CHAPTER5
LABORATORY GROUP
5.1
FUNCTIONS
The Laboratory Group was organized to provide technical assistance to the operations of
the Control and Decontamination groups, as well as service to the several radiological-safety
organizations of JTF-7. In this capacity this group was responsible for the maintenance and
repair of the various types of radiological-safety instrumentation in use throughout JTF-7, It
also processed and interpreted the photographic film badges of the Task Force. One section
collected, interpreted, and disseminated data on the nuclear nature of the radioactive contaminants.
5.2
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ELECTRONIC SECTION
The Electronic Section consisted of one officer and three instrument repairmen. They
serviced and maintained the densitometers, voltage regulators, scalers, count rate meters, and
scintillation counters of the laboratory, as well as the following portable survey meters: AN/
PDR-39, AN/PDR-T1B, AN/PDR-18, MX-5, 2610, and AN/PDR-27A of the Control Group.
The AN/PDR-39 was considered the basic survey instrument for all monitors and met the
stringent requirements of the Pacific Proving Grounds, although humidity leaks developed
after frequent use on small boat missions in the Bikini lagoon. At times data were lost because the meter had becomeinoperative on the higher scale. Shop rotation, inspection, and
drying remedied this primary difficulty. Other failures were noted in the electrical meter
movements and lucite screw mounts.
The MX-5 was considered the basic personnel-monitoring instrument and performed
satisfactorily when used for this function in low-level background radiation. The high background radiation level at Bikini caused a high loss rate of Geiger-Mueller tubes. Instruction in
the proper use of the instrument reducedthis loss rate.
Trouble was experienced by individuals when attempting to correlate 1- to 5-mr readings
on the two instruments since neither instrument was calibrated in this range.
The major problem in instrument maintenance was the procurement of adequate numbers
of appropriate batteries.
It was necessary to shift the personnel of this section from one shop to another to meet the
work load. In the interest of economy and efficiency, the repair personnel often would be sent
to the instrument rather than having the faulty instruments returned to the shop for repair.
Thus the instruments that suffered only minor faults were repaired and returned to service immediately, whereas those in need of more extensive repair were returned to the shop. The
number of repair personnel proved adequate, and at no time was there an abnormal backlog of
equipment in need of repair.
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