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Uranium-235 (235 U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nature as a primordial nuclide. Uranium-235 has a half-life of 703.8 million years.
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 ...
Uranium-235 makes up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a fission chain reaction. It is the only fissile isotope that is a primordial nuclide or found in significant quantity in nature. Uranium-235 has a half-life of 703.8 million years.
Uranium-235 is the only naturally occurring fissile element in non-trace amounts, which makes it widely used in nuclear power plants and nuclear weapons. However, because of the low abundance of uranium-235 in natural uranium (which is, overwhelmingly, mostly uranium-238), uranium needs to undergo enrichment so
The table in the next section ("Ordered by yield") gives yields for notable radioactive (with half-lives greater than one year, plus iodine-131) fission products, and (the few most absorptive) neutron poison fission products, from thermal neutron fission of U-235 (typical of nuclear power reactors), computed from [permanent dead link ].
The decay chain from lead-212 down to lead-208, showing the intermediate decay products. In this example: 234 Th, 234m Pa,..., 206 Pb are the decay products of 238 U. 234 Th is the daughter of the parent 238 U. 234m Pa (234 metastable) is the granddaughter of 238 U. These might also be referred to as the daughter products of 238 U. [1]
For natural uranium fuel, fissile component starts at 0.7% 235 U concentration in natural uranium. At discharge, total fissile component is still 0.5% (0.2% 235 U, 0.3% fissile 239 Pu, 241 Pu ). Fuel is discharged not because fissile material is fully used-up, but because the neutron-absorbing fission products have built up and the fuel becomes ...
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic process.