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The half-life of thorium-232 (14 billion years) is more than three times the age of the Earth; thorium-232 therefore occurs in nature as a primordial nuclide.Other thorium isotopes occur in nature in much smaller quantities as intermediate products in the decay chains of uranium-238, uranium-235, and thorium-232.
Two radiometric dating methods involve thorium isotopes: uranium–thorium dating, based on the decay of 234 U to 230 Th, and ionium–thorium dating, which measures the ratio of 232 Th to 230 Th. [e] These rely on the fact that 232 Th is a primordial radioisotope, but 230 Th only occurs as an intermediate decay product in the decay chain of ...
Its decay chain is the thorium series, eventually ending in lead-208. The remainder of the chain is quick; the longest half-lives in it are 5.75 years for radium-228 and 1.91 years for thorium-228, with all other half-lives totaling less than 15 days. [55]
This diagram illustrates the four decay chains discussed in the text: thorium (4n, in blue), neptunium (4n+1, in pink), radium (4n+2, in red) and actinium (4n+3, in green). The four most common modes of radioactive decay are: alpha decay, beta decay, inverse beta decay (considered as both positron emission and electron capture), and isomeric ...
The thorium fuel cycle is a nuclear fuel cycle that uses an isotope of thorium, 232 Th, as the fertile material. In the reactor, 232 Th ... decay to become 233 Pa ...
A relatively short-range dating technique is based on the decay of uranium-234 into thorium-230, a substance with a half-life of about 80,000 years. It is accompanied by a sister process, in which uranium-235 decays into protactinium-231, which has a half-life of 32,760 years. [citation needed]
Monazite contains 2.5% thorium, allanite has 0.1 to 2% thorium and zircon can have up to 0.4% thorium. [2] Thorium-containing minerals occur on all continents. [3] [4] [5] Thorium is several times more abundant in Earth's crust than all isotopes of uranium combined and thorium-232 is several hundred times more abundant than uranium-235. [6]
Another channel involves neutron capture reaction on small amounts of thorium-230, which is a tiny fraction of natural thorium present due to the decay of uranium-238: 230 Th (n,γ) → 231 Th (β −) → 231 Pa (n,γ) → 232 Pa (β −) → 232 U. The decay chain of 232 U quickly yields strong gamma radiation emitters. Thallium-208 is the ...