WT-939 

This document consists of 46 pages 

No. 1 70 of 225 copies, Series A 

Operation CASTLE . 

Addendum Report for Project 4.1 

PHYSICAL FACTORS AND DOSIMETRY IN THE MARSHALL ISLAND 

RADIATION EXPOSURES 

C. A. Sondhaus 

V. P. Bond 

This document contains restricted data as ’ ‘d ..‘, ‘. <-VI 

defined in the Atomic Energy Act of 1954. .a_< -“, ‘IIts transmittal or the disclosure of its 

contents in any manner to an unauthorized 

person is prohibited. 

’,_I> , “9 ., ‘.: 

LLL;,, QF, 

‘\ \ ‘2,‘0.3 U. S. Naval Radiological Defense Laboratory \ B '\ San Francisco 24, California \ 

‘, 
ENIWETOK ATOLL 

NORTH PACIFIC OCEAN 

I I /; ‘9 IIP CHANNEL--+ ,/‘j ‘\\ 5 Statute Miles / ,:J 

\\ ‘xoMJ ALVIN 

\ \ ,*-.-- ._._ _; ---- “_,) INlMl ,’ \ \ 

BRUCE ‘\ ‘\ 

F LEROY CLYDE _...._ \’ \ TAN

UAVIU? -y’ 

_,;F DEEP ENTRANCE RiGILl -\? 

,KEITH ARRY 

AMES ;’ 

_IRVfIN 

/MENRY / I ^..ENN 
Shots I8 2 “c!z% BIKINI ATOLL 

NORTH PACIFIC OCEAN 

N 

(CHARLIE) 

BOKONEJIEN Shots 4a5 

BOKOBYAADAA 

BOKORORYURU 

I( BRAVO) 

BOKOAETOKUTOKU 

I. A G 0 0 * 

I 

5 Statute Miles 

I 4) 

1,’ 

/’ 

*\ 

‘-. \% 

r ( ALFA) OURUKAEN 

( ZEBRA) 

n- rnrn ““I_ 

ENIIRIKKU ,/’ ,’ 

,/ 

,/ 

,I 

/’ ** 

,/ 

II’ 

1Shot 3 

ENYU 

(NAN) 

! 

\ 

I 

i 

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( 

, 

: 

: 

I 

i: 
GENERAL SHOT INFORMATION 

Shot I Shot 2 Shot 3 Shot 4 Shot 5 Shot 6 

DATE I March 27 March 7 April 26 April 5 Moy 14 Moy 

CODE NAME 

( Unclossifred ) 

Brovo Romeo Koon Union Yankee Nectar 

TIME* 06:40 06: 25 06: I5 06:05 06: 05 06: I5 

LOCATION 

Bikini, West of 

Chorlie (Nomu) 

on Reef 

Bikini, 

Croter 

Shot I Bikini, Tare 

(Eninman) 

Bikini, on Barge at 

of Arcs wrth Radii 

Dog (Yurachi) and 

from Fox ( Aomoen 

Intersectron 

of 6900’from 

3 Statute Miles 

). 

Enrwetok, IVY Make 

Crater, Flora (Elugelab) 

TYPE Land Barge Lond Barge Borge Barge 

iOLMES 8 NARVER N 170,617. I7 N 170,635.05 N lOO,I54.50 N I6 I ,698.83 N 161,424.43 N 147,750.OO 

COORDINATES E 76,163.98 E 75,950.46 E 109,799.OO E I I6,800.27 E ll6,668,15 E 67,790.OO 

+ APPROXIMATE 

. . , 
ABSTRACT 

This mport is an a&iendum to the final report of Project&J,

Operation CASTLE. Its purpose is to consider the physical factors 

and dosimetry of the fallout on the Marshall Islands from the first 

shot of Operation CASTLE. 

Data was summarized from field Radiological Safety surveys, 

'falloutradiochanical.studies, and fallout gamma spectral measurements. The Pnfluence of these and other facturs on an evaluation of 

surveymeter response and total dose estimates was considered. Estimates of fallout duration times and energy distrihtion of the dose 

fYcm a plane source were made and the effect of diffuse source-geometry 

on the depth-dose to air-dose relationship was considered. Superficial 

doses from soft gamma and beta Ilatiiation were also considered. 

Since the fallout incident created an initial emergency during 

which data collection was of secondary Importance, attanpts to reconetruct the event have been uncertain. Much of the data was indicative 

rather than exact. however, a fairly consistent estimate of external 

gamma dosage was possible, although the question of beta exposure 

remains mostly unanswered. It has been assumed that no significant 

neutron or alpha particle exposure occurred. Internal doses from inbaled or ingested material and the biomedical aspects of the incident 

have been discussed in other CASTLE Project 4.1 reports. 

It was concluded that: (1) the AN/PDR-39A requires a correction 

factor of about plus 20 percent in dose-rate readings made under the 

conditions described3 (2) decay of the ra 0activi.Q of the fallout is 

believed expressible by the factor of T4* dQ33 (3) the external. gamma 

dose was delivered primarily by radiation energies of 100, 700, and 

1500 kev; (4) the beta dose was delivered by beta radiation of maximum 

energiesof 0.3 and 1.8 Mev, mostly from fallout deposited on the skin 

itself3 (5) the exposures occurred between b and 78 hours after the 

detonation- the fallouts were probably of 120bars duration; (6) diffise source geometry increased the midline dose by about 50 percent 

canpared to the midline dose which would have resulted from a bilateral 

narrow beam exposure of the same air-dose; (7) error in the estimates 

is believed to be less than 50 percent; and (8) total air gamma doses 

were estimated as follows: Ibngerik, ,86 r; Rongelap, 182 r; Ailinginae, 

81 r; and Utirik, 13 r. 

5 
FOREWORD 

This report is one of the reports presenting the results of the 

34 projects participating in the Military Effects Program of Operation 

CASTLE. For readers interested in other pertinent test information, 

reference is made to WT-934, Report of the Commander, Task Unit 13, 

Military Effects Program. This summary report includes the following 

information of possible general interest. 

(a) An over-all description of each detonation, including yield, 

height of burst, ground zero location, time of detonation, ambient 

atmospheric conditions at detonation time, etc., for the operation. 

(b) Discussion of all project results. 

(c) A summary of each project, including objectives and results. 

(d) A complete listing of all reports covering the Military Effects Test l+ogxvun. 

ACKNOWLEDGMENTS 

The encouragwent and assistance of Dr. E. P. Cronkite, Project 

Officer of Project 4.1, Operation CASTLE, is gratefully acknowledged. 

LTJG R. Sharp (MSC) USN aided in the collection of much of the information in the field and assisted with the calculations. 

Data relevant to dosage calculation were made available by many 

sources. Information on energy distribution of the gamma radiation 

was furnished by Dr. C. S. Cook and the Nuclear Radiation Branch at 

the U. S. Naval Radiological Defense Laboratory (NRDL). Radiochepnical 

data supporting calculated radioactive decay rates were supplied by 

Dr. C, F. Miller, Dr. N. E. Ballou, and the Chemical Technology Division of NRDL, and Dr. R. W. Spence of the Los Alamos Scientific Laborat-y (WL).

CDR F. W. Chambers (MSC)USN of the Naval Medical Research Institute (MRI) kindly furnished field depth dose data obtained at Opera- . 

tion UPSK)T/KNOTHCLE. Particular thanks is due: Colonel C, E, Maupin 

(MC) USA of Field Command, Armed Forces Special heapons Project, and 

Dr. H. Scoville, of Headquarters, Armed Forces Special heapons Project. 
CONTENTS 

ABSTIWT............................ 5 

FOMWRD............................ 6 

ACKPJO~D~NW...;.................... 6 

IIUJSTRATIONS.......................... 8 

TAJ3IZS............................. 8 

CHAFTERl INTRODUCTION..................... 9 

CHAPTER2 FIELDDOSAa DATA.................. 10 

2.1 EarlyData ....................... 10 

2.2 Eqmture Condition................... s 10 

2.3 Later Surveys ...................... 12 

CHAPTER3 FAT.&XJTCIWiACTERISTICS............... 4 

3,1. ExperimentalDat.................... a 14 

3.2 CalculatedDecayRates.. ............... 14 

CHAPTER4 GAMMA ENERGX-DOSESPECTRUM. . . . . . . . . . . . . . 17 

4.1 Pbtonnux Spectrum.. . . . . . . . . . . . . . . . . 17 

4.2 Dose-EnergyDistributionsfor Plane Source Geatnetry.. . 18 

4.3 BetaEnergy,...................... 21 

CHAPTERS METERRESPONSE FACTORS.,.. . . . . . . . . . . . . 25 

5.1 Energy Response. .................... 25 

5.2 bometrg R=wnse. ............ : ...... 27 

CH4PTER6 aJRATIONANDTIMEDISTRIEKJTIONOFDOSES....... 30 

6.1 Available Data ..................... 30 

6.2 Estimates of Fallout Duration. ............. 31 
••••••••••••••••••••••• •

CH#&TER? EXR)SUFLEGEOMETRYEFFEC.............. TS 34 

7.1 Discussion 34 

7.2 ExperimentalSimulation and Gecmetry Factor ...... 35 

CHABTER8 !lDTALDOSEESTlMATES................ 38 

8.1 Calculated Values ................... 38 

8.2 Discussion....................... 38 

8.3 Soft Gamma and Beta Components. ............ 39 

CHAPTERY CONCLUSION..................... S 43 

REFERENCES,. ......................... 44 

ILLUSTRATIONS 

3.1 CalculatedTotal Activity Versus Time... . . . . . . . . 16 

Dose-Energy Mstribution, Shot 4 H + 5.3 Day Sample. . . . 22 

Dose-Energy Distribution, Shot 1 H + 4.1 Day Sample. . . . 

