Project Trinity 1945-1946
Carl Maag and Steve Rohrer
by Carl Maag and Steve Rohrer
United States Atmospheric Nuclear Weapons Tests
Nuclear Test Personnel Review
Prepared by the Defense Nuclear Agency as Executive Agency for the
Department of Defense
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LIST OF FIGURES
LIST OF ABBREVIATIONS AND ACRONYMS
REPORT DOCUMENTATION PAGE
1.1 Historical Background of Project TRINITY
1.2 The Project TRINITY Site
1.3 The Project TRINITY Organization
1.4 Military and Civilian Participants in Project TRINITY
2 THE ACTIVITIES AT PROJECT TRINITY
2.1 Preshot Activities
2.2 Detonation and Postshot Activities
2.3 Activities after 16 July 1945
3 RADIATION PROTECTION AT PROJECT TRINITY
3.2 Site Monitoring Group
3.3 Offsite Monitoring Group
4 DOSIMETRY ANALYSIS OF PARTICIPANTS IN PROJECT TRINITY
4.1 Film Badge Records
4.2 Gamma Radiation Exposure
LIST OF FIGURES
1-1 Location of Alamogordo Bombing Range
1-2 TRINITY Site and Major Installations
1-3 Tent Used as Guard Post at Project TRINITY
1-4 Truck Used as Guard Post at Project TRINITY
1-5 Organization of Project TRINITY
2-1 The TRINITY Shot-tower
2-2 The TRINITY Detonation, 0530 Hours, 16 July 1945
2-3 The South Shelter (Control Point)
2-4 Inside One of the Shelters
2-5 The Base Camp, Headquarters for Project TRINITY
2-5 The Base Camp, Headquarters for Project TRINITY
2-6 Project TRINITY Personnel Wearing Protective Clothing
2-7 "JUMBO" after the TRINITY Detonation
LIST OF ABBREVIATIONS AND ACRONYMS
The following abbreviations and acronyms are used in this volume:
AEC Atomic Energy Commission
DOD Department of Defense
LASL Los Alamos Scientific Laboratory
MAUD [Committee for the] Military Application of Uranium Detonation
MED Manhattan Engineer District
R/h roentgens per hour
UTM Universal Transverse Mercator
REPORT DOCUMENTATION PAGE
SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered):
1. REPORT NUMBER: DNA 6028F
2. GOVT ACCESSION NO.:
3. RECIPIENT'S CATALOG NUMBER:
4. TITLE (and Subtitle): PROJECT TRINITY 1945-1946
5. TYPE OF REPORT & PERIOD COVERED: Final Report
6. PERFORMING ORG. REPORT NUMBER: JRB 2-816-03-423-00
7. AUTHOR(S): Carl Maag, Steve Rorer
8. CONTRACT OR GRANT NUMBER(S): DNA 001-79-C-0473
9. PERFORMING ORGANIZATION NAME AND ADDRESS:
8400 Westpark Drive
McLean, Virginia 22102
10. PROGRAM ELEMENT. PROJECT, TASK AREA & WORK UNIT NUMBERS:
11. CONTROLLING OFFICE NAME AND ADDRESS:
Defense Nuclear Agency
Washington, D.C. 20305
12. REPORT DATE: 15 December 1982
13. NUMBER OF PAGES: 76
14. MONITORING AGENCY NAME & ADDRESS(if different from Controlling
15. SECURITY CLASS. (of this report): UNCLASSIFIED
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16. DISTRIBUTION STATEMENT (of this Report): Approved for public
release; distribution unlimited.
17. DISTRIBUTION STATEMENT (of the abstract entered In Block 20, If
different from Report):
18. SUPPLEMENTARY NOTES: This work was sponsored by the Defense
Nuclear Agency under RDT&E RMSS Code B350079464 U99QAXMK50608 H2590D.
For sale by National Technical Information Service, Springfield, VA
The Defense Nuclear Agency Action Officer, Lt. Col. H. L. Reese,
USAF, under whom this work was done, wishes to acknowledge the
research and editing contribution of numerous reviewers in the
military services and other organizations in addition to those writers
listed in block 7.
19. KEY WORDS (Continue on reverse side if necessary and Identify by
Los Alamos Scientific Laboratory
Alamogordo Bombing Range
Manhattan Engineer District
Nuclear Weapons Testing
20. ABSTRACT: This report describes the activities of an estimated
1,000 personnel, both military and civilian, in Project TRINITY, which
culminated in detonation of the first nuclear device, in New Mexico in
1945. Scientific and diagnostic experiments to evaluate the effects
of the nuclear device were the primary activities engaging military
Defense Nuclear Agency
Public Affairs Office
Washington, D C. 20305
Subject: Project TRINITY
Project TRINITY, conducted by the Manhattan Engineer District (MED),
was designed to test and assess the effects of a nuclear weapon. The
TRINITY nuclear device was detonated on a 100-foot tower on the
Alamogordo Bombing Range in south-central New Mexico at 0530 hours on
16 July 1945. The nuclear yield of the detonation was equivalent to
the energy released by detonating 19 kilotons of TNT. At shot-time,
the temperature was 21.8 degrees Celsius, and surface air pressure was
850 millibars. The winds were nearly calm at the surface; at 10,300
feet above mean sea level, they were from the southwest at 10 knots.
The winds blew the cloud resulting from the detonation to the
northeast. From 16 July 1945 through 1946, about 1,000 military and
civilian personnel took part in Project TRINITY or visited the test
site. The location of the test site and its major installations are
shown in the accompanying figures.
Military and Scientific Activities
All participants in Project TRINITY, both military and civilian, were
under the authority of the MED. No military exercises were conducted.
The Los Alamos Scientific Laboratory (LASL), which was staffed and
administered by the University of California (under contract to the
MED), conducted diagnostic experiments. Civilian and military
scientists and technicians, with assistance from other military
personnel, placed gauges, detectors, and other instruments around
ground zero before the detonation. Four offsite monitoring posts were
established in the towns of Nogal, Roswell, Socorro, and Fort Sumner,
New Mexico. An evacuation detachment consisting of 144 to 160
enlisted men and officers was established in case protective measures
or evacuation of civilians living offsite became necessary. At least
94 of these personnel were from the Provisional Detachment Number 1,
Company "B," of the 9812th Technical Service Unit, Army Corps of
Engineers. Military police cleared the test area and recorded the
locations of all personnel before the detonation.
A radiological monitor was assigned to each of the three shelters,
which were located to the north, west, and south of ground zero. Soon
after the detonation, the monitors surveyed the area immediately
around the shelters and then proceeded out the access road to its
intersection with the main road, Broadway. Personnel not essential to
postshot activities were transferred from the west and south shelters
to the Base Camp, about 16 kilometers southwest of ground zero.
Personnel at the north shelter were evacuated when a sudden rise in
radiation levels was detected; it was later learned that the
instrument had not been accurately calibrated and levels had not
increased as much as the instrument indicated. Specially designated
groups conducted onsite and offsite radiological surveys.
Safety Standards and Procedures
The safety criteria established for Project TRINITY were based on
calculations of the anticipated dangers from blast pressure, thermal
radiation, and ionizing radiation. The TR-7 Group, also known as the
Medical Group, was responsible for radiological safety. A limit of 5
roentgens of exposure during a two-month period was established.
