Non-destructive evaluation methods for degradation of IG-110 and IG-430 graphite

Shibata, Taiju; Sumita, Junya; Tada, Tatsuya; Hanawa, Satoshi; Sawa, Kôichiro; Iyoku, Tatsuo

doi:10.1016/j.jnucmat.2008.07.014

Cited by 18 publications

(6 citation statements)

References 6 publications

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“…This approach was chosen owing to the experimental findings at that time, but was not justified on a theoretical basis. Later work by Shibata et al examined the variation in the longitudinal wave velocity in two different isotropic graphites (IG-110 and IG-430) as a function of porosity [13] and found that their results could be interpreted using models put forth by Takatsubo and Yamamoto [20].…”

Section: Moduli Of Porous Mediamentioning

confidence: 99%

“…Operational temperatures can cause changes in stiffness and strength and creep can occur when graphite is subjected to fast neutron irradiation under mechanical loading [9][10][11]. Graphite oxidation has the effect of increasing material porosity and this can impact material stiffness and strength [6,12,13]. Also, neutron irradiation initially increases stiffness and strength, but beyond some dose, both decrease [14].…”

Section: Introductionmentioning

confidence: 99%

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Laser ultrasonic assessment of the effects of porosity and microcracking on the elastic moduli of nuclear graphites

Spicer

Olasov

Zeng

et al. 2016

Journal of Nuclear Materials

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Laser ultrasonic methods have been used to measure the elastic moduli of various nuclear graphites. Measurements were made to assess wavespeeds for longitudinal and shear waves in different propagation directions and these were used along with density measurements to compute the longitudinal and shear moduli as well as Young's modulus. All moduli decreased with increasing graphite porosity and these variations could be interpreted using models describing the effect of porosity on material stiffness. Extrapolations for these models to zero porosity were used to infer the moduli for theoretically dense graphite; the results were far below predicted values reported in the literature for fully dense, polycrystalline, isotropic graphite. Differences can be attributed to microcracking in the graphite microstructure. Using models for the effects of microcracking on modulus, estimates for microcrack populations indicate that the number of cracks per unit volume must be much greater than the number of pores per unit volume. Experimental results reported in the literature for irradiated graphites as well as for the stress dependence of graphite modulus are consistent with the influence of microcracking on elastic behavior and could be interpreted using concepts developed here. Results in this work for graphite structure-property relationships should allow for more sophisticated characterization of nuclear graphites using ultrasonic methods.

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Section: Moduli Of Porous Mediamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laser ultrasonic assessment of the effects of porosity and microcracking on the elastic moduli of nuclear graphites

Spicer

Olasov

Zeng

et al. 2016

Journal of Nuclear Materials

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“…The assumed linear variation of elastic modulus with volume fraction is based on a model used by Shibata et al to assess porosity effects on stiffness in two particular nuclear graphites, IG-110 and IG-430 [4]. At low volume fractions, this model predicts a linear variation of modulus with porosity.…”

Section: B Elastic Moduli Vs Porositymentioning

confidence: 99%

Effects of graphite porosity and anisotropy on measurements of elastic modulus using laser ultrasonics

Spicer

Zeng

Han

et al. 2014

2014 IEEE International Ultrasonics Symposium

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Laser ultrasonic techniques can be used to study the ultrasonic properties of nuclear graphites and can serve as tools in establishing relationships between materials microstructure and the macroscopic stiffnesses of graphite. Establishing structure-property relationships permits improved ultrasonic sensing of graphite microstructural changes related to service-induced degradation. Laser ultrasonic measurements were made using a pulsed Nd:YAG laser source and detection was performed using a Michelson-type interferometer. This source-receiver combination provides for non-contacting, highly linear transduction of broadbanded, ultrasonic pulses permitting simultaneous determination of longitudinal and shear stiffnesses. Measurements show that among the graphites examined, a change in density of 0.21 g/cm 3 (average 1.8 g/cm 3 ) results in a change in the longitudinal elastic stiffness of 7.1 GPa (average 12.2 GPa) and 3.2 GPa (average 4.3 GPa) for the shear stiffness. Larger variations in density were produced by controlled oxidation of IG-110 and NBG-18. Shear wave birefringence measurements using laser line sources in IG-110 and PCEA indicate that IG-110 behaves isotropically while PCEA displays texture characteristic of transversely isotropic materials.

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“…There are techniques available for measuring the distribution of internal strains/stresses in materials; however they are invasive, semi-invasive, require complex computer simulated modelling or may be applied to only a restricted class of materials. A few techniques such as X-ray diffraction, deep-hole-drilling (DHD), finite element simulations, micro-indentation and ultrasonic wave methods have been investigated for application in graphite (Nakhodchi et al, 2011;Shibata et al, 2008). In this paper, the internal (lock-in) stresses in various constituents of polycrystalline reactor grades graphite such as filler, binder, and along the peripheral of pores and at the tips of the cracks, have been evaluated using micro-Raman spectroscopy, a non-invasive analytic method for stress evaluation in near-surface submicrometer regions of reactor graphite.…”

Section: Introductionmentioning

confidence: 99%

Residual stress measurements in polycrystalline graphite with micro-Raman spectroscopy

Krishna¹,

Jones

Edge³

et al. 2015

Radiation Physics and Chemistry

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Non-destructive evaluation methods for degradation of IG-110 and IG-430 graphite

Cited by 18 publications

References 6 publications

Laser ultrasonic assessment of the effects of porosity and microcracking on the elastic moduli of nuclear graphites

Laser ultrasonic assessment of the effects of porosity and microcracking on the elastic moduli of nuclear graphites

Effects of graphite porosity and anisotropy on measurements of elastic modulus using laser ultrasonics

Residual stress measurements in polycrystalline graphite with micro-Raman spectroscopy

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