Microscopic stress and crystallographic orientation of hydrides precipitated in Zr-1Nb-0.01Cu cladding tube investigated by high-energy X-ray diffraction and EBSD

Abstract

The newly developed Zr-1Nb-0.01Cu fuel cladding tubes were hydrogen-charged using the electrolytic technique and cooled down to room temperature after thermal treatment by furnace cooling (FC) and air cooling (AC). High energy X-ray diffraction and electron backscatter diffraction techniques were employed to measure the microscopic stress and crystallographic orientation of hydrides precipitated in FC and AC tube samples. The FC δ-hydrides precipitated in the Zr-1Nb-0.01Cu cladding tube were under an average compressive stress of about (-262.2 ± 20) MPa. While an average compressive stress of about (-152.4 ± 20) MPa was determined for the AC δ-hydrides precipitated in the Zr-1Nb-0.01Cu cladding tube. Nearly all the inter- and intra-granular δ-hydrides obtained during FC and AC followed the conventional (0001)α-Zr∥ (111)δ-hydride orientation relationship (OR) with the α-Zr matrix. The unusual (0001)α-Zr∥ (100)δ-hydride OR was only occasionally detected in the FC and AC intra-granular δ-hydrides. Interestingly, for the FC sample, δ-hydrides were simultaneously detected in an α-Zr grain, obeying (0001)α-Zr∥ (111)δ-hydride OR and (0001)α-Zr∥ (100)δ-hydride OR with the same parent α-Zr grain respectively.