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Alfred J. Breslin and Melvin E. Cassidy, Atomic Energy Commission, New York Operations Office, “Radioactive Debris from Operation Castle, Islands of the Mid-Pacific,” 18 January 1955, Secret

Il t · •'r4 '-y t ' I irCI _ 1 f ' · ' r · • r • • U STATES NEW 1 • •• I ATOMIC tT---- ·• 4 ENERGY YORK 'OPERATION I GOMM ISSION OFFICE 410411 RADIOACTIVE DEBRIS FROM OPERATION CASn E ISLANDS OF THE MID-PACIFIC January 18 1955 -------------Copy 26A ---- • • N· ·-1 u J - _ _ J 1 cct1· 1co l • t_ L- - · V This docurne nt consists of 80 pa s3 No l of-ff Copies Series A NYO- 4623 Effects of Atomic Jeapons RADIOACTIVE DEBRIS F'RCil'i OPERATION CASTLE ISLANDS OF 'ffiE MID-PACIFIC by Alfred J Breslin Melvin E Cassidy Ja n uc ry 18 1955 UNITED STA'IES ATOMIC ENERGY COMMISSION New York Op2rations Office Health and Safety Laboratory RES 1RI CTED DA TA This documant contains restricte d ta as defined in the Atomic Energy Act of 1946 Its transmittal or the disclosure of its contents in any manner to an u'- iu-' -hori · J pe son is prohinited 8i Il Bi' -ii- • NY0-4623 Effects of Atomic Weapons SPECIAL DISTRIBUTION Copy No • Arned Forces Special Weapons Project Sandia Armed Forces Special Weapons Project Washington Atomic Energy Commission Washington Atomic Energy Commission Division of Biology and Medicine Washington Commander Joint Task Force Seven Department of Connnerce Weather Bureau Departnent of the Navy For CINCPAC Los Al lJl S Scientific Laboratory New York Operations Office Rand Corporation Sandia Corporation Santa Fe Operations Office USAF Office for Atomic Energy AFOAT-1 U S Naval Radiological Defense Laboratory Technical Information Service Oak Ridge • IPClb t -i·· 1 2 3 4 5 to 11 12 to 21 22 23 24 25 26 27 28 to 37 38 39 40 41 42 43 45 to 59 TABLE OF CONTENTS Page No LIST OF FIGURES V vi LIST OF TABLF S vii ABSTRACT I INTRODUCTION 1 II ME'lHODS III IV v 7 RESULTS 11 FACTORS RELATING 'ID DATA INTERPRETATION 44 EFF TIVENE 3S OF MONITORING 51 PROGru M INSTRUMENTATION 59 VII RECOMHENDATIONS 71 REFERENCES 73 VI 2• 1• -iv- -- LIST OF FIGURES Page No Figure No 1 Instrunent Monitoring Network 2 4 s 6 Aerial Survey Patterns Gamma l'allout at Majuro BRAVO Gamma l'allout at Kusaie1 • Gamma l'allout at Truka • Oanma Fallout at Ujelanga • 7 Gamma J'allout at Johnston • 3 8 9 10 u 12 l3 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 JO 13 1 1416 17 18 19 Gama Fallout at Johnston 21 • 20 GallillB Fallout at Ujel anga ICON Gamma Fallout at Jtwajaleina UNiml AND YANKEE 22 23 Gamma Fallout at Ponapea UNUB Oamna 'al lout at Truka UNDI Reconstructed Oartlna Radiation Intensity at 24 2 5 llongerik tollowing BRAVO Beta Dust Concentration at Ujelang1 B01'BO 26 Aerial Survey Measurements1 BRAVO · Aerial Survey Me S1U ementsa BRAVO and ROMEO Aerial Survey Heasurementsa BRA 10 Aerial Survey Measurements I Ram Aerial Survey Measurements KOON Aerial Survey Measurementsa UNION Aerial aurvey KeasuroDlllltsa IANJCEI Aerial Survey lleasurenentsa HJK TAR Isodose Chart Total Cumulative Radiation tor CASTLE Beta Dust Per Square Foot vs Gamma Intensity at 3 Feet · Comparative Fallout Activity Indicated by Automatic Monitor and Owrmed Film Samples at Majuro 33 34 36 Conver ion of Air Measurement to Ground Intensity 35 6 12 Gamma Fallout at Kwajaleim ROMIO and IDON Gamma Fallout at Majuro 1 • • Gamma fallout at Kusaiea Gamma Fallout at Ponape • Response or Survey Instruments Over Inergy Spectrum Aerial ionitoring Measuremnts Rongerik A erial Monitoring Measuremmts Ailinginae Aerial Monitoring Measurements Utirik Aerial Monitoring Measurements Ailulc 31 32 -4 Scint ameter -ta a -·- 27 29 30 31 32 33 3u 35 36 4l 43 45 49 _ 55 56 57 6o 62 LIST OF TABLES Table No I II Page No Cumulative Doses by Event and Location 37 Peak Gamma Intensity by Event and Location 39 6 88ftl I -vi- 81l8Ril ABSTRACT During CASTLE an offsite monitoring _program was conducted in the Central and Southwest Pacific to document and to provide current measurements of the radioactive fallout Navy patrol aircraft equipped with gamma rad ia tion instruments were dispatched over planned routes to measure fallou after its presence bad been detected by automatic gamma monitors Eleve of these were collecting a continuous record on selected atolls in the Marshall Caroline and Mariana Islands Air survey m easuremants were - inverted to ground intensities imnediately upon receipt by means of suit aole curves permitting appraisal of the radiological situation over a widespread area Auxiliary stations providing daily gamma measurements were located beyond the network of automatic stations Cwnulative and peak radiation dosage were measured or computed from indirect measurements for all islands in the automatic network and for islands within the two aerial survey patterns east of Bikini in the Marshall Islands BRAVO accounted for 89% of the total cwnulative radiation measured during the program The greatest radiation rate extrapolated from direct measurements 12 5 r hr occurred at Rongelap after BRAVO Values both greater and lesser than this probably occurred at various islands in the Rongelap a oll The greatest estimated cumulative radiation occurring from any event until the next following was 190 rat Rongerik after BRAVO The total cumulative radiation at Rongerik was 206 r The monitoring method combined fixed continuou stations and aerial surveyso The advantages of each rethod was utilized so that they were complementaryo Rapid accurate information about radioactive fallout was provided by a means which probably represents the maximum in econorey- for such exte sive coverage 'Ihe SCIInAMETER a sensitive ·o'll de range scintillation type ganma rr c e was demonstrated to be a depend able very portable facile i nstru ner a rial mnitoring use j Increased C ' cll acy raliability 3 and precision can be obtained for surveys of tr is nature through certain sugges•ed modifications aow -vii- ' H' 1 r- • IIHf I INTRODUCTION Purpose A t the request of CINCP A CFLT the Health and Safety Laboratory of the New York Operations Office organized and directed a program to document radioactive fallout from CASTLE in the Central and Southwest Pacific exclusive of the proving grounds Current fallout information was to be made available to CINCPACFLT following each detonation The program was to be atterr ed basically on the NYOO monitoring system developed for r vY - 1 The information derived was used in the immediate estimation of radiological hazards in heavy fallout areas The documented fallout consti tutes a record of cumulative radiation produced during the test serieso 2 Organization The mnitoring program was planned and directed by the Heal th and Safety Laboratory Bew York Operations Office and ac tively supported by several agencies HASL organized the unctions of the participating agencies developed procedures am furnished all m toring instruments employed The Director Health and Safety Laboratory was in over-all charge of the program The Project Officer HASL directed operations in the forward area Operations were executed in accordance with the operating plan HASL-154 -Operating Procedure Fallout Monitoring for CASTLE Monitoring instrument calibration and maintenance in the forward area was performed by the HASL staff Joint Task Force-7 Headquarters provided logistic support and made available communications facilities in the forward area The instrument monitoring program consisted of the following operational subdivisions l 2• Fixed Instrument Network a Automatic monitoring stations b Auxiliary moni taring stations A eria l Survey Monitoring Fixed Ini runent Network The u S Weath Bureau 11 the U s Navy and the USAF Air Weat •gr Service operated fixed automatic gamma mnitoring stations on sites selected basically to create a uniformly distributed pattern relative to the test area The availability ot facilities tor the operation of ronitoring equipment was a factor which limi ed the nwnber of atcl s which could be u tilized Uniform distribution was reaso bly wi ll achieved partiru _-irly within the Tl'ust Territory -1- iilOBif The nature of the automatic instruments was such that very little attention was required during normal operation The function of the station personnel was to read and transmit the indicated radiation data Except tor a simple briefing none of the personnel were pret ained in the use of these instruments nor in the field of radiation satety The sites as originally establishedt were Location Operating Agency Iwo Jima AWS AWS Guam Truk USWB USWB Yap Wake usw Midway Rongerik Majuro Kusaie Pona pe Kwajalein Ujelang USN •JTF-7 weather units HUjelang was unattended persomel AWS AWS A AWS USN HASLff Data was retrieved periodically by HASL A FOAT-1 operated six auxiliary stations in more remote locations which were equipped with portable Geiger-Mueller survey instruments The six locations were Manila Luzon Okinawa Yokota Japan Oahu Hawaiian Islands Shemya Aleutian Islands Anchorage Alaska on B • 1 a portable gamma instrument Scintameter as placed at Johnston Island AFB to intercept tbe BRAVO cloud believed to be traveling east from the r rward area This was replaced by an automatic gamma D1 nitor after Rongerik Atoll was evacuated and the automatic m nitor remved from hat site Johnston was the only location east of Bikini and approxima ely in the sane latitude as Rongerik with tacilities for m nitor operation JI Ml _ _ Shortly after the first event the first t ree listed stations were discontinued The locations of all the instrument monitoring stations are plotted in Figure 1 Aerial Monitoring Three Navy patrol squadrons were assigned to e Xecute aerial survey missions These were VW-1 at Barbers Point Oahu VP-29 at Kwajalein M I and VW-3 at Agana Guam They covered designated Pacific Island groups according to the folloWing patterns ABLE BAKER l Kwajalein 1 Kwajalein 2 Lae 3 Ujae 4 Wotho 2 Na Ill l 5 3 Ailinglapalap 4 Namorik 5 Ebon 6 Kili 7 Jaluit Bikini 6 Ailinginae 7 Rongelap 8 Rongerik 9 Taongi 10 Bikar 11 Utirik 12 Taka l3 Ailuk 14 Jemo 15 Lild ep 16 Kwajalein 00G CHARLIE 1 Kwajalein 2 Kusaie 3 Pingelap 4 Moldl 5 Ponape 6 Ujelang 7 Kwajalein 8 Mili 9 Arno 10 Majuro 11 Aur 12 Maloelap 13 Erikub 14 Wotje 15 Kwajalein EASY l Guam l ft ain 2 Rota 3 Agiguan 4 Tinian 5 Saipan 6 Farralon de· Medinilla 2 Nam' nuito Truk Losap Namcluk Lukunor 3 4 5 6 iilMI -3- FOX 1 Guam 2 Gaferut 3 Faranlep 4 West Fayu 5 Ifalik 6 Woleai ' G I I HSTllUt-lE IIT t-lf' U T R I HG NETWORK 60n I I 4 i I ET7 c r I r c I c - J - -I-- -I I I I I A o • o - --1--1 Uf I I ' Ht 4YA # I IJ • • o• • TFST SITFS AllXILIARY REPORTING STATIONS •• AFLOAT I AWS • tUSWB t l l' 1 11 • - · 1 o -1Nl TATl l' i IUSNI I' 'N'1ANr- EO 1 I•- '- P FY SOlJA 1 Q ' l_ 1 SN HASL • • Q OKINAWA • I I e I ' J I'-'A I 10° l J »A I • I I 130 lijO • MORET I I I ll ' CTns • I JI T l llF I t' • I 50° PONA F I 160° '' t I I I OAHU eJOHNSTON I If I eRONGERIK JAU IN e'1AJUf-' 170° 180° 110° I goo 150° SECRET 00G Cont'd 7 8 9 10 11 7 Sat a wan 8 Kuop 9 Pulap 10 Guam Anataha n Sariguan Goguan Alamagan Pagan Cont 1 r1 2 Cont'd 7 Eauripik 8 Palau 9 Ngulu 1 0 Yap 11 Ulithi 12 Guam 12 Agrihan 13 Asuncion 14 Maug i5 16 -vw-1 Farallon de Pajaros lluam GECRGE 1 Oahu 2 Midway over south beaches all isles in chain 1 Midway 2 Oahu over north