Dose-Energy Distrilxtion, Shot 1 H + 5.2 Day Sample. . . . Ii 

Energy Response of Survey Meter AN/PDR-TlB.... . . . . 26 

DirectionalResponseof SurveyMeterAN/BDR-TlB.. . . . . 29 

6.1 Fallout Dose Rate Versus Time Estimates, 

RongerikAtoll............. . . . . . . . . . 

7.1 Depth-Dcse Curves, 3641~ Bhantcm, 1.2 Mm. . . . . . . . . 

Depth-Dose Curves, 3&m Fkantm, 200 KVP.. . . . . . . . d•: •Cumulative Air-Dose with Time, Rongelap Atoll. . . . . . . 

8:2 Field Depth-Dose Measurement, Operation UPSHOT-KNOTHOLE. 

TABLES 

2.1 Radiation Intensity at Rongerik During Early 11 Fallout(Shotl) . . . . . . . . . . . . . . 

2.2 Early Dose Rate Data (2 to 3 March). . . . . 11 

2.3 Film Badge Readings cn Rcngerik.. . . . . . 12 

2.4 Later Dose Rate Data (8 to 11March) . . . . 13 

Shotl,H+%Hr.............. 18 

Shotb,H+5.3Days............ 20 

Shotl,H+b.lDays......... . . . 

FalloutandEvacuationTimes....... . 

86:: TotalGammaDoses............ . . 39 

Shotl,H+5.2Days............ z: 

Total Energy Response Factors for AN/FDR-39A 

:: 
-- 

CIWTERl 

INTRODUCTION 

The fallout on the Marshall Island atolls of Rongelap, Rongerik, 

Ailinginae, and Utirik from the first shot of the series beginning 

1March 1954 created an initial emergency during which the gathering 

of data was of secondary importance. This fundamental fact has resulted in uncertainty in all attempts to reconstruct the circumstances of 

the event. Calculationof the external doses received by the exposed 

individualshas required that available information be supplemented by 

assumptions.Much of the information itself was necessarilymore indicative than exact. In spite of these difficulties, the cooperation 

of many individuals and groups made it possible to develop a fairly

consistent estimate of external gamma dosage, although the question of 

beta exposure must remain mostly unanswered. 

It has been assumed that no significantneutron or alpha particle 

exposure occurred. Ths, the main consideration in this report is the 

total body gatmna radiation exposure. Internal doses from inhaled or 

ingested material have been discussed elsewhere (Reference 1). 

Data which form the basis of the analysis were furnished by several sources which are listed in the References. These represent 

measurementsmade both in the field and in the laboratory in the period 

Mediately following the exposure. Later information has also been 

included wherever it was available.A summary of these results appear9 

in Reference 16, which covers the biological and medical aspect9 of the 

incident. 
CHAPTER2 

FIELD DOSAGE DATA 

2.1 EAHLY DATA 

When the exposures began, no monitoring personnel were in the 

vicinity of any of the contaminated islands. One of the first indications of a fallout was visual, when a snow-like material was observed 

in the air on each of the islands. The reports on the times of observation, although conflicting, serve to establish the time of arrival 

of the cloud at each island, except at Rongerik (see Chapter 6). Here 

the first evidence of a radiation field was observed when a low-level 

gannnabackground monitiring instrument at the weather station began to 

register and then went off scale at100 mr/hr at approximatelyH + 7.1 

hours. Table 2.1 lists the readings of this instrument during the 

half hour preceding this time (Reference 2). These data are the only 

informationavailable on the initial rate of increase of gamma dose 

rate on any of the islands. 

At the time of evacuation of the military personnel from Hcngerik 

on 2 March and the Marshallese from Hongelap, Ailinginae, and Utirik 

on 3 March, dose rate readings were made on each island. This was done 

with AN/PI%39 radiation survey meters which were available at the time 

and which had not been calibrated beforehand. Their operating condition was not known at the time of use. The readings of these instruments are given in Table 2.2, and constitute the earliest data on gama 

dose rates in any of the areas (Reference 3). 

2.2 EXRWJHE CONDITIONS 

So far as is known, the individuals exposed on Hongelap and 

Ailinginae remained outdoors and had no access to shelter of any kind 

on the islands. No measures were intentionally taken to protect the 

skin, but clothing was worn to a degree sufficient to shield frm most 

of the deposited beta activity. In addition, much of the fallout skin 

contaminationwas removed from sane individuals, as a result of their 

swimming and fishing in the lagoon at the time. On the other hand, the 

heavy coconut oil hair dressing used by the Marshallese tended to concentrate radioactivity in the hair. The surface contamination on the 

gZ?OUAdwas apparently fairly uniform over the islands, so that the calculation of average gamma doses from this source appears justified. 

" 

. 
TABLE 2.1 - Radiation Intensity at Rongerik 

During Early Fallout (Shot 1) 

C 

c Time after Hhour GammaDose Rate 

(h4 (mr/hr, backg;round) 

.7+ Y.~ 6.5 (1345 1 March) 0.08 

-4 

7.37 6.87 0.18 I. 61 ro 

-4 

7K 10 7.+ll 6.91 0.70 

-3 -7.45 6.95 2.7 2.7-410 

-3 

7.5-t 7.04 3.6 3 6x10 

.L 

Y.&Z. 7.12 10.5 ,,OSXU 

-3

~~707.20 30 3 *I@ 

-rr7q 7.29 

7.s77.37 

TABLE2.2 - Early Dose Rate Data (2 to 3 March) 

Island Time after H hour (hr) Average Dose Rate (mr/hr) 

Rongelap H +36 ~500 ’ 

Rongerik H + 28.5 2000 . 

Ailinginae H+S8 445 

Utirik H + !% 160 

On Rongerik, the exposed individuals recognized the nature of the 

fallout, put on protective clothing, and took advantage of the partial 

gamma shielding afforded by Dutler-type buildings in the area, staying 

indoors as far as possible.- The radiation dose rate encountered by an 

individualon this island thus depended on his whereabouts and probably varied by a factor of two between maximum and minimum values in 

different areas at a given time. The estimation of dose received by 

arq one individual of the Rongerik group was thus subject to considerable uncertainty, since no canplete record of movements uas kept. 
I 

iWever, a group of film badge readings was obtained covering a 

range of values which varied with exposure conditions (Reference 3).

These readings are summarized in Table 2.3. Several badges were worn 

both outdoors and indoora. One badge which remained outdoors over the 

28&hour exposure reached the upper limit of 98 r given in the table. 

Several other badges kept inside a refrigeratorindoors gave the lowest 

value of 38 r. Skin contamination in the Rongerik group appeared to 

have been much reduced by the protective measures taken and the resulting beta doses appeared clinically to have been clearly lower than in 

the other groups. 

TABLE 2.3 - F'iLa Badge Readings on Rongerik 

Location of Badges Calculated Dose to Badges (r) 

Indoors and Out 44 to 52 

Outdoors only 98 

Inside Refrigerator Indoors 38 

2.3 LATER SURVEXS 

During the period 8 to 11 March, more extended surveys of each of 

the islands were made Qy a monitoring team equipped with five AN/FDR-39 

instruments (Reference 4). Twenty-fourhours previous to the departure 

of the =rve party, three of the instruments were calibrated on an 

8O-curie Co 6% source and cross checked at 0.320 r/hr, where they were 

found to be in close agreewent. Using these instruments, measurements 

were made in the inhabited areas of all four islands at waist height 

i;Lroximately3 feet above ground). Table 2.4 is a summary of these 

Since these later readings were made under better controlled 

conditions than the emergency surveys at the times of evacuation given 

in Table 2.2, the data of Table 2.4 were taken to be the bestmeasurement at a given time of the gamma dose rates in air and were used in 

the calculation of the total external gamma dose. 

No informationexisted on the quantity of beta contamination on 

the skin of any of the exposed individuals. Further, no experimental

data allowed any reliable calculation of the beta dose rate to an 

individual fran fission products on the ground. Thus the only basis 

for aw estimate of external beta dosage was data from other field 

tests and fallout measurements. This question is discussed further in 

Chapter 8, and a rough estimate for possible beta dose from the ground 

is made there. 
TABLE 2.4 - Later Dose Rate Data (8 to 11 March) 

Incation 

Rongelapr 

average 

max%num 

one point in village 

Rongerik: 

*average outdoors 

%aximum outdoore 

Ailinginaet 

average 

utirikr 

average 

Time after Hbur 

(dw) 

H+? 

H+7 

H +lO 

H+9 

H+9 

H+8 

Avg. Dose Hate 

bdh.4 

375 

450 

280 

170 

280 

300 

100 

40 

%ose rate inside structires found to be about * that 

outside. 
CHARTER3 

FALLOUT CHARACTERISTICS 

3.1 EXPERIMENTALDATA 

In order to calculate a totalgamma dose received by an individual in an area where dose rate was measured at a given time, a value 

for the rate of change of radiation intensity during the exposure 

periodmust be assumed. The latter quantit has often been approrimated using the well known Way-Wigner (t-l*s) decay law. In this case .& 

however, it was knownthat large amounts of ~p239 and Np2u were to be 

expected in the fallout of the 1March shot, making its early decay 

characteristicsas well as its energy spectrum somewhat different from 

those of previous detonations. It was therefore decided, that the 

value of decay rate assumed to exist during the exposures should be ••

based, as far as possible, upon experimental data from this test. 

