Archive for May, 2010

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Nuclear Collection (Part V)

May 13, 2010

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. As always, if you have something radioactive and in need of a good home, I buy and trade all the time.  Enjoy!

Uranium-glazed artistic pottery is hard to come by, in contrast to the mass-produced (and mass-collected) Fiestaware and similar.  Here are two examples of handmade ceramics.  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. Melstrom).  Melstrom is one of very few contemporary artists who have gone to the lengths required nowadays to work with uranium.  His adventuresome report on obtaining uranium compounds in France to formulate his glazes is a must-read.  The fluorescent light yellow glaze on this vase clocks in at 2200 CPM on a 2″ pancake GM tube.  At right is a hand-thrown and hand-glazed  decorative bowl from an unknown artist containing a typical “uranium red” glaze.  It registers 38,000 CPM on a 2″ pancake GM tube, making it among the hottest pieces of pottery in my collection.

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These raw ceramic underglazes containing uranium are a gift from William Melstrom, who made the vase pictured above.  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.  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.  Both are products of Thompson Enamel and both read about 12,000 CPM on a 2″ pancake GM tube.  At left is a “531 Burnt Orange” (when fired, of course), and at right is a “108 Forsythia.”

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This is a 6″ Corning uranium-glass optical filter I recently obtained on eBay.  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.

Some other interesting properties of uranium glass are dramatically demonstrated with this example.  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.  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).

Uranium glass is also apparently a fair scintillation medium.  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.  The glass glows its characteristic green color as the x-ray beam expands across its surface.

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Lanthanum and lutetium are two of the lesser-known natural radioactive elements.  Although there are other natural, primordial radioelements (e.g. 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.   Both could be used as check sources or energy calibration sources for scintillation detectors.  La-138 (0.09% abundance, T1/2 = 1.02E+11 y) decays by electron capture or beta emission, unleashing gamma rays in either branch.  A ~50-g specimen of the metal (inset, left) racked up 7.2 counts / sec above background into a 2″ NaI:Tl detector.  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.  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).  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.

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More radioactive vacuum tubes. At right are three similar radar TR switches and their packaging (left to right: Bomac JAN-CBNQ-5883 from 1961 originally containing 0.3 µCi of Co-60; a Westinghouse 1B37 from 1952 containing several µCi or Ra-226; a GE 1B35 containing a small amount of Co-60.  At left, a spark gap (in hand) originally with 5 µCi of Cs-137 and a dual TR switch originally containing less than 0.7 µCi of Co-60.

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Ionization smoke detectors contain an alpha emitter, typically Am-241.  The left-most pic shows industrial smoke detectors from ca. 1960, each containing a total of 80 microcuries of Am-241.  These detectors measured the current imbalance between an exposed “sense chamber” and a sealed “reference chamber,” both of which contained alpha sources.  In front of the detectors are examples of their sense-chamber sources, which hold the greater amount of activity (~60 microcuries).  Left is a Pyrotronics F5-B4 with its annular source holder bearing six thin sealed sources; at right is an F3/5A and its pedestal source, containing a single foil covered by a screw-adjustable bonnet.  More modern detectors are shown in the upper-right image: At left is a Simplex 2098-9508 with 4.5 µCi of Am-241, manufactured in 1980, and at right a run-of-the-mill modern detector with the typical  1-µCi source.  The lower right photo shows a Ra-226 foil source from a batch of smoke detectors, make unknown, that was intercepted on its way into a Pennsylvania junkyard.  Approximate activity is 1 microcurie.

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Tritium glow-in-the-dark devices include emergency exit signage and the button at right.  Self-luminous exit signs are undoubtedly the most radioactive items in peoples’ everyday experience, but few probably realize it.   They can contain up to 20 curies of H-3 (tritium) gas in the glowing phosphor-lined tubes, as does the example shown here.  They are regulated under a General License by the Nuclear Regulatory Commission (see yellow sticker in right image).  Though initially costly, these self-powered signs easily deliver value over the life of a building by eliminating the need to conduct tests and change light bulbs.  Numerous outlets sell them on the Internet; they can also frequently be found at bargain prices on eBay (when the NRC isn’t looking).   The lower pic shows an old luminous button that originally contained 0.1 Ci of tritium.  This item replaced more hazardous predecessors containing radium.   Common consumer goods containing tritium today include “Traser” keychain lights (technically illegal in the USA as a “frivolous use” of radioactive material) and Trijicon gun sights.

