Uranium-235,  235U
Uranium metal highly enriched in uranium-235
Name, symbolUranium-235,235U
Nuclide data
Natural abundance0.75%
Half-life703,800,000 years
Parent isotopes235Pa
Decay products231Th
Isotope mass235.0439299 u
Excess energy40914.062 ± 1.970 keV
Binding energy1783870.285 ± 1.996 keV
Decay modes
Decay modeDecay energy (MeV)
Complete table of nuclides

Uranium-235 (235U) 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 fission chain reaction. It is the only fissile isotope with a primordial nuclide found in significant quantity in nature.

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 584.994 barns. For fast neutrons it is on the order of 1 barn.[1]Most but not all neutron absorptions result in fission; a minority result in neutron capture forming uranium-236.

Natural decay chain

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