Unfortunately,no decay rates were followed closely in any of the 

immediate areas where the exposures occurred, and it is known that the 

radiochenicalconpositionand decay rate of the fission product mixture 

usually vary both with place and time. However, early decay rates in 

the Bikini lagoon itself had been measured in a series of fallout 

samples taken at other points marer the sits of the detonation 

(Reference 5). Since these values were the best data available, they 

were used in the calculations and were assumed to hold for the fallout 

on each of the islands. 

The early samples showed a consistent pattern among variouslocations and a decay exponent (n) of between 0.8 and 0.9 in Equation3.1. 

A = A1( t/t-$” 

where: A = activity (d/m) at time t. 

This decay exponent (n) was found 

for the period H + 5 to H + 50 hours. 

in Reference 5. 

3.2 CALCULATED DECAY RATES 

These decay ra 

the presence of Np 24% 

tions were made on the 

et- fj ‘. F), i- x (3.1) 

experimentallyto fit the data 

The observed values are given 
hours after detonation was 1 3 d/m per 10 4 fissions and that of 

84 tt was 2.7 d/m per 104 fissions'while the gross fission product decay followed the nter=Ballouexponents and its activity at hours 

was 13 d/m per 10 fissions (Reference 6). This value of Np2 9 activ- P 1

ity follow from a calculatedneutron captire-to-fission ratio of 0.78 

intheU2g tamper.

Using the half-life of 2.33 days for Np239 and lk for U240 and 

combining these data with those for the total rate of decay of the fission products as assumed above a total.activity curve was calculated. 

This is illustrated in Figure 3.1. It is seen that a decay rate exponent of 0.83 between H + 4 and H + 23 hours; ofl.l between H + 23 and 

H + 120 hours; and 1.6 fran H + 5 to about H + I& days fits these portions of the curve. The rjresence of the measured decay rates thus 

agreed with other parameters of the detonation &ring the exposure and 

survey periods. Figure 3.1 was used in the dosage calculations. Tbs 

effect on dosage of the energy spectrum resulting from this canposition 

is discussed in Chapter 8. 
- - 

- - 

-1.1 

-

+ EXPOSURE PERIOD 4 / 

MEASUREMENT Np23g 

-

(TABLE 2.4) 

/ 

Y-

/

/ 

-

I 

I - L I 

r * IO 2 I 

TIME 

Calculated Total Activity Versus Time 
CHAFTEH4 

GAMMA ENERGY-DOSE SPECTRUM 

4.1 PHOTON FLUX SPECTRUM 

The fallout material deposited on the ground produced a large area 

plane source of radiation. Before a total gamma dose could be calculated,it was necessary to correct the dose rate readings in air taken 

with the survey instruments with the meter response factors found to be 

necessary for different energy regions. Further, to estimate the distribution of dose with depth in tissue required a knowledge of energy 

distributionof the incaning flux in a given exposure geametry. 

For a source as large as these fallout fields, this energy dis.tributlon u%Ll be a function both of the original source energy and the 

energy degradation effect of passage through intervening air. A method 

of evaluating the latter, which was due mainly to Canpton scattering in 

air for the ftision product energy region, has been presented in 

Heference 7. This technique was employed here. Energy spectra of the 

CASTLE fallout itself has been measured with a scintillationspectrometer on a series of cloud samples as early as H+ 4 days. The data have 

been published in Reference 8. The preliminary data on the earliest of 

these, a 94-hour-old cloud sample, were used in the calculations summarized in Reference 16. These are given in Table 4.1 (Reference 9). 

This 9h-hour sample from Shot 1 represents the closest approach t.c the 

actual time during which the exposures occurred. 

After the conclusion of the test series, analysis of early data 

from other shots continued and later spectra for all shots were analfled. None of the other spectra are for times as early as H+ 94 hours. 

For the later detonations the proportion of Np239 (average gamma energies El= 24.3 kev, 40 percent; E2 = 105 kev, 11 percent3 E3 = 58 kev, 

49 percent) in the fallout samples was found to be much higher than 

that given in Table 4.1, An extme case, for example, is the data for 

Shot 4 on 26 April at H + 5.3 days which is given in Table 4.3. Here 

the low energy portion of less than 100 kev was measured as 60 percent - of the total photon flux. Two later determinations on another Shot 1 

sample (l-L, Table 3 of Reference 8) show these low energy proportions 

as 55 percent at H + 4.1 days and 54 percent at H + 5.2 days as well 

(Tables4.3 and 4.4). Later data thus tended to show that the initial 

estimate of low energy radiation was Pow. Hence, revised estimates of 

the total doses will be presented here on the basis of the additional 

data for which the counting statistics were better than on the Shot 1, 

H + 94 hour sample. These spectra, it must be emphasized, are for 
samples taken soon after the detonation in the cloud itself at some 

distance frcm the atolls (+erence 5). Again they represent the best 

data available and, in the absence of contrary evidence, had to be 

taken as typical of the fallout on the islands. 

TABLE4.1- Shotl, H+94 Hr 

Energy (Mev) Percent of Flux Cumulative Percent 

Dose (See Text) 

1.~9 7.04 100 . 

1.37 0.99 83 

1.27 0.80 

0.96 2.70 80 

0.84 3.71 66 

0.76 15.11 

0.66 19.24 36 

0.50 12.15 21 

0.27 4.82 

0.22 6.00 12 

0.10 20.24 

0.068 5.04 8 

0.018 2.17 

4.2 DOSE-ENERGY DISTRIBUTIONS RR PLANE SOURCE GEOMETRY 

To canpute the proportion of total air-dose due to a given energy 

interval in the degraded spectrum which resulted from the spectrum of 

the original sample, the &se from the spectrum due to the emitter distributed as an infinite plane source was calculated by sumning the 

contributionsover all path lengths in air. By dividing the original 

H + 94 hour spectrum into 13 energy regions and carrying out this process (Reference7) for each, a cumulative dose versus energy curve 

resulted. The cumulative doses are given in Tables 4.1, 4.2, and 4.3. 

Fran these curves, a differentialhistogram of percent dose versus 

energy interval. was de&mined which represents the percent of dose 
delivered to the surface of the exposed individual at a height of 3 

feet above the plane by photons with energies in each of these intervals (Figures 4.1, 4.2, and 4.3). 

The process consists essentially of the following steps; 

1. For each source energy, calculatingthe dose per photon contributed by the unscattered portion of the radiation from each increment of source area. This requires an expression involving ntrueW and 

total absorptLon coefficients in air, eqonen tial integral, source 

energy, and fraction of dose due to unscattered photons of that energy. 

2. For each source energy, calculatinga weighting factor (or 

relative dose) Qv multiplying the dose per photon in Step 1, above, by 

the number of source photons with that energy. 

3. For each source energy, estimating the fraction of dose due 

to source photons originally of that energy but degraded by scattering 

to energies less than each of a set of arbitrarily chosen energy values. 

4. Computing the total dose due to all photons with energies up 

to each chosen energy value by summing the product of Steps 2 and 3, 

above, for each of the original source energies. 

The result is an integral or cumulative air-dose spectrum; i.e., 

a plot of photon energy versus the air-dose resulting from all photons 

from zero to that energy. From this, a rough differential dose histogrem is obtained by subtracting ordinates on the integral curve at the 

endpoints of each chosen energy interval. The use of graphical and 

numerical methods makes the technique quite applicatile to the detennination of a number of such dose-energy distributions. 

Figure 4.2 of Reference 16 depicts the differential air-dose distribution for the Shot 1 H + 94 hour data, in percent of dose per 0.05 

Mev interval versus energy in Mev, Dose spectra based on the later 

data differed chiefly in the low energy region. The relative dose due 

to energy up to 100 kev averagedabout 40 percent as compared to 12 

percent in the above distribution. Three other dose distributions 

were calculated from Shot 4 and later Shot1 data and are shown in 

Figures4.1, 4.2, and 4.3. Figure 4.1, using the data of Table 4.2, 

is an extreme case with respect to the low energy component. All 

other samples for all the shots lie between this and Figure 4.2 of 

Reference 16, Figures 4.2 and 4.3 give the dose distributions for the 

H + 4.1 and H + 5.2 day times on the other Shot 1 sample. Figure 4.2 

also indicates estimated error in portions below 0.3 Mev. 

The dose spectra are all seen to group roughly into three regions 

with peaks at 100, 700, and l$IO kev. Since the spectra are those of 

4 to 5 day old fission products, at which time the Np239 activity is 

at its greatest relative value, the low energy proportion due to this 

nuclide is higher than it was at H + 2 days when the Np239 component 

was stFl1 increasing (Figure 3.1). Based on this distribution, dosage 

and meter corrections for the low energy region during the exposure 

period are therefore generous. During the several days before and 

afterthis time the general spectrum shape apparently did not vary 

grossly in the higher energy regions. A total correction factor for 

the survey instruments was therefore calculated for each of these spectra and was assumed to hold for the period between fallout and surveys, 

as is described in Chapter 5. 
Energy (Mm) 

0 - 0.1 

0.1 - 0.2 

0.2 - 0.3 

0.4 - 0.5 

0.6 - 0.7 

0.7 - 0.8 

0.8 - 0.9 

1.5 - 1.6 

Energy(Mev) 

0.100 

0.200 

0.250 

0.300 

0.486 

0.659 

0.79 

0.815 

lS90 

TABLE4.2- Shot4, H + 5.3 Deys 

b-cent of Flux 

59.6 

16.0 

8.1 

4.6 

4.3 

4.0 

1.0 

2.4 

TABLE4.3 - Shot 1, H + 4.1Days 

Fbrcent of Ilux 

0.%8 

0.136 

0.108 

0.042 

0.037 

0.055 

0.048 

0.012 

0.013 

cumulPtive 

percent Dose 

56 

70 

76 

90 

92 

100 

Cumulative 

Percent Dose 

31 

50 

65 

85 

92 

100 
TABLE4.4 - Shot 1, H+ 5.2 Days 

Energy(Mev) Percent of Flux cumulative 

Percent Dose 

0.035 5.97 10 

0.65 11.53 

0.100 36.47 36 

0.135 3.81 

0.210 IO.49 

0.250 5.23 52 

0.285 4.05 

0.320 2.21 

0.486 5.13 65 

0.659 6.35 . 

