Answer to Question #3477 Submitted to "Ask the Experts"

These old gamma radiation detection units contain a sodium iodide (NaI) crystal coupled to a photomultiplier tube (PMT) and respective electronics. They were used in the circa 1955 time frame for uranium exploration, as they can be adjusted to detect a specific gamma-ray energy and have high detection efficiency. Precision Instruments is no longer in business, nor do I know where you might get an operation manual. However, if the electronics of the unit looks in good condition, that is, no leaking battery acid all over circuit boards, and you can identify the battery requirements, you might just try replacing the batteries and turning it on. These batteries may be hard to find however, as they are often odd size and voltages, for example, 22½, 4½, etc., no longer in use. Nonetheless, it may still be set for operation. If the meter is at zero while off and starts to deflect and ramps up to several hundred counts per minute without a source, that's a good sign. You then might find a small (that is, an ounce or so will do) sample of uranium ore and place that in a couple of heavy ziplock bags so you don't get it on your hands while handling it. If the unit is functional, that uranium ore sample should make your unit "sing" with counts! There are many old government publications on uranium ore prospecting on eBay^® for a couple dollars. Similarly, look over this and other areas of ATE for other information on radiation and radiation safety. If you get the unit working, most states have rocks with elevated uranium concentrations, so you may want to get out and do some uranium prospecting! A colleague of mine brings his Boy Scout troop out to an area in central Pennsylvania to do this as part of the "Atomic Energy Badge."

See the US Geological Survey data generated during the US Department of Energy's (DOE) National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) Program, which was conducted from the late 1970s through the early 1980s. Related Web sites are http://energy.cr.usgs.gov/radon/DDS-9.html and http://energy.cr.usgs.gov/radon/usaeu.gif.

Good luck, happy hunting!

David J. Allard, CHP