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Title: Ultrasonic imaging in liquid sodium

Abstract

The fourth generation of nuclear reactor can use liquid sodium as the core coolant. When the reactor is operating, sodium temperatures can reach up to 600 deg. C. During maintenance periods, when the reactor is shut down, the coolant temperature is reduced to 200 deg. C. Because molten sodium is optically opaque, ultrasonic imaging techniques are developed for maintenance activities. Under-sodium imaging aims at i) checking the health of immersed structures. It should also allow ii) to assess component degradation or damage as cracks and shape defects as well as iii) the detection of lost objects. The under-sodium imaging system has to sustain high temperature (up to 300 deg. C) and hostility of the sodium environment. Furthermore, specific constraints such as transducers characteristics or the limited sensor mobility in the reactor vessel have to be considered. This work focuses on developing a methodology for detecting damages such as crack defects with ultrasound devices. Surface-breaking cracks or deep cracks are sought in the weld area, as welds are more subject to defects. Traditional methods enabled us to detect emerging cracks of submillimeter size with sodium-compatible high-temperature transducer. The presented approach relies on making use of prior knowledge about the environment throughmore » the implementation of differential imaging and time-reversal techniques. Indeed, this approach allows to detect a change by comparison with a reference measurement and by focusing back to any change in the environment. It is a means of analysis and understanding of the physical phenomena making it possible to design more effective inspection strategies. Difference between the measured signals reveals the acoustic field scattered by a perturbation (a crack for instance), which may occur between periodical measurements. The imaging method relies on the adequate combination of two computed ultrasonic fields, one forward and one adjoint. The adjoint field, which carries the information about the defects, is analogous to a time-reversal operation. One of the interests of the presented method is that the time-reversal operation is not done experimentally but numerically. Numerical simulations have been carried out to validate the practical relevance of this approach. The preliminary numerical results show a nice agreement between the guessed and the actual positions of the defect. After water-tests, in sodium-tests must be done in order to validate the water/sodium transposition. For this purpose, an under-sodium device is under development, which can move the transducers with four degrees of freedom in a 1.5 m{sup 3} sodium pot. (authors)« less

Authors:
 [1]; ; ;  [2];  [1]
  1. CEA Cadarache, DEN/DTN/STCP/LIET, 13108 Saint-Paul-Lez-Durance Cedex (France)
  2. Laboratoire de Mecanique et d'Acoustique, CNRS UPR 7051, 13402 Marseille Cedex 20 (France)
Publication Date:
Research Org.:
Institute of Electrical and Electronics Engineers - IEEE, 3 Park Avenue, 17th Floor, New York, N.Y. 10016-5997 (United States)
OSTI Identifier:
22531437
Report Number(s):
ANIMMA-2015-IO-48
TRN: US16V0382102378
Resource Type:
Conference
Resource Relation:
Conference: ANIMMA 2015: 4. International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, Lisboa (Portugal), 20-24 Apr 2015; Other Information: Country of input: France
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CRACKS; DEGREES OF FREEDOM; IMPLEMENTATION; INSPECTION; LIMITING VALUES; MAINTENANCE; OPERATION; PERIODICITY; REACTOR VESSELS; SENSORS; SIGNALS; SODIUM COOLED REACTORS; SURFACES; TRANSDUCERS; ULTRASONIC TESTING; WELDED JOINTS

Citation Formats

Lubeigt, E., Laboratoire de Mecanique et d'Acoustique, CNRS UPR 7051, 13402 Marseille Cedex 20, Mensah, S., Chaix, J. F., Rakotonarivo, S., and Gobillot, G. Ultrasonic imaging in liquid sodium. United States: N. p., 2015. Web.
Lubeigt, E., Laboratoire de Mecanique et d'Acoustique, CNRS UPR 7051, 13402 Marseille Cedex 20, Mensah, S., Chaix, J. F., Rakotonarivo, S., & Gobillot, G. Ultrasonic imaging in liquid sodium. United States.
Lubeigt, E., Laboratoire de Mecanique et d'Acoustique, CNRS UPR 7051, 13402 Marseille Cedex 20, Mensah, S., Chaix, J. F., Rakotonarivo, S., and Gobillot, G. Wed . "Ultrasonic imaging in liquid sodium". United States.
@article{osti_22531437,
title = {Ultrasonic imaging in liquid sodium},
author = {Lubeigt, E. and Laboratoire de Mecanique et d'Acoustique, CNRS UPR 7051, 13402 Marseille Cedex 20 and Mensah, S. and Chaix, J. F. and Rakotonarivo, S. and Gobillot, G.},
abstractNote = {The fourth generation of nuclear reactor can use liquid sodium as the core coolant. When the reactor is operating, sodium temperatures can reach up to 600 deg. C. During maintenance periods, when the reactor is shut down, the coolant temperature is reduced to 200 deg. C. Because molten sodium is optically opaque, ultrasonic imaging techniques are developed for maintenance activities. Under-sodium imaging aims at i) checking the health of immersed structures. It should also allow ii) to assess component degradation or damage as cracks and shape defects as well as iii) the detection of lost objects. The under-sodium imaging system has to sustain high temperature (up to 300 deg. C) and hostility of the sodium environment. Furthermore, specific constraints such as transducers characteristics or the limited sensor mobility in the reactor vessel have to be considered. This work focuses on developing a methodology for detecting damages such as crack defects with ultrasound devices. Surface-breaking cracks or deep cracks are sought in the weld area, as welds are more subject to defects. Traditional methods enabled us to detect emerging cracks of submillimeter size with sodium-compatible high-temperature transducer. The presented approach relies on making use of prior knowledge about the environment through the implementation of differential imaging and time-reversal techniques. Indeed, this approach allows to detect a change by comparison with a reference measurement and by focusing back to any change in the environment. It is a means of analysis and understanding of the physical phenomena making it possible to design more effective inspection strategies. Difference between the measured signals reveals the acoustic field scattered by a perturbation (a crack for instance), which may occur between periodical measurements. The imaging method relies on the adequate combination of two computed ultrasonic fields, one forward and one adjoint. The adjoint field, which carries the information about the defects, is analogous to a time-reversal operation. One of the interests of the presented method is that the time-reversal operation is not done experimentally but numerically. Numerical simulations have been carried out to validate the practical relevance of this approach. The preliminary numerical results show a nice agreement between the guessed and the actual positions of the defect. After water-tests, in sodium-tests must be done in order to validate the water/sodium transposition. For this purpose, an under-sodium device is under development, which can move the transducers with four degrees of freedom in a 1.5 m{sup 3} sodium pot. (authors)},
doi = {},
url = {https://www.osti.gov/biblio/22531437}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2015},
month = {7}
}

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