Operation Ivy, Project 5.4B, Fallout and Cloud-Particle Studies (November 1952)

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Results of beta ac?:vities for various time intervals of Mike shot faAl-oti$ollectors arc shwn ln T&c 6.1. These activities, in diaintcgrations per minute, are averages of the individual cotmUng cups in each tray which had eoough activity to bc counted. In the tables given in this chapter, tray 1 corresponds to the period from ‘4 to ‘A hr titer ehok time, tray 2 corrcepozuB to ‘,$ to ‘A br after shot time, etc. In a given tray the activities of the individual cupe eomctimce varied widely from the average; a8 aa example of this variati.~ the actlvttie8 of the individual cups at Mlkc shot Jn and Jv stations are shown in Table B.l. These two stations were the closest operating intermittent-fall-out collcctora to Mike shot ground zero and were in the region of hcavy fali-out. These activities may bc approximately cnovcrtcd into curiea per equare foot by applying the cooverslw factor wbcrc 0.545 sq in. is the arcrag@ area of cam 61-s counting cup. This equation eimplUice to TabAc 6.2 shows the activittts in curie8 per square foot for seven time intervals at 10 Kln(l bd beta wtivitlcs arc shown in Table 6.2. There r:tivitien arc lower than the f&kc rbd samplc activIties,,by a frctor of lo’ to ld. Table 6.4 shows the activity in curies per Met both 8hd8 M dctcctablc r8dioactivc airborne concentration of particulate matter was found war the surface of the ground on EE rttb the Trrccrlab air monitor.

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*In general, the 8ctlrltlcr tbrougbout We table are areroger of counting data from three cups In each tray. Lneomc two cup6 were counted,

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We 6.4 -KING SHOT MTERMJTTENT-FALL-OUT COLLECTOR BETA ACTIVITY §tatIoa 7‘ to ‘4 ‘A to 1 1% to 2 2% to 3 s% to 4 JSh to 5 5% to 0

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6.4 SPECIFIC ACTMTTES OF hfIKE SHOT GROSS-FALL-OCT SIZE FRACTIONS slide, weighed. and counted a8 Ceecribed in Sec. 5.2. The resdn, ia counts per minute per milligram, and the corresponding reighb of the fractions for four etaha ue &own in Table 6.5 DECAY KEASUREb4ENTS FROM INTERMITTENT-FALL-OUT COLLECTOR SAMPLES Beta decay slope8 are listed In Table 6.6 for Mike shot a& tn Table 6.7 for King shot. Representafire slope8 for Mike’ and King shots are shown tn Fig. 6.1. The numerical average King shot decay sloper were based on a small quanttty of fall-out. 6.6 DECAY SLOPES FROM FRRcI-I~NATED GROSS slopes (Table 6.6) were determked for the frnctioa retatned by each rte-e. Decay sloper were The qwsttaa arose as to wbetbcr the actlvtty ptcked up lo the intcrmlttent-fall& colsamples whlcb hsd been used to determtne Mtke shot decay8 were counted unttl IS + 26 dayr. King shot bstr decay #lopes, determined durbq thts same period of ttme, ranged from -0.62 to -0.99, with an average of -0.65. It I8 therefore believed tbs! the rctivlty of the King Tncerlab aluminum absorbers. Tbe resuitlng decay rlo~es are lfstsd tn Table 6.9. 6.9 PERCENTAGE OF MIKE Slim TOTAL FALL-OUT WHICIi WAS RADIOACTIVE FROY f&Mat collcetor nmpies are shown In Table 6.10. The average result Ir ehom graphkelly In Fig. 6.2 Renrlts are In three rcdioae for each 8tatloa and ts each rtze range. Column a b the cumulattve pcrcenta6e les8 than and tncludlng the 8tated 8Lu m of the total namber of particles counted. Column b 18 tbe Percentage of the number of prrtldes tn each rks range wblch are radlarcilve, and column c rhow8 the cumulative perce*e la88 than and tncluding the 8tated rtze r-e of radluctlve Particle8 taunted. The actprl eumber8 of radtorctive and total prvticler counted and the over-all percentage of the number d rsdtoactlve pvttcler counted at escb statton are at80 Itsted.

