The ultrasonic wave thermometer sodium test. 1. A summary of test results of the externally mounted ultrasonic transducer for pipe-flow

Based on the temperature dependence of the velocity of sound in sodium, an ultrasonic thermometer that measures the temperature of sodium non-intrusively is being developed. The principle of the device is based on the propagation time of an acoustic pulse wave, and the back calculation of the sodium temperature. As the part of the development a test was actually carried out in sodium pipe-flow in order to evaluate various aspects of realizing the ultrasonic wave thermometer. The results and conclusions to date are as follows: 1) Within the present test range, the ultrasonic wave thermometer appears relatively insensitive to flow velocity of sodium, pressure of the cover gas and the impurity concentration in sodium. The calculated error of the measured thermometry was in the experiment about 1degC, a smaller value than the expected 2.5degC of the system. 2) The ultrasonic thermometer has only been used wherein the thermal expansion coefficient was known and with 200degC as the reference temperatures. For the entire temperature range tested the difference between this approach and a two-point calibration over a temperature range is only expected to be about 1degC. 3) By using the mean value of multiple ultrasonic wave transmit and receive measurements, a value whereby the ultrasonic propagation time was stabilized is obtained. 4) As acoustic coupling material between the ultrasonic transducer and piping, a copper plate was found to be more suitable than a specialized acoustic bonding material. A weight equivalent, area distributed force of 2.0 kg/mm2 was used to press the test copper plate to the pipe. A slightly smaller force appears more than sufficient as well. (J.P.N.)