Radiative neutron capture.
A type of nuclear reaction in which an incoming particle (typically a neutron) is absorbed by the nucleus of an atom. In neutron radiative capture, the mass number of the atom is increased by one. The excess energy that the nucleus has gained from the capture is released by the emission of one or more photons. If the resulting isotope is unstable, it undergoes a beta decay in the time given by its half-life, during which the neutron in the nucleus is converted into a proton. This increases the atomic number by one. The process of neutron capture can produce heavier elements. Elements heavier than iron, which occur in the universe, were formed by neutron capture in the cores of stars.
In nuclear industry, the neutron capture process is used to absorb excess neutrons by control or shut-off rods. In breeder reactors, neutron capture produces fissile isotopes that are further used as nuclear fuel.
The production of tritium will be important for harnessing thermonuclear fusion on Earth. The plan is to produce it in tritium breeders, where tritium will be created via neutron capture in lithium atoms.