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Number of radioactirc partIclea counted Station J,, 59; Statlon Percentage of radioactive particler: Station J&, 0.21; Statha K, Tatal number of particIer counted: Station L, 10,598; Statioa M,

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Total number of partklee counted: Station N, 13,247; Station 0, Percentage of radioactive partlcler: S:aUon N, 1.00; Station 0, Number ofradiosctlrrpartldee countedz Statlm %, 86, !HaUaa

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Number of radioacrirc particlea counted: Station U, 73; StaUoa Percentage of radioactive pvticlcr StationU, 0.58; StationW, Total number of putlcle8 couutcd, Percantrge of radioactive prtfd6%

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An average of 78 per cent of the total paxtlcles counted N 4 1 or lees in diameter. Practically none of the particles ir. thle group wt:e radioactive. A.8 the size range increased, the number of particles in each stze range decreased. At the ru-ne time the percentage of particles ir. Trch .razg which vere :ad:cactlve in.--ens& 10 the extmt tha! In the range above 200 u an average of about one partlcle in three was i dioa-.tirc. / !llaregarding the size rangee, the over-all percentage of particle6 counted which were radioactive ranged from 0.02 to 1.09 per ck , with a numerical average of 0.36 per cent. King s.~ot fall-out activities were so low that it was impracticable to determine these 6.10 PERCENTAGE OF h .E SHOT 7 ,rAL FALL-OUT WHICB WAS RADIOACTIVE FROM THE GROSS-FALL-OUT COLLECTOR SAMPLES The percentages of Mike shot total particles counted which kerc radioactive are ahown ln Table 6.11 in the same manner am explained in Sec. 6.9. by pipetting (Sec. 5.3). The results from each fraction were then recombined into one set of resulta from each station. Eighty-five to ninety-four per cent of the particles counted were be!ow 4 p. Very few radioactive particle8 were in thts range. b the size range increued, the percentage of total particles which were radioactive also tncreucd, a&bough the increue In perceotage was not con isteat (8 to 34 per cent in thr 20- to 30-h range). The over-all percentage of particles wh ch were radioactive vvied from 0.20 to 0.39 per cent. Gross-fall-out ’ collector radioactive-particle results at 0, P, and R were spoiled by bad film. There wae not enough grors fall-out at Y, LL, sod MM to k fractionatect; eo It was analyzed from 2 to 50 p cent of the gros8 fall-out at My VoI La the same rize range. ti found elsewhere very few l . radloactke particlea were ia thta size range. The percentage of total particles whlcb were radioactive in each size range increlded, aa was usual, but the tie of Increase at bfM was much lower than the rate of Increase at the dher two stati- The wet-all percentage of t&al putlclea whtch were radtactlve varied from 3.8) to 2.?2 per cent; The actlvitier from King shot pees-fall-out samples nre too low for thie molyrlr. 6.11 DIT ERMlTTENT-FALL-OUT COLLECTOR TOTAL-FALL-OUT PARTICLE ANALYSIS Swaral group@ of lntermUt.eat-la%out collector total-la&oat slider were selected for analyak Tbo# 8lIde8 setected were from statioar in the regioa of radioactive fall-out. The nature of the umples o&alned and the analyticaJ techaiqueo wed limited the rlze range which could be determleed. ti meatloaed ln Sec. 5.4, kc&round limited the lore81 size d*(ermiaed to 0.1 JI. The determination of large p8rtlcies wa# ad limtted by background or tndIc8ted tht particlea fuger than about 500 p were ncl held tn place oo the slider by the A variety of partlcle eke, putids-el2e dlstributloq and cooce~ation parametera were obt8tned for each -pie. The nature ubd methcd ci ObtrLaig each of the perametero tabulated ue as follorr NMD (aamber medlln diameter): A rlze ruch that 50 per cent of the puttdee meuured were larger than the NMD, and 50 per cent nr ? rmaller, o&lad by Interpolatioa of two valuea neareat 50 per cent ctn a cumuiatlve graph of tba number di8ttikrtlOn.

