Uranium-235 (235U 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.
|Half-life (t1/2)||703800000 years|
|Isotope mass||235.0439299 Da|
|Excess energy||40914.062±1.970 keV|
|Binding energy||1783870.285±1.996 keV|
|Decay mode||Decay energy (MeV)|
|Isotopes of uranium |
Complete table of nuclides
Uranium-235 has a half-life of 703.8 million years. It was discovered in 1935 by Arthur Jeffrey Dempster. Its fission cross section for slow thermal neutrons is about 584.3±1 barns. For fast neutrons it is on the order of 1 barn. Most but not all neutron absorptions result in fission; a minority result in neutron capture forming uranium-236.