TABLE OF CONTENTS Dynamic response measurements are made in nuclear power plants for one or more of at least four reasons:
comply with a plant's technical specifications and/or regulatory requirements for response time testing;
troubleshooting to identify sensor or sensing line problems including blockages, voids, and leaks;
manage component aging, estimate residual life, and assess reliability of pressure sensing systems; or
establish objective sensor replacement schedules.
The dynamic response of nuclear power plant pressure sensors and their associated sensing lines is measured using the noise analysis technique as described in this chapter. This technique can also be used to evaluate the dynamic characteristics of RTDs and thermocouples.
The noise analysis technique is based on analyzing the natural fluctuations that exist at the output of pressure transmitters while the plant is operating. These fluctuations (noise) are caused by turbulence that is induced by the flow of water in the system, by vibration, and by other naturally occurring phenomena.
The noise analysis technique provides a passive method for the dynamic testing of pressure sensing systems. It yields the response time for both a pressure transmitter and its sensing lines in the same test. The tests can be performed remotely while the plant is operating, do not require transmitters to be removed from service, do not interfere with plant operation, and can be performed on several transmitters simultaneously. The test involves three steps data acquisition, data qualification, and data analysis which are described in the following paragraphs.
