Primordial Radionuclides

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Written and developed by Prof. Tor Bjørnstad (IFE/UiO) 

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Primordial radionuclides are left-over from when the world and the universe were created. They are typically long-lived, with half-lives often on the order of hundreds of millions of years. Radionuclides that exist for more than 30 half-lives are not measurable. The progeny or decay products of the long-lived radionuclides are also under this heading. Here is some basic information on some common primordial radionuclides:

Primordial nuclides
Natural Activity
Uranium 235
7.04 x 108 a
0.72% of all natural uranium
Uranium 238
4.47 x 109 a
99.2745% of all natural uranium; 0.5 to 4.7 ppm total uranium in the common rock types
Thorium 232
1.41 x 1010 a
1.6 to 20 ppm in the common rock types with a crustal average of 10.7 ppm
Radium 226
1.60 x 103 a
0.42 pCi/g (16 Bq/kg) in limestone and 1.3 pCi/g (48 Bq/kg) in igneous rock
Radon 222
3.82 days
Noble Gas; annual average outdoor air concentrations range in the US from 0.016 pCi/L (0.6 Bq/m3) to 0.75 pCi/L (28 Bq/m3)
Potassium 40
1.28 x 109 a
Soil - 1-30 pCi/g (0.037-1.1 Bq/g)

Some nuclides like 232Th have several members in its decay chain. You can roughly follow the chain starting with 232Th:

232Th[math]\rightarrow[/math]228Ra[math]\rightarrow[/math] 228Ac[math]\rightarrow[/math]228Th[math]\rightarrow[/math]224Ra[math]\rightarrow[/math]220Rn[math]\rightarrow[/math]216Po[math]\rightarrow[/math]212Pb[math]\rightarrow[/math]212Bi[math]\rightarrow[/math]212Po[math]\rightarrow[/math]208Pb(stable)

or starting with 238U:

Some other primordial radionuclides are 50V, 87Rb, 113Cd, 115In, 123Te, 138La, 142Ce, 144Nd, 147Sm, 152Gd, 174Hf, 176Lu, 187Re, 190Pt, 192Pt, 209Bi.