This video attempts to verify the authenticity of two purported high-purity radioactive metal samples—uranium and thorium—using gamma spectroscopy. The primary difficulty is that purified U-238 and Th-232 are weak gamma emitters, and their characteristic decay chain signatures are absent until equilibrium is reached over thousands of years. Using a sensitive Radiacode 110 scintillation detector, the analysis successfully identifies the uranium sample by detecting early decay products like Protactinium-234m, consistent with recently purified depleted uranium. The test on the small, 35mg thorium sample is inconclusive, yielding no identifiable spectrum. However, the spectrometer easily confirms the presence of thorium in consumer products (a gas lamp mantle and thoriated welding rods) where the element is in equilibrium with its gamma-emitting daughters.
Verifying Radioactive Metals with Gamma Spectroscopy
00:00:11 The Challenge of Identification: The video investigates whether samples sold as pure uranium and thorium are authentic. A standard Geiger counter is useless for this, as it only measures radioactivity levels, not the specific isotope.
00:01:16 The Right Tool for the Job: A Radiacode 110 gamma-ray spectrometer is used due to its high sensitivity, which is necessary for detecting weak signals from small, purified samples.
00:03:25 Uranium Sample Verified: After a 4-hour scan, a 0.5g sample of depleted uranium shows distinct photopeaks around 766 keV and 1001 keV. These are identified as fingerprints of Protactinium-234m, an early daughter in the U-238 decay chain. The absence of later decay products supports the claim that the sample is recently purified uranium.
00:05:07 Thorium Sample Inconclusive: A 6-hour scan of a much smaller (est. 35mg) and less active thorium sample yields no clear gamma spectrum. The result is ambiguous; it neither confirms nor denies the sample's authenticity, likely due to the sample's small size and purity.
00:07:08 Successful Thorium Detection in Consumer Goods: In contrast, thoriated items like a gas lamp mantle and 4% thoriated tungsten welding rods produce a clear thorium spectrum in just one hour. These samples contain thorium in equilibrium with its gamma-emitting decay products (Actinium-228, Thallium-208), making detection straightforward.
00:07:35 Watch Out for Fakes: The creator notes that a previous purchase of 2% thoriated welding rods from an eBay seller was fraudulent and contained no thorium.