beaches all isles 1n chain -ITEM l Oahu ·2 Lanai 3 Hawaii 4 Maui 5 Molokai 6 Oahu Survey patterns a re plotted in Figure 2 SECRET -5- oozom 111911 l Jl Y J oooozo OO ZIO oo i 10 I _ J oo 005010 - I- er a I- z 0 I- I cc z ' a cc 0011010 C _ _ - 0 I CL re I I O I ' ' I- z 0 u cc I- u ' - I ' I- · _'L 00 010 _ V - I 1 c- - I ' Lu - _ w1 U 0 s - 5 r ' ' I 0 - O oozo 18 J c Z d - u 001010 I 'S a - I I I I 8 8 0 ijH H - A11SN31NI WttiWll ONOOH9 ' I I •0 _J cc '0 I - - ' I- I- - I 1 · 0 00tt11u 0 0 I ' 111 i V H I r '•lb r FIG 2 AERIAL SURVEY PAfTE -S Jnubo Saki ' I •Hai hJJO luna I - - 'ihl- · I Uraaaa I Suauau J1nw y tut a I -1 1· t I SHt•TO _ Sh _ S1ah1no I mO lo lI W 1 t 'i ar1 I I • Ht M1 1lr hunaK nt o • u 'lll'll t uoto Hahuhuna RM t e t loSII I- Ka UUl l tlo lo J_ 41 uao llliulo v J _____GEORGE 8 f - - - - rl' nA cu • -1 l'l'UO 1i11DA111i lo J11D • ·S· -lJun J 'la DOG WOUll o• _ I P P I f E I HM _ M HI X AS J- EA BLE A u u · r nrw •t Ji ' ' 11 Jll T kl 2 I 'n' ' ' i' t It s - fJ I l ruo• - -•hill X t I S l 'i - ' lalliv - ' ' 1'· ' ·I ' _ •·w' · '·I · ' ·-· ✓ 1· 1 CII AR L I E_ · • i 1 _ o th -- l t · 't· x w knu ' '' A I _ l l-•- 1''• u V I l- w-iam pa F--t - nlu111 r 1 KE A• --a •• -- ------- -- - ------ ----- -- - A· Nlf- - w rai K I NG s 11rU ••· - w I _ 11u Noft09 T n•-' l ' lu nall - T-- u-- - lAlW'M PHf•t NJ'X lilt It an au1SLA s • ulu1mouo111'1 c- _ l'b - - _ IU'dn r-· NanuA N n • Y11 1 tur- ut •✓ · · AllAFURA SEA • k f • TOttlf£5 ICW 1t I sm · Nokut91Ml - N • klUM _ I --w -1 • _JtOll llel -· TOKELAU IS NRkHua -- _ r • la ·- - II HiTHOJS The program was an integration of two principles of monitoring The first was a network of fixed monitoring stations reporting data regu larly to the Task Force The second consisted of aerial monitoring flights by NaV'I patrol squachon aircraft over specified islands following each burst 1 Fixed Instrument Network General Description The fixed network initially consisted of eighte n garrJ' la rocmitoring stations chiefly in the Marshall l' aroline and Hariar i a Isla nds but extending to the Ph il1ppines Japan Hawaii and Alaska The nwnber and location of the sites were somewhat roodified in the course of the test series The stations with one exception were manned and reports of gaITllla radiation were transmitted regularly to the task force at six twelve or twenty-four hour intervals depending on their positions relative to the proving grounds The twelve sta tions within 1500 nautical miles of the proving grounds -were equipped with llO v AC automatic continuously recording gamma monitorsi having a range of 001 to 100 mr hr A battery operated automatic zoonito was placed on one island Ujelang where facilities for a manned station were unavailable Data was recovered from this station after each burst Si t remote stations beyond 1500 miles were provided with portable G N survey instruments having a range of 0 01 to 20 mr hr Twice daily measurements of local gamma activity were transmitted once a day from these stations to the task force Data was transmitted by administrative teletype messages from all but four stations which were weather observa ti on posts maintained by · he task force Fallout data from these locations we 'e appended to r- 11tine data transmissions to the task force weather central Operation Tt 1 e principls reason for e tablishing the instr u ment i 1- taring network wa s tu i 'c-·1i d a c - reliable fallout detection oyst t means cf - ri ch aerial su ·· - -- could te 2l 2cted and tirr ed to pl a l iini ' Jf nega- iv'3 fli t L I r u radiation int ns tl1e auto ntic mo1- tJj' 'ing tic i 3 er· 3 v· -1n d t Task Force Heal __ 1- y· - i thin do feH l ccrs af e - th-' ' - xr - - Instruments are dcsc-- - P 'ed in Ss- tL VL -1 The gamma intensity at each of the autornat c stations except Ujelang was recorded at 0600 1 1200 1 1800 1 and 2400 Z daily by resident operating personnel and transmitted to the HASL representative at Task Force Headquarters The instruments were routinely checked each day for proper radiation response This test which consisted in observing the meter response to a low intensity button source placed near the CM tube provided a means of detecting circuit failures Two HASL technicians at Guam and Kwajalein v1s·ited the monitoring stations periodically to adjust calibration and to effect repairs as required installed were designed to record the beta dust concentration continuously as well as gamma radiation Unfortunately all of the beta channels failed as a result of various mechanical and electrical difficulties after short periods of operation Maey of the monitoring units Twice dally the ground gamma intensity was measured _with the portable meters at each of the AFOAT-1 installations These measurerrents were obtained by scanning a small ground area from a height of three feet Meter readings of less than o oS 'mr br were attributed to background radiation and were reported as negative values Data was trans- mitted daily from each station to Task Force Headquarters The instruments were tested each day for correct operation and radiation response in a manner similar to that employed for the automatic mnitors Faulty instruments were replaced after notification of NYOO Project Headquarters thru AFOJ 1'-l channels Receitt and Utilization of Fixed Network Data Radiation intensity repor s were tabulated chronologically by location as they were received at the Task Force Headquarters 'When a reported increase · ras indicative of significant fallout a survey flight over a pattern which included the island from which the report originated was re- quested of the appropriate patrol squadron From the report received upon completion of the survey flight a comprehensive presentation of fallout intensities within the selected pattern was made available to the task force radsafe officer and other interested task force personnel In addition the continued transmission of radiation data from the monitoring stations provided an accurate measure of potential radiation exposure at these locations Weekzy sur unaries of cwrrul ative exposures were tabulated for eacl l st _ tion -8- 2 Aerial Mani taring General Description Aerial surveys were conducted by Navy patrol plo nes equipped with SCINTAHETERS sensitive wide range gannna scintillation instrUI lents capable of measuring ground intensities of as little as o o5 mr hr from altitudes of 200 ft or greater Survey flights were made over pre-determined patterns designed to achieve rraximum coverage in selected areas The patterns included the Marshall Caroline Mariana and Hawaiian Islands Data was transmitted to the task force occasionally f'rc survey aircraft in flight but more generally from the squadron base at the conclusi n of each flight Operation The scintameters were operated in flight by aircraft crew members trained in their use Usually two instruments were carried one reserved as a spare The scintameter operator recorded b ckground reading position altitude and radiation intensity for each island in the survey pattern Background was measured during the approach to each island at a distance of several miles These data were transmitted to Task Force Headquarters where the intensity at the stated altitude over each island was converted to ground intensity by means of a calibration curve Measurements were generally made from an altitude of 200 feet Where the upper range of the instrument 100 mr hr was exceeded at 200 ft the measurement would be repeated at higher altitudes until a value thin the range of the instrUI l3nt was obtained Altitude was measured with a radio altimeter The ratio of ground intensity to the intensity at the operators position within the aircraft at 200 ft is a iproxi mately 4 Scintameter calibration is desr ribed in Section VI The low end of the scintameter range is 0 003 mr hr so that theoretically the minimal detectable ground intensity is 0 012 mr hr In reality the minimal detectable value is controlled primarily by the gar na background This background can be caused b7 cosmic rays navigational instruments aircraft contamination and possibly residual bo mb debris in the air The practical lower lir -it during C STI 2 was in the order of O o5 mr hr Following BRAVO survey parties put ashore at several atolls in - area of -- -vie st fallout recorded larce ra diation intensi t r gr 3 Tl directicns approximately normal to the fallou path At Rcr--621 z ap- •roximately ninety miles from ground zero a difference of a cr er of magnitude in gamma radiation was noted between two opposite ends of the atoll a distance of about 20 miles This evidence was 9 cstar tiated by ABLE flights repeated on B t- 3 a i l B 18 durin • hich it'Inst ·ments are described in Section VI 'Ml800i -9- measurements were made over severJ l islands in each of eight atolls Tenfol i differences between islar d intensities were measured at Ron 6elap and four-fold differences at several other atolls These larGe a iients were not anticipated prior to BRAVO and scintameter operators had not been cautioned to identify the individual islands surveyed within each atoll To standardize subsequent aerial surveys a specific island in each atoll was selected for measurement All radiation re -orts beginning with ROl- 00 re in reference to the same island in each atoll The planned method of selecting survey flights based on reports from rnonitoring stations was inapplicable for pattern ABLE after BRAVO due to the evacuation of Rongerik the only ground station in the ABLE orbit With upper level winds generally from the west to southwest pattern ABLE proved to be the most useful and most used of all patterns It was dispatched routinely on D • 1 Before this was done air particle trajectory forecasts were reviewed for the possibility of the cloud being over the northern Harshalls on D 1 The forecasts were reasonably reliable for a period up to H • 24 to H 36 hours Usually the forecasts placed the cloud beyond the Marshalls by H 24 hours Surveys on D day were avoided because of the risk of contaminating survey aircraft The very least result of flying thru the cloud debris would probably have been the elimination of the aircraft from further low intensity measurements Fallout was generally not forPcast to be complete in the northern Marshall's until late on D day or early on D • 1 MJ8MI -10- SBOl l III RESULTS 1 Automatic Monitor1f Stations Twelve automatic monitoring stations were origicall7 stalled tor TL Eleven were operated continuously during the series These were Iwo Jim Guam Truk Yap Ponape Kusaie Majuro Kwajaleia Ujelang Wake and Johnaton Gamma intensit7 versus time alter burst is plotted in 11 gures 3 thru 16 for those locations where significant radia tioa generally greater than 0 1 mr hr was m asured follawing a partioula r event Rongerik-BRAVO Burst No monitor data are available after B 8 hours when the gamma intensity exceeded the upper scale limit 100 mr 'or Utilizing the ABLE survey masuremezit at B 32 hours an estimation of the peak radiation value ma y be obtained graphically by extrapolat1 Ag the automatic gamma mo ru tor curve ove 100 mr br and extrapolating the ABLE measurement back on at• • decay curve wrtil the two curves intersect This is ahon oa Figure 17 Cumulative radiation from BRAVO Paragraph 4 below is computed tor Roisgerik usiilg the