The Site and Offsite Monitoring Groups were both part of the Medical
Group. The Site Monitoring Group was responsible for equipping
personnel with protective clothing and instruments to measure
radiation exposure, monitoring and recording personnel exposure
according to film badge readings and time spent in the test area, and
providing for personnel decontamination. The Offsite Monitoring Group
surveyed areas surrounding the test site for radioactive fallout. In
addition to these two monitoring groups, a small group of medical
technicians provided radiation detection instruments and monitoring.
Radiation Exposures at Project TRINITY
Dosimetry information is available for about 815 individuals who
either participated in Project TRINITY activities or visited the test
site between 16 July 1945 and 1 January 1947. The listing does not
indicate the precise military or unit affiliation of all personnel.
Less than six percent of the Project TRINITY participants received
exposures greater than 2 roentgens. Twenty-three of these
individuals received exposures greater than 2 but less than 4
roentgens; another 22 individuals received between 4 and 15 roentgens.
From 1945 to 1962, the U.S. Government, through the Manhattan Engineer
District (MED) and its successor agency, the Atomic Energy Commission
(AEC), conducted 235 tests of nuclear devices at sites in the United
States and in the Atlantic and Pacific Oceans. In all, an estimated
220,000 Department of Defense (DOD)* participants, both military and
civilian, were present at the tests. Project TRINITY, the war-time
effort to test-fire a nuclear explosive device, was the first
atmospheric nuclear weapons test.
* The MED, which was part of the Army Corps of Engineers, administered
the U.S. nuclear testing program until the AEC came into existence in
1946. Before DOD was established in 1947, the Army Corps of Engineers
was under the War Department.
In 1977, 15 years after the last above-ground nuclear weapons test,
the Centers for Disease Control** noted a possible leukemia cluster
among a small group of soldiers present at Shot SMOKY, a test of
Operation PLUMBBOB, the series of atmospheric nuclear weapons tests
conducted in 1957. Since that initial report by the Centers for
Disease Control, the Veterans Administration has received a number of
claims for medical benefits from former military personnel who believe
their health may have been affected by their participation in the
weapons testing program.
** The Centers for Disease Control are part of the U.S. Department of
Health and Human Services (formerly the U.S. Department of Health,
Education, and Welfare).
In late 1977, DOD began a study to provide data to both the Centers
for Disease Control and the Veterans Administration on potential
exposures to ionizing radiation among the military and civilian
participants in atmospheric nuclear weapons testing. DOD organized an
o Identify DOD personnel who had taken part in the atmospheric nuclear
o Determine the extent of the participants' exposure to ionizing
o Provide public disclosure of information concerning participation by
military personnel in Project TRINITY.
METHODS AND SOURCES USED TO PREPARE THIS VOLUME
This report on Project TRINITY is based on historical and technical
documents associated with the detonation of the first nuclear device
on 16 July 1945. The Department of Defense compiled information for
this volume from documents that record the scientific activities
during Project TRINITY. These records, most of which were developed
by participants in TRINITY, are kept in several document repositories
throughout the United States.
In compiling information for this report, historians, health
physicists, radiation specialists, and information analysts canvassed
document repositories known to contain materials on atmospheric
nuclear weapons tests conducted in the southwestern United States.
These repositories included armed services libraries, Government
agency archives and libraries, Federal repositories, and libraries of
scientific and technical laboratories. Researchers examined
classified and unclassified documents containing information on the
participation of personnel from the MED, which supervised Project
TRINITY, and from the Los Alamos Scientific Laboratory (LASL), which
developed the TRINITY device. After this initial effort, researchers
recorded relevant information concerning the activities of MED and
LASL personnel and catalogued the data sources. Many of the documents
pertaining specifically to MED and LASL participation were found in
the Defense Nuclear Agency Technical Library and the LASL Records
Information on the fallout pattern, meteorological conditions, and
nuclear cloud dimensions is taken from Volume 1 of the General
Electric Company-TEMPO's "Compilation of Local Fallout Data from Test
Detonations 1945-1962, Extracted from DASA 1251," unless more specific
information is available elsewhere.
ORGANIZATION OF THIS VOLUME
The following chapters detail MED and LASL participation in Project
TRINITY. Chapter 1 provides background information, including a
description of the TRINITY test site. Chapter 2 describes the
activities of MED and LASL participants before, during, and after the
detonation. Chapter 3 discusses the radiological safety criteria and
procedures in effect for Project TRINITY, and chapter 4 presents the
results of the radiation monitoring program, including information on
film badge readings for participants in the project.
The information in this report is supplemented by the Reference
Manual: Background Materials for the CONUS Volumes." The manual
summarizes information on radiation physics, radiation health
concepts, exposure criteria, and measurement techniques. It also
lists acronyms and includes a glossary of terms used in the DOD
reports addressing test events in the continental United States.
Project TRINITY was the name given to the war-time effort to produce
the first nuclear detonation. A plutonium-fueled implosion device was
detonated on 16 July 1945 at the Alamogordo Bombing Range in
south-central New Mexico.
Three weeks later, on 6 August, the first uranium-fueled nuclear bomb,
a gun-type weapon code-named LITTLE BOY, was detonated over the
Japanese city of Hiroshima. On 9 August, the FAT MAN nuclear bomb, a
plutonium-fueled implosion weapon identical to the TRINITY device, was
detonated over another Japanese city, Nagasaki. Two days later, the
Japanese Government informed the United States of its decision to end
the war. On 2 September 1945, the Japanese Empire officially
surrendered to the Allied Governments, bringing World War II to an
In the years devoted to the development and construction of a nuclear
weapon, scientists and technicians expanded their knowledge of nuclear
fission and developed both the gun-type and the implosion mechanisms
to release the energy of a nuclear chain reaction. Their knowledge,
however, was only theoretical. They could be certain neither of the
extent and effects of such a nuclear chain reaction, nor of the
hazards of the resulting blast and radiation. Protective measures
could be based only on estimates and calculations. Furthermore,
scientists were reasonably confident that the gun-type uranium-fueled
device could be successfully detonated, but they did not know if the
more complex firing technology required in an implosion device would
work. Successful detonation of the TRINITY device showed that
implosion would work, that a nuclear chain reaction would result in a
powerful detonation, and that effective means exist to guard against
the blast and radiation produced.
1.1 HISTORICAL BACKGROUND OF PROJECT TRINITY
The development of a nuclear weapon was a low priority for the United
States before the outbreak of World War II. However, scientists
exiled from Germany had expressed concern that the Germans were
developing a nuclear weapon. Confirming these fears, in 1939 the
Germans stopped all sales of uranium ore from the mines of occupied
Czechoslovakia. In a letter sponsored by group of concerned
scientists, Albert Einstein informed President Roosevelt that German
experiments had shown that an induced nuclear chain reaction was
possible and could be used to construct extremely powerful bombs (7;
* All sources cited in the text are listed alphabetically in the
reference list at the end of this volume. The number given in the
text corresponds to the number of the source document in the reference
In response to the potential threat of a German nuclear weapon, the
United States sought a source of uranium to use in determining the
feasibility of a nuclear chain reaction. After Germany occupied
Belgium in May 1940, the Belgians turned over uranium ore from their
holdings in the Belgian Congo to the United States. Then, in March
1941, the element plutonium was isolated, and the plutonium-239
isotope was found to fission as readily as the scarce uranium isotope,
uranium-235. The plutonium, produced in a uranium-fueled nuclear
reactor, provided the United States with an additional source of
material for nuclear weapons (7; 12).
In the summer of 1941, the British Government published a report
written by the Committee for Military Application of Uranium
Detonation (MAUD). This report stated that a nuclear weapon was
possible and concluded that its construction should begin immediately.
