ANC Model 100 "Ray-D-TEC" Monitor (ca. 1962-1965)

The "Ray-D-Tec" Model 100 monitor was produced by the American Nuclear Corporation of Oak Ridge, Tennessee sometime in the 1960s. While American Nuclear produced a small line of detectors, their main business was the production of radioactive sources. In the late 1960s, contamination was detected in the Clinch River upstream from Oak Ridge and this contamination was traced to leaking tanks at the American Nuclear facility. The state revoked the company’s license and took control of the property.

The Model 100 Ray-D-Tec employs a small internal GM tube but it can also be used with the external probe shown in the preceding photograph. As can be seen from the instructions on the case (photo above left), its mode of operation is somewhat unusual. Light number 1 comes on in the presence of radiation. To make a measurement, the dial on the side of the case is turned until light number 2 goes out. The exposure rate is then read off the dial.

The fact that its range of measurement is so high, up to 100 R/hr, and the fact that the scale is non-linear, indicates that the GM operated in the current (integrating) mode rather than in the pulse mode. 

Case: ca. 3" x 4" x 1 3/8"

Batteries: Two 1.5 volt penlights

Reference

Product description. Nucleonics September 1962, page 87.