Memo for Record, Subject: Bravo Event, Operation Castle (Deleted)

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SUBJEOT: BRAVO Shot, Operatlon CASTLE pects that~onsidered prior to BRAVO event of Operation CASTLE and to analyze the resultant situationin light of GENERAL INFORMATION: OperationCi@Tfi is plaued to consist of a series of seven detonationsat the Pacific Proving ode name that was given the firing of at 0645 M on 1 March 1954, off NaMU I /’ Subsequentto BRAVO detonationradioactivedebris fell .Ra~ation titensitiesrose to levels sufficientto warrant evacuatlon of four atolls and all personnelwere removed from these atolls to Kwajaleb in accordancewith the operationalemergency Plan Or JI!ESEVEN. Areas evacuated and gamma dosages received ment plus 3 USA Signal Corps pers-elo c :4 All evacuees are under competentmedical care.. 3. PREVIOUS EXPERIEiJCE AND CHARACT=ISTICS OF NUCLEAR DETONATIONS: Radioactivedebris is an inherent characteristic of all nuclear detonations~ It originatesfrom fission fragments

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whioh are the residue of bomb elements and surfacematerials, soil and water, made radioactiveby accompanyingradiation fields. Debris is sucked high into the atmosphereby after winds of the explosion. Where this radioactivedebris will fall is a major pm-shot considerationand primarily influences the deoision to detonate a nuclear explosionat a certain time. The area over which radioactivedebris is spread and the intensityof fall-out on the ground sre determinedby the yield of the explosion as well as by wind pattern since the larger the yield, the more surfacematerials are sucked up into the cloud and the more fission fragments are available. The relationshipbetween yield and rail-out is known only qualitatively. BR4V0 experiencewere planned and conceived in the light of experiencegained frcm previous operations. These factors were a. The basis for forecastingwhere fallout will go is eqerience gained from overseas test operationsCROSSROAM, SANDSTONE,GREENHOUSEand IVY and to a certain extent from tests at the Nevada fioving Ground. Prior to the rlring or BRAVO, only one megaton yield device (IVY-M~)”had been detomted. Although conscientiouserforts were made to document the fall- 1 out from m, only about 5% of the total debris could ever be terns is to oonsider the cloud as a small area source (abouta 15 mile radius); then add vectoriallyforecastwinds from the surfaoe to approximately100,000 reet. The next step is to outltie en area on the ground where~falloutis expeoted. This area is oomputed by taking fito considerationpartiole size, diffusiontito the atmosphere,wind pattern, yield and source radiusl Such patterns have been largely oonfinuedby experience in Nevada as well as by the meager data available here. o. The surface radex was plotted, with an insurance factor added, i.e., smaller particles than previous experience . indicatednecessary were considered. This doubled distances from ground zero where fallout was predicted to occur. d. The upwind intensity of radiation levels at various distanceswas mnsldered to be of the same order of magnitude as for IVY-MIKE. Radiation versus distance lines were transposedto Bikini Atoll.

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volves forecastingthe stabilityor lack of stabilityof the wind pattern after shot time. Since radioactiveparticle travel is determinedprtiarily by the tinds at each level, it iS required mat winds must be fra favorable directionsor varYing within the outer limits M favorable directionsduring the time Or fallout. The oritical fallout perio~ was consideredto be on the order of twelve to eighteen hours~’forsignificant fallout to OCCUS. The variation in time arises from considerations of wind shear, with more diffuse and less significantintensitiesat a given time associatedwith large angular and speed shear. For this reason, it was required that actual wind observationsand forecasts immediatelybefore shot time and throughoutshot day be continuouslyconsideredin their relation with the forecast conditionsfor the first twenty-1’ourhours after the shot. 5. PRE-SHCW BRIEFINGS: The following were presented at the pre-shot command briefings: :j Weather oonditions during the five days prior to BRAVO indioateda favorable trend for BRAVO day with easterly winds below 15,.000feet and winds of a southerly oomponent t above. The situationpresented at H-6,hours for the subsequent 24 hour period (18 hours after shot the) was satisfactory.The b 24 hour period to begin 18 hours after shot time was predicted .; to give,an unfavorabletrend as northwest winds were forecast for the 10,000 to 20,000 foot levels. observedwinds and foreoast winds for H Hour and the 72 hour cloud trajectories,which gave a fallout pattern in a narrow “sector to the east northeast and a wide (140°) sector to the south with very slow resultantwinds. (See Figure 1)l (2) Surface radex, H to H plus 6 hours. (See qua rant fmm ground zero favorable, since resultantwtids in the direction of these areas were consideredtoo slow to move significantfallout to the atolls involved. ships moved out at least 50 miles.

