Nuclear Explosion 16 July 1945 (Health Physics Report on Radioactive Contamination Throughout New Mexico Following the Nuclear Explosion) (Trinity Event)

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0513118PRIVACY ACT MATERIAL REMOVED ' BEST AVAILABLE COPY LOS ALAMOS SCIENTIFIC LABORATORY OF THE UNIVERSITY OF CALIFORNIA o LOS ALAMOS NEW MEXICO NUCLEAR EXPLOSION lo JULY I9U5 Health Physics Report on Radioactive Contamination Throughout Nev Mexico Following the Nuclear Explosion

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February 20, 191+7 This dooument oontains page3 Health Physios Report on R&dioaotive Contamination Throughout New Mexieo Following the Muolear Explosion Classification changed to UNCLASSIFIED ^ by authority of the U. S. Atomic Energy Commisaion, JoaGph Ge Hoffma by EERXRT librae r ap i»ewmwv nsable ctowse

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JTOCLEAE EXPLOSION 16 July 1945 Health Physios Report on Radioactive Contamination Throughout New Mexico Following The Nuclear Explosion Part At Physics Report Written By Joseph 0. Hoffnan THIS DOCUMENT CONSISTS OF <^fPAGE{S) PRIVACY ACT MATERIAL REMOVED

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BEST AVAILABLE COPY List of Monitors I Monitoring Activities Before and After 16 July 1945. II Decay of the Precipitated Gaena Activity. III Geometrical Effects in the Distribution of Active Materials. IV Integrated Dose. V Procedure for Determining Safe Dosage Rates of Gamma Radiation. VI Examples of Town Monitoring. VII Methods for Calculating Doses. VIII Partical Sizes and Air Concentrations of Radioactive Material. H Distribution of Fission Products Over the Countryside. X Beta Dosage In Tissue From Cloud Materials. Appendix I. Health Instrumentation and Groaa Crater Activity. Decay. Compiled by Richard flfatts Appendix II. Itinerary of trip made by Colonel S. Warren, Captain H.O. Whipple and Dr. L.H. Hempelmann, on 12 August 1945. Appendix III. Monitoring trip northeast of Trinity, 11 December 1945 by Carl Bucklend and A. Reinert. PRIVACY ACT MATERIAL REMOVED

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BEST AVAILABLE COPY 1* Monitoring aottvltloa bafera and aftar tha nnelaar axploaiont 16 Jvljr 1945« ara daaerlbad brlafly, Tha apparent daeaj of f laa Ion product a aetlTlt? apraad aaraaa tarrain la dlaeuaaad, laar tha sratwr tha daaay aaa appraxlaataly aa t**2 with nldn Tarlatlana ahila at dlataaaaa graatar than 12 allaa tha daeay aaat aa t*^*^ 2. Tha gaoaatrioal affaota of tha dlatrlbutioa of aetira natarlal la daa* erlbad. Tha aaaauraaanta In tha alalnlty of Blnghan ahaaad that tha gaana doaa to paraomal aaa dm tot a) daaaga dallrarad ahila tha aatlaa olood part Is laa aara falling and b) doaaga dalirorad aftar tba partlalaa had aattlad to the ground* Tha nethnd for aalenlatlng tha total gmwmm doaaga la ootlinad. 3. Xxanplaa of toon Monitoring far gaana radiation are given for White, Binghaa and hot aaagron south of tha Chupadara Maaa* 4 Table of gaana doses for toaaa tfcrougheut Mow Mexlee la aoaqpilad* Batlaataa of tha danalty of gaaaa act Ire Material oa tha ground are eoaputad froa tha 4* Tha region of highest radio*aotlre eoneeatretion la ahaun to have bean In a swath 12 allaa long, 1 alia aide starting near White Store (oa read 3*0) and extending northeard aaroaa tha Ghopadire Mean* There aaa a daflnlta "skip" dlstaaaa of 15 allaa bstweea sore and tha regions of aaaaurabla gaaaa latanalty* It la astlaatad that one-half of all tha activity available aaa precipitated in tha teo aaaks aftar tha expleelon* This activity aaa 900 la Waa laxlao* dbout 70 of all radloactivity aaa praelpltatad In tha *hot" aaath ever Chupadara Maaa,

