es 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).

CHAPTER 4

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
exposures.

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