0.750 5.06 83 

0.815 1.82 89 

lS90 1.88 loo 

4.3 BETA ENERGY 

The beta radiation energy was not measured directly in any of the 

fallout or soil samples. However, franc available data on the radiochemical composition of the fallout (Reference 6), it ha8 been estimated that Fran 30 to 65 pe nt of the beta radiation &ring the exposure period was due to Np $8 andhadan avera@ I$,,,ofabout0.3 

Ilev. The balance of the radiaiionwas of higher energy, with an 

average Gax of about1.8 Mev. The half-value thickness in tissue for 

the low energy canponent is about80 microns, with a range of about 

800microns total. For the high energy ccmqorrent, the half-value thickness is about 800microns and the range about 8000microns. Since no 

estimate could be made of the amount of material on the skin surface 

or length of t&e it remained there, only rcrugh estiates based on 

clinical.evidence could be made of the skin beta doses, (gee deference 

16). 
4-L 

SHOT 4 H + 5.3 D 

GAMMA ENERGY (ME'.') 

Fig. 4.1 Dose-Energy Distri?xtion, Shot4 H + 5.3 Day Sample 

? 

-: 
::::::: 

....... 

....... 

....... 

....... 

....... 

....... 

....... 

....... 

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::::a ............... I.. .................. 

:::::::::::::::.:::::::::::::::::::: 

.................................... 

............ t.1.. ................... ............ ....................... 

. .................................. A.. ................................ .................................................................. ................................................................................................................................................ 

.” ..*m 

:::::::::::::::::::::::::::::::::::::I 

........................................................................... 

............................................................................ 

...................................................................... my.. 

::::::::::::::::::::::.::::::::::::::: ... .................................... . 

............................................................................................................. .I 

ci -

UN33 t13d) 3SO0 

23 
20 

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........ I-L .............

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::::::::::z: 

............. 

............. 

............. 

............. 

............. SHOT 1 H+5.2 D ............. 

............. 

............. 

............. 

............. 

............. 

............. 

............. 

............. f ............. 

ow............. 

............. 

............. 

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............. w .............

............. ......... al 0 ......... .............

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............. ii ::::::::::::L ......................................... y:::: 0 ................... ::::::: .. 

................... ..... :::o::: ....... ::::: 

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................... ....... ................... ....... ::::: ....... ................... ....... ............ *. ............ ::::: ....... .......................... 

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................... e:::::::::::: ....... ::::: .......................... ................... .............. ....... .......................... 

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...... . .......... ....... ................................. :::: ....... ......... ........................ 

....... -1.. ........ ....... ... . ............................ .............. 

.............. ........... ........ .............. ....... ................................. :::: ................... ... . ..... .... ....... ................................. ................... .............. ....... ................................. ::::: ................... :::::::::::::: ....... ................................. . . . ... . ........... ..................... ::::: ....... ........... I.. ................... ................................. ::::: ..................... . .......... 

................................. ::::: ................................. 

................................. ::::: ................................. 

............ ......... ............ ::::: . . . . . ... . . . . . . . . . . . . . . . . ... . . . . . . :::: 

::::. 

::::, 

. . . . 

0 

0 0.2 0.4 0.6 0.8 I .o I.2 I .4 1.6 

GAMMA ENERGY (MEW 

Fig. 4.3 Dose-Energy Distribution, Shot111 + 5.2 Day Satqile 

I ‘ , I 
CHAPTER5 

METER RESPONSE FACTORS 

5.1 ENERGY RESPONSE 

The response of the survey meter to the spectra calculated in 

Chapter & was evaluated in terms of a set of normalizing factors, one 

for each energy interval in the spectrum. By summing over the inter 

vals and weighting each response factor by the fraction of total 

air-dose in that interval, a total response factor is obtained. 

Thus, if Dl is a dose reading for radiation of a given energy and 

ki is the normalizing factor for that energy, thent 

kiDi= fiD (5.1) 

Where: fi= the fraction with the given energy of the total true dose D. 

Hence: 

D’ = CD;=DC 3 

Solving for Dt 

D = D' (5.2) 

-5 

c 7qThe fi may be taken the dose-energy distributions in Chapter 

4 and the ki from Figure which is_ a plotof the response factors 

found for the earlier model of the AN/BDR-3gA, then called the AN/PDR- * TlB (Reference 10). This is believed to be essentially identical in 

its response to the later models. For the spectrum used in the Reference 16 calculations, the total response factor was found to be 1.04. 

This value was used in the dose calculations of that report. 

For the spectra shown in the Figures 4.1 to 4.3, the total. energy

response factors for all energies above 20 kev were found to be as 

given in Table 5.1. The value of 1.12 for the H+ 5.2 day spectrum of 

Shot 1 (Figure4.3) is used in the revised dose calculations of this 

report, since this spectrum represents the beat data. 
1.6 

1.4 

- -0 INTERPOLATED 

w 1.3 

N 

5 

Qr 1.2 

Fi 

z 

2 I.1 . 

Ra- f5

I- 1.0 

z 

0.9 

0.8 

0.04 0.06 0.08 0.1 0.2 0.4 0.6 0.8 I 2 

ENERGY (MEV) 

Fig. 5.1 EnergyResponse of Survey Meter Aw/pDR- !l!lB 

. 
TABLE 5.1 - Total Energy Response Factors for AN/PDb39A 

Spectrum Shape Total Response Factor 

Shot 4 (4-L) H + 5.3 Days 1.17 

(Figure4.1) 

Shot 1 (1-L) H + 4.1 Days 1.06 

(Figure4.2) 

Shot 1 (1-L) H + 5.2 Days 1.12 

(Figure4.3) 

Shot1 (1-L) H + 94 Bours 1.04 

(Figure 4.2 of Reference 16) 

b 

5.2 GEOMETRY RESFVNSE 

The response of the instrument is known to vary also with the 

direction of incidence of the flux, but no allowancewas made for this 

factor in Reference 16. An attempt has been made to correct for this 

effect by using the plots shown in Figure 5.2. This figure, taken 

from Reference 10, is a graphical representation of the directional 

response to a lO_ng Radium source of a TlB instrument in the horizontal 

and in two vertical planes. It was felt to be sufficientlyaccurate 

to make the approximation shown in the graph by setting a straight line 

limitto the response vector in one region and, further, to assume that 

the response is cylindrically symmetric about the XX' axis. Maximum 

sensitivity,indicated by a vector length of unity, is then in the OX 

direction on the XX' axis. If a flux (F) per unit solid angle impinges 

on the instrument at an angle 0 with respect to OX', the reading on the 

meter will be (assuming that the response is linearly proportional to 

flux intensity): 

Dt= rD= rkF (5.3) 

Where: k = proportionalityconstant 

D = strue18air-dose 

r =vector response factor 

By the above approximation, the vector response factor (r) is 

given by: 

73 : 4= 0.6 set 8 

<v : r=l (5.4) 

The average value of r is given by: 

27 
7T 

F= / o rd8 (5.9 

I rde 

Using the above values of r, F"= 0.92; i.e., the instrument is 

about 92 percent efficient. Thus the average directional response correction factor is 1.39, implying that the reading inside a homogeneous 

cloud or over a hanogeneous plane source is about 9-percent low for 

this average errergy, which is roughly in the l_Elev region. 

For the very low energy component below 100 kev, it is not known 

whether the relative directional response varies grossk~ from the 

above. It is assumed here that it does not. The doses calculated in 

this report are therefore based on this directional correction. Combining this geometry factor with the energy correction of Table 5.1 

for the H + 5.2 day spectrum and Shot 1, a total correction factor of 

1.22 results which was used in the air-dose calculations in Section ’ 

8.1 of this report. 
X’ 

Y 

Fig. 5.2 Directional Response of Survey ICeter ~Jl/PDWllB 
CHAPTER 6 

DURATION AND TIME DISTRIBUTION OF DOSES 

AVAILABLE DATA 

In Chapter 2, the only existing field data on dose rates and todose are summarized. The information does not provide answers to 

important questions: (1) what was the time for each island at 

which the fallout cloud arrived; i.e., when did the radiation level on 

each of the islands rise above the normal. background and (2) how steep- T 

ly and for how long did the radiation-level rise before it reached its 

maxlmum value and decayed away at the rate determined by its own composition (discussed in Chapter 3); i.e., how heavy was the fallout at 

any time it was occurring and how long did it last? Since only the 

times of evacuationwere directly known, assumptions on both these .

questions were basic to an estimate of total dose. 

