Tin release from oxygenated Zircaloy-4

Characterized samples of oxygenated Zircaloy were heated in a Knudsen-cell apparatus to 2400 K. The vapour pressure of tin above the Zircaloy was measured as a function of temperature, oxygen content and time. Activity coefficients on the order of 10-2 were measured for tin in Zircaloy for oxygen contents up to 17 atom %. Above that oxygen content, the apparent activity coefficient was 10 times lower; however, this probably arose from diffusion control of the tin volatilization, and not from an enhanced attraction of tin to the Zircaloy lattice at high oxygen contents. The derived tin diffusion coefficient was high, about 3.8 x 10-5 cm2·s-1, probably dominated by diffusion through defects in the lattice and along grain boundaries. (author)