Thermodynamic considerations in the use of nickel-beryllium alloy to braze Zircaloy-4

To better control beryllium exposure during the manufacture of CANDU® fuel bundles, a nickel-beryllium brazing alloy to affix appendages to Zircaloy-4 is being considered. A Ni-2wt%Be shows promise in substantially reducing beryllium volatility while minimally perturbing existing fabrication processes. Thermodynamic models of the condensed phases of the binary Zr-Be, Ni-Be and Ni-Zr alloy systems provide a basis for the construction of a provisional ternary phase diagram that in particular identifies the domain of the liquid phase. The modeling also permits the computation of the partial pressures of Be and related matters associated with the control of surface oxide on Zircaloy-4.