TABLE OF CONTENTS Signals from sensors in nuclear power plants can be monitored while the plant is operating to verify the performance of the sensors and associated instrumentation and to diagnose process anomalies. This introduction provides some examples of this procedure. It also presents a review of computer-aided maintenance technologies as well as active methods for employing test signals to measure sensor performance and to identify problems in their cables and connectors. The remainder of the book will focus on nuclear plant temperature and pressure sensor operation and maintenance as well as active and passive techniques for remotely testing these sensors' performance after they are installed in an operating plant.
Fig. 1.1 illustrates a loop of a pressurized water reactor (PWR), which will be used as the reference plant throughout this book. The figure shows the reactor vessel, a primary coolant loop, a steam generator, a pressurizer, and the secondary loop. Typically, a PWR plant consists of two to four of these loops, with the exception of some Russian PWR models, which have six loops. The sensors typically found in a PWR plant are indicated in Fig. 1.1 by small circles. More specifically, the figure shows neutron flux detectors on the outside of the reactor vessel, core-exit thermocouples on the top of the core inside the reactor vessel, narrow-range and wide-range resistance temperature detectors (RTDs) in the hot-leg and cold-leg pipes, and pressure, level, and flow transmitters in the primary and secondary loops.
