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JOINT TASK FORCE SE’VElf To make a Utter of record operational asCAS!ZEand to analyze the rssultant situationin light of 2. GZ3iEML INFORMATION: OperationCASTLE is planned to consi8tof a series of seven detonationsat the Paoific Proving :s the code m.me that was given the firhg of the first device, Subsequentto BMVO detonationradioactivedebris fell on certati fibited atolls af the northernXarShall ZslaEds. Radiationtitensitiesrose to levels sufficientto warraat evacuationof four atollsand all personnelwere removed from these atollsto KwajeJ.ek in accordancewith the operationalemergenay ment plus 3 USA Signal Ccrps personnel. ( All evacuees are under competentraedicalcare. BEST COPY AVAILABLE
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which are the residue of bomb elements and surfacematerials, soil and water, made radi=ctlve by accompanyingradiationl-l ,.-’, fields. Debris is sucked M@ into the atmosphereby after;> (’-’ tinds of the e~lesion~ Hhera this radioactivedebris will fall is a mjor pm-shot comidaratio~ and pskrily influencesr’ the decisionto detonate a nuclear explosionat a certati time+. The area over vdzichradi=ctive debris is spread aM the intengityof fall-out on the ground are determinedby the yiela & the explosionas well as by wind pattern since the larger the yield, the more surfacematerials are sucked up into the cloud and the more fission fragnents are available. The relationshipbetween yield and fall-out is known oaly qualitatively BRATO experience were planmd and oanceLve& in the li~t of experiencegained from previous operations. These factors ware ( SANDSTONE,GREENIOUSZand IVY and to a oertain extent trom tests at the Nevada Proving Groud. Prior to the firiag of 31UV0, only oae msgatoa yield device (~-ki~) “hadbees detcrated. Although conscientiouseffortswere made to dooument the faUout from q, only abcut SK of the total debris could ever be f The techniqueused for forecastingfallout patk~ terns is to consider the cloud as a small area so~rce (abouta 15 mile radius); then add vectorially foreoas=wiads fmn the surface to approx-tely lQ0,000 fee%. The next step is to outline an area on the groundwhere fallout is expected. This area is cmmputad by taking tito considerationparticle size, Uiffusioutito the atmosphere,wtid patte~, yield and souzce radius+ Such yatterns have been largely ccufimnedby e~eri-’ enae in Nevada as well.es by the meager data available hm?e. was predicte~to be three to five ~egavo~s or one half t~e value of the IVY-HXX”@eLi. The upper Limit of~ leld was consideredto be of the o~der of eight megato~s. ( factor added, iaee, smallerpaStiCleS than previous experience ( from ground zero where fallout was predictedto OCCUX. d. The upwind intensity of radiationlevels at verious distances was consideredto be of the same order of magcitude as for Z7Y-UKE. Radiation versus distance lines were transposedto Bikini Atoll,
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,,. volvos forecastingthe stabilityor lack of stability of the “ (-‘ Tel is determinedprimarilyby the winds at each level, it is , required that winds must be from favorabledirections m nry- ‘L. tig Witti the outer lMts OQ favorabledirections duringthe ttie of fallout. The eritioalfalloutperiod was consideredto be on the order of welve to e@htaea hours for si~iticant fallout to osmr. The variationin time arises f’rom com3LieratiOQ8 of wind shear, with more dirfuseand less significantintensitiesat a given time associatedwith l~ge angular and speed shear. I’oz this reason, it was required that actualwind observatio~sand forecastshmediately betore shot the and throughoutshot day be continuouslyoonsidmed in their relation with the forecast condlzionsYor the first tweaty-tourhours after the shot. the pro-shot coman d briefings: Weather conditionsciuringthe tive days prior to BWLVO indioateda favorabletrend for 5RA.O day with Oasterw above. 2he situationpresentedat H-6 hours for the subsequent 24 hour period (18 hours after shot tire) ws satisfactory-The f 24 hour period to begin 18 hours after shot time was predicted . for the 10,000 to 20,000 toot levels. observedwindB and foracastwiads for H Hour =d the 72 hour ckoud trajectories, which gave a falloutpattern h a narrow sector to the east northeast and a wide (1400) seotor to the Uje\*: Favorable, and the native populated awILs h scatheast the directionof these areas were consideredtoo slow to ~ove significantfallout to the atolls involved. shipsmoved out at least 50 dies.
