The circumferential tensile properties of zirconium alloy fuel claddings under a simulated high burn-up environment

To study the circumferential tensile properties of fuel claddings under a simulated high burn-up environment, ring tensile tests were carried out at both room temperature and 350 °C for Zr-Nb based fuel claddings such as Zr-Nb based HANA-6 (Zr-1.10Nb-0.05Cu), HANA-4 (Zr-1.50Nb-0.40Sn-0.20Fe-0.10Cr) and Zircaloy-4 (Zr-1.26Sn-0.23Fe-0.12Cr) cladding after they had been differently charged with hydrogen up to 2,850 ppm. The results showed that the HANA-6 cladding maintained more than a 20% circumferential elongation at room temperature without a decrease in its maximum strength when it was charged with hydrogen up to about 1,500 ppm, although the maximum circumferential strength and elongation of the Zircaloy-4 cladding decreased with increasing hydrogen content above 500 ppm. The circumferential elongation of the above claddings decreased as the hydrogen content increased at both room temperature and 350 °C but the strength increased a little with the hydrogen content at 350 °C. The maximum circumferential strength of the HANA-4 cladding also increased with the hydrogen content up to a level of 1,109 ppm, even at room temperature. It seemed that the Nb in the matrix contributed to better circumferential elongation and resistance to hydrogen embrittlement in the Zr-Nb based HANA-4 and HANA-6 claddings than was present in the Zircaloy-4 cladding.