Isotopes of uranium

Isotopes of uranium are atoms with 92 protons and different numbers of neutrons. Their mass numbers and nuclear properties vary, affecting their stability, decay, and uses.

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Atomic number: The number of protons in an atom’s nucleus, which determines its chemical element. Every uranium isotope has atomic number 92, regardless of its neutron count.
Alpha decay: Radioactive decay in which a nucleus emits a helium-4 nucleus, reducing its proton number by two and mass number by four. Uranium isotopes commonly decay by emitting alpha particles.
Uranium fuel: Nuclear fuel containing uranium, commonly with uranium-235 as its principal fissile isotope. Fuel performance depends on the proportions and transformations of uranium isotopes.
Natural uranium: Uranium occurring in nature, composed chiefly of uranium-238 with smaller amounts of uranium-235 and trace uranium-234. Its characteristic isotope mixture is the baseline for enrichment and geological measurements.
Isotopic abundance: The relative proportion of each isotope of an element in a sample or natural reservoir. Abundance distinguishes natural uranium from enriched and depleted material.
Mass number: The total number of protons and neutrons in an atomic nucleus. Uranium isotope names distinguish nuclei by their mass numbers.
Uranium-238 decay chain: The sequence of radioactive transformations beginning with uranium-238 and ending at stable lead-206. It shows the successive products of uranium-238’s long radioactive history.
Uranium-235: A fissile uranium isotope containing 92 protons and 143 neutrons, with a half-life of about 704 million years. Its neutron-induced fission makes it central to many reactor fuels.
Uranium-234: A radioactive uranium isotope containing 92 protons and 142 neutrons, with a half-life of about 245,500 years. It forms within the uranium-238 decay series and is present in natural uranium.
Uranium enrichment: The industrial increase of uranium-235’s proportion relative to uranium-238. It deliberately shifts the isotope proportions found in natural uranium.