· Remove the dosimeter from the charger and
on the scale of the built-in optical system. The
IM-9/PD is primarily a health-physics device that is
check to ensure that it is still on zero.
particularly useful in areas of low dose rates.
· Replace the dust cover on the charger.
100 120 140 160 180 200
Figure 11-7. Dosimeter charger PP-4276A/PD.
Figure 11-6. Method of reading IM-9/PD dosimeter by
looking through it at the light. Inset shows a dose reading of
LIMITATIONS OF RADIAC INSTRUMENTS
RADIAC equipment can detect and measure
M-143/PD.-- The IM-143/PD is identical to the
IM-9/PD except in range. The IM-143/PD indicates
some limitations. None of the instruments are capable
gamma radiation dose in the range of 0 to 600 R. It is
of detecting and measuring beta and gamma radiation
used by repair locker personnel that are involved with
at the same time. Even those that can detect both beta
the survey, monitoring, and decontamination details
and gamma radiation do not automatically separate
during CBR evolutions. It keeps track of the dose they
these two types of radiation. Instead, the operator
have received up to the time they read the dosimeter.
keeps beta particles from entering the chamber by
The PP-4276A/PD dosimeter charger (fig. 11-7) is
manually pulling a beta shield over the thin window in
used to reset the self-reading dosimeters to zero. This
order to get a gamma reading only. Otherwise, you
action is accomplished by placing the dosimeter into the
would get a combined reading.
charger. The charger provides an adjustable voltage
source that is applied between the central wire and shell.
CALIBRATION AND REPAIR OF RADIAC
Because the quartz fiber and the fixed central wire of the
ion chamber are attached, each will receive the same
charge. As a result, when the dosimeter is charged, the
RADIAC equipment aboard ship is checked as
movable fiber is repelled from the fixed wire. By proper
required by the Ships' Maintenance and Material
adjustment of the voltage applied by the charger, the
Management (3-M) Manual. Ashore, radiac
fiber can be set exactly on the zero line of the scale. The
equipment is checked at least once each month or at
power source for the PP-4276A/PD is one alkaline
intervals specified by the applicable technical manual.
D-cell battery. When you charge a dosimeter with the
This check is accomplished according to instructions
PP-4276A/ PD, use the following procedures:
contained in the operator's section of the technical
· Remove the dust cover from the charger
manual. RADIAC equipment must be temporarily
transferred at regular intervals by shore activities to a
radiac repair facility for maintenance and calibration.
· Place the electrode end of the dosimeter into the
Ships, as far as practical within their operating
schedules, also must transfer their radiac instruments
charging receptacle and depress it firmly. This
illuminates the dosimeter scale and operates the
When equipment requiring outside maintenance is
f o u n d t o b e i n o p e r a t ive o r i s s u s p e c t e d o f
· Rotate the charging knob until the hairline on the
malfunctioning, it should be sent to the radiac repair
meter scale is located on the zero mark.