Book Description

The impact of hydrogen on the irradiation growth and creep of stress-relief annealed (SRA) ZIRLO® alloy and recrystallized annealed (RXA) Zr-1.0Nb cladding tubes is evaluated in this paper. The samples were charged with hydrogen in the range of approximately 160-720 ppm using the gaseous method. Biaxial in-reactor creep tests were performed after Cycle 1, Cycle 2, Cycle 3, and Cycle 4, on both as-received and precharged hydrogen cladding tubes. Outside diameter and axial length measurements were performed on the samples. The results showed that hydrogen had no effect on the axial irradiation creep but a relatively large effect on the axial irradiation growth. Increasing hydrogen decreased the axial irradiation growth in RXA Zr-1.0 Nb, which was opposite from the behavior of SRA ZIRLO cladding. This unique hydrogen effect on the irradiation axial growth of RXA Zr-1.0Nb could be due to the different intergranular stress resulting from the fabrication process or the absence of alloying elements, including tin. The total axial strain of both Zr-1.0Nb and SRA ZIRLO cladding increased with increasing fast fluence, and Zr-1.0Nb increased at a faster rate relative to SRA ZIRLO cladding. In the diameter direction, hydrogen had a minimal effect on the total diameter strain and the diameter irradiation creep strain for both SRA ZIRLO samples and the RXA Zr-1.0Nb sample. This finding from in-reactor test is contrary to the out-reactor tests results from the literature that have shown that hydrogen significantly decreases thermal creep. The total diameter strain and diameter irradiation creep behavior for the SRA ZIRLO samples and RXA Zr-1.0Nb were similar.