It would have been desirable to have had an instrumenton at 

least one of the islands capable of recording enough data to answer . 

these questions. As it is, it was fortunate that there was even a lowlevel monitoring instrument in operation on Rongerik (Table 2.1), although its full scale capacity was soon exceeded by the rapidly 

increasing dose rate of the fallout. The time at which the fallout 

began was at least quite definitely established on Rongerik and it coincided with the time at which the snow-like material was first seen. 

For the other islands, therefore, the times at which similar material had been seen to commence falling could be taken as the beginning 

of the radiation exposure ties. It only remained to determine what 

these times had been. 

Questioning the inhabitants of the other islands resulted in a 

group of estimates of arrival time which were in fairly good agrement, 

though the mannerof questioning sanetimes appeared to influence the 

answers. However the times estimated in this fashion were quite close 

to those resulting from other information; i.e., the wind velocities 

at the time, the time of beginning fallout on kongerik, and the relative distances of the other islands from Bikini. Only on Utirik was 

no actual observation of the fallout made; the estimate of arrival 

time there was made using only the time of arrival on Ebngerik and the 

wind-and-distance-factors.The values of fallout and evacuation times 

used are summarized in Table 6.1. 
TABLE 6.1 - Fallout and Evacuation Times 

Island Estimated Initial Evacuation Time 

Fallout Times (hours)

(hours) 

Hongerik H + 6.8 H + 28.5 (8 men) 

H + 3& (20 men) 

Rongelap H+4 H + 50 (16 people) 

H+a(L8 people) 

AllingiMe H+4 H+g 

Utirik H + 22 H+sStoH+78 

6.2 ESTIMATES OF FALLOUT DURATION 

The rate of increase of radiation intensity, the time at which, it 

reached its maxknum level due to decrease of fallout, and the total 

duration of the fallout can only be estimated on circumstantialgrounda.

The data of Table 2.1 for Hongerik are not sufficient to warrant an extrapolationover two orders of magnitude. It is unlikely that the 

increase of intensit;y was simply linear either on Hongerik or any of 

the other islands. But, if the rate of increase is assumed constant 

and extrapolated to a point for which subsequent decay alone would reduce the dose rate to the values found at later times, a falloutt&e 

of 16 hours on Rongerik, for example, is found to be a necessary consequence (Curve a Fi&ure 6.1). That is to say,16 hours would have 

elapsed at sueh'a constant fallout dose rate increase before the tie 

of maximum dose rats on the island would have occurred - the time at 

which the fallout was increasing the radioactivity level at the same 

rate that radioactive decay was reducing it. For such a constant 

build up, this equality would have occurred only for an instant, (Point 

Al), aftir which the fallout would have suddenly ceased. 

The actual fallout must, of course, have had a variabilerate of 

increase and decrease, reaching a maximum and gradually decreasing to 

the rate governed by decay alone. However, using the initial rate of 

increase and drawing a more gradual maximum would place ths cessation 

of the fallout at an even later tine (Curve b,, Point A2). Since the 

visible fallout is belietid to have ceased sometime after midnight on 

1 March or at about H + 18 hours (Point A3), an increase in the rate 

of increase after a short time was almost certainly the case (Curves 

3 3 and e). But the steepness of this rate of increase, the sharpness of thzmaximum point and the gradualness of the fallout diminution 

are unknown, so that there is no direct evidence to show whether Curve 

2 or Curve 3 for instance, is closer to representingthe event. 

There are, however, indirect indications. Monitor data frcm previous nuclear events have indicated that a radioactivecloud is not 
uniformly high in activity throughout, the first portion being the most I 

intense and the balance tailing off. Initially heavy fallout has been 

reported to produce a peak of airborne radioactivity soon after its arrival., with the airborne activity level then decreasing. The latter 

part of a fallout, though still observable as dust, may then add only 

a small fraction to the total dose due both to aerosol and material 

already on the ground, especially if radioactivity was mainly confined 

to the larger particles which fell outmost quickly. If this is the 

case, the total phenomenon would tend toward the effect of a shorter 

fallout, and the total dose would then be best estimated by assuming 

the fallout to have been complete in some shorter "effective" time, 

such as Curve f, 

The RongeFik film badge data in Table 2.3 may be used to derive 

such an effective fallout time estimate. This procedure was followed. 

The decay rate, energy spectrum, and meter response discussed in Chapters 3 and 5 were used and the later dose rate measurement on Rongerik 

(Table 2.4) was taken as a starting point. The upper limit of dose 

found with the outdoor badge readings (approximately 100 r Table 8.1) 

then resulted from assuming a 12.hour "effective constant fallout" 

time. This was, therefore, taken as a most probable time and the resulting straight line midway between Curves a and f in Figure 6.1 was 

used in calculating the probable 120hour dosg for gach island (Curve 

). Though this estimate differs appreciably from that of 1 hour 

%w ich was originally used as an effective time in Reference 16, the 

later spectrum, decay rate, and meter response estimates made a 120hour 

value more plausible if the film badge readings were accepted. 

Keeping a l-hour assumption would have resulted in a dose some 

50 percent higher than the outdoor badge readings showed. Since the 

accuracy of the film badge readings was believed to be better than 50 

percent, the 120hour value was therefore used, as it is more consistent 

with all the other available information. Nevertheless, the duration 

of fallout still remains the least known parameter of the exposures. 
c _ 

. 

I i 0 

0 

v) 0 

(YH/M) 32VU 3SOa 
CHArnR 7 

EXPOSURE GEOMETRY EFFECTS 

7.1. DISCUSSIGN 

In clinical and laboratory exposures, the radiation flux usually 

follows a narrow beam or at least a point-source lldivergent*' geometry. 

bhen an air-dose is used to specify the exposure conditions for a 

thick target, it is generally measured at the point subsequently occupied by the center of the proximal surface of the patient or experimental animal with respect to the source. For field exposures such as 

occurred on the islands, the radiation source is not a point and the 

exposure geanetry is ltdiffuset'rather than "divergent." 

When a cloud or a large planar area is the source, all surfaces 

of the irradiated individual are "proximal," in the sense that the airdose measured anywhere in the space subsequently occupied by the individual is the same. It is this air-dose which is measured by a field 

instrument; it does not bear the same relationship to the skin dose 

and depth dose as does the air-dose measured in a point source geometry. If a bilateral exposure is made in the laboratory, one-half the 

dose is usually given with one side of the individual facing the source 

and one-half with the other. This is a closer approach to the field 

geometry. But, if the air-dose has been measured at the center of the 

proximal surface as above, it is still not related to the depth dose 

in the same way as is the field air-dose. 

The doses received by the individuals on the islands were from 

both the cloud itself and the fallout, deposited on the ground. It is 

believed likely, as discussed in Chapter 6, that. the cloud dose was 

only a small part of the total dose and that the dose from the plane 

ground source contributed the major portion. This ccrresyonds to the 

assumption of early maximum activity and short effective fallout time 

which was made in Chapter 6 for the maximum dose case. Alternatively, 

if a long fallout actually occurred, the source would have remained a 

cloud longer and the cloud volume, rather than the surface distribution, would have accounted for more of the total dose, In either case, 

it would appear that the midline dose, rather than the dose measured 

in air, would be the better common parameter in terms of which to predict biological effect. Since most existing data tacitly assumes narrow beam geanetry, this distinction beccanes important in relating 

field air-doses and their consequences to known clinical or experimental results (References 11, 12). 
7.2 EXPEFZYENTA.L SIMULATION AND 05CMETRY FACTOR 

In such a diffuse field, the decrease of dose with depth in tissue is less pronounced than that resulting from a bilateral exposure 

tc an X-ray beam and the relationship to air-dose differs as noted in 

the two cases. The result is that, for a given energy, the dose at 

the center of the abdomen is considerably higher than a given proximal 

air-dose would imply for the narrow-beam or point-source case. 

Figure 7.1 illustrates the depth dose curve in a 36an diameter 

cylindrical masonite phantom from an experimental simulation of the 

field Jeometry (deference 13) using a Spherically oriented group of 

36 cosb sources. The phantom was placed at the center of the assembly. 

This is compared to a conventional bilateral dept -dose curve measured $ in the same phantom and obtained with a single Co o source. Both are 

normalized to air-dose, but the average air-dose at all points later 

occupied by the phantom surface is implicit for the diffuse case, while 

the proximal air-dose is used in the bilateral case. 

Fisre 7.2 is a similar comparison for 200~KVP, O.$mm, copperfiltered X-rays, with the diffuse geometry that of a plane rather than 

spherical source assembly. This was produced in this case by rotation 

of the phantom and ion chamber in the beam of a stationary X-ray unit. 

The useful beam angle of the unit was wide enough to include the whole 

phantom. The average air-dose around the circumference was here used 

for the diffuse geometry and the proximal air-dose again in the bilat 

era1 exposure. It is evident that for both these energies (the effective energy of the X-raybeam being about 90 KV), the diffuse-narrow 

beam depth dose ratio for either 2 7r radians (plane) or b7r steradians 

(volume) diffuse geometry is almost the same. That is, the midline 

dose is about 50 percent higher and the !&cm dose is 35 percent higher 

than the same air-dose (measured proximally) would imply in the narrow 

beambilateralexposure. It is therefore assumed that this approximate 

factor will apply throughout the field exposures. 

