研究目的
To determine the porosity and Young’s modulus in high burnup uranium dioxide nuclear fuel using high frequency acoustic microscopy and to correlate these properties with the local burnup profile and hardness data obtained by Vickers micro-indentation.
研究成果
The porosity measured via acoustic microscopy is consistent with that calculated via SEM image analysis. Young’s modulus does not show a significant variation in the burnup range corresponding to the radial positions investigated. The hardness values measured along the same fractional radial positions show the same trend as Young’s modulus. The ratio H/E is constant along the radius investigated and the value, higher than that obtained for unirradiated nuclear fuel, is consistent with literature data obtained with Knoop indentation on irradiated uranium dioxide.
研究不足
The spatial resolution of the technique at 90 MHz is larger than the width of the RIM region (between 100–200 micrometers in this pellet), limiting the study to areas adjacent to the outermost peripheral region of the pellet.
1：Experimental Design and Method Selection:
High frequency acoustic microscopy was used to investigate radial variations of porosity and elastic properties in a high burnup UO2 pellet. Ultrasound waves were generated by a piezoelectric transducer and focused on the sample after travelling through a coupling liquid (methanol). The elastic properties were related to the velocity of the generated Rayleigh surface wave (VR).
2：Sample Selection and Data Sources:
A UO2 pellet with a burnup of 67 GWd/tU was characterized. The pellet was embedded in epoxy resin, ground, and polished to obtain a smooth and flat surface.
3：List of Experimental Equipment and Materials:
Acoustic microscope installed in the hot cells of the JRC-ITU, shielded JEOL 6400? scanning electron microscope, MaxView? software package, ImagePro Analyzer 7.0?, Micro-Duromat 4000E microhardness Vickers tester, shielded LEICA Telatom 3 optical microscope.
4：0?, Micro-Duromat 4000E microhardness Vickers tester, shielded LEICA Telatom 3 optical microscope.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: VR was measured at different radial positions. Porosity values obtained via acoustic microscopy were compared with those determined using SEM image analysis. Young’s modulus was calculated and its radial profile was correlated to the corresponding burnup profile and hardness radial profile data obtained by Vickers micro-indentation.
5：Data Analysis Methods:
The velocity of the Rayleigh surface wave was calculated using Fourier Transform. Porosity and Young’s modulus were determined from the acoustic microscopy data. Hardness was calculated from the Vickers micro-indentation tests.
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