Zircaloy-2 corrosion in steam-water mixture under reactor radiations

Corrosion rates of Zircaloy-2 in steam-water mixture were studied in the following experimental conditions: out of pile at 285°C and 70 kg/cm2; under irradiation (Φ > 1MeV = 3.5 × 1012 n/cm2 sec) at 285°C and 70 kg/cm2; under irradiation (Φ >1MeV = 1.5 × 1013 n/cm2 sec) at 285°C and 70 kg/cm2; and out-of-pile autoclave tests at 400°C and 105 kg/cm2.Two closed-cycle loops were used for dynamic tests; most of the experiments were carried out in neutral conditions, that is, without any addition of chemicals to the feed water; only some preliminary tests were performed in an ammoniated environment.Experiments were conducted on corrosion coupons in as-pickled conditions; the exposure time for in-reactor tests was approximately 70 days.Results obtained on the corrosion of Zircaloy-2 samples showed that exposure to reactor radiation produces an enhancement in the oxidation rate, at least in the pretransition region, the extent of such an increase being related to the fast neutron flux. In the range of the fast neutron flux considered, the time to transition was found to be shortened by a factor of from approximately 10 to 50. For fractional hydrogen pickup no effect of reactor radiation was found.