TABLE OF CONTENTS In-situ response-time testing is performed on RTDs and thermocouples in nuclear power plants for one or more of the following reasons:
To measure the sensor's "in-service" response time to meet technical specification requirements, regulatory regulations, or both.
To verify that plant sensors bottom out in their thermowells and to test for air gaps, dirt, and foreign objects in the thermowell.
To provide for predictive maintenance, incipient failure detection, and aging management and to establish objective schedules for replacing sensors.
To distinguish between sensor problems and cable or connector problems.
To diagnose sensor or process anomalies.
In almost all U.S.-made PWR plants, testing RTD response times is required and is performed on one or more RTD channels once every operating cycle. For thermocouples, response-time testing is not mandatory, but some plants perform the tests for one or more of the reasons just noted.
