Abstract
When light water reactor (LWR) is subject to a cold shutdown, it needs to be cooled with pure water or seawater to prevent the core melting. To precisely evaluate the cooling characteristics in the fuel assembly, a measurement method capable of installing to the fuel assembly structure and determining the temperature distribution with high temporal resolution, high spatial resolution, and in multidimension is required. Furthermore, it is more practical if applicable to a pressure range up to the rated pressure 16 MPa of a pressurized water reactor (PWR). In this study, we applied the principle of the wire-mesh sensor technology used in the void fraction measurement to the temperature measurement and developed a simulated fuel assembly (bundle) test loop with installing the temperature profile sensors. To investigate the measurement performance in the bundle test section, it was confirmed that a predetermined temperature calibration line with respect to time-average impedance was calculated and became a function of temperature. To evaluate the followability of measurement in a transient temperature change process, we fabricated a 16 × 16 wire-mesh sensor device and measured the hot-water jet-mixing process into the cold-water pool in real time and calculated the temperature profile from the temperature calibration line obtained in advance from each measurement point. In addition, the sensors applied to three-dimensional temperature distribution measurement of a complex flow field in the bundle structure. The axial and cross-sectional profiles of temperature were quantified in the forced flow field with nonboiling when the 5×5 bundle was heated by energization.
Highlights
To quantify the thermoreactive flow field for some industrial applications such as column, chemical, and nuclear reactors, high tempospatial measurements for temperature, pressure, phasic velocity, and void fraction are required
The differential pressure technique can measure with high-speed performance, the detected information is limited to only spatial averaged value
To confirm the measurement capabilities of time resolution performance and multidimensionality, two types of temperature measurement tests were demonstrated in this chapter with experimental apparatus of both nonflowing and flowing settings
Summary
To quantify the thermoreactive flow field for some industrial applications such as column, chemical, and nuclear reactors, high tempospatial measurements for temperature, pressure, phasic velocity, and void fraction are required. Wang et al measured the volumetric void fraction of a gas-liquid vertical flow with dynamic differential pressure and quantitatively estimated the determination error [1]. F. Chen et al applied an optical fiber probe to detect the averaged cross-sectional void fraction of a vertically rising two-phase flow in oil pipes [2] and M. Prasser et al compared the void-fraction measurement in a vertical pipe between an ultra-fast X-ray CT and a wire-mesh sensor [4], while S. The optical probe apparatus can access inner volumetric areas with high void fractions in which a highspeed camera would be unable to visualize, but the technique is limited to a point measurement. Prasser et al [6] provided an innovative technique measuring multidimensional void fraction and gasphase velocity at high time resolution, so-called “wire-mesh sensor” (WMS).
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