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The oxygen consumed is used up in two processes: (a) solution in the metal, and (b) forination of an oxide fihn. Have the authors any estimate, either experimental or from diffusion calculations, of the amount used in each process? ~I. W. MALLETT AND W. M. ALBRECHT: Calculations based upon diffusion data indicate that about 0.5 1.5% of the total amount of oxygen consumed by a reacted specimen was used up in the diffusion process. Normal variations in rate data are greater than this. In the proposed mechanism, solution of oxygen must occur. However, not all of the dissolved oxygen diffuses into the metal core since much of it is incorporated into the advancing oxide fihn by further oxidation.

Low‐pressure solubilities were determined for H in α‐ and β‐Zr and in two Zr‐O alloys at 700°–1000°C and pressures of 0.1–4 µ Hg. The data followed Sieverts' law for each phase, and H solubility decreased with increasing temperature at a given pressure. Also, there was a slight increase in H solubility in α ‐Zr with increasing oxygen content. Diffusion coefficients for H in α‐Zr were obtained in the range 300°–600°C by analysis of prepared concentration gradients. In the range 600°–800°C, degassing coefficients were determined from rate of H evolution from Zr cylinders. Degassing coefficients were much lower than expected from diffusion theory, and it was concluded that the degassing was not a pure diffusion phenomenon. Terminal solubilities obtained from the gradient analysis were in good agreement with those found by previous investigators.

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The diffusion rates of oxygen in alpha and beta Zircaloy 2 and Zircaloy 3 were determined in the range 1000~176For alpha Zircaloy 2, the variation of the diffusion coefficient, D, in cm~/sec, with temperature is given by the equation D a ~ 0.196 exp (--41,000 _ 1500/RT) For beta Zircaloy 2, D~ ~ 0.0453 exp (--28,200 ___ 2400/RT)