Isotope

Half Life

Polonium-215

0.0018 seconds

Uranium-238

4.5 billion years

Radium-226

1600 years

Cobalt-60

5.26 years

Iodine-131

8.07 days

Sodium-24

15 hours

Bismuth-212

60.5 seconds

Holmium-166

1200 years

Selenium-79

1130000 years

Samarium-147

106000000000 years

Indium-115

years

Carbon-14

5730 years

Uranium-233

159200 years

Rhenium-186m

200000 years

Technetium-99

211000 years

Krypton-81

229000 years

Uranium-234

245500 years

Chlorine-36

301000 years

Curium-248

340000 years

Bismuth-208

368000 years

Plutonium-242

373300 years

Aluminum-26

717000 years

Selenium-79

1130000 years

Iron-60

1500000 years