The MAUD report, and to a lesser degree the discovery of plutonium,
encouraged American leaders to think more seriously about developing a
nuclear weapon. On 6 December 1941, President Roosevelt appointed the
S-1 Committee to determine if the United States could construct a
nuclear weapon. Six months later, the S-1 Committee gave the
President its report, recommending a fast-paced program that would
cost up to $100 million and that might produce the weapon by July 1944
The President accepted the S-1 Committee's recommendations. The
effort to construct the weapon was turned over to the War Department,
which assigned the task to the Army Corps of Engineers. In September
1942, the Corps of Engineers established the Manhattan Engineer
District to oversee the development of a nuclear weapon. This effort
was code-named the "Manhattan Project" (12).
Within the next two years, the MED built laboratories and production
plants throughout the United States. The three principal centers of
the Manhattan Project were the Hanford, Washington, Plutonium
Production Plant; the Oak Ridge, Tennessee, U-235 Production Plant;
and the Los Alamos Scientific Laboratory in northern New Mexico. At
LASL, Manhattan Project scientists and technicians, directed by Dr. J.
Robert Oppenheimer,* investigated the theoretical problems that had to
be solved before a nuclear weapon could be developed (12).
* This report identifies by name only those LASL and MED personnel who
are well-known historical figures.
During the first two years of the Manhattan Project, work proceeded at
a slow but steady pace. Significant technical problems had to be
solved, and difficulties in the production of plutonium, particularly
the inability to process large amounts, often frustrated the
scientists. Nonetheless, by 1944 sufficient progress had been made to
persuade the scientists that their efforts might succeed. A test of
the plutonium implosion device was necessary to determine if it would
work and what its effects would be. In addition, the scientists were
concerned about the possible effects if the conventional explosives in
a nuclear device, particularly the more complex implosion-type device,
failed to trigger the nuclear reaction when detonated over enemy
territory. Not only would the psychological impact of the weapon be
lost, but the enemy might recover large amounts of fissionable
In March 1944, planning began to test-fire a plutonium-fueled
implosion device. At LASL, an organization designated the X-2 Group
was formed within the Explosives Division. Its duties were "to make
preparations for a field test in which blast, earth shock, neutron and
gamma radiation would be studied and complete photographic records
made of the explosion and any atmospheric phenomena connected with the
explosion" (13). Dr. Oppenheimer chose the name TRINITY for the
project in September 1944 (12).
1.2 THE PROJECT TRINITY SITE
The TRINITY site was chosen by Manhattan Project scientists after
thorough study of eight different sites. The site selected was an
area measuring 29 by 39 kilometers* in the northwest corner of the
Alamogordo Bombing Range. The Alamogordo Bombing Range was located in
a desert in south-central New Mexico called the Jornada del Muerto
("Journey of Death"). Figure 1-1 shows the location of the bombing
range. The site was chosen for its remote location and good weather
and because it was already owned by the Government. MED obtained
permission to use the site from the Commanding General of the Second
Air Force (Army Air Forces) on 7 September 1944 (12). Figure 1-2
shows the TRINITY site with its major installations.
* Throughout this report, surface distances are given in metric units.
The metric conversion factors include: 1 meter = 3.28 feet; 1 meter =
1.09 yards; and 1 kilometer = 0.62 miles. Vertical distances are
given in feet; altitudes are measured from mean sea level, while
heights are measured from surface level, unless otherwise noted.
Ground zero for the TRINITY detonation was at UTM coordinates
630266.** Three shelters, located approximately 9,150 meters (10,000
yards) north, west, and south of ground zero, were built for the
protection of test personnel and instruments. The shelters had walls
of reinforced concrete and were buried under a few feet of earth. The
south shelter was the Control Point for the test (12). The Base Camp,
which was the headquarters for Project TRINITY, was located
approximately 16 kilometers southwest of ground zero. The principal
buildings of the abandoned McDonald Ranch, where the active parts of
the TRINITY device were assembled, stood 3,660 meters southeast of
ground zero. Seven guard posts, which were simply small tents or
parked trucks like the ones shown in figures 1-3 and 1-4, dotted the
test site (9).
** Universal Transverse Mercator (UTM) coordinates are used in this
report. The first three digits refer to a point on an east- west
axis, and the second three digits refer to a point on a north-south
axis. The point so designated is the southwest corner of an area 100
1.3 THE PROJECT TRINITY ORGANIZATION
The organization that planned and conducted Project TRINITY grew out
of the X-2 Group. LASL, though administered by the University of
California, was part of the Manhattan Project, supervised by the Army
Corps of Engineers Manhattan Engineer District. The chief of MED was
Maj. Gen. Leslie Groves of the Army Corps of Engineers. Major General
Groves reported to both the Chief of Engineers and the Army Chief of
Staff. The Army Chief of Staff reported to the Secretary of War, a
Cabinet officer directly responsible to the President. Figure 1-5
outlines the organization of Project TRINITY.
The director of the Project TRINITY organization was Dr. Kenneth
Bainbridge. Dr. Bainbridge reported to Dr. J. Robert Oppenheimer, the
director of LASL. A team of nine research consultants advised Dr.
Bainbridge on scientific and technical matters (3).
The Project TRINITY organization was divided into the following
o The TRINITY Assembly Group, responsible for assembling and arming
the nuclear device
o The TR-1 (Services) Group, responsible for construction, utilities,
procurement, transportation, and communications
o The TR-2 Group, responsible for air-blast and earth-shock measurements
o The TR-3 (Physics) Group, responsible for experiments concerning
measurements of ionizing radiation
o The TR-4 Group, responsible for meteorology
o The TR-5 Group, responsible for spectrographic and photographic
o The TR-6 Group, responsible for the airblast-airborne condenser
o The TR-7 (Medical) Group, responsible for the radiological safety
and general health of the Project TRINITY participants.
Each of these groups was divided into several units. Individuals were
also assigned special tasks outside their groups, such as
communications and tracking the TRINITY cloud with a searchlight (3).
1.4 MILITARY AND CIVILIAN PARTICIPANTS IN PROJECT TRINITY
From March 1944 until the beginning of 1946, several thousand people
participated in Project TRINITY. These included not only the LASL
scientists, but also scientists, technicians, and workmen employed at
MED installations throughout the United States. According to entrance
logs, film badge data, and other records, about 1,000 people either
worked at or visited the TRINITY site from 16 July 1945 through 1946
(1; 3; 8; 15; 16).
Although supervised by Major General Groves and the Army Corps of
Engineers, many Manhattan Project personnel were civilians. Military
personnel were assigned principally to support services, such as
security and logistics, although soldiers with special skills worked
with the civilians (7; 12). Most of the military personnel were part
of the Army Corps of Engineers, although Navy and other Army personnel
were also assigned to the project (4; 12).
THE ACTIVITIES AT PROJECT TRINITY
The TRINITY nuclear device was detonated on a 100-foot tower (shown in
figure 2-1) at UTM coordinates 630266 on the Alamogordo Bombing Range,
New Mexico, at 0530 Mountain War Time, on 16 July 1945. The
detonation had a yield of 19 kilotons and left an impression 2.9
meters deep and 335 meters wide. The cloud resulting from the
detonation rose to an altitude of 35,000 feet (5). The TRINITY
detonation is shown in figure 2-2.
At shot-time, the temperature was 21.8 degrees Celsius, and the
surface air pressure was 850 millibars. Winds at shot-time were
nearly calm at the surface but attained a speed of 10 knots from the
southwest at 10,300 feet. At 34,600 feet, the wind speed was 23 knots
from the southwest. The winds blew the cloud to the northeast (5).