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(c) Air routes through Wake and Kwajalein: dered.in its relation to all known transientshipping:favor- (1) High altitude sampltig operations - favorable. (2) Light transmissionfor scientificexpertientsof compar e yield was a serious handicap. . ri at more debris was carried UP end diffused over a much larger L area than was thought possible: o. The original source oannot be consideredas a point or a relatively small area but must be consideredto be 1 an area of about a hundred miles in diameter. This diameter also depends on yield. to yl.eld. Radioactivematerial h the oan only be auoounted for by assuming that It originatedh the stratosphere. For suoh parti.pies~toreaoh the ground at’ observedtimes, their diameter must have been in excess of 100 . miorona. f. Forecast for shot the winds at shot the wa; essentiallyoorreoto Variation from foreoast trajectorieswas 3)* The small variations observed at lower levels were also the winds aloft foreoast approached the limits of accuracy of the wind observationsthemselvesand were well within the normal foreoast error. . 43g. ~~T’hefallout pattern extended from the Bikini Atoll to e east northeast. Considerablewidening of the pattern took plaoe due to diffusion. The titensity of the

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pattern on the ground was due primarily to superpositionof mushro~ oloud fallout on the stem cloud pattern; and the superpositionoan be attributedto the narrow aone within whioh the winds were acting. The theory that a signific~t fallout does not come from the stratosphereis not substantiated by the facts of BRAVO. h. For future high yield shots, the forecast ant ‘ should receive as much emphasis as analyses made for shot ttie.. $27. EVAGUAZTON: Evacuationtook place in accordmce wit erational emergency plan and without incident. Evacuation was not effected prior to detonation because no significant falloutwas expected on inhabitedareas. WEST AVAILABLE COPY

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By the morningof E-1day, the wind pattarns(forecastandactual) marefavorablebutthetrendof theobservedresultintwind ptterns was towardan unfavorableor narginalcondition.No transientshipping was reportedon the B-2 day P2V sweep centeredon a slgnificat foreThe B-1 day search~ P2V out to 375 miles on a forecastsignificant cloud movementon a truebearing of 330°disclosedno transientshi~ outsidethe hazardousarea by shot time. At the midnightbriefing,the thousandfeet). Resultantwinds at about 20,000feet were forecastIn sideredthat the speedsand altitidesdid not warranta conclusiontbst significantquantitiesad levels of debriswould be carriedout so f-. TARE Site was forecastto be well in the fall-outarsa and NAN Site to , be in a fairly high intensityarea. Since the B-1 day forecastsgave night briefingto searchonB day ahead of the cloud, I.e.$ centeredon true bearing of65° out to6M)NM and to warn ships out of the450N?d blems on aix or surfaceroutes exceptsurfaceroutesbetweenZ75° clockwise to 80° out to a radius of 450 NM with possiblesignificantfall-out in this area. Uo lmown shippingwas in the forecastfa12-outarea. The surfaceradexwasforecastfor shot timeto shotplusSIXhourstobe orientedin a narrowseotorto thenortheastanda widesectorto the (F3*es 1 ad 2). The sectorpointingat Rongdlapwas consideredinsignificantdue to the low altitudesfrom which fall-outcould occur and due - to the V- light winds acting on the lebelslnVOIVdC servedin the midnightwinds received,howev~, a radsaferecomnmdation - was made to move the task force shipsradially,furtherout from the minicloudwasforecastto overrunt~e TARE camp and move on to the east with a &rong possibilityof overrdng NAN. The resultantwindspointingat Rongerikand Rongelapw&e light and were not forecastto transportsignificantdetiis to these atolls. At 0645the BRAVO detonationwas accomplishedwithouthazardto task force personnel. The Ixx&er firingparty reportedin safe,but by 0715 the radiationlevelsware reportedrisingat the bunker. These levelscontinued to rise to about 25 r/hr. The firingpsrtywascon-

