Noun
delayed neutron (plural delayed neutrons)
(nuclear physics) A neutron produced as a result of nuclear fission which is emitted upon the radioactive decay of a fission product nucleus seconds to minutes later, rather than at the time of the initial fission event. Less than 2% of fission neutrons are delayed neutrons (the exact proportion depends on the nuclide being fissioned).
Several of the heavier bromine isotopes from fission are delayed neutron emitters, important to the controllability of a nuclear reactor. Source: Internet
At the first level of control in all nuclear reactors, a process of delayed neutron emission by a number of neutron-rich fission isotopes is an important physical process. Source: Internet