A STUDY ON AN ULTRASONIC THERMOMETRY SYSTEM FOR MEASURING VERY HIGH TEMPERATURES IN SEVERE ACCIDENT EXPERIMENTS

摘要

LAVA (Lower-plenum Arrested Vessel Attack) experiments have been performed using high temperature molten material to be relocated into a linearly scaled lower head vessel, in which temperature measuring is a very important factor. In this paper, the measure of very high temperatures includes out of reactor room temperature studies of ultrasonic thermometer design, high temperature investigations of probe materials, and the implementation of a high resolution signal processing system using the split spectrum processing technique based on PC software control. This system is composed of sensors, a transducer, ultrasonic instruments, and a PC control system. To match the sensors, a tungsten rod was inserted in the centerline of the transducer, and the measured temperature was converted into an ultrasonic delay time from the reflected signal at the notch fabricated by an electric beam. The two sensor's lengths are 500mm and 1000mm, and the two notches at 50 and 80mm from the end of the rods could be used to measure the axial temperature in a molten material pool heated to about 2000 °C.