2.1 PRESHOT ACTIVITIES
Construction of test site facilities on the Alamogordo Bombing Range
began in December 1944. The first contingent of personnel, 12
military policemen, arrived just before Christmas. The number of
personnel at the test site gradually increased until the peak level of
about 325 was reached the week before the detonation (2; 12).
On 7 May 1945 at 0437 hours, 200 LASL scientists and technicians
exploded 100 tons of conventional high explosives at the test site.
The explosives were stacked on top of a 20-foot tower and contained
tubes of radioactive solution to simulate, at a low level of activity,
the radioactive products expected from a nuclear explosion. The test
produced a bright sphere which spread out in an oval form. A column
of smoke and debris rose as high as 15,000 feet before drifting
eastward. The explosion left a shallow crater 1.5 meters deep and 9
meters wide. Monitoring in the area revealed a level of radioactivity
low enough to allow workers to spend several hours in the area (3;
The planned firing date for the TRINITY device was 4 July 1945. On 14
June 1945, Dr. Oppenheimer changed the test date to no earlier than 13
July and no later than 23 July. On 30 June, the earliest firing date
was moved to 16 July, even though better weather was forecast for 18
and 19 July. Because the Allied conference in Potsdam, Germany, was
about to begin and the President needed the results of the test as
soon as possible, the TRINITY test organization adjusted its schedules
accordingly and set shot-time at 0400 hours on 16 July (3; 12; 14).
The final preparations for the detonation started at 2200 on 15 July.
To prevent unnecessary danger, all personnel not essential to the
firing activities were ordered to leave the test site. During the
night of 15 July, these people left for viewing positions on Compania
Hill,* 32 kilometers northwest of ground zero. They were joined by
several spectators from LASL (3; 12).
* "Compania" also appears as "Compana," "Campagne," or "Compagna" in
Project personnel not required to check instruments within the ground
zero area stationed themselves in the three shelters or at other
assigned locations. The military police at Guard Posts 1, 2, and 4
blocked off all roads leading into the test site, and the men at Guard
Post 8, the only access to the ground zero area from the Base Camp,
ensured that no unauthorized individuals entered the area (9; 12).
At 0100 hours on 16 July, military policemen from Guard Posts 3, 5, 6,
and 7 met to compare their logs of personnel authorized to be in the
ground zero area. The guards then traveled along the access roads to
clear out all project personnel. As individuals left for their
assigned shelters or stations, their departures from the test area
were recorded in the military police logs. By 0200 the area sweep was
completed, and the military police went to their shelters and
stations. A final check of personnel was made in each shelter (3; 9;
At the time of detonation, 99 project personnel were in the three
shelters: 29 in the north shelter, 37 in the west shelter, and 33 in
the south shelter. Dr. Oppenheimer, Dr. Bainbridge, and other key
personnel awaited the firing at the south shelter, which served as the
Control Point. Figure 2-3 shows the exterior of the south shelter;
figure 2-4 gives an interior view of one of the shelters, most likely
the south. Although most of the shelter occupants were civilians, at
least 23 military participants were spread among the three shelters
The remainder of the test site personnel were positioned at the Base
Camp 16 kilometers south-southwest of ground zero, or on Compania
Hill, or at the guard posts. Important Government officials, such as
General Groves and Dr. Vannevar Bush, Director of the U.S. Office of
Scientific Research and Development, viewed the detonation from a
trench at the Base Camp. The Base Camp is depicted in figure 2-5.
The military police of Guard Posts 1 and 2 were instructed to be in
foxholes approximately five kilometers west and north, respectively,
from their posts. The military police of Guard Posts 3 and 4 were
instructed to be in foxholes south of Mockingbird Gap. A radiological
safety monitor was assigned to the group from Guard Post 4. Guard Post
5 personnel were to be in the south shelter, Guard Post 6 personnel in
the west shelter, and Guard Post 7 personnel in the north shelter.
The military police of Guard Post 8 remained at that post, 400 meters
east of the Base Camp (9).
An evacuation detachment of between 144 and 160 officers and enlisted
men was stationed near Guard Post 2, about 14 kilometers northwest of
ground zero. These men were on standby in case ranches and towns
beyond the test site had to be evacuated. Five radiological safety
monitors were assigned to this detachment. Ninety-four men of the
evacuation detachment belonged to Provisional Detachment Number 1,
Company "B," of the 9812th Technical Service Unit, Army Corps of
Engineers, from LASL. The identity of the remaining evacuation
personnel has not been documented (3; 4; 8; 10; 15).
With the exception of the shelter occupants (99 personnel) and
evacuation detachment (between 144 and 160 men), the number of
personnel at the test site at the time of detonation has not been
documented. Film badge records show that approximately 355 people
were at the test site at some time during 16 July. The shelter
occupants and 44 men of the evacuation detachment are on this list.
It has not been possible to pinpoint the location of many of the
remaining personnel. Some were at the Base Camp or on Compania Hill.
Since many of these people returned to the test site after shot-time
to work on experiments, their film badges registered exposures from
residual radioactivity on 16 July. Based on the documented personnel
totals, at least the following 263 individuals were at the test site
when the device was detonated (1; 4; 8-10; 13; 15):
o 99 shelter occupants at shelters 9,150 meters north, south, and west
of ground zero
o 144 to 160 officers and enlisted men of the evacuation detachment,
located 14 kilometers northwest of ground zero near Guard Post 2
o Five radiological safety monitors assigned to the evacuation
detachment to perform offsite monitoring of nearby towns and
o One radiological safety monitor assigned to Guard Post 4
o Two military policemen at each of the seven guard posts (indicated
by photographs such as figures 1-3 and 1-4).
2.2 DETONATION AND POSTSHOT ACTIVITIES
Because of bad weather, the Project TRINITY director (Dr. Bainbridge)
delayed the detonation, which had been scheduled for 0400 hours. By
0445, however, the forecast was better, and shot-time was set for
0530. This gave the scientists 45 minutes to arm the device and
prepare the instruments in the shelters. The final countdown began at
0510, and the device was detonated at 0529:45 Mountain War Time from
the Control Point in the south shelter (3; 12).
No one was closer than 9,150 meters to ground zero at the time of the
detonation. With the exception of a few men holding the ropes of
barrage balloons or guiding cameras to follow the fireball as it
ascended, all shelter personnel were in or behind the shelters. Some
left the shelters after the initial flash to view the fireball. As a
precautionary measure, they had been advised to lie on the ground
before the blast wave arrived. Project personnel located beyond the
shelters, such as at the Base Camp and on Compania Hill, were also
instructed to lie on the ground or in a depression until the blast
wave had passed (1). However, the blast wave at these locations was
not as strong as had been expected.
In order to prevent eye damage, Dr. Bainbridge ordered the
distribution of welder's filter glass. Because it was not known
exactly how the flash might affect eyesight, it was suggested that
direct viewing of the fireball not be attempted even with this
protection. The recommended procedure was to face away from ground
zero and watch the hills or sky until the fireball illuminated the
area. Then, after the initial flash had passed, one could turn around
and view the fireball through the filter glass. Despite these
well-publicized instructions, two participants did not take
precautions. They were temporarily blinded by the intense flash but
experienced no permanent vision impairment (1; 17).
People as far away as Santa Fe and El Paso saw the brilliant light of
the detonation. Windows rattled in the areas immediately surrounding
the test site, waking sleeping ranchers and townspeople. To dispel
any rumors that might compromise the security of Project TRINITY, the
Government announced that an Army munitions dump had exploded.
