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UNITED STATES ATOMIC ENERGY G“OMMISSION NEW YORK ‘OPERATIONS OF FIGE (Sig of second reviewdr, title, organizdtiorf, date) -
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New York Op~ratiom Office This documnt containsrestricte~d~ta as Its trmsmitbd. or the disclosureof its
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Effectsof Atomic Weapons Commander,Joint Task Force Seven Departmnt of the Navy (For CINCPAC) USAF, Officefor Atomic Energy,AlXlAT-l
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LET OF FIGURES Gamma Falloutat Majum: BRA~ bum Falloutat Truk: “ at Majiro: II an at Xwjalelm UNIQN AND YANKEE at Ponape: YANEEE Beta Dust Concentrationat Ujelang8lWkEG AerialSurveyMeaswemmlts: BRAVO and ROMEO Beta Dust Per Square Foot m Gamma Mwnsiw at Responseof Survey InstrumentsOver Energy
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LIST OF TABLES I Cumulative Doses by Event and Location 37 II Peak Gamma Intensityby Event and Location 39
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DuringCASTLE,an offsite monitoringpogram was conductedin the Central and SouthwestPacificto documentand to providecurrentmeasurementsof after its presencehad been detectedby automaticgammamonitors. Eleven of these were collectinga continuousrecordon selectedatollsin the Marshall,Caroline,and Mariana Islands. Air surveymeasuremmts were ~mverted to groundintensitiesimmediatelyupon receiptby means of suitable curves,permittingappraisalof the radiologicalsituationover a widespreadarea. Atiliary stationsprovidingdaily gamma measurements were locatedbeyondthe networkof automaticstations. directmeasurements,for all islandsin the automaticnetworkand for islandswithin the two aerial surveypatternseast of Bikiniin the BRAVO accountedfor 89% of the total cumulativeradiationmeasuredduring the program. The greatestradiationrate, extrapolatedfrom directmeasurewnts, 12.5 r/hr, occurredat Rongelapafter BRAVO. Valuesboth greater and lesserthan this probablyoccurredat variousislandsin the Rongelap atoll. The greatestestimatedcumulativeradiationoccurringfrom any event until the next followingwas 190 r at RongerikafterBRAVO. The total cumulativeradiationat Rongerikwas 206 r. The monitoringmethod combinedfixed continuoutistationsand aerialsurveys. The advantagesof each mthod was utilizedso that they were complementary. Rapid, accurateinformationabout radioactivefalloutwas providedby a means which probablyrepresentsthe maximumin economyfor such extensive was demonstratedto be a dependable very Portablejfacileinstrumer.tf’fl
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Pur ose. At the requestof CINCPACFLTthe Health and Safety a programto documentradioactivefalloutfrom CASTLEin the Central and SouthwestPacific,exclusiveof the provinggrounds. Current falloutinformtion was to be made availableto CINCPACFLTfollowing each detonation. w programwas to be ~atterredbasicallyon the NYOO monitoringsystemdevelopedfor IW: The informationderivedwas used in the imumiiateestimationof radiotutes a recordof cumulativeradiationproducedduring the test series. 2. Or anization. The xmitoring programwas plannedand directedby tivelysupportedby severalagencies. HASL organizedtie -tio~ of the participatingagencies$developedprocedures,ad furnishedall mdtoring instrumentsemployed. The Director,Health and Safety brationand maintenancein the forwardarea was perfor=d by the HASL staff. Joint Task Force-7Headquartersprovidedlogisticsupportand made availablecommunicationsfacilitiesin the forwardarea. The Instrumentmonitoringprogramconsistedof the followingoperationServiceoperatedfixed automaticgamma monitoringstationson sites selectedbasicallyto createa uniformlydistributedpatternrelative +~ the test area. The availabilityof facilitiesfor the operation of monitoringequipmentwas a factorwhich limi$edthe number of atclls which couldbe ltilized. Uniformdistributionwas reasonablywell
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The nature of the automaticInstmments was such that very little attexxtionwas requiredduringnorml operation. The functionof the stationpersonnelwas to read and transmitthe indicatedradiation data. Exceptfor a simplebriefingsnone of the personnelwere pre- @rained in the use of these instrumentsnor in the field of radiaThe sites as originallyestablished *ujelang was unattended. Data was AFOAT-1operatedsix audliary stationsin more remotelocations which were eqpippedwith portableGeiger-Muellersurveyinstruments? The six locationswere: JohnstonIslandAl?%to interceptthe BRAVO cloudbelievedto be travellngeast from the f.,rwardarea. This was replacedby an automatic mmitor rennvedfrom ~hat site. Johnstonwas the only location east of BilcLniand approfimacelyin the saxm latitudeas Rongerikwith facilitiesfor mmitor operation.
