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- Pore orientation (3)
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Durch den großflächigen Einsatz der Computertomographie (CT) in unterschiedlichen Industriebereichen steigen auch die Anforderungen an die quantitative Bildanalyse. Subjektive Bildwahrnehmung muss durch objektive Algorithmen ersetzt werden. In diesem Artikel stellt die Bundesanstalt für Materialforschung und -prüfung (BAM), die seit den 1980er Jahren an der Entwicklung der industriellen CT beteiligt ist, anhand ausgewählter Beispiele den aktuellen Stand ihrer Analysemethoden an verschiedenen Anwendungsbeispielen der CT vor.
In the framework of the SARNET-2 WP5.1 the QUENCH-DEBRIS test was conducted as the 17th severe accident test using the QUENCH facility at KIT to investigate the formation and coolability of a prototypic debris bed. The test scenario was defined by pre-test calculations using the MELCOR code. This code was used also for post-test analysis. The test bundle with length of about 2 m contains the hafnium shroud tube and 12 heated peripheral rods with claddings made of hafnium. Hafnium was chosen because of its much higher melting temperature and the about one order of magnitude lower oxidation rate compared to zirconium. The claddings of the inner nine rods were made from Zry-4. They were filled with pre-fragmented zirconia pellets. The test started with an oxidation phase of 20 h at peek cladding temperature about 1800 K to reach complete oxidation of the Zry-4 claddings over a height of 500 mm. The temperatures expected from the pre-test simulation fitted well the experimentally observed evolution of the bundle conditions.
The possibly surviving inner Zry-4 claddings were destroyed by the application of an axial mechanical force resulting in material relocation and formation of a heterogeneous debris bed consisting of segmented pellets and larger cladding tube fragments at the grid spacer 2 (350 mm elevation) and in a smaller amount at grid spacer 3 (1050 mm elevation). The so destroyed bundle was quenched with 10 g/s water. The evaporation rate generally showed an increasing trend during the reflood, except at the time of water penetration through the debris bed at spacer 2 when stagnation was observed. All peripheral hafnium claddings survived the whole test. During the oxidation phase about 100 g hydrogen was released. The time dependence of the hydrogen release predicted in the pre-test calculations fits well the measured one. The post-test examinations comprise videoscope inspections, high energy X-ray-tomography and metallographic investigations of the debris bed.
Mechanisierte Durchstrahlungsprüfung - Innovative Techniken zur Bewertung von Rundschweißnähten
(2001)
Complementary to Part 1 of this work, the bi-continuous microstructure of porous synthetic cordierite ceramics for filtration applications was investigated using 3D x-ray computed tomography at different resolutions. Applying both Fast Fourier Transform and a newly developed image analysis algorithm, we quantitatively evaluated porosity and pore orientation. The statistical approach allows extraction of spatially resolved or average values. Porosity values based on x-ray absorption agree with mercury intrusion measurements, while pore orientation factors agree with x-ray refraction data (Part 1 of this work), and with published crystallographic texture data.