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a) Praparationa for tha Shott As a rasult of discussions aaeag all oonoemad, it was doe Id ad that thara wara two aain poaslbllitias as to where the cloud could fo aftar tha shot. They carat la tha northeast or la tha southeast direction. It was dsawed necessary to choose a weather condition which would not blow tha cloud over tbs toon of Carrlsosc* which lias slightly north of dua east of aero. Accordingly, tha town aonltoring plans consisted of three (a) Tha Worth blow in which tha cloud acwaa la tha north east direction inside s 20° scoter whoso south elds is not lass than 6° north of Carrlsoso. (b) Tha South bleu in which tha cloud novas in tha southseat direction inside a 20° scoter whoso north side la not lass than 6° south of Carrlsoso. (o) Tha —a in which tha cloud novas la any direction outside of tha sector whose sides are 26° north and south Of these three cases tha Worth bloc aaaaad to ba aoet likely to occur on 16 July. On tha l$th of July a final seating of radiation aonitors was held at Santa 7e for final instructions, for ssslgaaont with | G-2 man, and for asalgnaant of rsdlatiou detection asters. The final instruction* ooaoarasd chiefly the setter* of recording observations and getting ccBanmicstloas with headquarters in Albuquerque where |was stationed or with tha base eanp at Trinity whore taa stationed. Since tha aonitors wars spread over a large area it was essential for than to aalntain cousturt a antral aoaanmloation in PRIVACY ACT MATERIAL REMOVED

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ocdur i« fiai out whisk of %Im tbrm atia aaaaa had aaaarrod, Xaah aooiior aaa aaaifaad a aat of iha fallevlac laatnoMaUi 1. A aatbaaa fIliad proportional aoaatar far datoetlm alpha partialo radlatloa la tko pnraaawM of bota aad gaaaa radlatioa. 2. A Tlatoraan, aodal 247, thraa raaga, portabla gaaaa ray aanray aatar. Thla aaa tha aaat uaaful laatrwaaat for flald aorh, Tha thraa raagaa aorar tha fallaalag lataaalty raagaai 0,01 ta 0.1 R/hr, 3. tha lalllaraftar, Oalgar^lUllar Taha, Modal $, portabla aunray aatar for gana aad (Mbm plaa bata radiotlona. Tha taa raagaa ara 0.00001 ta 0.0011/d hr, aad 0.0000 ta 0.02 1/0 hr. In addition ta aatara tha aoaltara aara aappllad larga nauthad bottlaa la ahlah ta pat aarth aanplaa froa plaaaa ahora radiation aaa Tha dlapaaltlan of tha aanltarlag araa aaa aa fallaaai that tha avnavatlan of paayla aaa fond waoaaaary. Tha ahlaf nonltor and tae araaa aara atatlanod at Guard Oata 2 blaouaa araa in ardor to gat iafamatian froa Oal. Marram at Baaa Camp aa aoan aa paaalbla. Thla lafaraatlan aanaarnad tha halght of tha aland, ita ▼alaolty and diraatlan of noajntnt. T^a araaa oamaantratad at Quard Oata 2 baoauaa of tha praaanaa of tnor^a|d1^d laoalltiaa) tha fIta houaa

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BEST AVAILABLE COPY ud tho tom of Taka/ vhieh Xla sorthaaot at oata aad vlthla tha Janwda dal Maarto. Fito houaa la flftaao and Toko/ la to—ty allaa froo aoro. latoa— radlatloa, tram Qaard Oata 2 tha aoaltara ooald aloo go tooard earthaga, Binghaa* dlaaaah* and Carr la—a, Bhjor Falaar aarrlad with Ida Up to tha tlao at tha ahot aad for a— half hoar aft—* tha saro through Coord data 8, Thla a—at that aaaitora tight hava to go to dir—tioa «— aaparla—d at Caard Cato 1 aad lad to tha ballaf that tha la tho aorth—at dir—tioa, la tha tl— latorral tram 6 to 7 IB tho triad fr— aorthooat to a—thoaat. had tha a—hran^4Sfcad to shift toward down tha rood pant Caard Tow— 2 la aad— to go to Flto'o^Fara, Tha IF