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sideredto be in a reasonab~ safe positionsincethe personnelwere able to get into a well protectedar% deep in the bunker,reading or Ujclangat ten thousandfeet. The afternoonupwindmissionfor Wilson 2 was a 30 degree sectorout to 500 NM centeredon true bearingof readingswere froai100to 500mr/hrat ten thousaxdfeet. Luring the morningthe B Day P2V sweep in fkont of the cloud encounteredcontamination eariy in his mission. This P2V was replacedby another,which completd the search out to 600 NM. A report was receivedabout 1500 on B Day that the AEC/NYOOinstrument In the.@nds of the weatherdetachmenton Rongerikhad off-scalereport was not viewedwith concernsticetask force ships believedthat Rongerfkawlthetaskforceshipswarecaught in a genepactor)particlesover a wide area mofig ENE to IL TheweatherdKwajaleinFlightABLEwasrequestedat midnightto be runthefollodng north of Kwajalein,axd up to Taongl as the northern-mostturning“point. Aerial readingstaken.on the f13ght me extrapdated to the groud. ‘-- About 2000 the task force commanderwas briefd on the ovemll situationas was known at this time. This Includedthe r eeultsof some lnithl damaged radsafe survqyinformationtaken about noon by hellcop3). The upwhd missionfor lMleon3 was a 30 degreesectorout to 500 vectoredmissionto 17N 163Eto base at Mwetok. The task force tour manderwas advisedthat feirlyheavy contaminantion had been encountered by Wilson 2 in the sectorportionof hls flightand that one F2V aircrtit hadbean contaminatedb about the same region. The task force commanderwasadvisedthat the readingstaken at ten thousandfeet by the cloud tradsersware thoughtto be on the o.rdarof magnitudeof that encounteredby the task force tships.Since the only significantCOP BEST AVAILABLE COPY

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taminatlonwas found in regionswhich confimed the forecastcloudtraAs a result of the reportfrom Rongerik,the advisoryto CINCPACFLT at 2000 hoursB Day includedmentionof fell-outat Rongerikplus minor was attributedto an E@ hour change in the forecastair particletrajectoryfor the twentythousandfoot level. This trajectory,form=ti on BikiniAtoll, as well as danage to structures,would delay reentrysevDuringthe trip back to Uwetok on the night of ElDay, the fleet enoounterd a wide area of finely divided (apparentlyless than 5 micron) ro~iate measureswere institutedby the Navy Task Group Commanderto the ~ affectthat all personnelnot essentialto open deck duties wouldremain Moors. Shipca weatherdoors were closedand the wasMown systemsoperated Intermittentlyto hold down the levels. Bas~ on the advisoryfrom the weatherdetachmentthat theirinstrument was off-suale,the Air Task Group, on the morningof @l day, sent t monitorupon errlvingoverRongerlk,reportedthe atoll contaminatedand requestedpermissionto start evacuationof personnel. At about.1300 the monitorrqorted readingson Rongerikof ~0 mr/hr at 250 feet and 3.2 r/hr one inch off the ground. TheRongerik evacuationwas oompletd in two segmds, the ftist ~oup (8 people) comingout byl#30 hoursand~he (A ptiminary FlightABLE report indiated 1350 nn’/hron the groti at be off Rongelapready to start evacuationat dawn the followingday. A . IBM from xwajaleinto arriveat Rongehp at the same t~ee The SA-16WMJ set up, two responsiblemonitorswere especiallybriefedto make readings at waist height,use severalmetars of the sametype for comparison@ to use differenttypes for cross-check. An avaragereadingof l.br/~ made in the livingarea of Rongelap Islandby thesemonitorswas used in the decisionthe same night to order the destroyerto commenceevacuation operationsat dawn. Wacuation operationsbeginabut W30j 3 ~ch

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removed the remaining17 d proceededto Kwajalein. A totalof 17 males, 20 females,15 boysad 14 girls were removedby destroyerand dlsembarkd at Kwajalein. 16 old and sick ware moved at about 0930 by EBM to Kwajalel.n,Decontaminationof all nativeswaa accomplishedduring the trip to Kwajalein. , 2 March at Ailuk, the nearestpopulatedislandto the south. Bikw, the nearestislandto the north was determinedto be unpqulatei and contannearestislandto north was 1.5 mr/~ and qop~at~. Basedon these l facts a decision was made to startanotherdestroyerto Utirikto anticipatean order to start evacuationat dawn on 4 brch. In the mean- , time R FIBMwas set up to ground survey Uttiik on 3 Mrch while the destroy4rwas on the way. The infinitydose of the Uttifi nativeawas com--’.~ ‘A puted at 58 r. The decialonto evacuatewas made and the destroyeroron the d estrqy~ enroute to Kwajaleinand disembarkedou 5 Wrch. Questioningof nativesdisclosedthat all had been rem~ed. The destrq=s which evacuatulRongelapand Utlrik were directedto obtaindrinkx water samplesfrom these ato~s. A check of the water sam@es indicated j from 2 to 28 times the taak force standardfor full time usage. >.- Withthe decisionto evacuateUtirik made and the machin~ set b motionto acoompliahthis operation,the statusof Ailuk was put up for wasdeterminedat less thn 20 r, 1.e., less than the miti standard usd by the taak fore.for its samplingdrcraft cram. TM was t~ Duringthe ““afternoon-of 2 Marcha directivewas issuadto execu$+e ption that the twentythousandfoot trajectoryCOUM have broughtcontaminationaroundto the south and west and contaminatedsome of the ficantgroud contaminationwas famd. An additionalNYOO type flight was p~formed over the GilbertIslandsfor the Eame reasons. No Si@i-. L) On the basis of FlightsABLE, BAHR and CHARKK, it was determined that no tither atollswould need to be evacuated. The effortWZ16there-

