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The 4n+3 chain of uranium-235 is commonly called the "actinium series" or "actinium cascade". Beginning with the naturally-occurring isotope uranium-235, this decay series includes the following elements: actinium, astatine, bismuth, francium, lead, polonium, protactinium, radium, radon, thallium, and thorium. All are present, at least ...
Actinium-225 (225 Ac, Ac-225) is an isotope of actinium. It undergoes alpha decay to francium-221 with a half-life of 10 days, and is an intermediate decay product in the neptunium series (the decay chain starting at 237 Np). Except for minuscule quantities arising from this decay chain in nature, 225 Ac is entirely synthetic.
The actinium isotope 227 Ac is a transient member of the uranium-actinium series decay chain, which begins with the parent isotope 235 U (or 239 Pu) and ends with the stable lead isotope 207 Pb. The isotope 228 Ac is a transient member of the thorium series decay chain, which begins with the parent isotope 232 Th and ends with the stable lead ...
[12] [13] [14] Actinium-225 undergoes a series of three alpha decays – via the short-lived francium-221 and astatine-217 – to 213 Bi, which itself is used as an alpha source. [15] Another benefit is that the decay chain of 225 Ac ends in the nuclide 209 Bi, [note 1] which has a considerably shorter biological half-life than lead.
The decay chain of actinium. Alpha decay shifts two elements down; beta decay shifts one element up.. Soddy and Kasimir Fajans independently observed in 1913 that alpha decay caused atoms to shift down two places in the periodic table, while the loss of two beta particles restored it to its original position.
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In nuclear reactors, it is one of the few long-lived radioactive actinides produced as a byproduct of the projected thorium fuel cycle, as a result of (n,2n) reactions where a fast neutron removes a neutron from 232 Th or 232 U, and can also be destroyed by neutron capture, though the cross section for this reaction is also low.
Lead (82 Pb) has four observationally stable isotopes: 204 Pb, 206 Pb, 207 Pb, 208 Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide.The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series (or radium series), the actinium series, and the thorium series, respectively; a fourth decay chain, the neptunium series ...