United States Nuclear Regulatory Commission - Protecting People and the Environment
Home > NRC Library > Basic References > Glossary > Shutdown margin

Shutdown margin

The instantaneous amount of reactivity by which the reactor is subcritical or would be subcritical from its present condition assuming all full-length rod cluster assemblies (shutdown and control) are fully inserted except for the single rod cluster assembly of highest reactivity worth that is assumed to be fully withdrawn.

Page Last Reviewed/Updated Wednesday, April 02, 2014