However, immediately after the destruction of Hiroshima, the
Government revealed to the public what had actually occurred in the
New Mexico desert (12; 13).
Immediately after the shot, Medical Group personnel began the
radiological monitoring activities described in section 3.1.2. At
0815, when most of the monitoring activities were completed,
preparations began for entrance into the ground zero area. To
regulate entry into the area, a "Going-in Board" was established,
consisting of Dr. Bainbridge, the Chief of the Medical Group, and a
special scientific consultant. Its purpose was to determine whether a
party had a valid reason for entering the ground zero area. The board
functioned for three days.
Military police at Guard Post 4 and at three roadblocks set up along
Broadway controlled entry into the area. Guard Posts 3, 5, 6, and 7
were within 3,000 meters of ground zero and thus remained unmanned.
At the south shelter, the Medical Group set up a "going-in" station
where personnel were required to stop to put on protective clothing
(coveralls, booties, caps, and cotton gloves) and pick up monitoring
equipment before entering the ground zero area. Since it was not
known how much radioactive material might be suspended in the air, all
personnel entering the ground zero area wore complete protective
covering and respirators for the first three days after the
detonation. Figure 2-6 shows two Project TRINITY personnel wearing
protective clothing (1).
On the day of the shot, five parties entered the ground zero area.
One party consisted of eight members of the earth-sampling group.
They obtained samples by driving to within 460 meters of ground zero
in a tank specially fitted with rockets to which retrievable
collectors were fastened in order to gather soil samples from a
distance. This group made several sampling excursions on 16 and 17
July. The tank carried two personnel (a driver and a passenger) each
trip. No member of this party received a radiation exposure of more
than 1 roentgen (1).
Five other men from the earth-sampling group entered the ground zero
area in a second tank, lined with lead for radiation protection. The
tank, carrying the driver and one passenger, made five trips into the
ground zero area to retrieve soil samples on 16 and 17 July. On two
trips, the tank passed over ground zero; on the others, it approached
to within about 90 meters of ground zero. The men scooped up soil
samples through a trap door in the bottom of the tank. One driver who
made three trips into the ground zero area received the highest
exposure, 15 roentgens (1).
This lead-lined tank was also used by ten men to observe the radiation
area. These men, traveling two at a time, made five trips into the
area on shot-day but never approached closer than 1,370 meters to
ground zero. The highest exposure among these ten men was 0.3
The next party to approach ground zero consisted of a photographer and
a radiological safety monitor. Wearing protective clothing and
respirators, the two men were about 730 meters northwest of ground
zero photographing "JUMBO" from 1100 to 1200 hours. "JUMBO," shown in
figure 2-7, was a massive container built to contain the
high-explosive detonation of the TRINITY device and to allow recovery
of the fissionable material if the device failed to produce a nuclear
detonation. The plan to use "JUMBO," however, was abandoned when the
scientists concluded that a fairly large nuclear explosion was
certain. The container remained on the ground near the shot-tower
during the detonation. Both the photographer and the monitor received
an estimated radiation exposure between 0.5 and 1 roentgen (1; 7).
The last party to "go in" on shot-day consisted of six men retrieving
neutron detectors. They entered the test area at 1430 hours. Three
of the men went to a point 730 meters south of ground zero to pull out
cables carrying neutron detectors located 550 meters south of ground
zero. The group wore protective clothing and respirators and spent
about 30 minutes in the area. The remaining three men drove as close
as 320 meters southwest of ground zero to retrieve neutron detectors.
They got out of their vehicle only once, at about 460 meters from
ground zero, and spent a total of about ten minutes making this trip
through the area. Each man's radiation exposure measured less than 1
Most of the soldiers of the evacuation detachment remained in their
bivouac area near Guard Post 2. According to a report written by the
detachment commander, a reinforced platoon was sent to the town of
Bingham, about 29 kilometers northeast of the test site, while offsite
radiological safety monitors surveyed the area. The evacuation
detachment was dismissed at 1300 hours on shot-day when it became
evident from offsite monitoring that evacuations would not be
undertaken. The detachment returned to LASL at 0400 on 17 July (15).
Two B-29 aircraft from Kirtland Field, Albuquerque, New Mexico,
participated in post-shot events. Their planned mission was to pass
over the test area shortly before the explosion to simulate a bomb
drop. After the TRINITY device had been detonated, the aircraft would
circle near ground zero, while the men onboard would measure the
atmospheric effects of the nuclear explosion. This would enable them
to determine whether a delivery aircraft would be endangered.
However, because of bad weather on shot-day, Dr. Oppenheimer canceled
the aircraft's flight in the ground zero area. Instead, the two
B-29s, each with 12 men onboard, flew along the perimeter of the
bombing range and observed the shot from a distance of 19 to 29
kilometers. Among those observers was a Navy captain who was also the
MED Chief of Ordnance (6; 12; 13).
2.3 ACTIVITIES AFTER 16 JULY 1945
On 17, 18, and 19 July, all personnel and visitors had to receive
permission to approach ground zero from the "Going-in Board." On
these three days, 21 groups were authorized to go beyond the Broadway
roadblocks. Most of those who sought this authorization were
scientists and military support personnel whose job required that they
work near ground zero. Except for a group of two military men and
three civilians who went to ground zero on 16 and 17 July and a group
of two civilians who approached as close as 90 meters on 18 July, the
reentry personnel came no closer than 180 meters to ground zero. Of
these personnel, the individual who received the highest exposure
during the three days was an Army sergeant who received 15 roentgens.
During the same period, two civilians received 10 roentgens and 7.5
roentgens, respectively. All other personnel received exposures of 5
roentgens or less (1; 3).
After the "Going-In Board" was disbanded on 19 July, permission to
enter the ground zero area had to be obtained from Dr. Bainbridge or
one of his deputies. Many scientists entered the ground zero area
after 19 July to retrieve instruments or to perform experiments. The
population of the TRINITY test site was diminishing, however, as the
emphasis shifted to preparing the devices that were to be dropped on
On 23 July, a week after the shot, chain barricades with prominent
signs warning against trespassing were placed 910 meters north, south,
and west of ground zero. These barricades were supplemented with two
concentric circles of red flags 1,830 and 2,740 meters from ground
zero. Except during bad weather, the entire ground zero area was
visible from the roadblocks. No unauthorized person was ever detected
entering the ground zero area (1).
On 10 August, the Broadway roadblocks were removed, and mounted
military policemen began patrolling around ground zero at a distance
of 730 meters. Each guard was assigned to a daily six-hour shift for
a period of two weeks; in the third week, the guard was assigned tasks
away from the ground zero area. The mounted guards and their horses
wore film badges. No exposure greater than 0.1 roentgen was
registered. On 1 September, the mounted patrol moved to a distance of
460 meters from ground zero, just outside a fence installed a week
earlier to seal off the area. The same rotating patrol schedule was
used. The guards' film badge readings showed an average daily
exposure of 0.02 roentgens. The mounted patrol at the fence continued
until early 1947 (1).
Between 20 July 1945 and 21 November 1945, 67 groups entered the
ground zero area. Most of these parties entered in the month after
shot-day. These were the scientists and technicians conducting
experiments or retrieving data. By the beginning of September, most
of those who entered the ground zero area were invited guests (1).
Also during the period 20 July through 21 November, at least 71
soldiers were at the TRINITY test site. Twenty-five of these men were
support personnel who never went within 460 meters of ground zero.
The remaining 46 men were technical personnel, laborers who erected
the 460-meter fence, or military policemen who served as guides.
