The flow field or multidimensional velocity distribution of the coolant in fuel rod bundles of the reactor core in pressurized water reactors (PWRs) is an important parameter that is revealed through experimental investigations. This paper presents the two-dimensional (2D) velocity profile measurement using a two-element ultrasonic transducer with both elements acting as a transceiver. The size of the transducer is minimized for compactness, leading to a narrow sound field appropriate for applications in fuel rod bundle flow. Furthermore, the transducer’s sound pressure is evaluated via simulations and experimental measurements. In order to confirm the ability of the ultrasonic velocity profiler (UVP) with a two-element transducer, the experimental measurement is conducted in turbulent horizontal pipe flow. The 2D velocity vector profile is obtained, and then the measurement in swirling flow is conducted. The 2D velocity profile in an axial and radial plane is obtained utilizing the UVP measurement. Lastly, the ability of the UVP to derive the 2D velocity profile in the narrow area of the rod bundles is demonstrated. 

http://www.scirp.org/journal/PaperDownload.aspx?paperID=114584

Ultrasonic Measurement of Two-Dimensional Liquid Velocity Profile Using Two-Element Transducer

This study describes an ultrasonic velocity profiler that uses a new ultrasonic array transducer with unique 5-element configuration, with all five elements acting as transmitters and four elements as receivers. The receivers are designed to reduce the amount of uncertainty. As the fluid moves through this setup, four Doppler frequencies are obtained. The multi-dimensional velocity information along the measurement line can be reconstructed. The transducer has a compact geometry suitable for a wide range of applications, including narrow flow areas. The transducer’s basic frequency and sound pressure are selected and evaluated to be compatible with the application. First, to confirm the measurement ability, the measurement of the developed system in two-dimensional flow is validated by comparing it to the theoretical data. The uncertainty of measurement was within 15%. Second, the three-dimensional measurement in turbulent and swirling flow is proved experimentally to check the applicability of the proposed technique.

/pdf/three-dimensional-velocity-distribution-measurement-using-143x27us.pdf

Three-Dimensional Velocity Distribution Measurement Using Ultrasonic Velocity Profiler with Developed Transducer

Ultrasonic velocity profiler placement for flow over cylinder based on determinant greedy line selection method

In Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the fuel debris formed in the Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) at Unit 1 - 3. To accelerate and decide further decommissioning steps of the FDNPP, it is crucial to obtain realistic information of the debris and localize contaminated water leakage from PCV. Due to high radiation and dark environment inside the PCV, investigating instruments and techniques should necessarily to meet specification of radiation resistance, waterproofness, dust resistance and so on. This study focuses on development of ultrasonic measurement system using a couple of sectorial array sensors to localize contaminated water leakage and visualize shape of object that repre- senting fuel debris, simultaneously. In this study, Total Focusing Method (TFM) and Ultrasonic Velocity Profiler (UVP) methods are considered to visualize object shape and flow pattern around it, respectively. To demonstrate applicability and reliability of developed measurement system with sectorial array sensors, a mock-up experiment result of simulated water leakage and fuel debris shape were discussed in this paper.

/pdf/development-of-measurement-system-for-flow-and-shape-using-3c9cpb1kh0.pdf

Development of Measurement System for Flow and Shape Using Array Ultrasonic Sensors

In the decommissioning of the Fukushima Daiichi Nuclear Power Plant (FDNPP), the Japanese government has drawn mid- and long-term roadmap towards 1F decommissioning. However, the decommissioning work of the three reactors has faced difficulties due to the lack of realistic information about the damaged cores such as distribution of fuel debris. Since the radiation levels inside the reactor buildings have been too high for human access, remote detection, which combines robot and measurement technique, is required. In this study, we proposed a remote controlling method. The experiment has been conducted remotely controlling the ultrasonic measurement. Finally, the experiment data and results are successfully obtained through remote control.

Zeliang Zhang

Papers

Development of Measurement System for Flow and Shape Using Array Ultrasonic Sensors

Telemetry System for 2D Flow Map using Ultrasonic Velocity Profiler