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Kodak 8-mm film projector (left) and camera (right) with radioactive thorium lenses. High refractive index and low dispersion justified the use of thoria in optical glass formulations.  The film projector’s 22-mm, f/1.0 Projection Ektar lens clocks in at 1200 CPM on contact with a 2″ pancake GM tube, while the camera’s lens only reads about 250 CPM.

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Radium postcard, ca. 1930, from Luther Gable quack outfit. Ah, the good old days when you could just send loose radioactive contamination through the freaking mail! This postcard bearing a dollop of glow-in-the-dark radium paint (11,000 CPM on a 2″ pancake GM tube) promoted Dr. Luther Gable, the man responsible for the notorious Gable Ionic Charger.  A number of these cards were found in a collection of magician’s tricks.

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The “Becquerel Chemicals” educational kit manufactured by Damon contains six small plastic boxes labeled A through F.  The contents of three are yellow powders, the contents of the other three are white crystals.  Students were intended to exploit physical and chemical properties—including radioactivity—to identify these unknowns from a list consisting of uranyl sulfate, sodium sulfate, uranyl nitrate, sodium nitrate, thorium nitrate, and sulfur.

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Winter Trip to North Anna Nuclear Power Plant

May 13, 2010

Last December I had an opportunity to tour the North Anna Nuclear Power Plant with a few friends, thanks to the generosity of Michael Stuart, a nuclear training instructor at Dominion.  He took the day off to show the four of us around.  I brought along a sensitive BGO scintillation detector to check for gamma rays, but nothing above background is apparent at this spot.  We’re standing in front of the once-through cooling water discharge channel, where billions of watts of waste heat—enough power for several million homes—are carried off from the plant’s condensers into Lake Anna.  It’s hard to fathom from the appearance of that placid stream, but only about half as much energy leaves over the electrical transmission lines.  In any power station that uses heat to do work, Carnot’s Theorem fundamentally limits the efficiency of the process.

This control room is the scene of high drama and nasty surprises on most days. And just look at those yahoos at the controls!  No worries though—we’re actually in the simulator, where plant personnel come to take their NRC qualification exams  and practice reacting to accident scenarios they’ll probably never confront on the job.    The instruments may be fake, but for the operators being tested, the (employment-related) consequences of a single slip-up in here can be very real.

The first photo shows the main bench from the direction of the SRO’s desk.  On the far side are the reactor controls, followed by reactor cooling system controls, feedwater and steam controls, and finally the turbogenerator controls at the near side.

Though it’s not possible to replicate the ground-shaking, pants-crapping thunder of a large-break LOCA a couple hundred feet distant in containment, for instance, surprising fidelity does seem to attend many simulated responses.  Room lights go out when you remove the unit’s sources of electricity—disconnect offsite power and shut down the backup Diesel generators that fire up in response (controls for an emergency Diesel generator can be seen in the second photo).  Meter needles surge upward on area radiation monitors as primary coolant blows down in a simulated accident.  The turbine tachometer slows imperceptably during the first few minutes following a trip, mimicking the real machine’s enormous inertia.

We stopped by (actually, we went inside) this coolant chemistry sampling station beneath the turbine deck, where I foraged for radioactivity with the scintillation detector.  In 1987, a steam generator tube rupture occurred at North Anna 1 that led to radioactive primary coolant entering the secondary side.  We didn’t observe any noticeable radioactivity in the sample line leading to the affected secondary circuit, however.  The highest readings  (~100 times background) on my scintillator came from the Unit 1 refueling water storage tank (RWST), a large outdoor reservoir of borated water that covers the core during refueling and can also be used as an emergency coolant supply.