Eleven of these men, probably members of the fence detail, spent
several days at about 460 meters from ground zero. Working three to
five hours per day between 9 August and 25 August, they would have
been the only group to stay longer than one hour in the ground zero
area. Of the remaining personnel who approached within 460 meters
from ground zero, 25 spent 15 minutes and ten spent between 30 minutes
and one hour in the ground zero area. Only 11 people received
exposures of 3 to 5 roentgens between 20 July and 21 November. Most
received less than 1 roentgen. After 21 November 1945, no one
approached closer than the fence which was 460 meters from ground
zero, although about 200 civilian and military personnel worked at or
visited the TRINITY site through 1946 (1; 16).
According to dosimetry data, entrance logs, and other records, about
1,000 individuals were at the test site at some time between 16 July
1945 and the end of 1946. This number includes not only the
scientists, technicians, and military personnel who were part of
Project TRINITY but also many visitors. Some of the scientists took
their wives and children on a tour of the area near ground zero,
particularly to view the green glass called "trinitite," which covered
the crater floor. Trinitite was the product of the detonation's
extreme beat, which melted and mixed desert sand, tower steel, and
other debris (1; 8; 9; 16).
RADIATION PROTECTION AT PROJECT TRINITY
The TR-7 or Medical Group, shown in the figure 1-5 organizational
chart, was responsible for radiological safety at Project TRINITY.
Many of the physicians and scientists in the Medical Group had worked
with radioactive materials before and were trained in radiological
safety procedures. The Chief of the Medical Group supervised the
radiological safety operations and reported to the TRINITY director.
In addition to providing medical care to TRINITY personnel, this group
established radiological safety programs to:
o Minimize radiation exposure of personnel on the test site and in
o Provide monitors to conduct radiological surveys onsite and offsite
o Provide and maintain radiation detection instruments
o Provide protective clothing and equipment.
An exposure limit of 5 roentgens during a two-month period was
established. Personnel were provided with radiation detection
instruments to determine their exposures (1).
The Medical Group consisted of physicians, scientists, and
administrators, as well as radiological monitors. Many of these
personnel were nonmilitary, but all worked on the Manhattan Project
under the administration of the Army Corps of Engineers Manhattan
The Medical Group was divided into two monitoring groups, the Site
Monitoring Group, which was responsible for onsite monitoring, and the
Offsite Monitoring Group. Each reported to the Chief of the Medical
Group, and each communicated with the other during the monitoring
activities. In addition to these two groups, a small group of medical
technicians provided radiation detection instruments to Medical Group
personnel (1; 10).
3.2 SITE MONITORING GROUP
The Site Monitoring Group consisted of a chief monitor, three other
monitors, and several medical doctors. This group had the following
functions (1; 10):
o Conduct ground surveys of the test area and mark areas of
o Conduct surveys of the Base Camp and roads leading into the test
o Provide protective clothing and equipment, including film badges and
pocket dosimeters, to personnel
o Monitor all personnel for radioactive contamination and provide for
o Maintain a record of radiation exposures received by personnel.
The Site Monitoring Group monitored the radiation exposures of
personnel in the test area. The time spent by personnel in radiation
areas was limited, and radiation detection instruments were provided
to permit continuous monitoring of exposure rates. In many cases, a
monitor from the Site Monitoring Group accompanied project personnel
into the test area to monitor exposure rates (1; 10).
Two members of the Site Monitoring Group, a monitor and a physician
with radiological safety training, were assigned to each shelter. The
supervising monitor was stationed at the Base Camp and was in radio
and telephone communication with all three shelters and the offsite
ground and aerial survey teams. Before any personnel were allowed to
leave the shelter areas, a radiological safety monitor and a military
policeman from each shelter advanced along the roads to Broadway to
check radiation levels. They wore respirators to prevent them from
inhaling radioactive material (1; 10).
Since it was expected that any dust from the cloud would fall on one
of the shelter areas within 30 minutes of the shot, plans had been
made to evacuate personnel as soon as the monitors completed their
initial survey. Because the cloud moved to the northeast, the south
shelter (the Control Point) was not completely evacuated, although
nonessential personnel were sent to the Base Camp. The west shelter
was emptied of all personnel except a searchlight crew spotlighting
the cloud as it moved away (1; 10).
Only at the north shelter did an emergency evacuation occur. About 12
minutes after the shot, a detection instrument indicated a rapid rise
in the radiation levels within the shelter. At the same time, a
remote ionization monitoring device detected a rapid increase in
radiation. Because of these two readings, all north shelter personnel
were immediately evacuated to the Base Camp, 25 kilometers to the
south. Film badges worn by personnel stationed at the north shelter,
however, showed no radiation exposure above the detectable level. It
was later discovered that the meter of the detector in the north
shelter had not retained its zero calibration setting, and radiation
at the north shelter had not reached levels high enough to result in
measurable exposures of the personnel who had been positioned there.
However, fallout activity was later detected in the north shelter
area, proof that part of the cloud did head in that direction. This
also explains why the monitoring device detected rising radiation
levels (1; 12).
After ascertaining that radiation levels along the roads leading from
the shelters to Broadway were within acceptable limits, the
radiological safety monitors and military police established
roadblocks at important intersections leading to ground zero. The
north shelter monitor and military police set up a post where the
North Shelter Road ran into Broadway. The west shelter monitor and a
military policeman blocked Vatican Road where it intersected Broadway.
The south shelter monitor and military police set up a roadblock where
Broadway intersected Pennsylvania Avenue (1).
The monitor assigned to Guard Post 4 surveyed the Mockingbird Gap area
to ensure that it was safe for the guards to return to their post.
This position controlled access to the McDonald Ranch Road, which led
directly to ground zero (1).
At 0540 hours, the chief monitor departed from the Base Camp with a
military policeman to monitor the entire length of Broadway. They
first checked the roadblock at Pennsylvania Avenue and Broadway. Next
they drove to the roadblock at Vatican Road and Broadway. Upon the
chief monitor's arrival, the west shelter monitor traveled about nine
kilometers west on Vatican Road to monitor Guard Post 1 so that the
military police could reoccupy the post. The monitoring excursion to
Guard Post 1 continued until the chief monitor had returned from Guard
Post 2, located 17 kilometers northwest of the Vatican Road roadblock
on Broadway (1; 18).
The chief monitor arrived at Guard Post 2 at about 0550 hours and
found the post empty. He then continued five kilometers north along
Broadway to the foxholes from which the military police had watched
the detonation. There he found the guards, the five radiological
safety monitors assigned to the evacuation detachment, and the
Commanding Officer of the evacuation detachment (1; 18).
The military policemen refused to return to Guard Post 2, insisting
that they had received orders over their two-way radio from the Base
Commander to evacuate their post and head for San Antonio, New Mexico,
a town 28 kilometers northwest of the Guard Post. The Base Commander
had noted that portions of the cloud were heading northwestward and,
fearing that fallout from the cloud would contaminate Guard Post 2,
had ordered the military police to evacuate. The chief monitor,
however, had found no significant radiation levels anywhere along the
northern part of Broadway nor around Guard Post 2. The Base Commander,
after being contacted by the chief monitor, drove to the foxholes and
ordered the guards to return to their post. This was the only
unplanned incident during the onsite monitoring (1).
After Guard Post 2 was reoccupied, the chief monitor returned to the
roadblock at the intersection of Broadway and the North Shelter Road.