peak radiation value obtained trom this synthetic graph · Beta Dust Concentratio No beta dust concentrations were obtained from the manned automatic stations At Ujelang1 the unmanned station beta dust concentrations were obtaiJJed only tor ROMm Figure 18 • Though the eight head dust sampler was serviced prior to each event a variety of operational and iDStru mental difficulties generally rendered the instrument ineffectual 2 Auxiliary Monitoring Stations Remote stations at Oahu Shernya and Anchorage reported gamma radiation daily throughout CASTLE No significant radiation was detected i e there were ao measurements greater than o o mr hr 3 Aerial Monitoring Thirty-three aerial survey missions were flown during CASTLE Of these fifteen followed pattern ABLE and seven followed pattern BAKER · · With the except on ot pattern KING• all survey patterns were desig - ed prior t o the test series KING was improvised followiag BRAVO to survey the uilbert Islands It was not repeated As a result of the widespread and UDusua J ly heavy fallout from BRAVO all survey patterns except Hai were arbitrarily execu ted to detect any areas of unsuspected fal101 t In all of the following events HOW is identical to GIDRGE except tor the direction of flight -- •• • _TI _ ' ' _ _JI ' ' --- -·-· t---- '-·• i -· 'z ' z r • 0 C cc i 0 2 ·· •·7-- 0 ··•·• a r-- -- · 7 __ - ·- o ·· ·- 5 i--- ' 41·- r I r i 1--' I •·i i --- ·_ _r I 2•--····--· I 1 ' ·--- -·------ ·r-r-t- ' ' 1·-•·t ·•- j ··' ·r ' l - • ·•· -7J 1- j ' I - -J - 9'NI' _ _ I L 2 J ' 7 8 10 MARCH OATE 9 X ORI ¥ -13- ll 1Z 1J lll l 16 17 lJ -1 'r- - r ' t - -I - - -- · - lO• __ L - _ __ _ _ 7 ti •• ------i--- - - - - -- - -- I -- - -r- ' -IF 16 5 --r-- ---· f'l --'-- - 1-- T- --- - - ' · Al· --1'''' ·-1- -- -----i-- - __ - I 3 r ' -t'-- ·--'-- -·--r------- -- - - --- ·-- ------ A I 1 '' '' -' ' ' I I T I - __ _ __- - --_ - - -' - --1-4- '-' l ' '1 - --- -jFIXED INSTRUMENT NETWORK_ _- 1 1 1_j_ 1_r1_ __ _ 1_1 1 1 ··-· ·-L --l-··-·-r-· -1'r- _ _-- t 1 · · GAMMA FALLOUT AT TRUK ·- __ _ - ·- --t-- --· ------------i- RAVO EVENT lt H- --d - - h _ 2 -L --- ---- ----- - ---L--- • --c _ -c _' ·· '· I _ _· - _ -- _1_-•'4 · - - - - j I _ _e- 1_1 -•--•l_l I- l lO 7 Lt± -- t tte- L _ i - jT - It t ·-- ---- I I r --r---- ---7---- ---r--•-1 a 1 · 1· ' ' f i l --- - -r -r 7'-rri r- r- - ---- --t --h --- - - -7 7 a-M-lf i - • - -d- H I I 3 Hi -t1 -- i I a • f H I ' ' ' 8 1 · I I Ii I I I · i · I 1 ' - - •-rt· 3 _ __ _ _ · 1 ii •i T LJ •- rttt ' '- - - 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-- t -- _ u r -- -- -•------ -- • • • GOl L _ __ - - ________ __ __ • ' J • • 12 MAV DAT 1 u 91 Ullf -2s- 16 17 18 - 20 21 22 5 • ilL r L t •• 3 1 t l • • ' --• -· • _rrri l •· - ·• • • •• • • t ·- •-• • • _ _ __ •·- ·----- - t ---- -•- -f •- -1--- -t _ -· - -1-- • •_f • _ _ -• •· -•- - •-• •--• - - - t - - - - -1 -- -- - -• -st- -r-- -- -__ _- - 4• -•- - - ·• •·• - -·• -•· 1 - _ __ t ·t· - • • • -- - __t_ --- • · -• -t_ - H- 4-•-r t - · --- - -- -• m- • • • • • --r r· __ ···r - r· --·-_ - ' · -- - T _ _r•--• L t---' - -• • • - ·• f --•r-•· t • •· •• - -- _ - - --t--- · - -t-t- ·• 1 -- 1· · _• t----t r· •--• - i -J • •• - '-- ---1 - t - _ - -i- - - • - _ _ _ __ - -'-- I -- --- •----- i --- •• _ •• - -- q - r · -- -·1_ • -- - -- - 1 • • • i t J 1 •-- - • r-t t- r-i t c x r1 - trf - - -- 1 1t ·-•-·_--• - t-----1r•-·•- -·-_• -•-··-•_- •-·•-•-·• - - •---•---__ -f-· t- _ -__ - - -• -- -·-• -' •-• _-_-_-_•-4-_' · -_ _ _1 -- •- --_- _•--• t-----1' - -1 • • 1 - - --'· - -- -• ' •• · · 1- - ··• - • • _ t - - --r-t-- --r- - •· H t 10 7 g z 0 7 6 -r ' -I• _--r7'· • · -· _ i t •• •· • 1 - • • • •• - 1- -J 1 -P- -1' 1 1 i_ _ _ _ 1 t 1 ' 1 l- L • _ _ ' 1 • •-•- J t-' 1 - - - • J _ • • 1 1 1 1 1 - - - - __ •-· - - 1 1 · i H i- U l -t -ct Jc t · - cl i i I l l H · - f t 1 1 - ' T l 1 J tlii iii ·LU c tvrt· r·H1 ·r r·r tl L rn r-'lHL4 J- t-f- ½ lr ii-t-L •••• • I I -•• -•· ·•- - ' • f r-t -1· -tll ·r rr f l 1 r ·-r- ·- - - L J -- • - • •·• - - • · · -rrr -l J - i 4i i i- - t - ± h· r - t- - - 1j •- ·t-t j- l-t • 1-• · • • •· • _ t j- -l-•· ··• '· •- -- •t· -Hi --t -i If -i r1 -r-H- -- ··• - -4-i- - _ · •- '• _ L J 1-• ' i 1 1-j - -t t' r' _ l _ _ _J _ •- ·J I l l 1 1 ' d--rl t-il 1 J-t Pii' 0 _11 li 1 r ·-- ittthf t- t Pi ·n- - L i t·4 t tW- • i l-t-•· - 1-- f · • •Ii t i- ---l r _i_' · T • c 1 -_ ·-· ' ___ 1• 1 H t _- l _' - 1 1 r·r t 1 t t r-t-t- -t - · _-i f 1 ----- _ 't f f C I z 0 z C Q u u ' Q 1 115 116 117 118 119 50 HOURS AFTER BURST nue -27- 51 1 ilth 5J iB8B Bi monitoring station reports were used as basic criteria in determining the need of flights for all patterns except ABLE With the elimination of Rongerik after BRAVO there was no zoonitoring station in the ABLE pattern Consequently ABLE was flown on D t- 1 after each event This was necessary because of the consistent upper level westerlies The r survey ll19asurements extrapolated to ground intensi tie are plotted in Figures 19 thru 26 4 CWlllllative and Peak Radiation Cmnulative radiation is listed in Table 1 for all atolls in the ABLE and BAKER patterns all of the Marshall group east of Bikini and for the islands comprising the automatic monitoring network The values at atolls within the other survey patterns amounted to so little that they are not included except for those with automatic monitors For instance the total cumulative radiation e t Ponape in the CHARLIE pattern was less than 5% of the permissible exposure for the test series The cunmlative values were derived either by integration of direct measurements in the case of the fixed stations or by use of the WayWigner decay tormtl a applied to the initial nraasurements following each burst in the case of aerial monitoring The sum of the estimated CUllllllative gamma at the 40 listed locations for the 26 day period between BRAVO and ROMEO accounts for 89% of the total estimated for the entire series The approximate contributions from the remaining events are ROME0-5 3% KOON-3 2% UNION-0 9% YANKEE-1 2% and NECT 1 -0 -'2% 1hese values are computed for the period from the stated event until the next and for this reason undoubtedly include some carry-over of contamination The above values should not be interpreted to relate the total effective fallout from each of the devices since the sane meteorological conditions did not obtain for each event Peak radiation intensities following each burst are listed in Tablis II These values apply to one island within each a toll surveyed Intensi tics at other islands within the same atoll MS¥ have been greater or lesser than stated for any given event 5 Isodose Chart Figure 27 is an isodose chart of the Marshall Islands based on total cumulative radiation from CASTLE at each island 6 Correlation of Gama Intensity With Fallout Par Unit Area At of the automatic r mna ioonitoring stations gummed film sampl J were collected daily ab part of the World Wide Monitoring Netwo t'h c The gummed film analyse are reported as beta dis min ft 2• Comparative data from the two mor ring methods are available from these statior• · many 81111 if _ L t1· _ FIG 19 lERlll SURVEY MEASUREHl TS lSL- PATTER S ULE BlKER CHARLIE 110 Kl IG I ' I ALL 1trlo1 GS 111 MR tut j 11- r• 81k1n Atoll 'E 1'111'elok Aloi ll ' Aon 1• e _f lil AM na n•• Atolt ••n Ron1e o Alol1 n o 11--- ' 7 -I • Woltio Atoll C L-- A -- YeA IQ I ti ' ' lib I ' ' I 8 •2 · · · 7 - 2 I Ila -·- - Namor k Atoll 0 1 ' ··••ton n Atatl ' l n le1nAl a I N 1m Atoll 4 Wot aAIDII '' ' ' ' • 12-'-- 1710 • I 8 KEY 2 0 IRAVO • I OU •8 SIU¥ ' • J DOS 12 IHY0•18 DUS 1•0 - - • 3L- • MARSHALL u ---------- --'C ° Ant · I L---L--1---4 I BRlVO EVENT --- - ••to1 I I I 0 g J MalNlapAtol 1· I - 7 •-• I M• VTO AtotlU _ I J _ ' hl l H o • i• 1 AIDII -r----r-- -t- -_i___ L 6 i f lh I ' -- --- ---1----- - ------ ---- ---- ---- ----- --- --I' GILBERT a s J 7 --·1 I I I I I 2 1111 _IUATIU -1 I' ' 1 16' I 157 l 1 I '158' I I I I 159 · 160' I I 1 163' -29- ' 161' 162' I I 164' I 1 Ui5' 1 166 - i 0 16 1 168' • 1 169' 1 170' L i LL' ± 1 1 171' I 1 172' I l 1 1 173 1' 17 '- 1 1711' ISLANDS 1 176' 1 117' l' • 17Jr l l Y l L i_ _L l · • 1 - Afa t t C l• ·-·11 - ·y · - ' tµli_ - I1 - -- i • 11 1---- J _ _a I -- j '1 I It I ·-_ '- I I' I I ' • 2 -i t ' ' ' ' I i I I 1' I 11 n ' 77• • • ' • ' ··1 • 1·e J '· 0 1 I _ __ -f- •· - - ·• FIG 21 ' ITFM • 0 08 I f 'I l oc ALL READINGS IM MR ttRl 0 i 0 2 s e ·f 0 2 ' _ ·• f'- I - _ iil 0 2 • ·e r • ·f' 0 I HAWt IIAN I - i - I BRAVO EVE'IT I --- 6-------- 0 08 HOii AMO l I AE IAL s aVEY SUREMEHTS 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i z - -- - i 1 C I C 0 0 - -- -- -- ----l---- --- - - C 1 ' --- -- - 'J _- 7 f --·- -- ·--- ---- __ J l -t--- --- --J--- j _ __-i _ _- -_-- --- -'---¼- J JJ ' - -----f--- -----'--1 ·'· ·j -- -3- 1• f J J '' A '-----t----t-- ----- f---- --- -- ' L -J -j --fl AL SURVEY MEASUREMENTS 1------ ----- --- -1 - PATTERNS ABLE SHER ANO CHA LIE J -------1----------1 -----4-----l-------- ---t4L---J -- -- --·- ---- J - ''I i VNl N EVlH 1 I I _ lTeon11Ata'I ALL tFlDINII$ IO Mt Nt v-- - - -----l---- ----- ----'---- ----t-- --- - -- 110 llfO • ' ln tot AIOII Alal '- I 70 Y te_AIOI I - 1ti1- - ___ __ __ 1 -- MARSHALL 0 I ot U- • 0 1 1 o • 11 - '#octt AtOI -- - 1 f U I 1 __ UAloU I I ---r ' I ' --v· •I I I I I - l 00 - Alli 1 • i I 'MIIIAIDI I - •I I ''-- I · ' I I I l --· - - ·---- ' 1 -------- -1_i --1 •t'-' •-F G ·I L B E R T ' - - - - - - - - - - - - - ·1 7L- - _ EDOn Aloi t 1 · ' wo I- 0 IL • JetYNAlol Nemor k Atoll - _ O •·-1 ' • Ad1nC1•P - IDI --1 111111 I L - --- --- --- --- ---- ---- ----l---'I j lnkubAIDI y J t OOt PalunMDII 11 1 L 1 11 _ j I · 1 _____ u I o • 0 1 O o ___ wllAtall I J 0 1 •--------· I I 0 0 1 j i' J ---- ------ -- ---- --- ----- - u---- -I I O J 'WolhaAtol ' l Y T•kaAta1 ' 1 _ o 1 14' J 2 111101 • 1 on I 7 UIIOI' • 5 OATS j ° '- ' - -Ro -I ' n v8'11arAIOI _U l SJ_ __ L __L_ · J1 1 - ---f---- --- ---- --• - '-'1 --- -----'-- -- -----4----1'---' r--i rI I 16 iI 157° -· _1 __ I · 1511•_ i I' I 159° I 1 • I _ 31 161° ··' 162' I 163' 164° l I • ' - 186°- • 1 -L __' I 161 ' 167 LJ '- L • u L 169' 1 ' 0 1 1•' 172 1 1 -L _ W J - --L l 1 -'-U- 0 L l 1 W J w J J l 1 JW l_ - t r L i • - -7 ' I c 2s I 001 hon11 AIOI YOHE EVENT I I -- -- 1 I I •_lN- tottAtall - • II ' '' M A R S H A L - - I -·I ---- - ¾---_L - -- --- • '6• I LL- j ' 'i• I Namor 11 0 - J I -I __ i·--jf---t--- L ' I __ I 1 I - ··· · Ma ut0AIOII l ··i I - AffloAIOII I · -1----- '___ o• -- t t 1 --- --- -7 - --t---L 7L- 't' I -- - 1 1 - - -·- ---- --------- I I I I - I i I I I I I I I•• --4-- - I I l 1t• 1 J I I I • I ' _ - ' f I I I I - · ·GILBERT I 191' I - I II I I 1 7· '· I I I LLL a i l I lP- - t H '' -- --fr i 7 ---- --- i__y i 1 I • AIM pel•• I ----- - l· I I LAND Y• _ ·1 I J I 1 llalWI AIOI I l I 1- _ r -- ---j r-- --- -- ---t--JL__J__ 'J ·1 - l s s • • •- 1 1-- -··- - I 'l _ -- - - Y• I i - - i IOII I I Uloo• - - - • l · l I 0 1 THIE • t I TUU • 2 OATI l J TUii t i OATI •i- °• ' u I I I IET ••onu •AtOII • ' 16 - I ' _ _• •1 I j__ j LL OUDINGS 11 e 111 I - I -- - j---t--------------J--- - ----------- PATTERNS '8LE BOER AijD CHARLIE -·- · - - - - - - - - - · · - - 'I I I AERIAL SURVEY MEASUREMENTS l r j l '° I • -JS- 161' 112• I - I I I I • I I 113° I I I I l I I I 1 I I I I I 114 I I I I I I I I I I I I UII' 111· 1 1 1 1 j 1 - - t · j I s L A D s _j ___ _ - ---1-_ _- --- --- ---- lr• 1 _ 1 I I - 1 I 169' I I - I l-1 1 1 I· l o· I j ual • l l' 1 o I I I I _ I _I ' ' ' uu ' ' _- • I' - A ' -- i • • • lf'r 4 ' _ - •·- Uk1 _ _ •' 'I •- --- - _-·-- ___ __ i · i D •' l u· · f I ' I FIG 26 I_- -- ' I L ' _· ' I - -- j ' J I I ttn -l I ··1 -- ---- °'I B11P m1 Atoll 1 - J • l • P Aloi • j _ - • • u -RS I' ' - b l Pe - IO' I --zsa c L41J1 1 I I ---- - - - -- J - o re1 06 __ Wt A lmL __ _ 4 -- zk•• 1 A 191• ''01 •-• • 1 ' ·j • N 2 - I I 1 i --t- ' - Npt1•Ata1 I ' I I I '- I • 1_ _ • j j - A noAtoM 1 I 1 Mill Atol Jf -H -- -- -- - --o - ---- --- -----t------ --- ---f---- --- -o m I BL- -- - - _ i - 001 I j· '•' i-- ·•n - Ma uroAIGI M• 2- Namo 11 AIDII u ---l3 ____ i ' -- ------ I · --- ---- ---1--- -----t----- ----- ----II----- -0 ·°' 11 - • • Jelu1t AtOII I Wol Aloi I __ 17p Atoll rikub Atoll I I SLAN DS Cl __ •-• r l _OI' O l 0 J ' o 1 LJ-S Atol • O CII ' I 1£CTU I OlY 0 1 1£CT I • 2 OlYS - I ' --'I• I -- I U M Atol I IEY I oarJ• _ ' 1 '-· - I l -i 1 Hf A L 0L l •1••-• 6 • 11WOtnoAto61 • -I 1· - '' • I Utm• Atoll · -------t-- - - - - - - •lloftasr 11 A oll I I - • - i _ _t-1 ·•------------ •l1Wweto11Ato1I 0 ------- I I ··- · t- f - I I I I I J 1 - '- I · ' i ALL IUDIIIIS I• ✓ '·t· · ' I -t' ip 'y I I J 5 __ lbon Atoll - rt ' l I - I ------- ------------- --- - --- - i - - - 'I l 1 t - 1 16' 157' 158' 1 • -J - 161' 162' 163· 164' I I ------165 1 l66'Ne1 1r1 1 1 167 68' 169' 110' Ocean I I I i 172' 171' I ' ' I' ' I ' I'' I ' 173' - I I I I 2L- i- ' - 174' I ' ' ' ' I ' I G LIB ER l l 1--I -1 1 · -4L--'-- P5' -- j ' ' ' t I I s--t---1• -- I t I IS LANDS 76' I J ' 177' 171' J -' I • I i I l _J l J -1 -- I I • • I I I I TABLE I CUMULATIVE DOSES BY EVENT AND LOCATION Finite_Do e to_Next E nt -mr EVENT Days between events BRAVO ROHOO KOON UNION YANKEE 26 11 19 9 9 NECTAR 10 TOTAL Aerial Moni torin Lae Ujae Wotho Ailinginae Rongelap Rongerik Taongi 'I Bikar Utirik Taka Ailuk Jemo Likiep Nanru Allinglapalap Namorik EbOl Kill Jaluit Mili Arno Hajuro A1 r Hil · c llap Erilc' 1 Wotic- 5 5 6 250 6000 180000tt 190000i 280 60000if22000 1500 5000 1200 1700 1 8 7 2 20 20 20 20 60 60 200 12 32 270 3400 11000 9000 60 3000 1200 Boo 410 410 170 90 140 160 250 200 300 350 39J 160 200 200 200 120 200 l j J 300 40 12 17 110 3300 6000 000 9 5 1200 700 1000 110 130 80 100 100 10 so 10 70 200 JOO 50 50 50 50 200 itB-1 ed on arriv 1 1 1 imatcd fr·om Rongerik data 7 5 9 5 55 8 3400 550 10 650 100 120 100 18 30 0 8 2 8 0 8 20 8 20 8 0 0 13 78 48 95 600 1700 1400 10 1700 330 380 soo 200 200 25 0 0 25 0 0 0 25 0 40 25 0 220 95 1 4 4 70 300 280 - 150 so so 20 20 16 0 0 0 0 1 3 2 6 1 3 1 3 1 3 2 6 4 0 6 5 10 125 114 784 67000 202000 206000 370 67000 24000 17000 6140 1978 2196 216 255 252 I 1 353 ' 291 401 l 594 471 341 549 647 2543 ' ' TABLE I Cont 1 d CUHULATIVE DOSES BY EVENT AND LOCATION Finite Dose to Next Event -mr - EVENT Days between events BRAVO 26 ROMEO KOON UNION YANKEE NECTAR 11 19 9 9 10 TOTAL Fixed Instrunent Network Kwajalein Najuro Kusaie Ponape 'l'ruk 1 Yap Guam Iwo Jima Ujelanr Wake Johnston Oahu Sheiey-a Anchorage 150 156 85 5 5 29 1 - BS 4 3 3 110 480 137 4 2 20 1 J - 250 53 0 1 31 2 3 - -- 176 28 66 1 9 - J o 12 2 0 2 21 320 2 o 38 17 0 1 0 1 6 2 0 9 8 7 15 1 4 7 4 6 6 8 12 7 142 1 2 2 0 52 2 2 - - - 0 7 - 1235 351 90 122 49 18 455 12 95 -95 45 I TABLE II PEAK GAMMA INTENSITY BY EVENT AND LOCATION nrrLhr BRAVO ROMID Location ¥11 Lae Ujae Wotho Alinginae Rongelap Rongerik Taongi Bikar Utirik Taka Ailuk Jemo Likiep Uamu Ailinglapalap Namorik Ebon Kili Jaluit Mili Arno Majuro Auk Malgolap Erikub 'Wotje - UNION 0 2 0 3 1 1 57 0 12 0 2 0 9 1 6 61 82 0 12 20 12 16 1 7 2 11 KOON YANKEE NECTAR Aerial Monitorin 0 08 0 1 2 7 46oott 12$00it 8000it 3 1200 49 32 75 18 18 0 02 0 08 0 2 0 2 0 2 0 2 o 6 o 6 2 0 o 4 3 6 4 20 0 18 o 5 4 0 155 130 1 0 37 17 8 6 6 2• 5 o B 1 2 1 4 2 2 1 8 2 8 1 4 1 7 1 7 1 7 o B 1 7 2 6 95 0 2 11 2 o' 4 2 4 o 4 0 3 o 6 0 0 09 0 02 0 09 0 0 09 0 2 0 09 0 2 0 09 0 o 4 1 6 0 15 1 2 a a o a o 6 o 4 o 6 o 6 1 5 2 3 o 4 o 4 0 Extrapolated to e t-imated arrival based or Rongerik data 1 2 o B 1 6 10 30 24 0 2 34 6 5 6 1 1 3 4 3 2 0 3 0 0 0 3 0 0 0 0 3 0 o 4 o 3 0 2 5 0 2 0 03 o oJ 1 4 6 5 8 0 3 1 0 1 0 o 4 o 4 0 3 0 0 0 0 0 02 0 04 0 02 0 02 0 02 o o4 0 06 0 1 o 15 II TABLE II Cont• d PEAi GAMMA mTENSITY BY EVENT AND LOOATION nr Lhr BRAVO ROMEO Kwajalein Kusaie Ponape Truk Yap Guam tll Iwo Jima Ujelang Wake Johnston Oahu SheII Ya Anchorage UNION YANKEE NECTAR Fixed Instnunent Network Location Majuro -KOON 1 2 0 2 l J 0 005 - 1 5 0 2 o o5 o o5 o o5 1 s 1 -0 15 0 01 - - - 0 02 o 4 o o5 o o5 o o 2 0 1 o J o o 0 07 0 01 0 06 0 003 o a4 0 009 0 009 0 02 0 25 o os o o5 o os 1 7 o os o os o o5 o o5 1 0 0 01 4 5 0 003 o o4 o 3 0 15 0 03 0 1 7 0 0 007 o o o o5 o os o 4 -o oJ 0 03 - 0 001 o o o o o os II r - --r i 1 I • ' • · · 1- ' · · - -- -- -- - - I - - -- ·1 I IG 1 • 27 ISOOOII£ CWT RAOUTIC I FCII CASTLE r r --1 l I I I ' I i •- • t•-- I' - I· L I - 1 I 1 - ·- '----- J '· M '·· ' I -- _ _ -· • r · 'lI ' f --- -- le - I' · '--- ---- '----·t-'- a - --- i -r-- -----r-- -1i--r----t- · -· I ·• r-- • ---------t-'-----t- - - - - - - ·7 '- I I _ r --- I •TOTAL CINILUIVE • I --- 1 - T - -- · - ·l • 1· 'I - · I L I I I I ' - ti· CJ 'I I I I ' £ -AIDII 12 - • - - - - - ·- -- --- 11 _i I A U AIII 'j I I __ -- ---- ----- -- -- - - F-- t--1 - - --- --- -''---- - t ' ---------- --'--- -- -----r--- - - --- t l I' I - - _ · I t - -I J r r - I ' I - _ - • I I 7 • - --t--- -t---t-- --- ---t---t-- ---1t---- -- ---l--5 --i 2 I ·' c------h----t--- --- -- ---- ---t---t-'----t--r--r --- - ---- -- - - • 1• I I I I - 1 1 11' 159' • 1 • 161' I 162' · 163' -1 L j _ _ 1 J 164' I ·' ' I · _ I • - - l -r-- -1 GlLBER I f -- I 4 -•1 I I I I I I I - I 2 _ i - ----- _ --- ---- -- -----t-- --- -1 · '•-· - • ' ' 1 • I 168' J • 3L- I · • 1 I f I I 165' ' · 166'No 'i67' J L l 4 1 ' ·' - I I -- --- -- - __- -- -- ------r-'-i-' ' -t-----ti l L J LJ · I I I - ---- f · _ ' 1 7 I -· · r I 1 ·--- - --t-- --- -- ------t---i----- I 1 I i• I • e• 1 I I ---- · _ 4 - - 10 1 o• L J 1-- r' ' t r 1 1' 1 1r• · 172'' 1 _ -'· 1 ' 1 ' ½it · -- ' 111 1 • I · ' • · ·•V - • -- · -1 t' · I _ L - t r · • t ' A8fm To establish an empirical relationship between beta dust activity on the ground and gamma radiation intensity at three feet over the ground selected comparative da ta have been plotted Figure 28 The values selected are limited to the first 24 hour period of significant fallout following a given burst Beta activity has been extrapolated from counting date to sampling date The paucity of values is due to incomplete data dust samples are missing in certain instances and monitor failures occurred at various times The values presented are prelininary Further review of the available data Jllc Y disclose additional useful comparisons and a refinement of computations may alter the existing values somewhat -42- M OH f Fl G 28 BETA OUST PER SQUARE FOOT VS GAll tM INTENSllY AT 3 FEET ' z z ' - ' a Jff f1 · ' s f i1 1 ·· J c · · · i · I - • 1'· t I · l I l I ' -- · - - 1 · 1· r--1· J --r J o 1 · _ ·I • I 7 r · i j- ·· · I l 0 I JI 7 • • J 1 i i 1ii· 1 1· 1 l I ' ' I i I i - 1 t I '·· · J I •I l i ·· 1 11 --1·· i I i-H -1--l--J-·1-H-4 - ' -t-f- -r--t--L j _j nT · i i I TT7 I I 1' I 1 1 1- I I ' I •1 1 I · i i ✓i • v 1 ' 1 · · - I I I ' i r- ·i 1 i-- - i 'I I --r 1--·· 1 l • · 11 · I Ill I ' ' • ' • I · 'l I 'I '· i I 'i -- -1 -' i 1H i 1 ' L' ···-ii · · c - J 1' I -- -i----tH--t L I' J I' -••f -·- •m t 1-UV · Tl 1 r·1•··• • ·· j · hi · 1 • • ' t l i ' · ·- i lli f · · i Lf1 · i · LL' lLL Li --i- f-i ____ ·· · ·-·I··-· 1 1 01i 1o' · a f J · r r·r1i • ti e 7 8 I I '1 · 1 1· I ·1 ··· ·Fr· ij a S • ti 49 7 10 8 U _ 10 0l5 MIN FT 2 BETA DUST -43- 1 ·-f-·-1 _L __· --- ·••·•····• i I il i i ' _' 5 - 2 S i I 1 _ _J i I i LUJI 0 7 Q 10 6 LEI T•r -- J FACTORS RELATING TO DATA INTERPRETATION 1 Automatic Monitoring Stations A Diurnal Variation Shortly after their installation the AC operated automatic monitors displayed a regular diurnal vari- ation apparently due to temperature change humidity or both The variation was as great as an order of magnitude in some instrunents for this reason the practical lower limit of detection was about 0 1 mr hr although the design limit was 0 001 rnr hr Interpretation of radiation intensities less than O l mr hr was difficult and on one occasion fallout of low intensity was mnoticed when it occurred A later careful analysis of the data revealed that 0 15 mr hr occurred at Ponape after RCJIBO Had this been known a CHARLIE survey would have been executed and it is possible that significant fallout may have been detected at other atolls in the area A review of the data and_ the instruments• behaviour has indicated that the late night instrunent reading was in most cases a reliable measure of low intensity radiation In several instances of light fallout Ponape-ROMEO Truk-BRAVO Tru k-YANKEE only the 1800 Z value was used for plotting time graphs Similarly at several stations only the 1800 Z values were used in computing C' llmllative radiation The diurnal variation was consistently so high at Guam that none of those data all of which are low level are considered valid B Comparison with Gu nmed Film In those instances of ruspected falloutwhere diurnal variation rendered monitor data of questionable validity the data were compared with the appr priate gummed film analyses from the World Wide Sampling Network In each case the gummed film displayed an increase in activity correspondi i g to the monitor data Thus the roonitor data was qualitatively substantiated An example of the comparison of the gtnmned film results with automatic monitor values is shown in Figure 29 C Automatic Konitori Instruments Down Time Monitoring sta tior s were out of service for an average of 1 % of the time fro - Mc1 I·c •• to May 20 Fortunately much of the down tine occurred between events so that useful data was lost only at the follow stations during the stated fallout periods BRAVO- Kwajalein Wake Panape and Iwo Jir i a RONEO- Kusaie Ujelang Yap and I -10 Jima KOON- Yap and Iwo Jima UNION YANKEE AND NECTAR - John ston The presented cumulative radiation values are therefore in generJ 1 underestimations 'lb e values are based on the recorded data onl r which account on the average for 85% of the duration of CASTLE 8i1iaiii' -44- ·_ I '100 I' I I I lI I I I ' I • • ' I I II ' I I 10 I I 10 6 '1 •• • l I 3 a 1 0 I I I i 0 1 · - rr r r I1 · • I · • I rI I j I I I i j - i ' l I f 1 I '' II I I I ' I I I I I I t 01 i j ih· I ' ' ' ' ' 001 10 2 11 MARCH 2I ·Q I i I I I i' l ' I I I I tQO I I ' I I I I I • I '---·- ·- ---· 1 I I I I• I I I I 1C il APRIL DA rr -45- 20 JD 11 IAAY iiilMH Radiation during down tine was not estimated except at Ujelang where down time was in excess of 50% There the estimate is also low because no data are available for the fallout period ROMEO and NECTAR Peak intensities were obtained directly from the monitor data Where blanks occur in Table II data are unavailable due to instrument failure or incorrect calibration The values listed are the greatest intensities following each burst 2 Aerial Survey Monitoring A Fallout urival Tim Applied to Aerial Monitoring Data- Flight Fallout arrival times are not generally known for the