Assessment of Wave-Guided Ultrasonic Transducer System for Erosion-Corrosion Detection in Nuclear Applications
Authors: Aravelli Aparna , McDaniel Dwayne , Davila Clarice 
Published: December 2018

Abstract
Storage tanks and pipelines are used at nuclear waste sites across the Department of Energy (DOE) complex to store and transfer nuclear wastes. One of the significant aspects in such sites is monitoring the structural integrity of the waste transfer pipelines and the storage tanks. Literature indicates that the industry standard method of thickness measurements using ultrasonic sensors is mainly through manual inspections. As such, this procedure is expensive and exhaustive for nuclear applications. Hence, in this research, the authors assess a wave guided ultrasonic sensor system for erosion-corrosion (thickness change) detection in waste transfer pipelines at Hanford nuclear waste site. This ultrasonic transducer (UT) sensor system (from Permasense, a UK based manufacturer [2]) has the advantage of real-time remote monitoring. It is an integrated wireless sensor network system which uses a patented technology for the acoustic wave propagation and has proven applications in the oil and gas industries [3]. This UT sensor system meets the requirement of providing the actual thickness measurement in pipes, is capable for 2 inch pipes and elbows, and is customized for mounting with a mechanical clamping system. The sensors are also capable of operating at high temperatures up to 600°C (1100°F). This is due to their patented waveguide technology that holds the sensor head (containing ultrasonic transducers, electronics, and battery) away from the hot metal surface. The sensor's measurements are transmitted wirelessly back to a gateway (wireless access point) mounted near the main unit. Since there is no cost associated with measurement acquisition or measurement retrieval, the frequency of measurement can be configured to be as frequent as every 15 minutes. Connection of the gateway to the operator's existing information technology infrastructure allows the data to be viewed from personnel desks. Sensor battery life of up to 10 years allows continuous data delivery between turnarounds without access to a sensor's physical location. The sensor model chosen for the present research (testing and validation) is the WT 210 series [2]. It consists of the 304 stainless steel wave guides, sensor head, antenna, battery and a stabilizer. In addition there is a built in thermocouple probe to monitor the pipe surface temperature which also allows the wall thickness measurement to be temperature compensated when required. The sensors communicate using a customized wireless protocol, creating a self-forming and self-managing wireless mesh, which delivers continuous wall thickness measurements of the highest integrity and accuracy directly to the end user. Scope of the present research includes the initial verification and validation of the Permasense Guided Wave sensor system as a potential erosion/corrosion detection system for carbon steel pipelines under static conditions. The real-time erosion/corrosion detection is also investigated by measuring the thinning of the pipe sections by circulating simulants and continuous monitoring. This is achieved by passing abrasive solutions through an in-house designed pipe loop system. The loop has been designed to replicate the sections and carbon steel pipe material similar to the existing system at Hanford site. Varying concentrations of sand and water mixture is used as an eroding agent [5]. The erosion experiments are conducted for several months and the results obtained provide realistic wear rates on 2 inch and 3 inch carbon steel pipes with straight sections and elbows using the Permasense UT sensor system. Thus, the present research delivers solutions for sensor evaluations and conducts bench scale testing followed by data acquisition and analysis for corrosion and erosion assessment. This assessment of the UT sensor system will be useful for monitoring the real-time thinning of the waste transfer pipelines and to deliver more realistic estimates of the remaining useful life of the components and incorporate those estimates into future design/testing plans across the nuclear waste sites.