Source Influence for Focusing Potential of Guided Waves in Hollow Cylinders by Using a Circumferential Phased Array

2004 ◽  
Author(s):  
Li Zhang ◽  
Brian J. Gavigan ◽  
Joseph L. Rose
Keyword(s):  
Time Delays ◽  
Nuclear Power ◽  
Guided Waves ◽  
Phased Array ◽  
Angular Displacement ◽  
Excitation Source ◽  
Natural Gas Pipelines ◽  
Contour Plots ◽  
Array Position ◽  
Steam Pipes

The phased array focusing technique is being developed with the intent to inspect hundreds of feet of pipeline from a single array position. The single array position is beneficial if access to a pipe is limited, e.g. steam pipes onboard U.S. Naval ships, nuclear power plant pipes, oil and natural gas pipelines. The steam pipes have a protective coating which would ordinarily be removed and replaced for an inspection. From a single array position, ultrasonic guided waves propagate under the coating, down the length of the pipe and return information about potential defects. Focusing the ultrasonic energy at a predetermined location along the length of the pipe enhances the ability to detect defects that current state of the art inspection systems cannot. Focusing is achieved by applying excitation time delays to a multi-channel signal generation system. The excitation sources are equally spaced about the circumference of the pipe. Time delays are calculated using theoretically generated angular displacement profiles in a hollow cylinder. These theoretical displacement profiles are dependent upon excitation source influences. In this paper, the excitation source influence on focusing potential in pipe was studied. Further, focusing potential contour plots for different frequencies and distances from the excitation source were created. Based on the contour plots, sample focusing experiments were carried out.

Guided Waves as an Online Monitoring Technology for Long-Term Operation in Nuclear Power Plants: Experimental Results on a Steam Discharge Pipe

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Mauro Cappelli ◽  
Francesco Cordella ◽  
Francesco Bertoncini ◽  
Marco Raugi
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Guided Waves ◽  
Complex Structure ◽  
Theoretical Background ◽  
Guided Wave ◽  
Experimental Results ◽  
Term Operation

Guided wave (GW) testing is regularly used for finding defect locations through long-range screening using low-frequency waves (from 5 to 250 kHz). By using magnetostrictive sensors, some issues, which usually limit the application to nuclear power plants (NPPs), can be fixed. The authors have already shown the basic theoretical background and simulation results concerning a real steel pipe, used for steam discharge, with a complex structure. On the basis of such theoretical framework, a new campaign has been designed and developed on the same pipe, and the obtained experimental results are now here presented as a useful benchmark for the application of GWs as nondestructive techniques. Experimental measures using a symmetrical probe and a local probe in different configurations (pulse-echo and pitch-catch) indicate that GW testing with magnetostrictive sensors can be reliably applied to long-term monitoring of NPPs components.

Ultrasonic Phased Array: Detection of Detrimental Conditions in High-Density Polyethylene Butt-Fusion Joints

2010 ◽  
Author(s):  
Caleb J. Frederick
Keyword(s):  
High Density Polyethylene ◽  
Nuclear Power ◽  
Power Plants ◽  
Phased Array ◽  
Cold Fusion ◽  
High Density ◽  
Visual Examination ◽  
Full Spectrum ◽  
Ultrasonic Phased Array ◽  
Joint Integrity

Today, commercial nuclear power plants are installing High-Density Polyethylene (HDPE) in non-safety-related and safety-related applications. While this material has numerous advantages over the carbon steel pipes that historically have been used for the same applications, developing a way to accurately inspect for joint integrity in HDPE has become increasingly important to utilities and the U.S. Nuclear Regulatory Commission (USNRC). This paper will investigate the ability to quantify the levels of detection of flaws and detrimental conditions using ultrasonic phased array, in butt-fusion joints throughout the full spectrum of applicable HDPE pipe diameters and wall-thicknesses. Perhaps the most concerning joint condition is that of “Cold Fusion”. A cold-fused joint is created when molecules along the fusion line do not fully entangle or co-crystallize. Once the fusion process is complete, during visual examination, there is the appearance of a good quality joint. However, the joint does not have the strength needed, as the required co-crystallization along the pipe faces has not occurred. Performing a visual examination of the bead, as required by the current revision of ASME Code Case N-755, does not provide adequate guarantee of joint integrity. Therefore, volumetric examination is of special concern to the USNRC to safeguard against this type of detrimental condition. Factors addressed will include pipe diameter, wall-thickness, fusing temperature, interfacial pressure, dwell (open/close) time, and destructive verification of ultrasonic data.

Development of On-Line Health Monitoring System for Pipes in Nuclear Power Plants

2006 ◽  
Vol 321-323 ◽  
pp. 441-444
Author(s):  
Heung Seop Eom ◽  
Sa Hoe Lim ◽  
Jae Hee Kim ◽  
Young H. Kim ◽  
Hak Joon Kim ◽  
...  
Keyword(s):  
Health Monitoring ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Guided Waves ◽  
Guided Wave ◽  
Wave System ◽  
Ultrasonic Guided Wave ◽  
On Line ◽  
Series Of Experiments

This study was aimed at developing an effective method and a system for on-line health monitoring of pipes in nuclear power plants by using ultrasonic guided waves. For this purpose we developed a multi-channel ultrasonic guided wave system for a long-range inspection of pipes and a few techniques which can effectively find defects in pipes. To validate the developed system we performed a series of experiments and analyzed the results.