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The locationsof all the instrumnt monitoringstatiom are plotted Three Navy patrol squadronswere assignedto aecute aerialsurvey groupsaccordingto the followingpatterns:
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1 Oahu 1 Midway 1 Oahu 2 Midway (over 2 Oahu (over 2 Lanai chain) chain) 5 Molokai
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The programwas an integrationof two principlesof monitoring. The first was a networkof ftied monitoringstationsreportingdata regularly to the Task Force. The secondconsistedof aerialmmitori.ng flightsby Navy patrol squadxonaircraftover specifiedislandsfolGeneralDescription. The fixed networkinitiallyconsistedof eighteen ana Ishnds but exterdingto the Philippines,Japan,Hawaii,and Alaska. The numberand locationof the sites were somewhatmwiifiedin the courseof the test series. The Stations,with one exceptionwere manned,and reportsof gamnaradiationwere transmittedregularlyto the task torte at six, twelve,or twenty-fourhour intervalsdepending on their positionsrelativeto the provinggrounds. The twelvestations wit’in1S00 nautical.miles of the provinggroundswere equipped with 110 v AC automaticcontinuouslyrecordinggammamonitor~ having was placedon one island (Ujelang)where facilitiesfor a mannedstation were unavailable.Data was recoveredfrom this stationafter Six remotestationsbeyond 1S00 miles were providedwith portableGM measurementsof localgamma activitywere transmittedonce a day from these stationsto the task force. Data was transmittedby administrativeteletypemessagesfrom allbu$ four stationswhichwere weatherobservationposts maintainedby ‘he tine data transmissionsto the task force weathercentral.
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The gammaintensityat each of the automaticstations(exceptUjelang) was recordedat 0600$ 1200, 1800, and 2400 Z daily by residentoperati43 personneland transmittedto the HASL representativeat Task Force The instrumentswere routinelycheckedeach day for properradiation response. This test,which consistedin observingthe meter response to a low intensitybutton sourceplacednear the GM tube,provideda means of detectingcircuitfailures. Two HASL technicians,at Guam and Kuajalein,vis”itedthe monitoringstationsperiodicallyto adjust calibrationand ta effectrepairsas require& Many of the monitoringunits inst~led were designedto recordthe beta dust concentrationcontinuouslyas well as gammaradiation Unfortunately,all of the beta channelsfailedas a resultof various mechanicaland electricaldifficultiesafter short periodsof operation. Twice daily,the groundgamma intensitywas measuredwith the portable were obtainedby scanninga smallgroundarea from a heightof three feet. Meterreadings of less thanO.OS’mr/hrwere attributedto backgroundradiationand were reportedas negativevalues. Data was transThe instrumentswere tested each day for correctoperationandradiation responsein a manner similarto that employedfor the automatic monitors. Faulty instrumentswere replacedafter notificationof NYOO Receiptand Utilizationof fixed NetworkData. Radiationintensity reportswere tabulatedchronologicallyby locationas theywere receivedat the Task Force Headquarters.When a reportedincrease‘Jas indicativeaf significantfallout,a surveyflightover a pattern which includedthe islandfrom which the reportoriginatedwas requestedof the appropriatepatrolsquadron. mom the reportreceived upon completionof the surveyflight,a comprehensivepresentationof falloutintensitieswithin the selectedpatternwas made availableto the task force radsafeofficerand other interestedtask force personnei. In addition,the continuedtransmissionof radiationdata from the moniposureat these locations. Weekly summariesof cumulativeexposures were tabulatedfor each st..tion.
