Burn-up credit is a safety approach that accounts for the reduction in the reactivity of configurations with spent nuclear fuel due to the change in their composition after irradiation.

Impact of Isotopic Inventory Changes due to Control Rod Insertions on Reactivity and the End Effect in PWR UO₂ Fuel Assemblies

Nuclide Composition and Neutron Multiplication Factor of a Boiling Water Reactor Spent Fuel Assembly for Burn-up Credit and Criticality Control of Damaged Nuclear Fuel

A criticality excursion (also referred to as a criticality accident) is the accidental production of a self-sustaining or divergent chain reaction of fissionable material. 

Criticality safety relates to accident prevention and protection from an uncontrolled nuclear fission chain reaction, or a criticality accident.

Criticality is the state of a nuclear reactor when there is a self-sustaining chain reaction of fissionable material. Criticality safety analysis relates to evaluation approaches in data and computat...

Criticality is the state of a nuclear reactor when there is a self-sustaining chain reaction of fissionable material. Criticality experiments are controlled tests using fissile materials, like pluton...