Printer Friendly PDF

Thallium 204

Chemical Symbol: Tl-204 Half-Life: 3.783 years
Atomic Number: 81 Decay Constant: 0.183227 years-1
Mass Number: 204 (123 neutrons) Decay Mode: Beta
U.S. NRC Exempt Quantity Limit: 10 μCi (370 kBq) IAEA Exempt Quantity Limit: 0.27 μCi (10 kBq)

Betas From Tl-204

End-Point Energy (keV)

Intensity (%)




  • Health Physics and Radiological Health, 4th Edition by Thomas E. Johnson PhD, Brian K. Birky Ph.D.
  • National Nuclear Data Center database –
  • Table of Radioactive Isotopes (ToRI) database – http:/

Prepared by:

Spectrum Techniques, LLC.