REVIEW AND CORRELATION OF IN-PILE ZIRCALOY-2 CORROSION DATA AND A MODEL FOR THE EFFECT OF IRRADIATION
A review and a correlation of many of the data obtained for the in-pile corrosion of Zircaloy-2 in uranyl sulfate solutions at elevated temperatures are presented. The correlation is based on the following equation for the relationship between the corrosion rate, R, and the fission power density in solution, P: 1/R = K/sub 1//KP alpha + 1/K, where alpha is the factor by which the effective power density at the corroding surface is greater than that in the solution and K/sub 1/ and K are constants. A semiempirical model for the radiation effects on Zircaloy-2 corrosion which leads to this equation is described and discussed. In the model it is assumed that the major effects of radiation, in interaction with corrosion, are in the metal. The results of the correlation of the experimental data indicate that a general relationship between corrosion rate and solution power density of the form given by the above equation is obeyed within the power-density-range tested (up to 110 w/cc). The extrapolated value of K is essentially independent of solution composition but varies with temperature. The observed values are expressed fairly well by the equation K = 4.44 x 10/sup 10/ exp (-22,900/RT), where K has the units mpy, and R in this case is the gas constant. The correlations further indicate that the value of the ratio K/sub 1//K does not change appreciably with temperature and has the value of 2.3 w cc/sup -1/ mpy/sup -1/ in the temperature range tested (225 to 330 deg C). The value of alpha prevailing during exposure depends upon the solution composition and the velocity of solution flow past the test surface. In some solutions the observed value of alpha is unity even at low velocities. In others, notably those with low concentrations of uranium and other sulfats additives, alpha values of 6 to 7 or more occur at low velocities. When alpha values greater than unity occur at low velocities, the values at higher velocities are nearer unity and, under some flow conditions and in some solutions, are equal to unity. The observed alpha values and the effects of velocity and solution composition are reasonably interpreted in terms of the amounts of uranium sorbed on nonprotective oxides near the specimen surface and the fractional contribution of this sorbed uranium to the total intensity of fission-recoil irradiation of the surface. (auth)
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-15-025157
- OSTI ID:
- 4019975
- Report Number(s):
- ORNL-3039
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- United States
- Language:
- English
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