On this basis the air-dose values calculated from the survey meter 

readings (Table 8.1) should be multiplied by 1.5 in order to compare 

the situation to that of a bilateral exposure to a source with the same 

energy distribution but using a point source geometry and a proximally 

measured air-dose. Alternatively, if a point source of higher energy, 

say ~060, were used bilaterally in the same way to simulate a field 

exposure to only the higher gamma ccmponents, then the meter energy 

correction factor would be unity. In this case, to specify a bilateral 

exposure yielding a midline dose equal to that with diffuse geometry, 

the point source air-dose should be the diffuse field air-dose measured with the meter and multiplied by (1.09 x 1.5) only. 

The doses are discussed further in Chapter 8. 
47r EXPOSURE, -

MANY SOURCES 

- RATIO I.56 

BILATERAL EXPOSURE, 

DIVERGING SOURCE 7

39 % 

IO 

0 5 IO I5 20 25 30 36 

CM MASONITE 

Fig. 7.1 Depth-Dose Curves, 3&m Phantom, 1.2 Mev 

I , . . 
••

ln I 7’ 

. .

TX 

\ 

% 

\ 

0 

_:_ -’ 

. 7

f 

0

-2 -

r /

F 

33WtlflS 1W 3SOCl tllW IN33 Eld 
CHARTER 8 

TOTAL DOSE ESTIMATES 

8.1 CALCUUTED VLLLIES 

The total doses calculated for each of the islands for hypothetical fallout times of 8, 12, and 16 hours are given in Table 8.1, 

together uith the doses calculated in Reference 16, in order to illustrate the difference in the estimates due to the later information on 

gamma spectra, meter response, and decay rates. 

The 120hour fallout value is considered most probable, being most 

consistent with the Rongerik film badge data (see Section 6.2). Doses 

based on this value are multiplied by the geometry factor discussed in 

Chapter 7, in order to express them in terms of the air-dose fran a 

source of similar energy under bilateral exposure laboratory conditions 

which would have produced the same midline dose. A plot of dose rate 

versus time based on Figure 3.3 was used and the total dose was graphically determined by normalizing ordinates and dose rates for a given L 

time and measuring the area under curves similar to Figure 6.1, This 

was done assuming all three fallout times for each island. 

The air-dose rates measured at later times (Table 2.4) were multiplied by the total correction factor for geometry and energy dependence 

of the survey meter (see Section 5.2). Fallout beginning times and 

evacuation times used were those of Table 6.1. It was found that doses 

calculated using the decay exponents of Section 3.2 were in good agreement with those determined graphically. 

8.2 DISCUSSION 

Figure 8.1 illustrates the cumulative air-dose as a function of 

time on Rongelap atoll, based on the 12 hour fallout assumption. It 

can be seen that the rate of delivery of the dose varied continuously, 

the major portion being received at the higher dose rate prevailing 

in the mid-portion of the exposure period. By the time that 90 percent 

of the dose had been received at H + b3 hours, for exmple, the dose 

rate had fallen to 2.7 r/hr, less than 40 percent of its maximum value 

of 7.1, r/hr at H + 16 hours. At H + 16 hers, 25 percent of the dose 

had been received. Thus the dose rate during exposure differed markedly Fran that usually encountered using X-ray units. 

The dose values for Rongerik gi.v-en in Table 8.1 are 75 percent of 

the computed values, averaged for the 2d.5-and-3&-hour exposures. This 

38 
was felt to best express the average air-dose received by personnel 

who spent roughly half their time inside structures where the dose 

rate was later found to be roughly half that outdoors. On the other 

islands no such shielding was present, and no reduction factor was applied. The same procedure was followed for all the calculations. 

TABLE 8.1 - Total Gemma Doses 

Island Dose 12.Rour l&Hour Ref. 16 124bur Bilateral 

8-Bour Fallout Fallout (r) Air-dose (Point 

Fallout (r) (r) Source of Same 

(r) Energy) for Equal 

B Midline Dose f ,j 5 ‘! 

(4 

Rongerik* 106 86 11. 70 78 130 

Rongelap 209 182 159 175 270 

Ailinginae 92 81 72 69 120 

Utirik 15 13 12 4 20 

*See Section 8.2 

8.3 SOFT WA AND BETA COMFONENTS 

In addition to the total body gamma dose, the very soft gamma and 

higher energy beta radiation from the plane scurce contrihted to the 

skin dose. tirthsr skin irradiation resulted from local deposits of 

fallout material on the body surface itself. The latter is impossible 

to estknate, tn~t the former may be roughly attempted as follows. 

The beta dose rate in air at a height of 3 feet above the surface 

of an infinite plane contaminated with mixed 240hour-old fission products is estimated to be about three times the air ganuna dose (Reference 

14). The midline gamma dose is approxtnately 60 percent of the portion 

of the air gamma dose due to 1004X radiationor above (Reference 13). 

This portion, in km, is estimated to be 60 percent of the corrected 

gamma dose measured in air by a calibrated instrument. TIus, the dose 

at the surface of a phantom exposed to mixed fission product radiation 

from an external plane source might be expected to be about eight times 

(3/(0.6)2) the midline dose, if both occur at 3 feet off the ground. 

Such a depth-dosemeasurementhas in fact been made experimentally 

at a previous field test (Reference ls), using a phantom man exposed to 

both the initial and residual radiation. The depth-doses for each situation are shown in Figure 8.2 with all data as percent of the 3-m 

doss. With the diver,@.ng initial radiation from the point of explosion, 

the exit dose was seen to be 63 percent of the3-a-a dose. But, with 

the diffuse residual field of fission product radiation, a surface dose 

39 =---~jBlmllm 
T- ‘4 7 

EVACUATION 

AT 51 HR 

c -

, -

12 HR FALL-OUT 

4-16 HR 

I .l I I I I 

'0 IO 

TIME AFTER H-HOUR (HR) 

Fig. 8.1 CumulativeAir-Dosewith The, 

Y 
DEPTH DOSE IN PHANTOM MAN 500 : 

V INITIAL RADIATION I 

-lcT- RESIDUAL FIELD 

I : 

D 

9 

2 200 

0 

50 

0 20 

DEPTH (CM) 

Fig. 8.2 Field DeptJkiose Measurement, Operation Ul?S~OT-KNO’IVOLE 
sane eight times greater than the 3-czn-and-deeper dose from the harder 

gamma ccmponents was observed. This is seen to be of the same order 

of magnitude as that estimated above. 

At heights above and below the 3-foot level, this surface dose 

would becczne lower and higher, respectively. But, since it is due to 

soft radiation of short range, it probably would not exceed 50 tines 

the j-foot air g-a dose or 80 times the midline dose, even in contact with the ground. 

An estimate of skin dose due to ground contamination for the 

Ftongelap case would result, for exa;nple, in a figure of about 2000 rep 

to the dorsum of the foot, 600 rep at the hip level, and 300 rep at 

the head if continuous exposure with no shielding occurred. Some reduction in dose undoubtedly resulted from shielding and movetnent and 

it seems probable that the external beta dose from local skin contiination far outweighed in importance that from the ground. This is 

emphasized by the probability that clothing reduced the beta dose from 

the ground by 10 to 20 percent. 
CHAPTER9 

CONCLUSIONS 

The AN/PDR-39A is estimated to require a correction factor of 

about plus 20 percent in dose-rate readings made under the conditions 

discussed. 

The decay of the radioactivity of the fallout duri the exposure 

period is believed to be expressible by the factor T- 0 ••13. 

The external gamma dose was delivered primarily by radiation energies of 100, 700, and 1500 kev. The beta dose was believed to be 

delivered by beta radiation of maximum energies of 0.3 and 1.5 Mev, 

mostly from fallout deposited on the skin itself. 

The exposures occurred between 4 and 78 hours after the detordtion. The fallouts were probably of about 120hours duration. 

Diffuse source geometry increased the midline dose by about 50 

percent canpared to the midline dose which would have resulted from a 

bilateral narrow beam exposure of the same air-dose. 

Error in the estimates is believed to be less than 50 percent. 

Total air gamma doses are estimated as follows: Rongerik,86 r; 

Rongelap, 182 r; Ailinginae, 81 r; and Utirik, 13 r. 
REFERENCES 

- 1. Cohn, S. H. et al; Addendum Report, Project b.1, hT-936,Operation CASTLE; OFFICIAL USE ONLY. 

2. Maupin, C. E.; private Communication; AMSRGS, Walter Reed Anny 

Medical Center, Washington, D. C. 

3. F&d Safe Narrative Sequence of Events; Memo for Record, BRAU) 

Shot, Operation CASTLE; Hqs JTF-7,Washington, D. C. 

c 4. Scoville, H . et al; Report of the Radiological Safety Group; 

USNRDL ltr 0010755, 12 March 19%; Hdqtrs JTF-7 Rpt No. TU-13-54-375; 

SECRET-RD. 

5. Tompkins, E. R. et al; Chemical, Physical, and Radiochemical 

Characteristicsof the Contaminant; Project 2,6a, WI!-917, Operation

CASTLE;SECRET-RD. 

6. Ballou, N. E.; Private Communication. Also: mnter, H. F. 

and Ballou, N. E.; fission Product Decay Rates; Nucleonics, 9t5, 1951. 

7. Gates, L. G, and Eisenhauer, C,j Spectral Distribution of Gppnma Rays Propagated in Airi Tech Analysis Report 502A, January, 1954. 

8. Cook, C. S. et al; Gamma Ray Spectral Measurements of Fallout 

Samples fran Operation CASTLE; USNRDL-TR-32, 1955. 

