Neutron diffraction investigation of phase compositions in as received and modified Zr\u20132\ub75Nb pressure tube materials

Zr-2.5Nb alloy is used for the pressure tubes in CANDU\uae reactor fuel channels. Three phases (\u3b1, \u3b2, and \u3c9) of zirconium are known to exist in Zr-2.5Nb alloy pressure tube materials. An as received pressure tube is composed mainly of \u3b1-phase and approximately 8% \u3b2-phase material. In the last step of production, the pressure tube is given a steam-autoclave treatment (i.e., thermal ageing at 400\ub0C for 24 h). This treatment results in decomposing the \u3b2-phase into an Nb-enriched \u3b2-phase and a metastable \u3c9-phase material. In this present experiment, as received pressure tube materials were modified by high-temperature annealing and thermal ageing treatments. This paper presents a neutron diffraction investigation into the phase compositions in the modified materials at room temperature using the C-2 high-resolution neutron powder diffractometer at the Canadian Neutron Beam Centre.Peer reviewed: YesNRC publication: Ye