Read Ebook: Project Trinity 1945-1946 by Maag Carl R Rohrer Steve

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o The TR-6 Group, responsible for the airblast-airborne condenser gauges

o The TR-7 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 .

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 .

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 . 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 .

THE ACTIVITIES AT PROJECT TRINITY

The TRINITY nuclear device was detonated on a 100-foot tower 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 . 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 .

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 .

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 .

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 .

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 .

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 .

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 .

With the exception of the shelter occupants and evacuation detachment , 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 :

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 residences

o One radiological safety monitor assigned to Guard Post 4

o Two military policemen at each of the seven guard posts .

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 . 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 .

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 .

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 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 .

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 each trip. No member of this party received a radiation exposure of more than 1 roentgen .

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 .

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 roentgens .

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 .

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 roentgen .

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 .

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 .

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 .

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 Japan .

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 .

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 .

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 .

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 .

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 offsite areas

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 .

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 Engineer District.

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 .

The Site Monitoring Group consisted of a chief monitor, three other monitors, and several medical doctors. This group had the following functions :

o Conduct ground surveys of the test area and mark areas of radioactivity

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