isiands covered in the aerial surveys The few exceptions are those which were automatic monitoring installations Cumulative and peak radiation computations are necessarily based for the IIX st part on estimated arrival times ABLE For BRAVO the arrival ti I E at Rongerik is exactly known from the automatic monitor record For other atolls the sane general bearing as Rongerik from Bikini the arrival times were arbitrarily assumed to be proportional to the respective distances from Bikini referred to Rongerik Allowance was made or the initial rapid lateral cloud growth in the first minutes after the burst Data obtained from Task Uni t-1 indicated that at -t 10 minutes the cloud diameter had grown to 335 000 teet and the rate of growth had diminished to a relatively slight amount Peak radiation values w re computed by extrapolating the observed intensities to the estimated arrival times on For the northern Marshall atolls on widely different bearings from Bikini than Rongerik hence well removed from the direct fallout path the intensities observed during the aerial survey on B l are the reported peak values in the results Cumulative radiation computations are based on decay assumed to start from these peak intensities For the other events the peak values are taken as those observed on the D 1 aerial surveys unless later surveys of the same isl i nd s indicated additional fallout after D 1 In these cases arrival tinE was arbitrarily assumed to be D 1-- 2 and the intensities measured on the repeat flight were extrapolated back to D 2 Cumulative radiation values were computed assuming t-1- 2 decay from the peak values iiiiH 11 -46- CUilllll ative values are not corrected for the slower decay rate of residual contamination from previous bursts The neglect of previous contamination is partially compensated by erosion by wind and rain a variable factor Fllgpt BAKER Fallout definitely occurred at Majuro during BRAVO But there seems no valid method of relating these to the arrival of fallout at other atolls in the southeast Marhsal ls short of a detailed analysis of the pertinent meteorological situation However over Majuro BAim fiight on B • 2 very nearly coincided with peak fallout there as measured by the automatic monitor Arbitrarily the peak intensities 'or all islands covered by that flight are taken as the observed intensities and RCltEO and the arrival tines were accurately established For R J F 0 all survey values are extrapolated to R 4 again to conform with the arrival at Majuro With the lack of difinitive data for the time or arrival in all remaining events it is asswned to be D 3 as a compromise value B A ir Survey Background Radiation Background was recorded prior to each a toll measurement while the aircraft was several miles from the island In computing atoll radiation intensities the background value which varied by as much as an order of magnitude during arr t one mission might be attributed to sources such as navigation instrunents aircraft contamination skyshine or a combination of these It has been reasoned that the background could be validly subtracted from the atoll 11»3asuremmt to obtain a net value of ground intensity Intensities were computed by this neans during the test series Late in the series it came to our attention that significant intenait ies may be emitted from the ocean surface for several days after the burst This phenomenon may be another factor in the measured background and cannot be disassociated unless an additional background measurement such as at a different altitude is available For any gi ven measurement there exists the possibib ty in one extreme that substantially the entire background is due to ocean surface intensity This value would not be subtracted f'rc n the toll measurement In the other extrene the entire value of background must be subtracted as was done in reporting data during the series In no case did the background value exceed a ground 12asurement as might hypothetically occur if currents moved contaminated sea water near an uncontaminated island -47- The values presented on Figures 3 thru l 7 and used in computing cunrulative and peak radiation are net radiation values i e background has been subtracted from the observed a toll intensity It should be noted that low intensity values may be considerably in error where background levels are of the same order as the measured atoll intensitye C Relation of Aerial easurements to Ground Level Intensities Certainly' one intrinsic factor limits the agreement which may be achieved between any particular pair of corresponding aerial and ground measurements This is the vast difference in the effective areas scanned by the two IJJ thods of survey A single ground level measurement with a portable ganma instrument registers activity emitted from an area of a few square yards while the SCINTAMETER a an altitude of 200 feet or more sees an area of perhaps 101 000 to 15 000 square yards It is weU known that measurements on the ground will show considerable variation over a relatively small area This was particularly evident on Eniwetok Parry after the late fallout carried back by the low level trades after RCMID Gamma intensities in the open over horizontal surfaces were up to two times greater than intensities in the lee of large obstructions Similarly measurements near the windward side of -vertical surfaces -2re greater than measurements over open horizontal surfaces In the like manner 1 aerial measurements can be distorted by uneven terrain scanning the lee or 'Windward side of a mountainous island 1 and perha s other factors After BRAV0 1 survey par-ti s reported substantial variations in outside radiation measurezneats on all of the islands surveyed Generally I one aerial measurement should approximate the average of many individual outside ground measurements taken over the sa --ne general area however the factor o instrumentation nru st be recognized as a variable The energy response characteristics of portable instrwrents conmonly used during CASTLE differ from each otaer somewhat and differ from the SCINTAMETER rather markedly Tb esponse of the TlB for instance is nearly fiat above O l Mev The characteristics 0£ the AN FDR 27C are somewhat J ess uni form but above 0 3 Mev are reasonably fiat The SCINTAMETKR1 on the other hand peaks at about 0 25 Mev and has a uniformly decreasing response from the i eak as the gamna energy increases The characteristics of the three instruments are plotted in Figure 30 If the instru rrents are all calibrated w i th Co60 or radium sow·ce I as in iil8MI -48- - tl - -P ll 00 - - -IL l -t-t 4 •ttt 't- t ·r- -t· 4 6 1$0 1· 1i-l·t·ij_·' -u t·t1r1 t -1 1 l - r' r· - 1· - - - J • • • ·r ·1 I • 1 --' - -• iJ_ -t-1 -•- •·•· • 1H- -j J •rrt· -t _ - 1-l t___ _ _ -_-t· •-r - 1 i 1 t- 1 tf- l • · I •·• l •·1 i q j • • •• 1 •• I ' 1 o 20 ' 0 4- - • l- i ' ' I 1 t • J ' • - •• r · ' 1 i t 1- • - 1-• 1 ' '1 · '· •' 4- • -4 -11t-t H' I t J 110 1_r -i- •·-r ·t- - - i- - 1· •--rt- - - --- i z 20 - -- -- f- - • -_- - 1 W±Jr -t-r-r-jr-t- - f I • ' ' • l 1 • l i f 1' • 1 • • t c I 7 i l 80r- -i- -T -____ 4- - - cc l Ht t t · ' ' i I ' • I · ' ' • • 1 1 · 4 • • ' • • T ' • 1 1 ' I ·1 L t t--•-t· - - ·• I ' t r t I j j 1- ' t- t • 1 t ·• J 1 •• i ' • t • I ' • - - ' ' • I• ' I 1 i ·-tr· ' ' • I • 1 - l ' I I - - • _ _ _ __ t • ·· l I t t • • 1i i • I • '' i i l' t- I i J I 11 · ' •'i • ' ' I ' ' • -• • 1 • t • • 1 l ' t ' l I ' j 1 -· j ' '-- - ' • • • 1 t·• · TH 3 9 ' 1 r • ' 1 - K- -·--· I I 1 • K _ · · • ' 1 · • • • _ _ _ • 1 •• 1 -•- I f11-l - i j ' i '' i I · ' 'T 1 ' • ' 1 1 I ---7 · i - - - - • • · · • 1 · ·11 i • t -_ ' l-1 r I • • ' t 1· •• t ' ' •· i • • 1 • I • ' ' t '· • f rl 1 t · l r·• - • r4 ' I I ' ' j_ t - t• 1 1' l 1 I- t • j ------ I l I j J_• • - -•-- ' l l ti ' l l · i • -- -----1---- --t- - -t- - - -t- u - ·T4•- - l - - - ·- --r·--- -t- l '· ' - t - - ---I--ii • ' · •• • j • i 1 t • I ' • i' ' I ' · 1 --4- - -- -- ---- -- - ' --i---- - - --- ----j 'j t t· 1-i • - ' 1 ' • · I t t 4- t • _- - -- --4 --f-__ -- --- ---r --- 1 I t I 1 f I -1 1 • • - - • - ---- --1· - - - t • 't ' t 1 1·tt·• - • · t r - I t 1 t ' ' ' ' O · _ - J-t · t r-r- 1 -t-r- - r-r•r1-· 1 l I •· - -· · J t-t- · · r12 o • r _ · rt _· _- ' '_ t' t r-1 '-1i' 'i' - r · iii° ' _ • i tt- ti h· f - -1-•- Tt t 2 80 ' ' ' ' ' - 41 · ·q tt l J r - rt t t tf1 2 60 ' l ' t-i 11-t- r • ' T r - - • -' _ - - - -t- ---- i- _ _ I it-ti-- _ ·• • SURVEY INSTRUMENTS 1 'OVERENERGYSPECTRUM• - -r t-- i----- - ---f- ---t-lrt t i - tr J LjJ_ j -1 1 · r · I'-i- t·- -4 f- - -1 l • q t ·r I ti uJ1 • • ' r r - rr-r i -t t r r· · 1 o ·- -•-- '- i-1-lr • r' r•'• IO 30 -·-·1-- 1 1 I '--' -' • -'-t- - - -- - -i J_ RESPONSE OF t L I· ' J • '' -t- _-ir·t- -i_j_T__r___- ·G - ri ' - -t -1ti_ t_--t -1t-·t- -t- -t·-_ · t t-· ·-t - SO ' t tl l t t -1 j - l- - i ' ' i·· · l I '·I • t I •- 1 -• ' - • - ' 1· - 7 t l 1 't-1- t ' I 200 600 800 MEV 1 000 1 200 1 400 Figure 30 the response of the SCINTAMETER at o 7 Mev 5 the average of gamma fission product activity is about 6o% greater than both the nB and the 27C internal probe and about 100% greater than the 27C external probe Thus it can be readily understood that readings of two different instruments in the salll ganma field may be different and even two overlapping scales of the sane instrument may not agree The size of the islands surveyed within the range of this study apparently does not effect the validity of the altitude to gc-ound intensity conversion curve Calibration for the SCINTAMETERS was performed over areas of various sizes including both small and large islands in the Eniwetok and Bikini atolls Data from these several locations agreed very closely Obviously I judgement is needed in evaluating radiation intensity in tel'I ls of potential· exposure whether ground ueasurements or aerial measurements are the source of data OiliiWI -50- V EFFECTIVENESS OF MONITCRING PROGRAM The aerial surveys and the automatic mnitoring network mst be reviewed together to analyze the effectiveness of the program properly for they were designed to complement each other The program was a practical compromise between two extreme monitoring methods one being a monitoring network comprised of stations on each of the islands included in aerial survey patterns 66 in the Marshalls Carolines and Marianas or the other being daily or more frequent flights over each of the survey patterns from D • 1 repetitively for a number of days following each event It is believed that the monitoring program did successfully fulfill the basic requirerents of providinq timely fallout information concerning the cantral and Southwest Pacific and of documenting cumulative radiation in those areas The infu --ma tion developed by this system following the BRAVO burst is an excellent illustration of its effectiveness in perfonni ng the former function · -lb t 1540 M on B day the automatic oonitor on Rongerik 130 NM East of Bild ni went off scale Ma xirrrurn scale reading is 100 mr hr This infornation received at the Task Force Headquarters aboard the Estes at about 1600 M was the first indication of excessive fallout outside of the ships of the Task Force and Bikini atoll itself A radsafe monitor was sent With a scheduled island resupply flight on the following morning