Neutron Radiation Damage in Zr-2.5 wt % Nb Alloys

There has been much speculation recently concerning the nature of radiation induced defects in zirconium and its alloys. In particular, the absence of voids in pure zirconium and in Zircaloy-2 at high fluences and at temperatures in the range 0.3 to 0.5 Tm is inconsistent with observations made on most elemental f.c.c., b.c.c., c.p.h. metals, on stainless steels and on Nimonic PE16 alloys. Wolfenden and Farrell have reviewed the evidence and discuss the importance of dislocation density and/or gas content on void formation. The specimens examined in this study were.3 m.m. discs of Zr-2.5 wt % Nb fuel sheath material irradiated to 1.24 × 102 1 n. cm−2 (E > 1 MeV) at 380-390°C (∼ 0.31 Tm, where Tm is the melting temperature of the β phase) and to 1.37 × 102 1 n. cm−2 at 470 - 490°C (∼ 0.36 Tm) in the WR-1 organic cooled reactor.