History

By mid 1944 Los Alamos scientists had decided that the plutonium version of the atomic bomb that was being built needed a field test. The triggering mechanism of the plutonium weapon had proven so complex that the scientist wanted a trial run. They worried that if it a bomb dropped in battle did not explode as expected, the enemy might reassemble the components and drop it on an allied target.

The scientists wanted a site near Los Alamos that was sparsely populated and suitable for extensive photographic coverage. In addition, Secretary of the Interior Harold Ickes had insisted that no Native American group be removed because of this experiment.

The Trinity Site is located in the desert of central New Mexico. It is thirty miles east of Socorro in what is now know as the White Sands Missile Range. Originally the area was named Jornado del Mureta (The Dead Man's Route) by Spanish explorers. Oppenheimer nick named it Trinity after a line from the poem The Litany by John Donne.

Planning

While planning the Trinity test, Los Alamos scientists were concerned about weather. Clear skies were necessary in order to observe and document the test. There was also concerns that rain immediately before or during the test would damage the electrical machinery and instruments. Another reason for being concerned about the weather was fallout. This was first suggested by Joseph Hirschfelder a few months earlier. High winds threatened to send the radioactive cloud over inhabited areas. If it began to rain too soon after the test it would cause concentrated amounts of fallout onto a small area. A meteorologist, J. M. Hubbard, was hired to pick the final day. He felt that the ideal dates were between July 18 and the 21st. The window of July 12 to the 14 was his second choice. On June 30 all division leaders had to submit the earliest possible date that their work would be ready. After a meeting on this day July 16th was decided as the final date.

Explosion

The nuclear weapon to be tested, code named The Gadget, had been built at at Los Alamos. The core of the bomb was 239 Pu obtained from the Hanford production complex. Resting on 100 foot steel tower it was detonated at 5:29 a.m. Mountain Time. The blast was seen in three different states and the mushroom cloud rose over 40,000 feet in seven minutes. This massive cloud sucked up tons of dirt particle that slowly returned to earth as radioactive fallout. The steel tower was completely vaporized. The areas on the ground that the fire ball touched fused the sand and soil into a radioactive greenish-grey glass which scientist would later call "trinitite."

After the Test

After the test an eight foot-wire fence was erected, 1600 feet in radius around ground zero, that was guarded by military police. Extensive Radiation measurements were taken for two weeks after the test. The Los Alamos Health Group made periodic regional spot checks over the next few months. Two months after the ,radiation levels in the region that was in the cloud's path had fallen to tolerant. Although health physicians closely monitored the effect the Radiation had on the 1000 people at the site on the day of the test, the effects the blast had on the environment would not be studied for another two years.
Stafford Warren, dean of the UCLA Medical School, a veteran of Los Alamos and one of the first physicians to visit Hiroshima after the war, had been trying to convince the Atomic Energy Commission to allow a group to study the effect the test had on the area. The AEC was reluctant, but allowed it as a means to prevent future legal problems. Warren's team went to the Trinity site every summer from 1947 to 1951. Only thirteen copies of each year's report were printed and from 1947 to 1949 they were classified top secret. The initial investigations found ground zero clogged with radioactive tumble weeds. The trinitite was still visible although most had broken apart into pieces about two to three inches long.

Within the fenced in area of the site, radioactivity was found at a depth of 42 inches below the surface. This was neutron-induced radiation, which meant that the neutrons would continue to penetrate into the soil until they exhausted their energy. The area would essentially be radioactive forever.

The scientists saw clear evidence of fallout throughout the region. Unfissioned plutonium was found in desert rats, plant leaves, and soil samples, some from as far as 100 miles northeast of ground zero. Scientist tried to wash the plutonium particles off the leaves but found it impossible to remove them. The early reports state that radioactive contamination seemed to be concentrated in the upper one to two inches of soil, but scientists worried it was seeping deeper. In 1952 it was believed that the fallout had not had an extensive impact on the local ecology. The scientists felt that plutonium and other particles were only present in the top levels of soil and had not entered the food chain. Warren wanted to continue to visit the area around Trinity since he felt it was the best case study of fallout patterns. The AEC felt that since the exposure levels were low it wasn't worth the financial support.

Today the Radiation levels at Trinity are about 10 times higher than normal.

References

Szasz, Ferenc M. "The Impact of World War II on the Land: Gruinard Island, Scotland, and Trinity Site, New Mexico as Case Studies" Environmental History Review. Vol 19, Number 4 (http://www.jstor.org/stable/3984690).

http://www.cfo.doe.gov/me70/manhattan/trinity.htm

http://www.eyewitnesstohistory.com/atomictest.htm

http://www.cfo.doe.gov/me70/manhattan/publications/LANLBeginningofEraPart5.pdf

http://ohst.berkeley.edu/publications/oppenheimer/exhibit/index.html