ISO 22765:2025 pdf download,Nuclear fuel technology — Sintered (U,Pu)O2 pellets — Guidance for ceramographic preparation for microstructure examination.
ISO 22765:2025 provides guidance for preparing ceramographic samples of sintered (U,Pu)O2 pellets so that the pellet microstructure can be examined both qualitatively and quantitatively. It focuses on the ceramographic procedure used during fuel fabrication, defining how to prepare specimens for observation and measurement. Examinations are performed before any treatment or etching, and again after thermal treatment or after chemical or ion etching. The standard enables assessment of key microstructural features such as cracks, intra- and intergranular pores, and inclusions. It also supports quantitative characterization, including grain size measurement, porosity evaluation, and determination of plutonium homogeneity distribution. Grain size may be measured using classic methods such as counting/intercept approaches or comparison with grids and reference images, while plutonium cluster and pore distribution can be analyzed using automatic image analysis, with plutonium distribution revealed by chemical etching or alpha autoradiography.