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
maintained (1).


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