The north shelter monitor informed the chief monitor of the sudden
evacuation of the north shelter, whereupon the chief monitor surveyed
the north shelter area and found intensities of only 0.01 and 0.02
roentgens per hour (R/h). The chief monitor then contacted the south
shelter and informed Dr. Bainbridge that the north shelter region was
safe for those who needed to return, that Broadway was safe from the
Base Camp to Guard Post 2, and that Guard Post 2 was now manned so
that personnel leaving for LASL could be checked out (1).
The chief monitor then returned to the south shelter and assembled the
monitors from the three roadblocks and Guard Post 4 to prepare for
entrance into the ground zero area. The time was about 0815 hours.
The military police at the roadblocks were given radiation meters to
survey the adjoining area. Broadway from the south shelter to Guard
Post 2 was remonitored occasionally to reassure the military police
that there was no radiation problem. Monitors also surveyed the Base
Camp for 24 hours after the detonation. No radiation above background
levels was detected there (1).
The following brief description of the radiological environment in the
TRINITY test area is based primarily on the results of the remote
gamma recorders situated in the test area and on results of the road
surveys conducted after the detonation (1).
Within about 1,400 meters of ground zero (except to the north),
radiation intensities between 0.2 and 1.3 R/h were detected during the
first few minutes after the detonation. These readings decreased to
less than 0.1 R/h within a few hours. At greater distances to the
east, south, and west, radiation levels above background were not
The cloud drifted to the northeast, and higher gamma readings due to
fallout were encountered in this direction. About five minutes after
the detonation, a reading of 3 R/h was recorded 1,400 meters north of
ground zero. Several minutes later, the intensity there had increased
to greater than 7 R/h, and it continued to increase for several more
minutes. Gamma detectors 9,150 meters north of ground zero, however,
recorded no radiation above background levels. This indicated that
the cloud had passed over or near the 1,400-meter area and only
partially over the 9,150-meter area where the north shelter was
located. Subsequent ground surveys of this area found no gamma
intensities higher than 0.02 R/h (1).
Gamma radiation levels at and around ground zero were much higher than
in other onsite areas because of induced activity in the soil.
Twenty-four hours after the detonation, the gamma intensity at ground
zero was estimated to be 600 to 700 R/h. This estimate was based on
data provided by the tank crew that drove to ground zero to obtain
soil samples. The intensity decreased to about 2 R/h at 725 meters
from ground zero. Gamma intensities of 0.1 R/h or more were confined
within a circular area extending about 1,100 meters from ground zero
(except in areas of fallout). One week after the shot, the gamma
intensity at ground zero was about 45 R/h. After 30 days, intensities
at ground zero had decreased to 15 R/h, and intensities of 0.1 R/h or
more were not encountered beyond about 365 meters from ground zero.
Gamma intensities of 3 to 10 R/h were found at ground zero three
months after the detonation (1; 19).
3.3 OFFSITE MONITORING GROUP
Four two-man teams and one five-man team supervised by the chief
offsite monitor constituted the Offsite Monitoring Group. Before the
detonation, the four two-man teams established monitoring posts in
towns outside the test area. These towns were Nogal, Roswell, Fort
Sumner, and Socorro, all in New Mexico. The five-man team remained at
Guard Post 2 to assist in evacuation of nearby residences if the
TRINITY cloud drifted in that direction. These residences, the Fite
house and the homes in the town of Tokay, were 24 and 32 kilometers
northwest of ground zero, respectively. Since the cloud drifted to
the northeast, evacuation was not required. All offsite monitoring
teams were in radio or telephone contact with personnel at the Base
Offsite monitoring teams in areas northeast of ground zero encountered
gamma readings ranging from 1.5 to 15 R/h two to four hours after the
detonation. Three hours after the detonation, surveys taken in
Bingham, New Mexico (located 30 kilometers northeast of ground zero)
found gamma intensities of about 1.5 R/h. Radiation readings at the
town of White, nine kilometers southeast of Bingham, were 6.5 R/h
three hours after the detonation and 2.5 R/h two hours later. Another
team monitoring in a canyon 11 kilometers east of Bingham found a
gamma intensity of about 15 R/h. Five hours later, the intensity had
decreased to 3.8 R/h. It was estimated that peak intensities of gamma
radiation from fallout on shot-day were about 7 R/h at an occupied
ranch house in this canyon area (1; 11; 19).
Monitoring teams resurveyed these towns about one month after the
TRINITY detonation. At Bingham, gamma readings of 0.003 R/h and
0.0001 R/h were found at ground level outdoors and at waist level
inside a building, respectively. At the town of White, the highest
outdoor gamma reading was 0.008 R/h. Inside a building, the highest
reading was 0.0005 R/h (11).
Surveys taken in the canyon area one month after the detonation
indicated that gamma intensities at ground level had decreased to
0.032 R/h. The occupied ranch house was also surveyed, both inside
and outside. The highest reading outdoors was 0.028 R/h, and the
highest reading indoors was 0.004 R/h (11; 19).
Monitoring was also conducted in offsite areas other than those to the
north and northeast of ground zero. Monitors found no radiation
readings above background levels (11).
Significant fallout from the TRINITY cloud did not reach the ground
within about 20 kilometers northeast of ground zero. From this point,
the fallout pattern extended out 160 kilometers and was 48 kilometers
wide. Gamma intensities up to 15 R/h were measured in this region
several hours after the detonation. One month later, intensities had
declined to 0.032 R/h or less (11).
DOSIMETRY ANALYSIS OF PARTICIPANTS IN PROJECT TRINITY
This chapter summarizes the radiation doses received by participants
in various activities during Project TRINITY. The sources of this
dosimetry information are the safety and monitoring report for
personnel at TRINITY, which includes a compilation of film badge
readings for all participants up to 1 January 1946, and film badge
data from the records of the Reynolds Electrical and Engineering
Company, which contain readings through 1946 (1; 16). These sources
list individual participants with their cumulative gamma radiation
4.1 FILM BADGE RECORDS
During TRINITY, the film badge was the primary device used to measure
the radiation dose received by individual participants. The site
monitoring plan indicates that film badges were to be issued to
participants. The film badge was normally worn at chest level on the
outside of clothing and was designed to measure the wearer's exposure
to gamma radiation from external sources. These film badges were
insensitive to neutron radiation and did not measure the amount of
radioactive material that might have been inhaled or ingested (1).
Personnel from the Medical Group had responsibility for issuing,
receiving, processing, and interpreting film badges for Project
TRINITY. The Site Monitoring Group compiled the film badge records
for both onsite and offsite personnel. Radiological safety personnel
and military police recorded the names and identification numbers of
individuals as they entered the test area. This information was
recorded in an entry logbook and on a personal exposure data card.
Upon leaving the test area, individuals returned their film badges to
the check station. When the film badges were processed and
interpreted, the reading was entered on the individuals exposure data
card. In this manner, the number of times an individual entered the
test area and his cumulative exposure history were recorded and
4.2 GAMMA RADIATION EXPOSURE
The safety and monitoring report lists film badge readings for about
700 individuals who participated in Project TRINITY from 16 July 1945
to 1 January 1946 (1). This list includes both military and
nonmilitary personnel who were involved with the TRINITY operation and
postshot activities. However, records are available for only 44 of
the 144 to 160 members of the evacuation detachment (1). In addition,
some of these film badge listings may be for personnel who were only
peripherally involved with TRINITY activities, such as family members
and official guests who visited the site.
According to the safety and monitoring report, by 1 January 1946, 23
individuals had received cumulative gamma exposures greater than 2 but
less than 4 roentgens. An additional 22 individuals received gamma
exposures between 4 and 15 roentgens. Personnel who received gamma
exposures exceeding 2 roentgens represent less than six percent of the
Project TRINITY participants with recorded exposures. As described
below, these exposures generally resulted when personnel approached
ground zero several times (1).