to clarify the fallout situation which had been indicated by the autonatic m mitor At 2000 M on B day a mssage to Squadron VP-29 was originated on th Estes requesting the immediate execution of 11 ight ABLE The request was delayed until that hour to diminish the possibility of the survey aircraft passing thru the radioactive cloud Due to communications difficulties the ressage did not clear the Estes for about twelve hours after it was originated and the flight did not leave Kwajalein until about noon on B l day At 1535 M on B 1 the first inflight report was received from the survey aircraft The report included measurements over Ailinginae Rongelap and Rongerik It confirlood m9asurements of dangerous radiation ma de on Rongerik by th'3 radsafe -om tor a few hours earlier On his recommendation evacuation of Rongerik had begun immediately and was complete when the first inflight message was received By 2000 M t he radiation intensities at all atolls in the ABLE pattern were known and plans were formulated for the evacuation of additional north Marshall atolls By B • 5 days all survey patterns had been executed including an improvised pattern to survey the Gilbert Islands and the extent and severity of contamination in the Pacific were clearly defineda MJ6Dii -51- 'Ir re were t1Jo locations from which repetitive practical comparisons t Jtw sn aerial and t -round measurements are available during CASTLE S n•- ra r arties visited Rongerik frequently Ver a period of man y weeks after BRAVO and recorded gamma radiation intensities each tire AN PDR-TlBs portable ionization type ters and other portable gaili la meters wre employed for the measurements The averages of those measurements taken outside of buildings agree very closely with aerial survey measurements over Rongerik These data are plotted on Fig 31 Certain of the comparative reasurements were taken on the same days others were not The gr-ound measurements taken on days in between aerial measurements lie very close to the values expected from theoretical decay calculations Comparative measurements are also plotted for Ailinginae Utirik and Ailuk Figuree 32 33 and· 34 although these are locutions where only one set of ground measurements were taken The follow-up survey measurements made after the D 1- 1 surveys show reasonably close agreement With the theoretical decay curves shown on these figures For simplicity the decays were computed from each new ma x iml llll measurement following each event without regard to residual contamination from previous a vents Since there was no method of accounti ng for the effects of wind and rain in reducing contamination there seemed no reason for more elaborate theoretical decay computations At Majuro the site of an automatic monitor there are comparative data for ea 1 h burst except NECTAR Here again the agreement between aerial and ground measurerents is good These data may be found in Table 2 The signiiicant contamination of sea water following a burst has now been amply demonstrated The possibility exists that this phenomenon contributed to the background values recorded during the aerial surveys and that those values were incorrectly applied to the atoll measurements in computing net intensities Suitable procedures must be established to differentiate kyshi ne water activity and aircraft background in future applications of the aerial survey Several of the ir stalled automatic monitoring instrw-rents were desic r ed tJ measure ani record beta dust concentrations as well as gam na radiati-- n All of the btta channels failed within a few days after their installati 1n The failures resulted from various mechanical and elect ical difficulties No data was obtained regarding beta dust TL 1 desiraLi z ty of obtairJ n 6 such measurements has probably increased ratl-ier thar- dimir ished in light of the renewed interest in offsi te fallout It is desirable that the instrur nts be perfected for future tests In iJff ita wnitoring conJucteci by this office for previous Nevada tests th 3 iriscl G rs-1 e ••t of b ta ctivi ty in dust collecte d on filter papers was fuL i d t0 te a rwre ser sitive measure of bomb debi·is arrival time anJ · HM - - - _FIG 31_ leRI_U MONITORING MEASUREHEIITS - ROtiGER IK 10000 I t--------t-------1-------- ---0----1------- -------r- I I I I _J_ ------------- ir-- -- ----t- I I V 1000 I i J · _ -l- r I ' 1' i l o · - 100 I z 0 - - - S E E SECTION 11 1 - £ rs J f Q I C -Ci let - I i '- C '- 1 J l_ J - JJI •O z 1 I I I I lrs ' 1- I I I- L · C I I I I - -- Q I f II I I I I II ' I 'I _j o - IC I 1 I I I I I I I I j I j I • 0 J I J J '•r' '• 11 I ls I 1$ I 1 ft I I 1° - _j '' I '' ·- 0 AVG OF RAOSAFE GROUND MEASURE''E TS 3 ' I 0 7 LJ 21 I »AYS AFTeR MARCH 1st 9E IM r -$1 - B A 28 35 I l I I __l_ _ j i I I I · I -I i 1 rt l I 1 ± 1 L_ 2 9 56 63 J 70 I 77 IMilRET FIG 32 AERIAL MONITORINi E SUREHENTS - AILINGINS 1000 ·-- - x' _ _ roQ 0 ' I ' Ill '' SEE ECTION ' IE ' ··- ' g ' I • - ·1- - i - •I• '·- ·- tt · · • ' ' lit t' · 1' l t - -_ -- I I I I ' '- - -- ' ' ·- ·-- ·-L tI I I I AER lAL MEASUREMENT • ' ' I ' ' 1 RADSAFE GROUND MEASUREMENTS 3 • 1 - n£0RETrCAL DECAY t•U ·'· - · - J' ' l Yl 7 AFTER 0 ' - _- - - I MARCH I st - · t··· ' ' f ' - • •·· · ' ' I 't ' • - HHH ' -55- I I I i ' 21 BRAVO' I 35 1l2 9 56 - t - rt 28 I J 1 ' ' 0 -- I I - 'l r ' 0 1 I - 1t I i t I -- ' I - I I I • ' ·•• ' _ - °' u w z 1-- 0 - - - ' '1 tt - I - • · ·· ' - - t _ Jil i h · ·· · - _ '_ - _ ' ' -1 •i-j J · - '- C •· · -- - · _ ' · · · 'J I •' • _ _ _ _ Q 'i s C C '- ' t' -'' I ' J '· ' z I - - ' ' 10 '-- I I ' 0 C ·' o·· • ' ' · ·· ' _ 1 W D S '· - I ll ' °' w z § 63 I 70 ' n l I - ' · ·a· ·· ff • ' it '- 4 ' t floM RE lo FIG 3 AERIAL l•OHITORING 111 ASUREMF NTS - UTIRIK 1000 ·-- I I I ·- I ' t 100I a 0 0 z i ' uJ c t iuJ 'Cz • z I ' IX z ' - IX z u ' •t- ·' - u ' z ta i a uJ z 0 u z 0 I ----'o -- I I SEE SECTION 11 1 t- c 1-- l- Q C QC C ' - _1 ' ' ' I IC IC C c ' ct I r-- I' I 'W I -- I - • RADSAFE GROUND MEASUREMENTS 3 1 l - THEORETICAL DECAY t• J 7 2J DAYS AFTER MARCH 1st· BRAVO I 0 - r- -- I o AERIAL MEASUREMENT I ' - 0 - I ···-· I - ' ' · t 28 35 ll2 n 9 · -56- ' ' ' r L' _ · - 1•· I Wiil'lft f F IG 34 AERIAL MONITORING MEASURHIENTS - 41LIJK 100 -1 -1 I I I I I 1 ' r I I 0 - - z a E -' ' ' - ' -- z « t - - I SEE SECT I ON I I•1 ' -- ---- r- I- laJ z ' ' z I I -z 0 0 0 r er r- a z - 10 I I 0 ' 0 I- z -z -c -c 1- - ' ' _ 0 1 - I- ' ' a -c E z -c c 0 1 -' Q - ' A I'- ' I' ' l ' -- r-- __ ' -- 1--- _n AERIAL MEASUREMENT o o u • RAD SA FE GROUND MEASUREMENTS 3 1 - THEORETICAL DECAY t-ii ' - IU 21 DAYS AFTER MARCH 1st ' -5' - BRAVO -- _ 3 - 71 7 activit - than ground gamma measurement particularly where fallout ias of low intensity It was also found to give earlier indication of arrival this probably because of its g eater sensitivity There is reason to believe that these characteristics would apply in Pacific tests and might prove useful in warning of fallout arrival A particularly gratifying achieverrent of this program was the utilization of personnel untrained in radiation instrumentation for the operation of the automatic monitoring equipmant This represents a tremendous economy in the use of the scarce nu -- iber of personnel trained in radiation safety techniques It has been demonstrated that a fairly comprehensive monitoring program can be continued over a protacted period without tying up a large nwnber of trained personnel -58- VI INSTRUMENTATION 1 Aerial Survey Monitoring The SCINTAMETER General Description The SCINT AMETER r a selfcontained waterproof battery operated scintallation type gamma detector with a fast response time was used for all aerial surveys Tre unit weighs slightly less than five pounds with batteries The single 1TEter scale is divided logarithmically enabling several decades ot radiation intensity to be read Without switching arrangements Two models the TH-3-B and TH-3-C have a range from 0 003 to 100 r rtr 'nr and differ only in battery complement A third model the TH-7-A has a range from 0 001 to 10 r «r This nigh level instrument was developed for the use of cloud tracking aircraft and was used extensively on the WILSON fiights it was not utilized in atoll surveys but was serviced by HASL personnel A B Conversion of Aerial Measurements to Ground Level Intensities An afr to ground calibration procedure was performed for the SCINTANETER at Eniwetok in February prior to CASTLE and repeated at Bikini a few days after BRAVO Similar calibration work had been conducted for the SCINTn oo l predecessor to the SCINTAMETER prior to its use during IVY The calibration procedure consisted first of Conducting a thorough survey of the radiation intensity at 3 ft over an area contaminated by fission products followed by measurements using identical instruments over the same area from an aircraft at altitudes of from 50 to 1000 ft The ratios of the average ground intensity to values measured at selected altitudes constitute an attenuation curve which may be used in adjusting aerial readings taken over areas of unknown contamination to ground level intensities There are several possible errors and variables which may cause variations in the attenuation factors derived These are radiation instrument error this includes energy dependence which is discussed in Section V altimeter error human error irregular di stribution of fission products on the ground fission product age and variation in the absorption of different sections within an aircrai t and between aircraft Both P2V aircraft and helicopters were utilized Variation in the area of the radioactive source may also be suggested as a cause of variation in attenuation factor however although the islands used for calibration sites varied markedly in size q Z1d shape the attenuation factors were not reasurably different For detailed description of instrunents see FALLOUT MONITORING FOR CASTLE 11 6il8niilf -59- 11 HASL-154 OPERATING PROCEDURES u i Fig - 35 SCINTAMET R - · '· ' • - sr • 0 -- ' I - - J · s L • _ • ' awr The following calibration studies were conducted in connection with CASTLE Location and Date Instrunent Eniwetok Feb 1954 JANET GENE SCINTAMETER SCINTAMETER Nuclear Inst Corp 26lOA GENE Bikini March 1954 SCINrAMETER SCINTAMETER WILLIAM YOKE In addition neasurements taken by independent survey parties at Rongelap Rongerik and Utirik using several different types of survey instrunents have been re ated to corresponding aerial neasurements with tha SCINTAMETER during the routine execution of the ABLE survey pa1 tern One other set of factors was obtained by persoIU1el of the Weather Reporting Element with both a SCINTAMETER and TlB The record of the identity of the atoll where this was obtained has been lost Air to ground calibration for the SCINTil OG was performed by HASL personnel in Nevada in 1952 using TUMBLER-SNAPPER test sites as sources Another set of data obtained by an independent group using a TlB during the UPSIDT-KNOTIDLE series is available for comparison The attenuation curve applied during CASTLE is shown in Figure 36 This curve is based upon data obtained at JANET then later substantiated by studies performed at Wil LIAM and YOKE aIXi by miscellaneous coincidental data obtained during CASTLE These sites represent a variety of source areas for instance YOKE and JANET