9. Mather, R. L.; USNRDL ltr 0010709, 17 June 1954; SECRET-RD, 

'lurke J. K. and Reardon D. A •• Evaluation of the AN/PDRrTlB 

Gamm~&vey M&J USNRDL Insdent E&ration Report NE Oslss5, 

October 1951. 

11. Tullis, J, L. et al; Mortality in Swine and Dose Distribution 

Studies in Phantoms Exposed to Supervoltage Roentgen Radiation; Amer. 

J. Roent. Rad. Ther. Nucl. Med., 47, 620427, 1952. 

12. Tullis, J, L. et al; Mortality in Swine Exposed to Gamma Radiation from an Atomic Bomb Source; Radial., 62, 409-15, 1954. 

13. Sondhaus, C. A.; Unpublished Data. 

4. Teresi, J. D. and Broido, A.; Discussion of the Ratio of Beta 

Surface rep Dose to Gamma Dose Associated with Fission Product Contamination; USNRDL-TM-2, 1954; CONFIDENTIAL-RI). 

15. Chambers, F. W. et al; Unpublished Data; NMRI, Operation 

UPSmT-KNOTHXE. 

16. Cronkite, E. P. et al; Study of Response of Hunan Beings Accidentally Exposed to Significant Fallout Radiation; Project 4.1, 

WT-923, Operation CASTLE, October 1954; CONFIDENTIAL. 
. DISTRIBUTION 

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2 

3 

4- 6 

7 

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15 

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19 

20 

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22 

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29 

30 

31 

32- 33 

34 

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36- 37 

3& 39 

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Militavy Distribution 

ARMY ACTIVITIES 

Asst. tip. Chief of Staff for Military Operations, D/A, 

Washington 25, D.C. ATM: Asst. tiecutfve (R&SW) 

Chief of Reeearch and Dwelopnant, D/A, Waehington 25, 

D.C. AlTN: Special WeaponaandAir Defense Divieion 

ChiefOP o~-dnan~e, D/A, waahingta 25, D.C. ATTN: 

ORDTx-AR 

Chief Signal Officer, D/A, PM) Divieion, Washington 

25, D.C. ATPN: SIGOP 

me s~g0o11 ce~~rai, D/A, washingtan 25, D.C. ATTN: 

Chief, R&D Divieion 

Chief Chemical Officer, D/A, Washington 25, D.C. 

The Quartermaster General, D/A, Washington 25, D.C. 

AlTN: Research and Dsvelopmsnt Div. 

Chief of mineere, D/A, Washington 25, D.C. ATTN: 

ENGNB 

Chief of Transportation, Military Planning and Intelligence Div., Washington 25, D.C. 

Colllnanding General,ContinentalAnqy Command, Ft. 

Monroe, Va. 

Reeldent, Be.rd'#l, Headquarters, Continental Arnly 

Conumnd, Ft. Sill, Okla. 

Fresident, Board #2, Headquartera, Continental Arnpi 

Cormand, Ft. Knox, Ky. 

Resident., Board #3, Headquartera, Continental Army 

Command,Ft.BannIng, Ga. 

President, Board #4, Headquarters, Continental Am 

Conmrmd, Ft. Bliss, Tex. 

Commanding General, First M, Governor's Island, New 

York 4, N.Y. 

ConxnandingGeneral, Second Army, Ft. George G. Meade, 

Md. 

Conmending General, l%ird w, Ft. McPherson, Ga. 

AT.'ITi: ACofS, G-3 

ConurandingGeneral, Fourth w, Ft. Sam Houston, Tex. 

Al-l"N:G-3 Section 

Conumnding General, Fifth Arvy, 1660 E. Eyde Park 

Blvd., Chicago 15, Ill. 

C-ding General, Sixth b, Freaidio of San Franciaco, Calif. A'l!TN: AMXT-4 

Co~ln,s General, U.S. Am Caribbean, Ft. Amador, 

C.Z. ATl'N: Cdl. Off. 

Camaandlng General, Uf?ARFANT &MDPR, Ft. Brooke, 

Puerto Rico 

C-ding General, Southern European Task Force, 

AI% 168, New York, N.Y. AlTN: ACoPS, G-3 

Commander-in-chief,Far -Bat Command, APO 5M), San 

Francisco, Calif. ATTN: ACoPS, J-3 

Conmrrndti General. U.S. Armv Forcea Far East (Main), 

APO 343; sari ~&ciec0, caiif. AITN: mfs, O-3 '. 

ConmmndLng General, U.S. m Alaska, APO 942, Seattle, 

Waeh. ColmoandingGeneral, U.S. Am Europe, APO 403, New 

York, N.Y. ATPN: OFOT Diu., Combat DBV. Br. 

Co-ding General, U.S. llrnor Pacific, APO 958, San 

Fnmcieco, Calif. ATTN: Cml. Off. 

Comdant, Conmrrhdand General Stiff College, Ft. 

Leavenworth, Kan. AlTN: AI&IS(AS) 

Commandant, A& War College, C&lisle Barracks, Pa. 

ATTN: Libra?: 

Commandant, The ArtiLlery and Guided Mlseile School, 

Ft. Sill, Okla. 

Secretary, The Antiaircraft Artillery and Guided 

Missile School, Ft. Bliaa, Texae. ATl'N: Paj.

George L. Alexander, Dept. of Tactice and 

Combti,adAnne 

Commanding Caneral, Am Medical Service School, 

Brooke Army Medical Center, Ft. Sam Houston, Tsx. 

Director,SpecialWeapons Cevelopment Wfice, 

Headquarters, CONARC, Ft. Bliss, Tex. ATTN: 

Capt. T. E. Skinner 

Category 

46 

47 

40 

J+9- 50 

51- 53 

54 

55 

56 

57- 58 

59 

60 

61 

62 

63 

64- 65 

: 

68- 69 

IO 

71 

72 

71 

i'( 

75- 76 

77 

78 

79- g 

a2 

83- 86 

:i 

89 

90 

5-70 

Comdant, Walmr Reed Arw Inetltute of Research, 

Walter Reed Am Medical Center, Washington 25, D.C. 

Superintendent,U.S. Military Academ, West Point, N.Y. 

ATTN: Prof. of Ordnance 

Conmmndant, Chemical Corps School, Chemical Corps 

Training Cormrand, Ft. McClellan, Ala. 

Co-ding General, Research and Fzgineering Conmmnd, 

Arrw Chemical Center, Md. ATI'N: Deputy for RW and _ . Non&xic Material 

Cormuandinabeneral. Tne &eineer Center. Ft. Belvoir. 

Va. Ati: Aast..&ax&t, &gineer School 

Commanding Officer, tigineer Research and Development 

Laboratory, Ft. Belvoir, Va. All'N: Chief, Technical 

IntelligenceBranch 

Conmending Officer, Picatinny Arsenal, tier, N.J. 

ATTN: ORDBB-TK 

Commanding Officer, Anqy Medical Research Laboratory, 

Ft. mox, &?. 

Commanding Officer, Chemical Corps Chemical and Radiological laboratory, Array Chemical Center, Md. ATTN: 

Tech. Library 

CormxxndingOfficer, Transportation R&D Station, Ft. 

Euatis, va. 

Colmnandant,The Traneportation School, Ft. Euatis, Va. 

ATTN: Security and Xnformetion Officer 

Director, Technical DOCuzente Center, Evans Sipal 

Laboratory, Belnmr, N.J. 

Director, Waterways Experiloent Station, m Box 631, 

Vicksburg, Miae. A'ITN: Library 

Director, Operations Research Office, Johns IIopkina 

Univereit!f.7100 Connecticut Ave., Chew _ Chase.Md. 

Waahingto;'l+,D.C. 

Comrmnding General, Quartermaster Research and Ceveloprmzznt, QuartermasterResearch and Development Conrmand, 

Center, Natick, Mas~l. ATPN: CBR Liaison Officer 

Conmandant, The Aw Aviation School, Ft. Rucker, Ala. 

President.,Board No. 6, CONARC, Ft. Rucker, Ala. 

NAVY ACTIVITIES 

Chief of Naval Operations, D/N, Waehington 25, D.C. 

AT!IW:OP-36 

Chief of Naval Operations, D/N, Washington 25, D.C. 

ATTN: OP-03M: 

Director of Naval Intelligence, D/N, &shin&x 25, 

D.C. ATTN: OP-922~ 

Chief, Bureau of Medicine and Surgery, D/N, Washington 

25, D.C. AlTN: Special Weapona DeP&e'Div. 

Chief, Bureau of Ordnance, D/N, Washington 25, D.C. 

Chief of Naval Personnel. D/N. Waahinaton 25. D.C. 

Chief, Bureau of Ships, b/N; ifaahingt& Z5;n.C. ATTN: 

code 348 

Chief, Bureau of Yards and Docks, D/N, Washington 25, 

D.C.ATTN: D-&O 

Chief,Ehe-eau of Supplies and Accounts, D/N, Washington 25, D.C. 

Chief, Bureau of Aeronautics, D/N, Washington 25, D.C. 

Conrmander-in-chief, U.S. Pacific Fleet, Fleet Post 

Office, San Francisco, Calif. 

Commander-In-Chief,U.S. Atlantic Fleet, U.S. Naval 

Base, Norfolk ll, Va. 

Cadant, U.S. Marine Corps, Washington 25, D.C. 

ATTN: Code A038 

&s&dent, U.S. Naval War College, Nevport, R.I. 

Superintendent,U.S. Naval Poetgraduate School, 

Monterey, Calif. 

Corrrmanding Officer, U.S. Naval Schoolo Command, U.S. 

