Introduction

12.32. The purpose of the engineered safety features is to prevent or limit the escape of radioactivity to the environment in cases of a highly unlikely transient or accident that is too severe to be accommodated by the reactor protection system alone. The major engineered safety features are: (1) the emergency core-cooling system to supply water to the reactor core in the event of a loss-of-coolant accident, (2) the containment vessel (or structure) to provide a barrier to the escape to the environment of radioactivity that might be released from the reactor core, (3) the cleanup system for removing part of the radioactivity and heat that may be present in the containment atmosphere, and (4) hydrogen control to prevent for­mation of an explosive hydrogen-oxygen (air) mixture in the containment.