Abstract
Because of harsh radiated environmental conditions, it is necessary to use thermocouples (TCs) in the temperature instrumentation channels of a reactor coolant system (RCS) in an integrated pressurized water reactor vessel. Conventionally, resistance temperature detectors (RTDs) have been adopted for RCS temperature measurement.Therefore, we have conducted an analysis and review of instrumentation error factors in the measurement circuits of RTD and TC sensors to specify the influence on measurement accuracy for application of TCs instead of RTDs for RCS temperature instrumentation.From the review and analysis results, it is anticipated that a measurement accuracy deterioration would be an issue and that a drift range should be investigated for the anticipated operational temperature conditions.
Highlights
resistance temperature detectors (RTDs) are typically used for measuring reactor coolant system (RCS) temperature because an accurate and stable sensing is needed for calculating the thermal output power and regulating the reactor during a normal operation
If we narrow the full span of measurement range to be 250 ~ 350 °C in the signal conversion module to obtain a better accuracy for RCS temperature application, the accuracy limit will be approximately ±0.5 °C, considering other factors related to accuracy such as power supply effect, stability(drift) effect, etc
This paper addressed the issue of accuracy with regard to the use of K-type TCs for RCS temperature measurement in an integrated reactor
Summary
Resistance temperature detectors (RTDs) and K-type thermocouples (TCs) are the most common devices for measuring the temperature of fluid in nuclear power plants (NPPs). The effect of resistance of the lead wires is not negligible, even in the case where the distance between RTD sensors and instrumentation circuits is a couple of meters. In industrial RTD instrumentation systems, it is necessary to use a compensation method to remove this wire resistance effect for measuring the process temperature correctly. In the case of industrial RTD-based temperature instrumentation systems, it is necessary to use a technical solution for reducing or eliminating the effect of wire resistance change. Such a solution often requires the use of at least one extra lead wire from the sensor to the instrumentation electronics. An appropriate choice of cancellation method for wire resistance can ensure that any error due to a change in lead wire resistance will be negligible
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