man at about 1051 a few lours_ after the s t_ i _ he should cross the region at untrorm speed along ita diameter This i• 107 times the tolerance level ·1t mixing occurred ao that the fission pro ducts were un1 torm ly distributed 1n a layer one meter thick the dosage rate would decrease by a factor ot ten based on formulas b7 Morrison in Chap v or The Chicago Handbook I and mixing to a greater depth would decrease the e ffeote in proportion to the 4epth RG 326 us ATo mc E 'ERGY COMMl§S f l' LoC14tion L£ 'H l C- l D- r 1i COPIED DOE Colleeti nllecqy s c Jfsc lANl RC Fol ler 310 1 ss- r y 7clf Form Z Thus unl torm mixing to a depth ot CONFIRMED TO BE BY 'UTHORllY INC SSIFlED 0100£ 0 -L 4' IS r 3 oc C W1 11VlfWH IY llA'Q l IJu tt 1 2 1' 7 1000 m nearl1 to the bottom would reduce the radiation level to l This level is still too high for an1 kind ot sustained activity and the assumptions are no longer ver7 pessimistic since it bas been assumed that the surface water is no more contaminated than that at a depth Induced radio- activities such as 30 min Cl and 14 hr Na may make the situation appreciably worse tor times not long after the shot While it is unsafe to assume that water will not rise to the surface it is quite possible that clean water will be carried in by wind or current The thickness of this layer to give full protection need be only 2 or 3 meters-tor protection actors of io4 and 106 respectively might be obtained by a or 12 inches The same reductions or steel Unless it can be shown fairly conclusively that none or the contaminated water will reach the surface difficult7 may be anticipated in boarding and inspecting test ships which have not been sunk by the explosion The test ships should be so disposed as to take every possible advantage ot wind and current which might wash at least the top layer ot contaminated water away trom them The same difficulty is tar more likely in the case of a surface explosion Here the ball of fire will roll over the sea to a radius comparable to that at TrinitJ and the fission COPIED DOE LANL RC products will undoubtedl1 be apread even farther by the large waves generated b7 the explosion As was pointed out before surface mixing will not reduce the dosage by a great deal It the ball of tire should actually touch a test ship and that ship survive it might not he possible to board it for days Paint melted by the radiation would be en excellent collector of fission products delivered either by the ball of fire or a dust cloud It the bomb were dropped from a plane no very important deposit of tission products would occur 1t it exploded 1000 feet or more in the air Japanese experience However should the ballot fire touch ships or water the same effects could be expected on a lesser scale Induced radioactivity will in general be much less of a nuisance than fission products Its effect may predominate for a high drop but it will be much less serious than fission products are in the other types of test Furthermore it may be pre- dicted tairl1 accuratel1 from a tew simple experiments The activation of the steel bulls ot ships will probably cause trouble for no more than 24 hours A piece ot reinforcement iron taken trom the base of the Trinity tower showed no activit1 about three weeks atter the shot The 2 4 hour manganese activity ia by tar the most prominent effect in iron bombarded by slow neutron The most intense fast reaction induced periods are even shorter CCP E O OOE LJ NL RC · The air and surface explosions will certainl7 give rise to clouds ot tission products which are def 1nitel7 dangerous Witness the hast1 retreat from N 10 000 at Trinit7 Thia should be handled b1 earetul study of the wind at all altitudes • IJo observer or any other human being should be alee of the explosion In addition onl7 fast vessels should be ·near so that they may outrun a sudden shift of the cloud Planes with - sealed cabins should be able to maneuver rather freely over the whole region The water near a recent surface explosion will be a witch's brew tests and this will be true to a lesser extent tor the other There will probably be enough plutonium near the surface to poison the combined armed forces or the United State at their highest wartime strength will be worse The fission products The probable number ot fish casulaties 1n addition to those caused by the explosion can probablJ be caleuleted when more is known about the probable mixing conditions and the fish population Considerable study ot this general problem has been made in connection with the Hanford and Clinton Plants Effects ot the Actual Explosion The protection ot personnel from the effects ot the actual explosion is relativel1 simple We know from the Japanese experience that an unprotected man two miles from the bomb -4COPIED DOE LANL RC D is tairl1 sare trom all ettects except the tl7ing debris ot I flimsy structures Special precautions could shorten this distance but the uninvestigated ettects - water shock waves untavorable distribution of radioactivit7 ·'etc - would make - an1 such procedure foolhardy Unless there are very compelling reasons no man should be within tive milvs ot the explosion and the bulk ot the personnel should be much farther However it might be well to populate the test ships which seem likely to survive the explosion with experimental animals Thia would be a considerable undertaking 1t the results ot the experiment were to simulate the ettect of radiations on the crew The protection ot experimental equipment located on test shipa particularly photographic plates will be very difficult and special calculations will be necessary tor each case Henry BWN cl cc w Newson N E Bradbury Roger s Warner Jr John Williams -5- COPIED DOE LANL RC -------------- IL - -···-··