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mr/M at Hplus u hours and which were not e=cuated. For this purpose a specialsurveywas set up under the technicaldirectionof Dr.. SEVEN,to start from Kwajaleinon 5 March by ~M. Followingthe surveyutier Dr. White and Wjor Crea, the next effortwas directedtowardacquiringdata on the evacuatedatollsin ordw that the affectsof the radiationcouldbe bett= emduated. The investigationincludedgroundmonitoringand the taking of soil and water samplesfkom livingareas. Secondarypurposeswere efforta to reiucethe adverseImpacton real and personalpcperty of the hasty departure,to determineradiationdata of scientificinterestand to evaluatethe ttie of reoccupancyby the formerinhabitants.This effort was assignedto a destroyerin order that working~ties would “ have a floatingbase for operationsashoreand decontaminationfacilities dloat. The technicaldirectionof the effortwas placedu.ndm Forces SpecialWeaponsReject, assistedby reyesentativesof CASTLE FToject 2.5a. The rehabilitationportionof the effortwas placed under the eupervisfonof the commandingofficarof thedestroyer. The party with equipmentdeparted7 March for Kwajaleinto join with the Trust Territoryrepresentativeh a FBM rendemnxs with the d+troyer at Rongelapeuly morningof 8 March. .,,”.. ,, Arrangementsw-e made to air ship sotl and water kmmpleato ‘‘ tion Mr. krril Bisenbud. Mr. Eisenlmd was requestedto providethe taskforce with dec~ Mormation and activitypm tit area on the soil samplesand activityper unit volume on the water -lea l . * was also requestedto make such othar analysisas he thought,necessaxy consideringthe unusual circumetenteu and ,interestin BRAVO Event. been distributedseparatelyto interestedagencies. Continuingsweys of the evacuated.atolls have been made for pickingup of animalsfor reed-.” ical studiee,rehabilitationand for studiesof marinelife. Reprts on theseactivitiestill be includedIn the abovedistributionas they beat Cud Briefingsfor BRAVO.

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1. Resultant wind diagram, forecastwinds for HOW Hour. 2. Surface RAIXX: H to H plus 6 hours, bearings, radius, hot areas, cool areas. 3* 72 hour cloud trajectoriesgiven by ~ Officer to adarea; need for penetrationauthority. 4. Air RADEX: Not used at briefing unless requested. Air WEX plotted ~d displayed In RadS~e ‘ffice” Does not basically affect decision. samplingregion given by hodograph h. Surface routas inside 500 miles (approx1 day cloud travel ). plot of transient ship chart at briefing (hodograph) AIL ABOVE ~C3XDED IN CLOUD I!RACEING PLAN 6. Summary: Evaluation as (very favorable) (Favorable)

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Brierings for BRAVO Attached hereto are coples of material presentedto CJTF Briefing for CJTF SEVEN M/R: Final Weather and

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MEMORANDW IUR RECORD: wind9 : Surface, easterly 15 to 20 knots; 10,000, easterly 10 to 15 Lots; 20,000$ easterly 15 to 20 knots; 30,000, southeasterly 15 to 25 knots; 40,000; southerly15 to 25 knots; 50,000, southwesterly10 to 20 knots, 60,000, southeasterly5 to 15 tiR: Compiled by Bonnot, House and Xay&rd.

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Weather outlook as of 270500Z for Bravo day follows: and weather: Scattered cumulus, scattered cirrus, very-widely scattered showers. Wtids: Surface to 15,000 feet; easterly 15 to 20 knots; 15,000 to 25,000 feet, easterly 10 to 15 knots; 25,000 to 30s000 feet, southerly 5 to 10 lmots; 30$000 to …