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(c) Air zoutes through Wake end Kwajalein: favorable. (d) Surface routing inside 500 miles consiP1 “ dered in its relation to all known Wmsieat shipphg: favora. Laok of fellout informationfroa of comparableyield was a serious nmdicap. bable value md mica the probable upper Liait with the result ( that more debris was carried up and Uffased over a much larger petit or a-relatively-$mallarea but must be consideredto be an emu of about a hundred miles in diameter. ~is diameter awo depends on yield- ( d. The radioactivityof the debris can be considered cloud was thus two to three times was was e~eeted. e. An appre~iablefraction of the observed fallout aan only be accountedfor by assundng that It originatedin . observed:i&es, their diemetermst have been in excess of 100 r. Forecast for shot tim winds at shot time was essentiallycorrect. Variation from forecast trajectories wm “ approxhately 10 degrees in significant upper levels; unfor3). The small variations observed at lower levels were also la an unfavor~bledirections Heverthelessjthe accuracy of the wimi observationsthemelves and ware welJ.within the nor- +3” The fallout pattern extended frm the Bikini Atoll to the east northeast. Considerablewidening of the pattern took plaoe due to ditfusion. Tne titensityof zhe
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pattern on the ~und was due Pr-ily to superpositionof ~.. mushrom cloud fallout on the stem c20ud pattera; ead the superposition can be attributed to the narrow cone “Atldn r which the winds were acting. The theory $hat a significant fallout does not come from the stratosphereis not substantiated by the facts of 3RA..O. h. Fo? future high yield shots, the forecast and shoLU4 receive as much emphasis av analysesmade for shot z’ime. with operationalemergeaeyplan and without incident. Ihacuation was net effected prior to detonation because no significant fallout was erpeotedOQ inhabitedareaso Soientlfic Director Xajor Gmeral, W+S. Jumy 4. Tab WAW - Weather 5. Tab JDB*- lla~fe, Nsrmtive Sequeme of Events
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files of Grouad Zero. It was ;oiQt@~ out t-t 3 -w 2 =6 s casts. Snce the winas Shiftad uound to l aurm had to tha ltie approxbately 05 degrees be laid OS. (3) No i~tartarenco 0: tho alr and su-fae9 rauwso at Bti shot ato~.
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1. h gsneral, th UOO, 28 Fobruuy 195& brlofhg l u confimed exeapt iadicatioaswera pmsmtod tbt eondltlms son gettlag less favorable. ad sat, Osrkar
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are as. TM lower leml rumlag from 260 degr$~s ammd t=oq 22 Gles out fru groaaad zero. The M@ level radax aaa tm~
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of the torecast was that thesc atolls shoul~ :e&ala fa~orablo euc to the :mcast long ttie of travel for feU-out to these ;-c-8. south of GZO g. No closuro was reco-nded on ati ~. Task Force SUPS: It was roc-mdcd that, duo to tb cbso prozLdty of Taak Force shtps to tho mtu ldge of the six
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mm Sttipof Contadmtim l Fallout m tho tmsitiu of lYX siUAmcitgms per hour m clas est to the cuber of tbe fdbut pth b by a oeM-reco~ radiatim detection statioa placed them ~ tho Basal upn query fma e$r weather pereonnel l miter w dis~tebd pemaael on his O= hitiatioa sad reco~ccded mseustion of the m mtiaer as soon u pssible Wed UPB the blgh mdiation lmeb. Tbie 95 r. This - is fti agmesmt with madiags of fila b~m m p for 1, Us for 1, @r for 9. Avemge dote for aU p-melt 54 s-
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ationcoqlete 1245 h=, L Laz%h. Esttite of dose b actual evacuation against the fast that such a dose wmld not be a =edicalpmblan it w dad ded sat to evacute the at olL
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~he BRAVO Air Rad Safe Operations were conducted and cre~~s were exposed but the levels encowtered appear lc:e;t-
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appe=s that the .s~osures were wall uier task fmee lQ.2:ati~~ turaed to service well priot to the aefi shot. Tha PZ7 see~”ity sweep sectors will be modified oa futwe shots to reduce tha b. No hazcdous areas or lir coatamUat ioa wwe lac makaitprobable that such coattition tid exist tcr l kart el IXprwed mofitortig, data raportiag aad csualcatlons factiltles era raqulred. do Lower” saareh lltitudes my hprom tha abllit~ te l . NO hazardous fallout appears llksly In the ~wail, Foaapa OT Gu8m ueas.
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IS tha lntke dlmw C*I.S With timtor 8 to satire msultsnt Vector.
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with Isrge quint tties of tisibleperticuhte oatt4rfallfigthmug= W siace tie falkxst problam for surfaceor new shots of kge y:e~d8 x to
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