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<1 77.38 0.15. l 35.19 71.47 No radioacttvc particles 2-4 93.73 93.78 were counted owtng to

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dXD hrfaee mcdh dlametcr): A surface median, dmlhr to, and othhedinthcsamc YMD (mu6 median diameter): A ma80-ilze puameter, etmllar to, and ol%ained in the same txmrawras, the X&EDbut based on the third moment of the data. Dq (arcrage diameter): The ovcrlge diameter of the particles counted, o&wwd from ThisvahedogiaQottbegeometrlc studud deviatioa of the dlstrfbutioa as couated. It Is, In Zacf., the ~1~ ata&ud deviation of a logurthmarormrl dtstrtbutlon with the same rztlo doer not tndlc&e the percentage al tbe particles to be found ln a crrtata rtze rafqe. Theqg bbulabd ia a coarse seaeure of tbe em kterogeae&ty indicated by tbe dkqxrtty of the 6.12 PETSCAL D- ION OF TEE RAEWICL.E bbal8td u m prr mtmU per mlillgrun In Ttie 6.12. It may be noted tlpt there appear

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hum at about 100 IJ, w (3) mlnfmum at about 100 IL The atCuac.ioa !a compllced by the 8t.mmgSri-e that wtlrlty wu depoaiced m tbe partlciee from solution. Is accordance ritb tbe umsal coovsntione, R fnctora with respect to Man and Zt= arc &van In Tables 6.14 throqb 6.16. The R factor la defined aa vbere A and B are the coucta per minute from 8ny two station8. In tbia manner tbe work of different laboratories may be directly compared_ For Lbk rork the ptle fIgurea were o&abed by a thermal-aeutron bombardmen. f U- In tbe Brookbaven An MrntMtlaa of the R factora Micated the likelihood of a peculiar fractionation of acUvt&lea between the li4uM and aolld pbaaeo. Tbls phenomenon rw verified by the data of Table 6.17, lticb were c.aleuIated in the following namer: the IQuid depths were measured in 11.6 hers at U. From 8 590 ml and from U 683 ml were each diluted to 1 ltter for analyalr. From these figurer tbe total courti per ml&e In each 1tquM sample were e8tlmated. The X&M fall-out nlgbed II-4 g at 8 um3 0.8 g at U. Average couata per minute per milligrd were cakdatd from the data of Table 6.13. (Note tie very quertladle asmmptfou Unt thue average@ are va.Xdfor the total mple.) Fran these fIgurea tbe total cowt8 per Al&m@ ti data d Table 6.17 are (svea to two atgalfiarnt f&urea, they are probably not -amIJbL Bowaver, the #ata aawune cwaidstibie rigntficance wnue they differ by

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*The R factors are given in unitaxld. 0 FOR SOLID FALL-OUT, MIKE SROT

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The statittlcal-counting accuracy of tha acth+fty measuremmtswas limited by practical cooeideratione which have been described tn Sec. 5.1. However, the accuracy lr enough to show the random nature of fall-out In a amall area, whlcb Is probably due to verytng and chuqeabie weather cnodlUone. The activitiee reported here do indicate the order of magnitude of the It would be de&able to sample a luger araa of fall-out at a giveo rtath to obtain more ~informatioa on the random nature of fall-ad. For Mike ehot too tntermittent-fall4 colhctore web glaced abcmt 10 ft aport at eight stattone; however, fire of tbs efgbt atpttoae either did not operate or were oa’.aide the area d fall-out. The averaged rezuib at J, end R, were +puanU, less random than reeult8‘at moet individual stattons In the eune areae. The averaged reeulte at LX,_ ere qutte random; Immwer, the intenelty of fall-out wae much leee at theee etattone. Activity data from the We L et&ion are probebly not eo W u activtty reoulto from th other rtatto~. &me time after tray 2 had sampled, a driving chin came off Ita rprockd It b tmknown whether the artbltiee reported for Mike are from (1) actual fail-out e the proper eamplw interval, (2) the reeult of a looee gaeket between the top cover ul the tray In eampllfg poeition, or (21,a combination of both. ’ Activity end per&lo-riw date from tray 24 are not eo meaningful and r&able u most of the data from the other tray. Tray 24 wae poeitioned under tbe eamplw ope&g in the tlgbtly end sometimea did not close properly. Radioacttve mb inert duet end rrtsr my kave been deposited 00 the elides 4ad In the cupe before end after the regular lf-mia aampUag period had been completed. Wgurw 7.1 tbroagh 7.6 repreeent graphically the vartattan d utlvtty wltb dletancr baeed hdflal actl~Itlee ci the cumttng cupe varied from 10L:to 10” dte/min during the ftret i8 pobably due to the redtactive fall-out being eampled at lb min after slmt time while the lntermitte&faU-out collector ie ln the proceu of openlag. xlntmum eamplo activltiw durtng

