Fig. 1. Metallographic micrographs of the chemical interaction layer of the D13 sample (a) 0°, (b) 45°, (c) 90°, (d) 135°, (e) 180°, (f) 225°, (g) 270°, (h) 315°

Fig. 2. High-magnification metallographic microscopy image of the chemical interaction layer

Fig. 3. SEM micrographs of the inner side of the chemical interaction layer near the fuel pellet, where (a~c) represent the SEM images at different locations

Fig. 4. SEM micrographs with magnification of the inner side of the chemical interaction layer near the fuel pellet

Fig. 5. SEM-EDS micrograph of different areas on the inner side of the chemical interaction layer near the fuel pellet (a) SEM images of specific areas, (b) EDS spectrum of area 1, (c) EDS spectrum of area 2

Fig. 6. SEM-EDS mapping micrograph of different areas on the inner side of the chemical interaction layer near the fuel pellet (a) SEM micrograph, (b) Zr distribution map, (c) U distribution map, (d) O distribution map

Fig. 7. Optical micrograph of the chemical interaction layer (a): scanning direction (1) →(2), 2-D projections of the Raman spectra (b) (color online)

Fig. 8. Raman spectra of the D13 intact fuel rod samples at the cross section