Posts Tagged ‘scintillation’


Videos from my recent trip to Chernobyl

September 17, 2011

Two videos from my most recent radioactive scavenger hunt in Ukraine’s Chernobyl exclusion zone are now on YouTube.  One features a pinhead-sized piece of spent nuclear fuel (pictured at left) that was carefully excavated from under about six inches of soil with the aid of a CDV-700 Geiger counter probe, taken back to our hotel through Checkpoint Lelev (where the scintillation portal monitor was conveniently out of service), and analyzed using a scintillation detector and Marek Dolleiser’s “PRA” software—a clever MCA emulator that uses one’s computer audio device as a nuclear ADC.  Check it out (I recommend selecting the HD format at the bottom of the window):

The second video illustrates some environmental radiochemistry at work, namely the affinity of the beta emitter Sr-90 for the phosphate matrix of deer antlers.  In this video I show that although the gamma activity (i.e. Cs-137 activity) in a pair of shed antlers is no different than local background, the beta activity is much higher.  The reasons for Sr-90’s notoriety are tangibly apparent: a decades-long half life that keeps it cracklin’ long after the accident, and alkaline-earth chemistry that favors uptake in bone.


Scintillation Crystals and X-Rays

May 7, 2008

Here are a few photos of inorganic scintillators glowing from exposure to a ~ 300 R / hr x-ray field. These were all long digital exposures, 5-15 seconds, taken last year, and all had to be de-speckled extensively due to radiation noise on the camera CCD.

Bismuth germanate (BGO) crystals from a PET scanner. Lovely cyan glow, not particularly well-matched to photomultiplier tubes but gorgeous to the human eye. Dense, and a wicked photoabsorber of gamma rays, BGO is well-suited to portable homebrew scintillation detectors.

Barium fluoride, a material of choice for fast pulse-mode gamma detectors. Much of the light emission is in the ultraviolet, and to the eye the glow appears a deep purple color. Perhaps there’s a use for this in fast neutron detectors based on inelastic scattering on F-19?

Sodium iodide doped with thallium (NaI:Tl), the old standard for gamma spectrometry and high-class uranium prospecting. This 3″ x 1″ crystal is hermetically sealed because the NaI is hygroscopic. The rich blue glow resulting from exposure to a 60 microcurie radium source is literally bright enough to read by. Next to the x-ray machine, it shines like a spotlight!


Uranium Chemistry

February 20, 2008

Uranyl peroxide Uranium and its pure compounds are just not readily available to the amateur scientist, element collector, or student in 2008. So what is one to do? Make these materials oneself, of course. (At left is a quantity of home-baked yellowcake.)

This is the inaugural post in what will become a short series, detailing how uranium and various pure compounds can be refined from the brute earth to serve personal needs. There are differences between what is done in industrial mining / milling operations and what can be realistically accomplished in a typical American domicile. There are also differences in the raw materials that could be obtained back in the good old days when our favorite applied inorganic chemistry texts were written (“Borrow a gallon of fuming nitric acid and some glycerin from your science-teacher…”), versus what can be obtained in the paranoid, restrictive world of today. Thus, my approach to uranium chemistry emphasizes practical techniques and materials that are available to today’s home-dweller. The foregoing discussion assumes a decent background in chemistry and mature attention to safety.

Uranium chemicals

Uranium compounds that can be easily prepared at home are shown in this photo. In vials, left to right: uranyl oxide (UO3); uranyl peroxide (UO4·nH2O); triuranium octoxide, U3O8; sodium diuranate (Na2U2O7·6H2O); uranium tetrafluoride (UF4·2.5H2O); “sodium peruranate” in solution; uranyl chloride (UO2Cl2) in solution. In front is an electroplated layer of uranium dioxide (UO2). Click “more” below for content (I will upload it as time permits).

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