Local Study of Defects During Sintering of Uo2: Image Processing and Quantitative Analysis Tools

Abstract

This paper describes the image analysis tools developed and used to quantify the local effects, of heterogeneities during sintering of ceramic materials applied in nuclear fuels. Specific materials, containing a controlled dispersion of well defined heterogeneities (dense or porous aggregates) in the ceramics matrix have been prepared and sintered. In order to characterize the materials in the vicinity of these likely isolated heterogeneities, large SEM images are first acquired around heterogeneities. Image processing tools are used to segment the relevant elements of the microstructure: ceramic grains and porosity (intra-and intergranular). An analysis procedure is then developed to analyse the evolution of the main microstructure features (pore volume fraction, pore size, grain size) during sintering, with the distance to the matrixheterogeneity interface as reference parameter. An evaluation of the anisotropy of repartition of pores and grains around the heterogeneities is also proposed. Some illustrative results are presented, which evidence a rather short range of mean interactions, and a significant rather long range of the anisotropy effect related to the matrix-heterogeneities interactions during the undidirectional compaction.

Conversion of Ceramic UO2Pellets for HTR-10 Fuel Elements into Nitrate with N2O4

“…The surface of the ceramic UO 2 pellet was smooth as shown in part a of Figure , whereas there were small pores on the surface of the U 3 O 8 particle as shown in part b of Figure . This was because there were small pores formed inside of the ceramic UO 2 pellets during preparation; ,, when ceramic pellets were cracked during heat treatment, those small pores were also exposed.…”