are l 8 mile and 5 8 mile across respectively There is good agreement among the studies at the three selected islands and between the resultant curve developed from these stu1ies and the miscellaneous data The extrapolation of the atterru ation curve to zero altitude yields a factor of 2 ich is approximately equivalent to the aircraft hull absorption Individual sets of the GENE attenuation data differ markedly from each other and their average attenuation curve differs markedly from the bulk of the CASTLE data The two sets of data taken in iiQiliilfn 1- • I' I ' i - ' I' ' ' ' ' I • ' ' • • I ' ' I I iI - - I ' i ' I • • I I' l • ' ' 'I t ' I 'i ' I l • I I I i I • J l ----- - - - 1 ' ' LTl iclf v POVf oOv POU'H -62- l401i F T Nevada on different occasions agree remarkably well with each other but differ from both sets previously nentioned The averages of the GENE and Nevada data are plotted on Figure 36 The reasons for the discrepancies are not clearly understood Any combination of the possible errors mentioned above may be responsible It is felt that the effects of fission product age type of bom and instrunent energy dependence are factors which require f'urther investigation c Field Calibration Radium was used in the calibration of low level SCINTAMEiW and low end of the high level uni ts Co was used for checking the upper end of tre TH-7-A scale • g'fr The original meter scale calibration on the TH-3-B and the TH-7-A · units remained unchanged throughout CASTLE The TH-3-C was found to saturate above 20 mr rrr requiring a special calibration curve · ·· · · ror correct interpretation of the scale above that value The latter uni-t was used only where intensities were expected to be less than 20 mr br i e flights originating at Guam_and Oahu SCINTAHETER calibration was generally checked before each use by VP-29 at Kwajalein and WILSOH cloud tracking aircraft at Eniwetok D J Field Calibration Difficulties Humidity SCINTAMETm maintenance was perfonned at Eniwetok Kwajalein and Guam Air conditioned working space was available · only at Eniwetok Because of the high resistances employed in t circuit the excessive hum ldi ty altered their value ·whenever the SCINT AMETIR case was opened Setting the noat point was accomplished by trial and erro_r With the instrunent out of its case the noat point would be set so that the meter indicated the proper radiation intensity th n the instrument would be reassembled with a package of de ic t within the case and after a few hours the error differe nce between neter · · reading and true radiation background was noted The case was · then reopened and the noat point adjusted to compensate ror the noted error The procedure was repeated until agreement or· instrunent · reading w1 th true background was achieved 0 Whenever the float point was checked a reading was taken in a radiation field equivalent to greater than half scale deflection to insure that the remainder of the circuit was operating properly -63- Calibration was likewise a tedious procedure becau e of high humidity Calibration controls were accessible only by opening the instrument case so that a waiting period was required everytime an instrument was resealed to allow the desicant to become effective Occasionally calibration of one instrument would require several dqs because of the waiting periods Frequently the humidity was so high the package of desicant could not completely absorb all the moisture within the instrument case after it had been sealed High Background The frequent use of several large sources by personnel from other projects 1n the vicinity of the radsafe building where the HASL instruments ere serviced on Parry prevented calibration or the low end of the 'lll-3-B and TH-3-C scales An increase in background of as mch as ten times over the normal or 01 to ol 5 mr br was noted at such tinEs Fallout from BRA VO raised the background at Eniwetok so that low end scale calibration was impossible at any time in order to continue the program all low level SCINT TERS were moved to Kwajalein tor servicing On occasion the fall out even on Kwajalein was sufficient to prevent low end calibration although these periods were of relatively hart duration Background radiation rarely interferred with the calibration of the high level SCINTAMETERS the minimum scale reading being l tar hr E Field 9Reration In field use the SCINTA ETERS_ were found to be mat satisfactory by task force personnel who used the instruments Those characteristics which were commented about mat frequently are1 dependable operation stable calibration simple controls single scale wide range and sealed circuit _The last characteristic was particularly helpful for cloud tracking service since the instruments were insensitive to altitude changes Position in Aircraft Our experien e has shown that the positi n of the instru111 1nt within the alrcraft mst be selected so that the radiation from radiwn dials on navigational instruments is negligible and the absorbing material 1 mderneath is minimal and constant A position over a gasoline tank is undersirable If repetitive surveys are planned the sane position within the aircrai't should be used each time -64- At times either aircraft vibration or rough handling affected the 'vibrator-transformer vitran reed adjustment causing erratic behavior To correct this foam rubber pads were provided to cushion the instru nent within the survey aircraft Operating Difficulties Minor circuit difficulties became evident shortly after arrival at the forward area but these were easily corrected Circuit component failures were infrequent Faulty compenents were replaced from a stock of spare parts maintained in the forward area Battery replacement was necessary on the average after 20 hours of meter operation Rep a cen ent necessitated opening the instrument case Each time this was done where an air conditioned room was unavailable the instru nent remained out of service for up to · 24 hours until the IOOistur had dried The vitran in the power supply was the source of two troubles which -were corrected after they were discovered These were 1 f allure of the vi tran to start when the instrument was turned on 2 nois causing erratic meter nuctuations The first difficulty was easily eliminated by a simple adjustment of the vitran reed The latter problem required a more critical reed adjust ment or cleaning of the contact It was found that much of this noise was being coupled into the circuit through a common ground from the vitran and filament batteries Running separate ground leads from these two sets of batteries directly to the connector joining the battery section to the circuit section eliminated the necessity of a fine adjustment of the vitran reed and also stabilized several instruments for which a noise free operating point could not be found by adjusting the reed F Recommended Modifications l Float point and gain controls should be accessible from outside the sealed circuit case 2 Battery eha nges should be possible without destroying the moisture seal of the circuit case Greatest utility cculd be realized if batteries could be integrated in a case tbat could ·as p1ugged into the circuit case such that a spare battery set coul l be easily interchanged in the field by a non-trained oper 1 tor J The vitran should be modified possibly by shock mounti 11g or eliminated i n favor of a f 'lnt e stable power supply if one could bs found with comparable high efficiency -61 - 4 l · 2 A means should be devised to flatten 'the erier zy response ··caaracteristicii ' · Fixed Instrument Network Each automatic nr nitoring station was equipped with one or two each of our types of autonatic gamma monitor In addition several stations close to the proving grounds were equipped with AN PDR-18 Bs port able gamma survey instrun8nts The unmaDMd station Ujelang was equipped with an automatic eight bead air sampler as well as a battery operated automatic gamna instrwrent The auxiliary monitoring stations were each equipped with two lfuclear Instrument Corp Kodel 26lOA portable gamma survey instruments A Description o Instrunents-tt The automatic ganma lll nitors consisted ofa l Tt« units of NYO type TN-l-A a UO volt 60 cycle 014 tube gamma monitor with a quasi-logarithmic response allowing a range of 0 01 to 2$ mr br to be recorded on a linear 0-1 ma recorder 2 Ten units of NYO type TN-3-A a llO volt 6o cycle combination monitor alternately measuring 1 the beta radioactivity from dust co1lected on a filter paper and 2 surrounding gamma intensity is reoarded tor fifty minutes every hour during which the dust is col1 Nted on filter paper The beta from the dust sample is counted tor five minutes and then the background f'rom a clean section of tilter paper is counted for the remaining five minutes of the hour Both channels use CH tubes and the circuits are logarithmic with the ganma range from 0 01 to 100 mr hr and the beta range from l 00 to 10 1 000 1 000 dpm The recorder is a standard 0 1 ma linear recording mi lliameter 3 Two units or NYO type TN-4-A a 110 volt 50 cycle CM tube gamma monitor with a logarithmic response allowing a range of 0 1 to 100 'l lr hr to be recorded in a linear 0-1 ma recorder 4 Two uni ts of NYO type TN-2-A a battery operated gamma moni- tor with a logarithmic response allowing a range of 0401 to 100 mr hr The surrounding gamma intensity is recorded for five minutes each hour on a 0-1 ma linear recorder •For detailed dNcription of instruments see HASL-154 OPERATING PROCEDURE FALLOUT MONITORnm FOR CASTLE If e1 8RifJ -66- The battery operated eight-head air saI Jllers NYO type TN-5-A take eight consecutive one hour dust saq les on one inch diameter ilter papers Dust sampling begins automatically when the surrounding gamma radiation exceeds a predetermined value 0 l mr b r was used during CASTLE The PDR-18B scintillation type survey meters nufactured for the avy have full scale ranges of o 5 5 50 and 500 r hr These were provided to certain automatic monitoring installations to supplement the automatic units it radiation intensities exceeded - 100 mr hr The Nuclear Instrument Co Model 2610A survey meter uses a Gh tube three scales provi e maximum readings of 0 2 2 0 and 20· mr sr These instl u l Snts were sent from the NYOO via AFOAT-1 channels to the auxiliary stations No maintenance on these instrun8nts was performed in the forward area Field Calibration The auto11Btic roonitoring instrwnents were assembled at Parry Island for maintenance and calibration prior to their distribution to the m mitoring stati ons The remarks made preViously concerning the effects of sources on SCINTAHETER calibration are equally applicable to the automatic units B C Field gperation Diurnal Variation The TN-2-A TN-4-A and the gamma channel of ffl-3-A xhibited a diurnal variation in radiation reading which adversely affected the dependability of t radiation measurements below 0 l mr hr This was a continuous source of difficulty during CAS'lLE Field tests were conducted Without success dur ing the mnitoring program to determine the cause The investigation was continued a t HASL New York w re the resistance of the bakelite insulation on the base of the Anton 310 it tube was f'ound to change with temperature There are other actors likely to contribute to the diurnal