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Proceedings Paper

Characterization of nuclear graphite elastic properties using laser ultrasonic methods
Author(s): Fan W. Zeng; Karen Han; Lauren R. Olasov; Nidia C. Gallego; Cristian I. Contescu; James B. Spicer
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Paper Abstract

Laser ultrasonic methods have been used to characterize the elastic behaviors of commercially-available and legacy nuclear graphites. Since ultrasonic techniques are sensitive to various aspects of graphite microstructure including preferred grain orientation, microcrack orientation and porosity, laser ultrasonics is a candidate technique for monitoring graphite degradation and structural integrity in environments expected in high-temperature, gas-cooled nuclear reactors. Aspects of materials texture can be assessed by studying ultrasonic wavespeeds as a function of propagation direction and polarization. Shear wave birefringence measurements, in particular, can be used to evaluate elastic anisotropy. In this work, laser ultrasonic measurements of graphite moduli have been made to provide insight into the relationship between the microstructures and the macroscopic stiffnesses of these materials. In particular, laser ultrasonic measurements have been made using laser line sources to produce shear waves with specific polarizations. By varying the line orientation relative to the sample, shear wave birefringence measurements have been recorded. Results from shear wave birefringence measurements show that an isostatically molded graphite, such as PCIB, behaves isotropically, while an extruded graphite, such as H-451, displays significant ultrasonic texture. Graphites have complicated microstructures that depend on the manufacturing processes used, and ultrasonic texture in these materials could originate from grain orientation and preferred microcrack alignment. Effects on material isotropy due to service related microstructural changes are possible and the ultimate aim of this work is to determine the degree to which these changes can be assessed nondestructively using laser ultrasonics measurements.

Paper Details

Date Published: 12 May 2015
PDF: 7 pages
Proc. SPIE 9485, Thermosense: Thermal Infrared Applications XXXVII, 948511 (12 May 2015); doi: 10.1117/12.2176885
Show Author Affiliations
Fan W. Zeng, Johns Hopkins Univ. (United States)
Karen Han, Johns Hopkins Univ. (United States)
Lauren R. Olasov, Johns Hopkins Univ. (United States)
Nidia C. Gallego, Oak Ridge National Lab. (United States)
Cristian I. Contescu, Oak Ridge National Lab. (United States)
James B. Spicer, Johns Hopkins Univ. (United States)

Published in SPIE Proceedings Vol. 9485:
Thermosense: Thermal Infrared Applications XXXVII
Sheng-Jen (Tony) Hsieh; Joseph N. Zalameda, Editor(s)

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