IM-153/PDR Alarming Dosimeter (ca. 1960s)
The IM-153, manufactured by Nuclear Corporation of America, is described in the Directory of Radiac Equipment NAVSHIPS 94200.5 in 1961 as follows: "Radiac Alarm Dosimeter IM-153(XN-1)/PD is intended for use by working parties entering an area which is radiologically contaminated. The dosimeter indicates dose and dose rate by giving an audible beep for each recorded 100 milliroentgens plus a continuous alarm activated when the counter indicates 1, 10, or 11 [100?] roentgens." The IM-153(XN-1), produced by Victoreen, was probably an experimental unit, hence the "X."
The sensing element of the IM-153 is an ion chamber.
The Defense Atomic Support Agency's 1966 List of Military and Civil Defense Radiac Devices simply states that the IM-153 "gives an alarm, either visual by a light or aural by a buzzer when a preset dose has been reached." It does not state what that preset dose was or which light they are referring to—the only light on the unit is the one used to illuminate the display.
The counter is reset via an adjustment screw on the right side of the case (not visible in above photo).
The List of Radiacs in the Navy Program P-9670-1 states that the IM-153 and IM-153(A) were obsolete at the time of publication: 1975.
Range: 0-999.9 R
Size: 2 1/4” x 4 1/4" x 7"
Batteries: Two 1.5-volt D cells
Weight: ca. 2 lbs.
Manufacturers: Nucor, Nuclear Research Corporation
References
- Directory of Radiac Equipment NAVSHIPS 94200.5, no date, ca. 1961-62.
- Defense Atomic Support Agency, List of Military and Civil Defense Radiac Devices. DASA 1243 revised, 1966.
- Naval Electronic Systems Command List of Radiacs in the Navy Program P-9670-1, February 1975.