Modeling of Subcritical PWR with Fixed Neutron Source Using MPACT

Neutron source assembly inserts are used in some light water reactors (LWRs) during low flux subcritical conditions to ensure the excore source range detectors are both operational and responding to core multiplication neutrons. These source range detectors are used for sensing any approaches to criticality, either by controlled assent or accidental reactivity insertion (i.e. boron dilution event or unintended control rod withdrawal).