Information is available regarding the activities of some of these
personnel. One of the drivers of the earth-sampling group's
lead-lined tank, an Army sergeant who traveled three times to ground
zero, received an exposure of 15 roentgens. A second tank driver,
also an Army sergeant, received an exposure of 3.3 roentgens. Three
members of the earth-sampling group, all of whom traveled in the tank
to ground zero, received exposures of 10, 7.5, and 5 roentgens. An
Army photographer who entered the test area six times between 23 July
and 20 October received 12.2 roentgens (1).
Four individuals involved with excavating the buried supports of the
TRINITY tower from 8 October to 10 October 1945 received gamma
exposures ranging from 3.4 to 4.7 roentgens. Film badge readings for
this three-day period indicate that the two individuals who operated
mechanical shovels received 3.4 and 4.3 roentgens, while the two who
supervised and monitored the excavation received exposures of 4.2 and
4.7 roentgens. The individual receiving 4.7 roentgens during the
excavation operation had received 1.3 roentgens from a previous
exposure, making his total exposure 6 roentgens (1).
An Army captain who accompanied all test and observer parties into the
ground zero area between 1 September and 11 October 1945 received a
total gamma exposure of 2.6 roentgens (1). The activities and times
of exposure are not known for other personnel with exposures over 2
According to the dosimetry records for 1946, about 115 people visited
the test site that year. No one ventured inside the fence surrounding
ground zero, and no one received an exposure greater than 1 roentgen
The following list of references represents the documents consulted in
preparation of the Project TRINITY volume.
An availability statement has been included at the end of the
reference citation for those readers who wish to read or obtain copies
of source documents. Availability statements were correct at the time
the bibliography was prepared. It is anticipated that many of the
documents marked unavailable may become available during the
declassification review process. The Coordination and Information
Center (CIC) and the National Technical Information Service (NTIS)
will be provided future DNA-WT documents bearing an EX after the
Source documents bearing an availability statement of CIC may be
reviewed at the following address:
Department of Energy
Coordination and Information Center
(Operated by Reynolds Electrical & Engineering Co., Inc.)
ATTN: Mr. Richard V. Nutley
2753 S. Highland
P.O. Box 14100
Las Vegas, Nevada 89114
Phone: (702) 734-3194
Source documents bearing an availability statement of NTIS may be
purchased from the National Technical Information Service. When
ordering by mail or phone, please include both the price code and the
NTIS number. The price code appears in parentheses before the NTIS
National Technical Information Service
5285 Port Royal Road
Springfield, Virginia 22161
Phone: (703) 487-4650
Additional ordering information or assistance may be obtained by
writing to the NTIS, Attention: Customer Service, or by calling (703)
PROJECT TRINITY REFERENCES
*Available from NTIS; order number appears before the asterisk.
**Available at CIC.
***Not available, see Availability Information page.
****Requests subject to Privacy Act restrictions.
1. Aebersold, Paul. July 16th Nuclear Explosion-Safety and
Monitoring of Personnel (U). Los Alamos Scientific Laboratory, Atomic
Energy Commission. Los Alamos, NM.: LASL. LA-616. January 9, 1947.
2. Bainbridge, K. T. Memorandum to All Concerned, Subject: TR
Circular No. 18--Total Personnel at TR. [Base Camp, Trinity Site:
NM.] July 3, 1945. 1 Page.**
3. Bainbridge, K. T. TRINITY. Los Alamos Scientific Laboratory.
Los Alamos, NM.: LASL, LA-6300-H and Washington, D. C.: GPO. May
1976. 82 Pages.**
4. Bramlet, Walt. Memorandum for Thomas J. Hirons, Subject: DOD
Participants in Atmospheric Tests, wo/encl. Los Alamos Scientific
Laboratory. Los Alamos, NM. ISD-5. February 20, 1979. 4 Pages.**
5. General Electric Company--TEMPO. Compilation of Local Fallout
Data from Test Detonations 1945-1962. Vol. 1: "Continental US Tests."
Washington, D. C.: Defense Nuclear Agency. DNA 1251-1(EX.). 1979.
619 Pages. (A99) AD/AO79 309.*
6. Groves, Leslie R., LTG, USA. Memorandum for Secretary of War,
[Subject: TRINITY]. [Washington, D.C.] 18 July 1945. 13 Pages.**
7. Groves, Leslie R., LTG, USA (Ret.). Now It Can Be Told: The Story
of the Manhattan Project. New York, NY.: Harper and Row. 1962. 444
8. Headquarters, 9812th Technical Service Unit, Provisional
Detachment No. I (Company "B"). [Extract from: Daily Diary,
Provisional Detachment No. 1 (Company "B"), 9812th Technical Service
Unit.] Army Corps of Engineers, Department of War. [Santa Fe, NM.]
14 July 1945. 2 Pages.**
9. Headquarters, Special Service Detachment. Supplemental Special
Guard Orders, with Appendix. Los Alamos Scientific Laboratory,
Manhattan Engineer District. [Alamogordo, NM.] 14 July 1945. 4
10. Hempelmann, L. H., M.D. [Extracts from: "Preparation and
Operational Plan of Medical Group (TR-7) for Nuclear Explosion 16 July
1945."] Los Alamos Scientific Laboratory, Atomic Energy Commission.
Los Alamos, NM.: LASL. LA-631(Deleted). June 13, 1947. 32 Pages.***
11. Hoffman, J. G. [Extracts from "Health Physics Report on
Radioactive Contamination throughout New Mexico Following the Nuclear
Explosion, Part A--Physics."] Los Alamos Scientific Laboratory,
Manhattan Engineer District. [Los Alamos, NM.] [1945.] 31 Pages.**
12. Lamont, Lansing. Day of TRINITY. New York, NY.: Atheneum.
1965. 331 Pages.
13. Los Alamos Scientific Laboratory, Public Relations Office. "Los
Alamos: Beginning of an Era, 1943-1945." Atomic Energy Commission.
Los Alamos, NM.: LASL. 1967. 65 Pages.**
14. Oppenheimer, J. R. Memorandum for Group Leaders, Subject:
TRINITY Test. Los Alamos Scientific Laboratory. Los Alamos, NM.
June 14, 1945. 2 Pages.**
15. Palmer, T. O., Maj., USA. Evacuation Detachment at TRINITY.
[Manhattan Engineer District, Army Corps of Engineers.] [Los Alamos,
NM.] [18 July 1945.] 2 Pages.**
16. Reynolds Electrical & Engineering Company, Inc. [Personnel
Radiation Exposures, 1945, 1946] Las Vegas, NV. Microfilm.****
17. Warren, S. L., COL., USA. Directions for Personnel at Base Camp
at Time of Shot. Los Alamos Scientific Laboratory, Manhattan Engineer
District. [Alamogordo, NM.] 15 July 1945. 1 Page.**
18. Warren, S. L., COL, USA; Hempelmann, L. H., M.D. Extracts from:
Personal Notes, Subject: Events in Camp Immediately Following
Shot--July 16, 1945. 1945. 2 Pages.**
19. Weisskopf, V.; Hoffman, J.; Aebersold, Paul; Hempelmann, L. H.
Memorandum for George Kistiakowsky, Subject: Measurement of Blast,
Radiation, Heat and Light and Radioactivity at Trinity. [Los Alamos,
NM.] 5 September 1945. 2 Pages.**
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