Thallium-204 10
Thorium (natural)c/ 100
Thulium-170 .10
Thulium-171 10
Tin-113 10
Tin-125 10
Tungsten-181 10
Tungsten-185 10
Tungsten-187 100
Uranium (natural)d/ 100
Uranium-233 0.01
Uranium-234 0.01
Uranium-235 0.01
Vanadium-48 10
Xenon-131m 1,000
Xenon-133 100
Xenon-135 100
Ytterbium-175 100
Yttrium-90 10
Yttrium-91 10
Yttrium-92 100
Yttrium-93 100
Zinc-65 10
Zinc- 69m 100
Zinc-69 1,000
Zirconium-93 10
Zirconium-95 10
Zirconium-97 10
Any alpha emitting radionuclide not listed above or
mixtures of alpha emitters of unknown composition 0.01
Any radionuclide other than alpha emitting radionuclides,
not listed above or mixtures of beta emitters of unknown
composition 0.1
c/ Based on alpha disintegration rate of Th-232, Th-230 and their daughter products.
d/ Based on alpha disintegration rate of U-238, U-234, and U-235
Note: Where there is involved a combination of isotopes in known amounts, the limit for the combination should be derived as follows: Determine, for each isotope in the combination, the ratio between the quantity present in the combination and the limit otherwise established for the specific isotope when not in combination. The sum of the ratios for all the isotopes in the combination may not exceed “1” — that is, unity.
