Reactor Protection & Engineered Safety Feature Systems


Function

The Reactor Protection Systems are designed to shutdown the reactor and maintain it shutdown when needed. These systems are automatically actuated and may be manually actuated.

The Engineered Safety Feature Actuation Systems are designed to provide cooling for the reactor and to reduce the potential for offsite releases of radioactive materials. These systems are automatically actuated and may be manually actuated.

Terminology

Several terms that you may hear or see used are - Scram - Trip - Engineered Safety Feature Actuation - Containment Isolation - Anticipated Transient without Scram (ATWS) - Loss of Coolant Accident (LOCA). What does each of these terms mean?

Common Design Features of Reactor Protection and Engineered Safety Feature Actuation Systems

These systems have the following features:

In older plants, devices as relays and bistables are used. In newer plants, computerized equivalents may be used. The systems are designed to oerate if there is a loss of offsite power.

Parameters Sensed for Reactor Protection Systems (RPS)

Most plants use many of the diverse parameters listed below in their reactor protection systems. At specified setpoints, the reactor will shutdown by opening the circuit breakers that supply electrical power to control rods (or cause valves in the BWR hydraulic system to operate and accomplish the same purpose). The control rods will then insert. The circuitry is setup so that opening of any one circuit breaker will cause the rods to insert.

In the 1980's, plants in the United States were required to install diverse methods of shutting down the reactor to address the possibility of the anticipated transient without scram (ATWS) event. In the ATWS event, it is assumed the rods cannot insert. Other methods as chemical addition, steam generator heat removal, and pressure relief valve opening are provided.

Parameters Sensed for Engineered Safety Features Actuation Systems (ESFAS)

Functions provided by ESFAS include:

In some cases, depressurization of the reactor cooling system may be purposefully done:

Most plants use many of the diverse parameters listed below for ESF actuation:


Copyright 1996-2006.  The Virtual Nuclear Tourist. All rights reserved. Revised: February 6, 2006.