Keywords: response time, temperature sensors, plunge test, estimation tests, biot modulus, LCSR, loop current step response, nuclear power plants, NPP, RTDs, resistance temperature detectors, thermal conductivity, heat transfer coefficient, Rohsenow and Choi correlation, Perkins and Leppert correlation, nuclear energy, nuclear reactors, reactor design
Accuracy in temperature sensor response time estimation for new nuclear reactor designs
One method for measuring the response time of temperature sensors, the plunge test, verifies that the sensor has a suitable response time in the laboratory before installation. However, plunge test results cannot be extrapolated to the response time in an operating plant because response time is affected by multiple factors such as the ratio of internal heat-transfer resistance to the surface heat-transfer resistance, or Biot Modulus. The estimation method presented here can be used to extrapolate laboratory response-time measurements to determine sensor response time in another medium, in different test conditions, or in actual applications such as a nuclear power plant. However, experiments conducted at Oak Ridge National Laboratory have confirmed that the effect of temperature on sensor response time cannot be estimated confidently in an operating environment. Therefore, the loop current step response (LCSR) method was developed to measure the actual in-service response time of nuclear plant temperature sensors.