This Section provides an overview of the important safety related systems of the plant. This includes the reactivity control systems, the plant radiation protection system and the instrumentation employed to monitor neutronic and radiological parameters. The largest and most extensive system protecting the plant personnel and the environment from radiation in the case of an accident, is the Accident Confinement System (ACS). Also very important are the Emergency Core Cooling System (ECCS), the ECCS ensures protection of the core from overheating if a loss-of-coolant accident occurs in the primary circuit. The water Purification and Cooling System (PCS) provides not only emergency core cooling, but also continuous purification of the primary circuit water from chemical and radioactive contaminants during normal operation. These important systems are described in more detail in the following Sections.