5 December 1946 MEMORANDUW FOh Maj or General L R Groves Subjeots Underwater Teets of Atomi c Bombs Against N val Vessel 1 fter a disoussion on 30 November 1945 with Colonel warren Commodore Parsons Co nder Rivero and others we came to the preliminary conclusion that an underwater test against l' naval vessels would contain so many IDIijor hau rds that it should J l- j be ruled out at this time The people concerned ith the plan b 1l 0 of carrying out the test against naval v ssels s 'b« to determine hether or not there will be any practical ay to overcome the hazards and permit a test to be made with reasonable safety 2 A lHrge part of the radioactive fission products released by the bomb would get into the water before the ball broke through the surf ce alld the contaminated water might well drift all a Wlirm current toWhrd inhabited islands or aoross shipping lane •• Vessels in the area would pick up considerable contamination in their pumping of salt water There would be a spray covering a lar ge surrounding area hioh would be heavily oontaminated That ould make most difficult the obaerv tions of the test The shiJs th emse lves ould be 90ntaminated through their hulls J I r tfrPd Wo C le If ddAlafjPo All of the above considerations make the underwater test dangerously hazardous and it should not be listed as being feasible at this time 3 4 The above surface test hih more difficult t'u n our dry land Trinity t 8t appears feasible P an iDg should continue for such a test 5 Commodore Parsons has notified Admiral Blandy of the conclUSions Attached is a copy of Commodo re Parson s ' memorandum NIJ - Cl'C 73U039 I n olosure Memo I I Lj ARREU • ' tflajor Genere 1 USA Op06 bg 3 December 1945 TIP ••• RIiI' s From Con modore l'l Parsons TOl Rear Adlniral W H P GUbJect Underwater Tests of Atomic Bombs Against Naval Vessels Blan 1 on 30 November COIIIDOdore Parsol s Commander Rivero and Commander Aphworth attended a discussion held in the ottice ot aJor General Farrell General Oro S' deput7 The occaaion tor the discussion Vlaa the point raised b7 Colonel ¥larren 1I C •• who is t e Jlanhattan District radiologist Colonel Warren having been through the experience ot the New Uex1co tes presented the case against detonation of an atomic bomb under water 2 It may be assumed that approximately fitty percent ot the radioactive tission products released by an atomic bomb would end up in the ocean in the immediate vicinity ot the point of detonation What percentage would be directly transterred to the water and what percentage would later tall in the form ot spra r are ditficult to est1mate but it is certain th t a territic contamination would obtain in this pocket ot water tor e considerable time say three weeks tollowing the detonation One result would be that until measurements showed otherwise ever ship in the target group would be aaswned to be dangerously contaminated Another requirement would be that the location tor the conduct ot the test be chosen to avoid currents which might carry thc contaminated water toward inhabited islands or acrOBS shipping lanes 3 It is probable that the lIanhattan District will take the position that an underwater test against naval vessels should onl y be conducted it the intormation which Yilli be obtained therefrom can be demonstrated to be absolutely vital and obtainable in no other manner The District will insist a130 that radioactive hazards be taken tully into account and that adequate steps be taken to safeguard against these hazards • OECL SS lfllD EO n Gji Sec 31 0 11 A Nt ftt 7 y ' IJ n C i lE 0·08-·9 • 1'1 s Parsons ''' 5'17 f'e us 7I Y'