Sample container was provided with an overflow tube to prevent damage by hvdrostatic pressure.
An EG&G radio timing Signal activated the timing circuit to (1) start the GITR at H—5 minutes: (2) open the cover of the OCC at H—0.5 minute: (3) close the cover of the OCC at H-4
minutes; and (4) wash the tray with 750 cc of concentrated hydrochloric acid at H+5 minutes.
The combined acid-and-fallout sample drained into the sample container and remained undis-
turbed for 53 hours, during which time two 12-hour records of gamma dose rate were obtained.
The time period chosen for fallout collection was based upon estimates of the time required to
collect a sufficiently large sample of fallout in a short time so as to start decay measurements
as early as possible.
2.2.4 GITR Calibration and Maintenance.
Primary calibration of the GITR detectors had
been performed with an accurately calibrated Cosource at NRDL. At the Eniwetok Proving
Ground (EPG), the project used 120 curies of Cs'*” in a lead-shielded source holder mounted
inatrailer for calibration of GITR’s. The field calibrations with the Cs! source were re-
lated to the primary Co®° calibrations by means of Victoreen 70A r-meters (known to be accurate within =5 percent), which were utilized as transfer standards. The detectors were held
in a fixed orientation in the broad-beam radiation field by means of a jig. However, the chosen
orientation— which was used in order to insure reproducibility —led to biased calibration, because the directional responses of the detectors were not uniform. The responses to various
gamma energies between 0.07 and 1.3 Mev were determined by means of filtered X-rav beams,
Cs'* sources, and Co® sources. These responses were used to estimate calibration-bias
corrections for various assumed radiation-source geometries and gamma Spectra. The details
are given in Appendix B.
The field maintenance facility consisted of a dehumidified room equipped with tool kits, standard test equipment (oscilloscopes, and the like), and portable beta-radiation sources. The airconditioned calibration trailer also contained tool kits and standard test equipment in addition
to the gamma-calibration range. These facilities were established for use byall projects uti-
lizing the NRDL GITR’s.
2.2.5 Film Badges. The GITR gamma-dose measurements were augmented bythe use of
film badges. Approximately 1,700 standard Rad-Safe film-badge packets were supplied and
processed by Task Unit 6 (TU-6).
The standard Rad-Safe film pack consisted of two films: (1) DuPont 502, covering the dose
range between 0,1 and 20 r; and (2) DuPont 834, covering the dose range between 10 and 1,200 r.
The films were partially covered by lead strips 0.028 + 0.002 inch thick, to discriminate against
beta radiation, thereby permitting determination of gamma dosage. The exposed film was given
5-minute development, with 4.5-minute agitation, in Eastman X-ray film developer at 68 degrees F. The developed film under the lead strip was read with an Eberline-Angus densitometer
at the EPG and reread with a Macbeth-Ansco densitometer at NRDL, which permitted scanning
the film for damage, pinholes, etc.
The film-badge packets were used in pairs in order to obtain statistical estimates of random
errors. Four to eighteen pairs of film-badge packets were either taped to stanchions or suspended with twine 3 feet above deck level in each compartment or area being investigated. Figure 2.8 presents the area locations of the film-badge packets aboard the destrovers. Detauled
locations of the packets are presented in Appendix C.
2.3
OPERATIONS
This project participated in Shots Wahoo and Umbrella.
The GITR’s were checked, repaired
if necessary, and calibrated before and after each shot, so far aS was practicable.
Project personnel mounted the GITR’s on the three ships by D~2 days of each shot. Instru-
ment checkout continued until D-1 day, at which time the system was readied for test participation. Personnel of Task Element 7.3.1.5 were briefed on film-badge locations and recovery