Damage Imaging of Pipes in Nuclear Power Plants Using Torsional Guided Wave Modes

2013 ◽  
Vol 577-578 ◽  
pp. 661-664
Author(s):  
Zhao Xiang Wei ◽  
Hong Xu ◽  
Hong Yuan Li
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Power Plants ◽  
Guided Waves ◽  
Axial Position ◽  
Imaging Method ◽  
Long Distance ◽  
Torsional Mode ◽  
Damage Imaging

Ultrasonic guided waves can propagate a long distance in pipeline with little attenuation. This means the damage in nuclear power plant can be detected from a remote single position. In the paper, the propagation of the guided waves are analyzed for the nuclear power plant pipes, and the axisymmetric torsional mode T(0,1) is chosen as the detection mode. An imaging method based on the synthetic focusing algorithm is used to obtain the damage information. The method is then verified by the finite element model. Results illustrate that the damage can be detected and located accurately by the damage imaging method. Not only the axial position, but also the circumferential position can be located simultaneously.

scholarly journals Ultrasonic Phased Array Evaluation of Control Rod Drive Mechanism (CRDM) Nozzle Interference Fit and Weld Region

2011 ◽  
Author(s):  
Anthony D. Cinson ◽  
Susan L. Crawford ◽  
Paul J. MacFarlan ◽  
Royce A. Mathews ◽  
Brady D. Hanson ◽  
...  
Keyword(s):  
Boric Acid ◽  
Nuclear Power ◽  
Phased Array ◽  
Crystal Form ◽  
Electric Discharge Machining ◽  
Interference Fit ◽  
Control Rod ◽  
The North ◽  
Ultrasonic Phased Array ◽  
Inner Diameter

Ultrasonic phased array data were collected on a removed-from-service CRDM nozzle specimen to assess a previously reported leak path. First a mock-up CRDM specimen was evaluated that contained two 0.076-mm (3.0-mil) interference fit regions formed from an actual Inconel CRDM tube and two 152.4-mm (6.0-in.) thick carbon steel blocks [1,2]. One interference fit region has a series of precision crafted electric discharge machining (EDM) notches at various lengths, widths, depths, and spatial separations for establishing probe sensitivity, resolution and calibration. The other interference fit has zones of boric acid (crystal form) spaced periodically between the tube and block to represent an actively leaking CRDM nozzle assembly in the field. Ultrasonic phased-array evaluations were conducted using an immersion 8-element annular 5.0-MHz probe from the tube inner diameter (ID). A variety of focal laws were employed to evaluate the interference fit regions and J-grove weld, where applicable. Responses from the mock-up specimen were evaluated to determine detection limits and characterization ability as well as contrast the ultrasonic response differences with the presence of boric acid in the fit region. Nozzle 63, from the North Anna Unit-2 nuclear power plant, was evaluated to assess leakage path(s) and was destructively dismantled to allow a visual verification of the leak path(s).

scholarly journals Delayed Station Blackout Event and Nuclear Safety

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Andrija Volkanovski ◽  
Andrej Prošek
Keyword(s):  
Time Delay ◽  
Time Delays ◽  
Nuclear Power ◽  
Electrical Power ◽  
Event Tree ◽  
Power Sources ◽  
Ac Power ◽  
Complete Failure ◽  
Station Blackout ◽  
Safety Systems

The loss of off-site power (LOOP) event occurs when all electrical power to the nuclear power plant from the power grid is lost. Complete failure of both off-site and on-site alternating current (AC) power sources is referred to as a station blackout (SBO). Combined LOOP and SBO events are analyzed in this paper. The analysis is done for different time delays between the LOOP and SBO events. Deterministic safety analysis is utilized for the assessment of the plant parameters for different time delays of the SBO event. Obtained plant parameters are used for the assessment of the probabilities of the functional events in the SBO event tree. The results show that the time delay of the SBO after the LOOP leads to a decrease of the core damage frequency (CDF) from the SBO event tree. The reduction of the CDF depends on the time delay of the SBO after the LOOP event. The results show the importance of the safety systems to operate after the plant shutdown when the decay heat is large. Small changes of the basic events importance measures are identified with the introduction of the delay of the SBO event.

Non-Invasive On-Line Monitoring for Nuclear Power Plants Using Guided Waves Propagating in Steel Pipes With Different Types of Structural Complexity

2016 ◽  
Author(s):  
Francesco Bertoncini ◽  
Mauro Cappelli ◽  
Francesco Cordella ◽  
Marco Raugi
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Guided Waves ◽  
Structural Complexity ◽  
Ultrasonic Waves ◽  
Steel Pipes ◽  
Non Invasive ◽  
Different Types ◽  
On Line

On-line monitoring for installed piping in Nuclear Power Plants (NPPs), as well as for Oil & Gas and other kind of plants, is crucial to early detect local ageing effects and locate single defects before they may result in critical failures. All the actions able to prevent failures are of great value especially if non-invasive and allowing an In-Service Inspection (ISI). In particular the Long Term Operation (LTO) and Plant Life Extension (PLEX) may be invalidated from radiation, thermal, mechanical stresses besides their own ageing. Hence on-line monitoring techniques are of much interest especially if they assure the required safety levels and at the same time are simple and cost-effective. Guided Waves (GW) satisfy these requirements since they are structure-borne ultrasonic waves that propagate themselves without interfering along the same pipe structure, which in turns through its geometric boundaries serves as a confining structure for the GW used to test its integrity. The frequencies used for GW testing extend up to 250 kHz, thus allowing a long-range inspection of pipes (tens of meters in favorable circumstances). The experimental conditions (e.g. temperature, complex piping structure, wall thickness, materials) have to be considered since they strongly affect the results but GW generated through magnetostrictive sensors are expected to overcome such issues due to their robustness and positioning ease. In this paper, new experimental tests conducted using the proposed methodology for steel pipes having different types of structural complexity are described.

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