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aova In. Tfy TijO had aaawrad paraiaaloa for go la alaaa, hat tjr that tlaa It aaa aartala that tha aajor part of tha eload aaa aerial aorthaaat, Maaa# tha aooltari aorad aarthaaat alaag Hlghaaar 3t0« Latar la tha aaat ta Tlta'a ran Haag tha raad taaard aha had feaad raadihli gaaaa radlatloa at 1*7 tan. aftar tha ahot at palata 19 ailaa froa aara. Thla fadlaatad that tha aatlra dvat falilag froa hlghar altltadaa had haan aaught hr tha aorthaaatarlr «lad naar tha grand aad hUaa la tha dlraatlaa af Aa tha party aorad aaatsard, thay aat who alaa had favad gaaaa radlatloa in laaraaaiag lataadlMCaa af tha ndar of fraatlaaa of aa R par hoar toaard aara dlapatahad taaard Raaaaaharg. | party aaat boyoai Rlaghaa takiag Road 1A1 to ftaarthUght Station L-M, at ahlah plaaa thay arrirad at 4 hoara aftar tha that jaat ahan tha aaaaarad gaaaa lataaalty at that point had droppad hy a faotor 2 la 10 alaatoa, froa 8 ta 1 gaaaa roaatgana/hr. 15 R/hr at a point 3 allaa aaat af X»4. laarlag thara, to Bla^aa and aaat ta Rhlta tiara, thda rattta aaariy parallallag that af Bhgaa hut oloaar ta aara. Tha hlghaat Intanaltlaa fond aara 3 R/hr. Raturnlag froa taaard aaaauraaanta aara aada alaag tha highaay naar all rlalbla raaahas. Alfnd Aadaraaa «*• att aa hla aqr fraa jaat ratumad froa a trig aarthaaat alaag 161 and rapartad raadlaga vp to 10 R/hr. Thla aaa at about llil5 AX. Tha Intanaltlaa at Rhlta, Adaba, Binghaa, aad Z^t had apparazitly -jattlad dmn to tbalr ataady daeay raluaa PRIVACY ACT MATERIAL REMOVED

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BEST AVAILABLE COPY Radio ccmciunication with Base Camp was unsuooesaful, so Boffaan sent a message by Courier to Warren stating that the gamma intensities were about 90% of allowable value. {Referenoei See Section VI, Examples of Town Monitoring, 1. Town of Shite, ^^^^^^Pwrty was joined by ^^^^t this time and the company went east along 161 from Station L-8 to Investigate further the high intensitios reported by^^^| At the first place at which measurements were attempted, it was found that Magee's ear was heavily contaminated under the fenders and the chassis where road dust could cling. The cetera recorded 4 gamma R/hr above the general background when held near the fenders Moreover, inside the car the intensity was higher than outside* This east some doubt on tha validity of readings. ^^^^^|had earlier compared the reading inside and outside the car near Adobe at 10 AM and found a factor of 2 reduction inside the ear. It wee decided to return to Blnghan and aat since it was noon. At Bingham, the entire monitoring group except ^^^^Jwere present. arrived from Bees Camp and plans were made for continued monitoring of the region. Briefly, these were as followsi Ito go along 161 toward Claunch and Investigate the ranch#a and hot regions ist and north of Bingham. 3, to go along 161 and find spy roads leading off to the aide from it, in the first 15 miles from Bingham. 4. measure carefully along 380 and any roads to the south of 380. At this conference it was decided that alpha particle radiation was PRIVACY ACT MATERIAL REMOVED

