![]() These detectors measured the current imbalance between an exposed “sense chamber” and a sealed “reference chamber,” both of which contained alpha sources. 1960, each containing a total of 80 microcuries of Am-241. The left-most pic shows industrial smoke detectors from ca. Ionization smoke detectors contain an alpha emitter, typically Am-241. At left, a spark gap (in hand) originally with 5 ♜i of Cs-137 and a dual TR switch originally containing less than 0.7 ♜i of Co-60. At right are three similar radar TR switches and their packaging (left to right: Bomac JAN-CBNQ-5883 from 1961 originally containing 0.3 ♜i of Co-60 a Westinghouse 1B37 from 1952 containing several ♜i or Ra-226 a GE 1B35 containing a small amount of Co-60. The 23-g chunk of lutetium in the right inset veritably boils a 2″ NaI:Tl detector with more than 120 counts / sec above background. The peak at 509 keV in the spectrum is not a real gamma energy, but rather a “sum peak” caused by 202- and 307-keV gammas simultaneously entering the detector (this happens to be an “anomalous” sum peak, larger than would occur by random summation, precisely because the two radiations involved are frequently part of the same decay sequence). Lu-176 (2.6% abundance, T1/2 = 3.78E+10 y) undergoes beta decay with a high yield of several gamma energies, most notably at 202 and 307 keV. A ~50-g specimen of the metal (inset, left) racked up 7.2 counts / sec above background into a 2″ NaI:Tl detector. La-138 (0.09% abundance, T1/2 = 1.02E+11 y) decays by electron capture or beta emission, unleashing gamma rays in either branch. Both could be used as check sources or energy calibration sources for scintillation detectors. V-50, Rb-87, Sm-147, Re-187, In-115), these two stand out (along with good old potassium) for their usefully high gamma activity. Although there are other natural, primordial radioelements (e.g. Lanthanum and lutetiumare two of the lesser-known natural radioactive elements. The glass glows its characteristic green color as the x-ray beam expands across its surface. In the lower photo, a thin face of the Corning filter abuts the output window of a commercial x-ray machine, where exposure rates are on the order of 1000 roentgen / hour. Uranium glass is also apparently a fair scintillation medium. Based absorption of the lamp’s harsh 254-nanometer UVC radiation, it’s easy to distinguish a quartz crucible (casting the central shadow) from the nearly-opaque borosilicate tube (left) and soda-lime glass vial (right). In the second photo, ultraviolet light from a distant Sun-Kraft lamp (an electrodeless quartz-mercury discharge tube) excites the uranium glass, provoking the characteristic green fluorescence. Some other interesting properties of uranium glass are dramatically demonstrated with this example. The uranium concentration is through the roof: it emits 11,000 CPM into a 2″ pancake GM tube, making it more than twice as hot as the hottest decorative vaseline glass items I own. This is a 6″ Corning uranium-glass optical filter I recently obtained on eBay. At left is a “531 Burnt Orange” (when fired, of course), and at right is a “108 Forsythia.” ![]() Both are products of Thompson Enamel and both read about 12,000 CPM on a 2″ pancake GM tube. Because so few artists use or even know about uranium glazes now, old bottles such as these sometimes present surprise disposal problems when studios are cleaned out. Before Melstrom owned them, they were in the possession of a radiation safety officer at the Texas Department of State Health Services, slated for official disposal as radioactive waste. These raw ceramic underglazes containing uranium are a gift from William Melstrom, who made the vase pictured above. It registers 38,000 CPM on a 2″ pancake GM tube, making it among the hottest pieces of pottery in my collection. At right is a hand-thrown and hand-glazed decorative bowl from an unknown artist containing a typical “uranium red” glaze. The fluorescent light yellow glaze on this vase clocks in at 2200 CPM on a 2″ pancake GM tube. His adventuresome report on obtaining uranium compounds in France to formulate his glazes is a must-read. Melstrom is one of very few contemporary artists who have gone to the lengths required nowadays to work with uranium. Especially interesting is a vase made in 2010 (left) that is representative of the work of crystalline-glaze artist William Melstrom, who has a studio in Austin, Texas ( photo courtesy of Mr. Here are two examples of handmade ceramics. Uranium-glazed artistic pottery is hard to come by, in contrast to the mass-produced (and mass-collected) Fiestaware and similar. As always, if you have something radioactive and in need of a good home, I buy and trade all the time. Today’s long menu includes more radioactive pottery, more radioactive vacuum tubes, smoke detectors, a couple lesser-known radioactive elements, and a few interesting odds and ends.
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