The effect of final heat treatment on the corrosion characteristics of Zr-based new alloys for nuclear fuel cladding

The corrosion behaviors of the Zr-based new alloys, Zr-0.8Sn-0.4Nb-FeMo(alloy A) and Zr-1.0Sn-1.0Nb-FeCu(alloy B) were investigated after the specimens of the alloys had been taken some different thermo-mechanical treatments including the final heat treatments as stress-relived (SR) at 470.deg. C and recrystallized (RX) at 520.deg. C for 2.5 hours, respectively. The corrosion tests of the specimens were carried out for 270 days in the autoclaves containing 360.deg. C water, 400.deg. C steam and 360.deg. C aqueous LiOH(70ppm) solution. The microstructres of specimens were analyzed using an TEM, and those of their oxides using small angle XRD method. The test results showed that the corrosion rates of the specimens in the steam were faster than those in the water or the aqueous LiOH solution. It was found that the alloy A containing lower Nb and Sn content showed a little better corrosion resistance in all the test environments than the alloy B containing higher Nb and Sn content as well as the specimens had been taken SR heat treatment showed higher t-ZrO2 fraction to m-ZrO2 than those had been taken RX heat treatment