Primordial Radionuclides
Return to Naturally Occuring Radioactivity - NORM and TENORM
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 | |||
Nuclide |
Symbol |
Half-life |
Natural Activity |
Uranium 235 |
235U |
7.04 x 108 a |
0.72% of all natural uranium |
Uranium 238 |
238U |
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 |
232Th |
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 |
226Ra |
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 |
222Rn |
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 |
40K |
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
228Ra 228Ac 228Th 224Ra 220Rn 216Po 212Pb 212Bi 212Po 208Pb(stable)or starting with 238U:
238U 234Th 234mPa 234U 230Th 226Ra 222Rn 218Po 214Pb 214Bi 214Po 210Pb 210Bi 210Po 206Pb(stable)
Some other primordial radionuclides are 50V, 87Rb, 113Cd, 115In, 123Te, 138La, 142Ce, 144Nd, 147Sm, 152Gd, 174Hf, 176Lu, 187Re, 190Pt, 192Pt, 209Bi.