AN/PDR-77 Radiac Set: Choosing the Proper Probe - Defense Centers for Public Health

The AN/PDR-77 is a multipurpose radiation detection system.

Versatile and rugged design
Ideal for nuclear accident and incident response

Major Components

Meter
Alpha probe
Beta/gamma probe
X-ray probe

Capabilities

The capabilities of the PDR-77 may be augmented by the Radiation Protection Officer (RPO) Kit, which contains the micro-R probe and the pancake probe.

AN/PDR-77 Radiac with Beta/Gamma b/g Probe (DT-616)

AN/PDR-77 Standard Probes

X-ray Probe (DT-674)

Alpha (a) Probe (DT-669)

Beta/Gamma (b/g) Probe (DT-616)

AN/PDR-77 RPO Kit

Pancake Probe (DT-695)

micro-R Probe (DT-696)

		Probe Type
		β/γ Probe	α Probe	X-ray Probe	Pancake Probe	micro-R Probe
		Alpha Emitters
Measuring Objective	Detection or Measurement¹	C	A	b⁴	A	C
	Detection or Measurement¹	(Open Window)	A	b⁴	A	C
	Locate Missing Source²	C	C	A	A	C
	Locate Missing Source²	(Open Window)	C	A	A	C
		Beta Emitters
	All Types	B	U	b⁴	A	C
	All Types	(Open Window)	U	b⁴	A	C
		Gamma Emitters
	Detection or Measurement	A	U	A	A	A
	Detection or Measurement	A	U	A	A	A
	Locate Missing Source	A	U	A	A	A
	Locate Missing Source	A	U	A	A	A
	Basic External Radiation Dose Measurement Survey³	A	U	U	U	b⁴
	Basic External Radiation Dose Measurement Survey³	A	U	U	U	b⁴
		Unknown sources
	Detection or Measurement	B	U	b⁴	A	b⁴
	Detection or Measurement	B	U	b⁴	A	b⁴
A = First Choice; B = Second Choice; C = Use If No Other Probes Are Available; U = Unacceptable
1. Determine the presence or intensity of radiation.
2. Find a radioactive source.
3. Determine ambient radiation doses and dose rates in a given area.
4. Most alpha and beta emitters have associated gamma rays and/or x rays. Therefore, these probes can be used to detect the presence of many alpha and beta emitters. If there are no associated gamma rays or x rays emitted, then these probes will not detect the radioactive material.

Probe Considerations and Limitations

The AN/PDR-77 does not have the ability to detect neutrons.
The alpha probe responds to alpha particles above 3 MeV.
On the X-ray probe, the 17 keV channel has lower and upper discriminators of 12.5 keV and 21.5 keV, respectively; the 60 keV channel has settings of 50 keV and 70 keV; and the “PEAK ALIGN" channel has settings of 70 keV and 95 keV.
Despite the display, the beta/gamma probe is calibrated in mrad/hr.
The beta/gamma probe is compensated to provide a tissue dose response; the response begins to fall off at energies below 100 keV.
The difference in dose rate between the beta/gamma probe's two positions (window open and window closed) does not yield the beta dose rate.
The pancake probe entrance window effectively blocks beta particles with energies less than about 35 keV and alpha particles with energies less than 4 MeV.
The response of the micro-R probe is highly dependent on photon energy. See response curve in the technical manual for more information.
The micro-R probe is useful as a radiation detector, but not as a dose meter.