adings 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).

CHAPTER 3

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 G