variation a1though specific inforna tion is as yet unavailabl The effect of hund dity is strongly suspected The tJ tube and certain high resistance components are sealed in a tubular casing which constitutes the probe on the automatic instru nent Since this tube is not disturbed during normal maintenance the humidity has no inmediate effect on calibration as is the case when SCINTAhETERS are opened However the daily heating and cooling of moisture Which may seep into the probe over a period of time may be partly responsible for erroneous meter indications manifested in the di urnal variation 88 i i -67- Hi Voltage Boards A failure comn on to these units occurred inhe high voitage boards These boards were also bakellte and apparently the high humidity encountered reduced the insulation resistance to the point where sufficient current flowed from high voltage points to ground to burn the board The leakage reactance of tm transformer in the A C units TN-3-A and TN-4-A was high enough to prevent excessive current in the primary so that the short would burn through without the circuit breaker opening In the D C unit TN-2-A the excessive current drawn discharged the battery Bakelite boards should not be used in the high voltage section of equipmmt to be used in high hwn i di ty areas Unregulated Line Voltage At most of the installations line voltage and frequency were maintained at standard levels only during the upper level wind observations Voltages as low as 85 volts were observed during maintenance visits and near the end of tha operation conditions may have been worse due to the fuel shortage at several stations · Water QS ma ge caused temporary failure of several instrumsnw Vater entered the instruments due both to heavy wind driven rain and condensation The former was the greater factor and WpS eliminated by placing shecls over the units These sheds were usually · constructed with the m mitor packing case supported by our legs inverted over the instr llll3nt The condensation could not be stoppef but this alone did not cause any instrument failures • TN-2-A • Several mercury batteries Mallory 308448 went bad long · before the expected end of their life and showed signs of leakage Except tor one case this occurred only in those batteries trom which several' cells were removed to obtain B• voltage• Evidently the stress placed on the cells by- this operation is excessive and another method ot varying B should be devised A few or these batteries were received with the polarity as iildicated on the casing reversed The two bars supporting the recorder are not strong enough and · under the weight of the recorder pressed on the batteries cutting · their casings Olyptal paint which was used to insulate rivets from the metal base plate did not stand up and several shorts occurred TN-3-A The major failures in this type unit occurred in the beta · section The paper drive mechanism broke down in alzoost every every unit The contributing factors here were the tendency of the friction gear to tighten up against the munting plate and metal corrosion The former prevented reeding of the fi1 ter paper which stalled the drive iootor Tbe overheating of the motor in addition to the rust caused by excessive hwnidity usually froze the DDtor sba tt putting the dust monitor out of commis sion until the 111ptor could be replaced · TN-5-A Betore being placed on Ujelang the dust samplers were preset to trigger at O l w br On subsequent visits after bursts was often greater than the trigger setting In order to _dy the instrument for the following event the trigger setting necessarily halt to be raised uove the current background value J ri existing control on the instrument _permitted accurate · djustment only by cumpersome trial and error proce hµ ie utilizing a portable ource _and ganma surv instrQ ment Generally there being insuff'icient time tor this procedure the setting was adjusted to s'om Tal ue onl¥- approx imateJ T knolin such that the unit would not trigger in the ganma field Be use of this the sampling time tor the next event could not be ac ate cy- establl s d the baQlpQund D Reconmiended Modifications The friction clutch shoul d be made 111th a reversed thread so that it would tend to loosen The paper drive motor is ' heavier and taster than required A smaller motor would allow t1le paper reel supporting plate to drop lower all owing easier loading of the paper ilso the slower drive motor will elimin te over-running or the detent on ·the stop c TN-3 A method of stopping ·'tlle paper after it bas traveled three inches # would increase the lite of a filter paper roll tram 8 to a pproxi tely lo ys At present the amount of pap r per sample is controlled by the radius of the takeup reel which increases with the IlUlli er· of samples 'taken Since it 1s necessary to have the drive set so that three inches is traversed with the minimum radius the open· space between samples becones excessively long as the roll is used A rubber pinch wheel assembly which would be simple in design could be used to fix the amoW1t or paper travel Replacing the beta GM tu be or servicing the circuit mounted wi t un the lead shield is difficult requiring almst a complete dismantl ing of the nxmitor which is extremely difficult in the field This whole section should be mounted to a plug in the rear of the lead shield which 1s easily removed without disassembling other parts of the unit To simplify calibration the comnx n filament voltage control of the beta and gamma amplifier tubes should be eliminated in tavor of individual controls TN-5-A A calibrated control should be provided so that the trigger setting can be changed easily to a different lmown value in the field A device to provide a record of the start of sampling t ne should be incorporated in the sampler unit General To ease field maintenance and calibration of the continuous monitors a switch disconnecting high voltage should be incorporated in the circuit and provision ma de for inserting a portable meter in the output circuit at the monitor The latter modification would be a coIIV enience because the recorder is usually some distance from the monitor and it is not possible to adjust controls and watch the recorder deflection simultaneously sw a• -70- 'IM • m RBCCJ MElIDATIC NS On the- basis· o experience gained during this operation the fol l diing mcdi£ications are proposed for use in any further mnitoring programs or this nature l In addition to tho general pattern ot automatic mnit oring stations included tor CAST LB ovide suppleman tary stations at several atolls 'ormi ng·a semicircle oriented to the east and within 300 miles of the teat site The mst practical installation or these supplemental stations uld be automatic battery operated unmanned equipment U possible they should be equipped to telemeter The locations should be selec ted on the basis of accessibillt r tiy air or surface vessel as well as distribution around the test area ·· ' - I•• • ' •• Weekq· r bi-weeklq-visits would be necessary tor maintenance am data in the event telemetering cannot be utilized • · · ·recovery ' ·· · 2 J upllcate iastruamtati on is essential at unmanned stations and is strongly dasira le at manned _stations • 3• £11 al tern tive to fl would be more frequent survey nights covering pa rugbt ·patterns tolloving ea h evmrt although this would not provide ·the same precision of fallout arrival measurements as would be obtailled by the ground ·stations nor wo'lll d peak values necessarilly be obtained Daily flights each of the ABLE am BilBR patterns up to -· An or six divs after each ffen in addition to normal scheduling -' -WOtlld euttice to detect late occurring tall011t and establish 'al lout -arriva1 time to Wi tbi n a 24 hour period · · £s a m 1mmm requirement each fllght · pa ttern aho'llld be executed shortly · ' bet e each event atter the first to maaaur esidual contaminat on in tensiti9s It is only by thi S JIBan that tq e fallout troni successive bursts can be a9curatel y co_mputed ' tram Jll9asµi-ed val ues During CASTLI it was taund to be impossible to schedule tHeae re-survey fiights on D - l because of unpred1ct·able delays _in ae tonat1 ng the test devices · and frequent connicts With tbe surv91 sqtlach - n•s other commitments J · which were heaviest prior to tJ day · fhlt'elot • in- cases ot long periecla 1 stveen bursts re- eys at regulir t1ve dat ihterv l s are suggested to ensure the ency of residual containinat1on data 4 De elop procedures tor·· night survey· tlights Such procedures should p obabl 1 _·provide tor mitting islands with muntainous terrain S ·l evel op ·proc edures for ditterentiatiDg among· the several sources ot in-night radiation t o permit proper evaluation ot ground intensity • Li 71 SB SiCk i measure nts The sources which may obscure background measurer ' ent for correction are skyshine and sea activity The proper application of shielding at the survey instruioont could eliminate substantially all radiation originating in and on the aircraft 6 Autom i tic fission product dust measuring instrunents should be perfected and utilized at stations within three hundred miles of the test area 7 A continuing e f'i'ort should be made to correlate fallout density per unit area of ground with radiation intensity Sampling by gummed film or equivalent should be done at monitoring stations 8 The successful measurement of fallout over the open sea from aircraft has been demonstrated 3 Perfection of this technique holds great promise for accurate evaluation of fallout patterns up to two to three hundred miles downwind t'rom megaton range bursts Although the aerial survey program described herein was not designed for that particular service the programs could be coordinated for mutual benefit A Survey aircraft enroute between two atolls can measure sea radiation as a corollary mission Toward this end survey patterns could be modified 'Wi thin certain limits to examine areas of particular interest w 1 thout impairing the atoll survey functions Wasteful overlapping of survey missions could be avoided in this manner B Atoll radiation data would supplement the sea surface data broadening the scope of the study C Under suitable circumstances the atoll data would provide a direct relation between sea measurements and ground activity D Inmediate exact knowledge of the fallout path direction derived from sea surface neasurements would be useful in an ticipating appropriate atoll survey requirements 9 The conversion of radiation neasurement from the air to ground intensity should be more accurately defined Phenomenon necessary tc be studied are µistrumental energy dependence effects of fission product age and composition and the relationship of ground intensities as determined by air measurement to ground intensity measurement by conventional portable survey instruments 10 Recommendations concerning instrumentation are included in Section VI --72- 3MPW REFERENCE'S l Radioactive Debris From Operation IVY NY0-4 522 April 1952 2 Radioactive Debris From Operation CASTLE Worldwide Fallout To be released 3 Radioactive Debris From Operation CASTLE A erial Survey of Open Sea Following YANKEE-NECTAR NY0-4618 4 Survey Instrument Characteristics Measured by HASL Instruments Branch staff 5 The Effects of Atomic Weapons Page 2 58