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Itro inftial peak of radioactive fall-out, 15 to SO mtn after sampling time, occurred 7 miles from ground zero and moved 9 to 10 miles from ground zero durtug the first 1% hr. A secondary peak appeared ‘/r hr after shot tlme about 6% to 7 mile8 from ground zero and continued until 3 hr after ehct time. Another sec&darp peak appeared 4 mile8 from ground zero 1 hr after shot Ume. Fall-out fn these arean continued for moat of the remaining samOther recondarp peaka of activity occurred iandomly 7 to 10 mile8 from ground zero during the 1-t 3 hr of eampllng. DepositIon of fall-out during the first 2 or 3 hr after shot time w probably lesr influenced by weather conditlonn than the dcpoaftfm of later fall-out. it ia fntererting to note that, except for the periods 2’4 to 4% hr and 5 to 5% hr after shot time, actl&ty ievele at J station are signiftcantly lower than the peak activities of dher Fall-out activftfes from GC were so low that they were not recorded on the activity-vsFigurer 7.7 through 1.9 represent&he vartatlon of activity with time baued on the T%e moat radioactive fall-out from bflke shot arrived at all etatiorm less than SO min after abet time, except at LL, where It occurred ‘A to 1 hr after shot time. LL w south-southwest from Mike tit ground zero, whereas all the other rtatlona were generally southeast from ground sero. The beavleat radioactive fall-out on Operation Jangle alao occurred within a abort time after each detonation. I’ lbcrt wouldappear to be an external radlatlon haxard to personnel remaining in the areaa of highly radfoactlve fall-out during the ftrst few hours after ktivittee decreased fairly ref@arly with Ume at J and R, altkqb, durtng the last 2 to 2 ht, tfm radloactfve fall-out appeared to be more random than it had ti earlier. S~SIUOIUJ I,, and Ra, are averages of actlvfties of two fndfvtduai cofktctore, whfch may be thu cause of Umo. R bad a small peak at 2% to S’/; hr. Fall-out at S, 0, and W became quite sporadic after about S hr. Actfvftler at there three elation13 are generally ellghtly Mgtber toward the end of tbo umpling period th8n the activitier abaut midway through the aamplI4g Period. Meaourable Activftier from tray 24 are not neceuarily indlcatlva of the fall-cat during 6 to 6% hr after llbd time. When the fntermfttent-fall-out collector cover door opena, the spider la In the procau of movtng tray 24 from under thr cover opening and movtng tray 1 In lta place; beoce, a rmrU amount of early fall-out may have baen depoelted in tray 24 7.4 VMUATfON OF ACTIVITY WITR TIMX AND DISTANCE, KING SROT a 2 to 4 mlle8 nom of ground zero, the clooert operathq 6taUon11, received falkmt durbg very few time fntervala. Radfoactfve fall-out M deposited over a majority d the lwzlpuly the at rtatlone S to 5.6 mile4 northwort of ground zua. R8cUcally no uztivtty wu looad at r: md P, 6.2 …