Here are a couple photos from the visitor center. Our tour guide, Michael Stuart, stands next to an exhibit illustrating the size and strength of a containment building’s walls.  At right is a model of GE’s ESBWR power plant design.  In 2007, Dominion received an Early Site Permit for siting a third nuclear unit at the North Anna, and applied for a Combined Construction and Operating License (COL) to build an ESBWR.  More recent news indicates that Dominion now intends to build an APWR designed by Mitsubishi.

Thanks to Michael Stuart for all photos.

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Virginia Uranium

May 2, 2010

This undulating farmland is situated about 20 miles north of Danville, Virginia (best known as the last Confederate capital).  From the surface, it could be anywhere in rural Southside Virginia: cattle graze in pastures surrounded by pine forest, and stately homes—some more than two hundred years old and occupied by descendants of the settlers who built them—stake out the high ground.  What’s so exciting about this particular piece of land is what lies beneath the surface: uranium!  And this is not just your minor pegmatite outcropping or localized radioactive anomaly.  With an estimated 110 million pounds of U3O8 reserves  (at a cutoff grade of 0.025%),  it’s considered the largest uranium deposit in the United States.

The Coles Hill Uranium Deposit, as it is known, contains resources currently worth billions of dollars.  That’s a lot of money.  So naturally, there is a commercial venture aiming to profitably extract the uranium.  Virginia Uranium, Inc. is owned mostly by the families under whose land the deposit is located.  Last January, Chief Geologist Joe Aylor (second from right) was kind enough to show us core samples and discuss the geology of the deposit at the firm’s office in Chatham before taking us out to an exposure of the radioactive ore along Coles Hill Road.

The 500-million-year-old Leatherwood Granite harbors the uranium at Coles Hill.  Specific uranium minerals are reported to be poorly-soluble phosphates, e.g. barium uranyl phosphate; the mineralization is of epigenetic origin—perhaps hydrothermal activity or  transport out of newer Triassic sediments.  In any case, our scintillation detectors were pleasantly excited by Dr. Aylor’s cores, and we couldn’t wait to hit the field to collect our very own specimens.

Here we are, atop America’s largest uranium deposit! We parked our cars in a spot where the scintillators indicated an exposure of the radioactive orebody, walking distance from Mr. Coles’s farm (see below).  Ordinary rockhounding is virtually impossible in the snow, but snow does not stop gamma rays.

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Richard Hull (left) excavates the berm beside the freshly-bladed road for a spicy chunk of rock.  At right is Richard’s bagful of  radioactive granite chunks, all located with his trusty TSA plastic scintillator.  These would be sparkling, gleaming things if only we could see gamma radiation.  But since we can’t, the ore appears mundane and unappealing, clad as it is in a tenacious layer of pasty red clay.

The hottest pieces of radioactive saprolite I collected read about 5000 CPM on a Ludlum 44-9 pancake GM tube.  This is respectable to be sure, but it doesn’t hold a candle to the more concentrated ore that can be found near Moab, Utah.  Richard Hull pulverized some average ore collected at Coles Hill and compared the gamma radiation countrate with that from samples in a calibrated ore grade test kit.  He arrived at an equivalent concentration of 0.253% U3O8.  Richard also noted UV fluorescence along fractures in the rock.

This is the Coles Hill farmhouse, just north of where we found our specimens.  The Coles family has lived on this land since 1785.  If uranium mining goes forward, Walter Coles says he’ll stick around to watch, and any mining will leaving the historic home intact.  But the big question of whether mining will occur is unresolved; Virginia has had a moratorium on uranium mining since 1981.  Coles Hill has become a focal point for contention over the moratorium, as well as the broader nuclear energy debate.  Virginia Uranium claims the positive impacts of mining will include the creation of 300-500 new jobs and an annual gross revenue of $300 million, while providing a valuable domestic energy source (most uranium for nuclear fuel is currently imported).  In 2008, then-presidential-candidate Barack Obama offered a cautious endorsement of sorts: “Virginia has the potential to be a national leader in uranium mining, and development of uranium resources in Pittsylvania County could create hundreds of jobs in that part of the state.”  Opponents, such as the Southern Environmental Law Center, cite the threat of water pollution, the industry’s poor environmental legacy in states where mining has occurred, and the high population density of Virginia as reasons to continue the moratorium.

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