View source for Radionuclides of natural origin

Radionuclides that occur naturally on Earth. They include <sup>3</sup>H, <sup>7</sup>Be, <sup>14</sup>C, <sup>40</sup>K and radionuclides in the decay chains of the primordial radionuclides. The primordial radionuclide decay chains are: the thorium series, headed by <sup>232</sup>Th, the most abundant of all naturally occurring radionuclides and constituted mainly by <sup>228</sup>Ra, <sup>228</sup>Ac, <sup>228</sup>Th, <sup>224</sup>Ra, <sup>220</sup>Rn, <sup>216</sup>Po, <sup>212</sup>Pb, <sup>212</sup>Bi, <sup>212</sup>Po, and <sup>208</sup>Tl; the uranium series, headed by <sup>238</sup>U and constituted mainly by <sup>234</sup>Th, <sup>234m</sup>Pa, <sup>234</sup>U, <sup>230</sup>Th, <sup>226</sup>Ra, <sup>222</sup>Rn, <sup>218</sup>Po, <sup>214</sup>Pb, <sup>214</sup>Bi, <sup>214</sup>Po, <sup>210</sup>Pb, <sup>210</sup>Bi, and <sup>210</sup>Po; and, less important in the context of this term, the actinium series, headed by <sup>235</sup>U and constituted mainly by <sup>231</sup>Th, <sup>231</sup>Pa, <sup>227</sup>Ac, <sup>227</sup>Th, <sup>223</sup>Fr, <sup>223</sup>Ra, <sup>219</sup>Rn, <sup>215</sup>Po, <sup>211</sup>Pb, <sup>211</sup>Bi, and <sup>207</sup>Tl.

''ICRP Glossary entry -  June 2019''


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