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C~neralDescription.Aerial surveyswere conductedby Navy patrol Surveyflightswere made over pre-determinedpatternsdesignedto achieve ITEKLmUmcoveragein selectedareas. The patternsincluded transmittedto the task force occasionallyfrcr,surveyaircraftin flightbut more generallyfrom the squadronbase at the conclusion of each flight. Operation. The scintameterswere operatedin fl.igh~by aircraft crew memberstrainedin their use. Usuallytwo instrumentswere carried,one reservedas a sparee The scintameteroperatorrecorded each islandin the surveypattern. Backgroundwas measuredduring the approachto each isltandat a distanceof severalmiles. These data were transnd.ttedto Task Force Headquarterswhere the intensity at the statedaltitudeover each islandwas convertedto groundintensityby means of a calibrationcurve, Measurementswere generallymade from an altitudeof 200 feet. Where the upper range of the instrument(100mr/hr) was exceededat 200 ft., the measurementwouldbe repeatedat higheraltitudesuntil a value tithinthe range of the instrumentwas obtained. Altitudewas measured with a radio altimeter. The ratio of groundintensityto the intensityat the operatorspositionwithinthe aircraftat 200 ft. is The low end of the scintameterrange is 0.003 mr/hr so that theoretically the minbal detectablegroundintensityis 0.012 mr/hr. In gavnabackground. This backgroundcan be causedby cosmicrays$ dual bomb debrisin the air. The practicallower Iid.t duringCASTLZ was in the order of 0.0S mr/hr. of magnitudein gammaradiationwas notedbetweentwo op~site ends of the atoll,a distanceof about 20 miles. This evidencewas sub-
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measurementswere made over sever~lislandsin each of eight atolls. Rongelapand four-folddifferencesat severalother atolls. neter operatorshad not been cautionedto identifythe individual islandssurveyedwithin each atoll. To standardizesubsequentaerialsurveys,a specificislandin each atollwas selectedfor measurement.All radiationreportsbeginning with IWHI =e in referenceto the same islandin each atoll. The plannedmethod of selectingsurveyflightsbased on reportsfrom monitoringstationswas inapplicablefor patternABLE after BRAVO due to the evacuationof Rongerik,the only groundstationin the ABLE orbit. With upper level winds general~yfrom the west to southwest, patternABLE provedto be the most usefuland most used of all patair particletrajectoryforecastswere reviewedfor the possibility castswere reasonablyreliablefor a periodup to H l 24 to H + 36 hours. Usually,the forecastsplacedthe cloudbeyond the Marshalls by H + u hours. Surveyson D day were avoidedbecauseof the risk of contaminatim~survey aircraft. The very least resultof flying thru the cloud debriswould probabljjhave been the eliminationof the erallynot forecastto be completein the northernMarshalllsuntil late on D day or early on i)* 1.
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continuouslydiringthe series. These were; Iwo Jima,Guam, Truk, Yap, Ponape,Kusaie,Majuro,Kwajalela,Ujelang,Wake, and Johnston. Gaxna intensityversustime afterburst is plottedin Figures3 t~ than 0.1 mr/hr)was masured followlnga particularevent. when the gammaintensityexceededthe upper scalelimit (1OO mr/ti). of the peak radiationvalue may be obtainedgraphicallyby extrapolating the automaticgammawaiter curve * ove 100 mr/hr and extrapalatfig the AELE measurementback on a t-~o decw curveuntil tie two curvesintersect. This is slxwno~ F$~e 17. Cumulativeradiation from BRAVO (Paragraph~ below) is computedfor Bc@gerlkusiag the peak radiationvalue obtaiaedfrom this synthsticgraph. Beta Dust Concentration.No beta dust concentrationswere obtained from the mnned automaticstations. At Ujelang,the unmannedstation, beta dust concentrationswere obtainedonly for ROMED (Figuren) l Thoughthe eight head dust samplerwas servicedprior to each event, a varietyof operationaland Instrunmtal clifficultiesgenerally 2. Auxiliary MOIlitOIiUg Stations. Remote stationsat Oabu, SheWa, and Anchoragereportedgamma radfation daily throughoutOASTLE. No With the exceptionof patternKING, all surveypatternswere de si~i.ed prior to the test serieso KING was iqrovised followiagBRAVO to survey the GilbertIslands. It was not repeated. As a resultof the widespreadand unusuaQy heavy falloutfrom BRAVO, any areas of unsuspectedfal.loutcIn all of the fo~~q eventss
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s- 9 10 Ii 12 13 is Is 16 l?,,~~s 19 -.