Naval Station, Treasure Island, San Francisco, 

Calif. 

Commanding Officer, U.S. Fleet Training Center, Naval 

Base, Norfolk ll, Va. ATITi: Special Weapons School 
91 

92 

93 

94 

95 

96 

97 

98 

99 

100 

101-104 

135 

106 

107 

108 

109 

110 

1l.l 

1l.Z 

113-114 

115 

116 

117 

118 

119 

l20 

I.21 

122-123 

124 

177 

:l?h 

127 

Coxmranding Officer, U.S. Fleet Trei::ing Center, Naval 

Station, San Diego 36, Calif. ATT!?: (Sr"n'F Schoolj 

Comnand?ng Officer, U.S. N-w1 Zax%e Control Training 

Center, Naval Baas, ~iladelphia l,', Pa. A'ITN: ABC 

Defense Coxrse 

Commanding Officer, U.S. Naval Unit, Cherxical Corps 

School, Army Chemical Training Center, Ft. McClellan, 

Ala. 

Commander, U.S. Naval Ordnance Iaborator3,, Silver 

Spring 19, Md. A'ITN: R 

Counmnder, U.S. Naval Ordnance Test Station, Inyokern, 

China Lake, Calif. 

Officer-In-Charge, U.S. Naval Civil Engineer&? Res. 

and Evaluation lab., U.S. &.vol Conotrllctiorl Battalion Center, Port H,~eneme, Calif. ATT??: Code 753 

Co-ding Officer, U.S. Naval Medical Eerearch Inst., 

National Naval Medical Center, Betheoda 14, Md. 

Director, U.S. Naval Research Iaborat.ol_i, WashingtOn 

25, D.C. ATTN: Mrs. Katherine H. Cafis 

Director, Ihe Material laboratory, New York Naval Shipyard, Brooklyn, A. Y. 

Co-nding Officer and Director, 11.5. IhvS !‘leCtrOnf= 

Laboratory, Sun ~ie~o 52, Calif. ATTN: Code 4223 

Commanding Officer, U.S. iiaval Fadiolo~iCal Defense 

laboratory, San Francisco 24, Celif. ATTN: Technical 

Informetion Division 

Commending Officer and Director, mvid k'. Taylor Xcdel 

Bwin, Washi.yton ;, D.C. A'ITN: Library 

Commander, 7J.S. Naval Air Developwnt Center, Johnmsville, PP.. 

Commanding Officer, Cl&hi% SUpply Office, Code lD-13, 

3rd Avenue and 29th St., BrookLyr., N.Y. 

Comnandant, U.S. Coast Guard, 1300 E. St. N.W., Waehington 25, D.C. A!Pl'N: Capt. J. R. Stewart 

AIR FORCE ACTI'v'I:IEX 

Asst. for Atoaic tieray, iieadquartero, llSAF, Waehlnuton 25. D.C. Al"!'?r: IXX/O 

Directo;'of Dper8tionn, !3eadq;artern, !'JAF, SI'nshin@on 

Z", D.C. Al-?N: operations knalysis 

Director of Plans, Headquarters, USAF, Washington 25, 

D.C. ATEi: War Plans Div. 

Director of Research and Development, t.eadquarters, 

iI=, Washiilgton 25, D.C. ATTN: Combat Comwnento 

Div. 

Director 0:' Intelligence, Headqrlerters, 1'33, Llashington 2:>, D.C. AI"l'N: AFOIN-'32 

The Surgeon ;eneral, Headqarters, TJSAF, '&.shiryton :';, 

3.C. ATIT: Rio. kf. Br., Pre. Med. Div. 

Dsuutv Chief of Staff. Intelliaence. Headauarters. U.S. 

&r'Forces Europe, liro 633, ;;,w T&k, N:Y. A'X'N: 

Directorate of Air Targets 

CornDander,lr97th Reconnafsuance Tectlr.ical Squadron 

(Augmented), AH) t3i, New York, N.Y. 

Concumder, far East Air Forces, APti i)2', :k%nFrmcioco, Calif. 

Conmumder-in-C!lief,Strategic Air Corwxld, Off.tt Air 

Force Base, @aha, Nebraoka. ATTN: Special Weapontt 

Branch, Inspector Div., Inepector '%neral 

Conwander, %.ctical Air Camand, Lawleg AFI?, Va. 

ATTN: Documents Security Branch 

Conmumder, Air Defense Couas.nd, Znt AFP, Cola. 

Coomumder, Wright Air Developmnt Center, WriyntFatterson AFB, niyton, 0. All?J: WCP,RN, Flast 

Effects Research 

Cocnoander,Air Training Comand, Scott AF'B, Belleville, 

Ill. AWN: ES/O ';TP 

Assistant Chief of Staff, Installationa, Headquarters, 

USJZ, Washington 25, D.C. ATl’N: AFCIE-E 

Commsnder, Air Reseorc'l and Development Command, PO 

Box 1795. Baltinore. Md. AITN: RDDN _, , Conmander, Air Prcwl& Ground Corzuzand, E&in AFB, Fla. 

ATTN: Adj./Tech. Report Branch 

. . 

46 

l2&1T:, 

130-137 

135 

139 

140-141 

142-144 

14>-146 

147-149 

1;0 

151 

152 

153.154 

155 

156 

157 

156 

159 

160 

161 

162 

170-171 

172-l& 

181 

l&'-l@+ 

165-186 

187-191 

19?-194 

l9? 

196~225 

Dlrector, Air University Library, Marvel1 AFB, Ala. 

Conmurnder, Flying l'mining Air Force, Waco, lkx. 

ATTN: Director of Observer Training 

Commander, Crew Training Air Force, Randolph Field, 

Tex. ATTN: PGTS, X3/0 

Commander, Headquarters, Tschnical Training Air Force, 

Sulfport, Misc. ATTN: TA&D 

Commandant, Air Force School of Aviation Medicfne, 

Randolph AFB, Tex. 

Commander, Wright Air Development Center, WrightPatterson AFB, Dayton, 0. AlTN: WCOSI 

Commander, Air Force Cambridge Research Center, IG 

Hanscorn Field, Bedford, Mass. Al'TN: CRQST-2 

Cowuder, Air Force Special Weapona Center, Kirtland 

AFB, N. Mex. ATTN: Library 

Cormnandant,USAF Institute of Technology, WrightPatterson AFB. Cavton. 0. ATTN: Reaident CoIlem 

Cozmander, Io& Al+, D;tnver, Cola. AlTN: l&pa&&t 

of Armament Training 

Commander, 1009th Special Weapons Squadron, Headql18rt9r8, USAF, Washington 25, ~.c. 

me FAND Corporac.ion,1700 Main street, Santa Monictr, 

Calif. ATTN: Nuclear Enerm Division 

Commander. Second Air Force, Barkedale AFB, Louieiana. 

ATTN: 0;erations Analysis'OfPice 

Conmander, Eighth Air Force, Weatover AFB, Mass. ATl'N: 

OperatiOn8 haly8iE Office 

Commander, Fifteenth Air Force, March AFB, Calif. 

ATTN: Operations Analysis Office 

Comx?wder, Western Development Div., (ARE), P.O. Box 262, 

Inglewood, Calif. ATTN: WCGIT, Mr. R. G. Weitz 

OTHER DEPAR?MEp.'OF DEFENSE ACTIVITIES 

Asst. SecretarJ of Defense, Reeearch and lhvelopment, 

D/D, WashIngton 25, D.C. A'I'ITi: Tech. Library 

U.S. Documents Officer. Office of the U.S. National 

Militar,, Representative, SBAPK, AF'C 55, New York, 

. 

NY.._. Director, Weapons Systems hialuation Group, OSD, Rm 

2~1006. Pantwon. Washlnutan 25, D.C. 

Axned S&ices &pioeiv.e &fety-8-d, Dp, Building 

T-7, Gravelly Point, Wwhlngton 25, D.C. 

Comnandant, Ar!md Forces Staff College, Norfolk fl, 

Va. A'i.i?i: Secretary 

Co-ding :eneral, Field Conmxnd, Armed Force8 Special Weapone I'ro:iect, Fo Box 5100, Albuquerque, N. 

Mex. 

Connandlng ':eneral, Field Conmumd, Armed Forces, Special 

Weapons Project, PO Box 5100, Albuquerque, N. Mer. 

ATT:?: Technical Training ;roup 

Chief, Armed Forces Special Weapone Project, Washington 

?',, D.C. ATTN: Docluzenta Library Branch 

Co-nding General, Military District of Washington, 

Room 1513, Building T-'I, ;ravelly Point, Va. 

ATOMIC ENE+;Y COM1ISSION ACTIVITIES 

U.S. Atomic Ener~ Colmniseion,Claseifled Technical 

Librac;, 1901 Constitution Ave., Waehfngton 25, D.C. 

ATTN: Mrs. J. M. O'Leary (For m) 

Los Alamos Scientific Iaboratorv. Report Library, PO 

Box 1663, Las Alamos, N. Me=.-J&N: Helen Red& 

Sandia Corporation, Classified Document Division, 

Sandia 3sase, Albdqderque, N. Mex. AWN: brtin 

Lucer0 

'Jniversity of California Radiation Iaboratory, PO Box 

808, Livermore, Callf. AlTN: Margaret Edlund 

Weapon Data Section, Technical Inforrmtion Service 

Extension, Oak Rid+%, Term. 

Technical Information Service Extension, Oak Ridge, 

Term. (Sxpllls) 

t 
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