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BEST AVAILABLE COPY negligible as far as aeasureraents up until noon lixiioated. The aajor ha sard appeared to be gaana and its accompanying beta radiation. In the afternoon. went east froa Binghaa along 161 and north along I46 using Palmer's map of inhabitad localities as a guida. The ranches west of Road 146 were in the midst of a region of intensity of about 0.25 R/hr at 2-3 PU. This was considered to be safe. The ranches named on the map were T. R. Ooker, W. Lucero, and SadiUo. In another direction, namely due eaat from the junction of roads 146 and 161, along 146 the highest Intensities were recorded, namely 6.0 R/hr at 2 PM. This high intensity waa callad to the attention of the military guard aecoaipanying The readings wars taken up to a point 3/4 miles from the Raltllff house, whose presence was unknown to the monitors since it wns not marked on the G-2 map. At about 2 miles from the 146 - 161 road junc tion, I46 runs through a steep gorge. In this gorge the high gamma Intensities were found which caused the gorge to acquire the name "Hot Canyon". The swath of high intensity which began at the hot canyon, about 30 miles from saro, la known to have extended north slightly east for about 12 miles. where it crossed High my 161 and took soil samples at a point whare a gamma intensity of 7 R/hr was found at 3 PH, 16 July, on the south side of Road 161. For detailed information on flald monitoring in the five months subsequent to the shot we refer the reeder to the transcript of flald notes of all monitors. PRIVACY ACT MATERIAL REMOVED

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The physical picture of eveoie leet inj t«- spread of radioactivity over terrain far removed froa aero point waa aa followst 1. Fine particles of sand would fall from the cloud carrying radio* active aateriala on theai. These particles will be carried in many different directions after leaving the cloud on account of differing wind directions at 2. At a given place on the ground a ulnlouai tlae Bust elapae after the shot before radioactivity appears in aaaaurabla amounts. This tine depends on tha cloud velocity and its extension. It also depends on the tiae it takes for particles to fall froa the cloud, 3* After the cloud has passed and the radioactivity has Arisen to its maxiaum Intensity there will occur a deeay of intensity with tlaa. This decay will be due to two aaln causesj the change in the geaaetrieal distribution of active material and the natural radioactive decay of the eleaente concerned, The apparent decay of the activity aa eeaaured on the ground will be influenced by the rate at which the particles Battle. There will be a tlae at which a fog of particles is hanging in the air just above the ground. At e certain tiae later these particles will have settled to the ground. If there Is wind| these particles will aove into the interstices of the ground surface. Further*ore, rain will wash them further into the ground. At each of these stages the geoaetricel distribution of the active material is diffarant froa the preceding stage. There will result an apparent decay of activity because tha progressiva changes are toward obscuring the active particles. This kind of deeay waa well demonstrated by the measurements of the searchlight crew at whose date are shown In Figure 3. In about ten minutes the measured activity dropped by a factor of two, fro* a maximum of two down to one R per hour. b). Fission products daeay law The decay of garaa and bets activity xa fission products ia summarised

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E. P, Winner and K. Way "Sunmary and Congelation of Data on the Rate of Decay of For purposes of health aonitoring the 1/t deeay Is «ost ©orrrenlent for estimating Intensities and is cOBserratlTe in estimating integrated doses fron measurementa made in the first 24 hours after the shot. However, at longer times, for conservative monitoring, it is necessary to assume an Inverse power of t larger e). Measured decay rates of radioactivity The decay of radioactivity as messured by gasaca roentgenometers varied considerably as can be seen by reference to the deeay curves in Appendix I compiled by Richard Watte. Fragments from the crater et sero decayed with time varying from t ^ to t"^*^. At fixed points around the crater the apparent decay was as t“^*® to t . This was assumed to be due to obscuration by dust. In one [lace the activity actually increased with time. This was interpreted aa being due to wind blowing active material toward this place. At great distances (greeter than 12 miles) the activity seemed to follow the law t”1*^ as shown in Figs. 1 and 4.

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geoaatrical disposition of tha radioactive natarlal wara described in a general way. Following i* a detailed discussion of the gasses ray intensity measured by an observer a* a cloud of radioactive partielea fella to the ground. Let the …