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monitoringstationreportswere used as basic criteriain determining the need of flightsfor all patternsexceptABLE. With the elimination of RongerikafterBRAVO,therewas no nmitoring stationin the This was necessarybecauseof the consistentupper levelwesterlies. The air survey measurements,extrapolatedto groundintensitiesare 4. Cumulativeand Peak Radiation. Cumulativeradiationis listedin Table 1 for all atollsin the ABLE and BAKER patterns(all of the automaticmonitoringnetwork. The values at atollswithinthe other surveypatternsamountedto so littletkt ~eY are not includedexcept for tiosewith automaticmofitors. (For instance,the total % of the permissibleexposurefor the test series). The cumulativevalueswere derivedeitherby integrationof direct measurementsin the case of the ftied stationsor by use of theWayWigner decay formqlaappliedto the initialmeasurementsfollowing each burst in the case of aerialmonitoring. The stun of the estimatedcumulativegamma at the 40 listedlocations for the 26 day periodbetweenBRAVO and ROMEO accountsfor 89% of the total estimatedfor the entire series. The approximatecontributions periodfrom the statedevent until the next and for this reasonunThe abovevalues shouldnot be interpretedto relate the totaleffectivefalloutfrom each of the devicessince the sam meteorological conditionsdid not obtainfor each event. Peak radiationintensitiesfollowingeach burst are listedin TableH. Thesevalues applyto one islandwithineachatmll surveyed. Intensitiesat other islandswithin the S- atoll may have been greater or lesserthan statedfor any givenevent, Islandsbased on total cumulativeradiationfrom CASTLEat each island. 6. Correlationof Gamna Intensitywith FalloutP= Unit Area. At many of the automaticpuma monitotig stations~gummedfilm saql~s were collecteddaily w part of the World Wide Monitori The gumnedfilm analysesare reportedas beta dis/min/ft. Cmpa.rative data from the two mor+”aring methodsare availablefrom thesestatior..-
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To establishan empiricalrelationshipbetweenbeta dust activity on the groundand gamma radiationintensityat threefeet over the The values selectedare limitedto the first24 hour periodof significantfalloutfollowinga givenburst. Beta activityhas been extrapolatedfrom countingdate to samplingdate. The paucityof values is due to incompletedata; dust samplesare missingin certain instancesand monitorfailuresoccurredat varioustimes. The valuespresentedare preliminary.Furtherreview of the available data mqy discloseadditionaluseful.comparisonsand a refinementof computationsmay alter the existingvalues somewhat.
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AC operatedautomaticnmitors displayeda regulardiurnalvariation apparentlydue to temperaturechange,Wdity, or both, The variationwas as greatas an order of magnitudein some intion was about 0.1 mr/hr althoughthe designlimit was 0.001mr/hr. Interpretationof radiationintensitiesless than 0.1 mr/hrwas difficultand on one occasion$falloutof low intensitywas unnoticedwhen it occurred. A later, carefulanalysisof the data revealedthat 0.1S mr/hr occurredat Ponapeafter RCMEO. Had this been known,a CHARLIEsurveywould havebeen executedand it is possiblethat significantfalloutmy have been detectedat other stillsb the area, A reviewof the data and,tieinstrumentalbehaviourhas indicated that the late night instrumnt readingwas inmost cases a reliablemeasureof low intensityradiation. Inse~eral titances the 1800 Z value was used for plottingtime graphs, Simil~lY~ at severalstationsonly the 1800 Z valueswere used in computing The diurnalvariationwas consistentlyso high at Ouam that none of those data, all of which are low level,are consideredvalid. B. Comparisonwith GumnedFilm. In those instancesof suspected able validity,the data were comparedwith the appr priate gummed the gummedfih displayedan increaseh activitycorresponti.ag to the monitordata. Thus, the rwmitordata was quali.tative~y resultswith automaticmonitorvaluesis shown b Figure29. tiorswere out of servicefor an averageof 15% of the ti~ fr~-~ betweeneventsso that usefuldata was lost only at the following Wake, Ponapeand Iwo Jima;ROMEO- Kusaie,U~elang,Yap, and Ixo The presentedcumulativeradiationvalues are therefore,in genera underestimations.me valuesare based on the recordeddata o.ti~
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Radiationduringdown time was not estimatedexceptat Ujelang where down time was in excessof 50%. There the estimateiS also low becauseno data are availablefor the falloutperiod ROMEO ad NECTAR. Peak intensitieswere obtaineddirectlyfrom the monitordata? Where blanks occurin TableII,data are unavailabledue to inare the greatestintensitiesfollowingeach burst~ ABLE. Falloutarrivaltimes are not generallyknownfor the =nds coveredin the aerial mrveys. The few exceptionsare those whichwere automtic monitoringinstallations.Cumulative and peak radiationcomputationsare necessarilybased for the For BRAVO, tie arrivaltim at Rongerikis exactlyknownfrom the automaticmonitorrecord. For other stillson the sam general bearingas Rongerikfrom Bikinijthe arrivaltimes were arbitrarilyassumedto be proportionalto the respectivedistances from Biti referredto Rongerik. Allowancewas made for the initialrapid lateralcloud‘growthin the first minutesafter the burst. Data obtainedfrom Task Utit-1indicatedthat at + 10 minutes the clouddiameterhad grown to 335,000feet and the rate of growth had diminishedto a relativelyslightamount. Peak radiationvalues were computedby extrapolatingthe observedintensitiesto the estiBikinithan Rongerik,hencewell removedfrom the directfallout are the reportedpeak valuesin the results. Cumulativeradiation computationsare based on decay assumedto start from thesepeak For the other events,the peak valuesare taken as thoseobserved on the D + 1 aerialsurveysunlesslater surveysof the same islar.ds tim was arbitrarilyassumedto be D + 2 and the intensitiesmeasured on the repeatflightwere extrapolatedback to D + 2. Cumu-
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