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IN-PILE RADIATION CORROSION EXPERIMENTS WITH ZIRCONIUM, TITANIUM, AND STEEL ALLOYS IN 0.17 m UO$sub 2$SO$sub 4$ SOLUTIONS AT 280 C

Technical Report ·
DOI:https://doi.org/10.2172/4704064· OSTI ID:4704064
In-pile loop experiments L-2-15 and L-4-16 were designed to test the radiation corrosion of Zircaloy-2 and other possible reactor construction materials in UO/sub 2/SO/sub 4/ solutions. The solutions employed were 0.17 m UO/ sub 2/SO/sub 4/, 0.015 m CuSO/sub 4/, and 0.03 m H/sub 2/SO/sub 4/ in H/sub 2/O for experiment L-2-15, and 0.17 m UO/sub 2/SO/sub 4/, 0.015 m CuSO/sub 4/, and 0.025 m H/sub 2/SO/sub 4/ in H/sub 2/O for experiment L-4-16. The mainstream temperature in the experiments ranged from 278 to 280 deg C. Construction material for the loops was type 347 stainless steel. Specimens of types 347 and 309SCb stainless steels titanium-55A and -110AT, platinum, Zircaloy-2, crystalbar zirconium, and a variety of other zirconium alloys were tested. The power density at core specimens ranged from 19.8 to 4.6 w/ml in L-2-15 and from 5.7 to 1.3 w/ml in L-4-16. For loop L-2-15, the total time of hightemperature operation with UO/sub 2/SO/sub 4/ was 792 hr, during in-pile exposure, and the reactor energy was 1632 Mwh; for loop L-4-16, 1032 hr and 2325 Mwh. During both experiments most of the reactor energy was accumulated at 3-Mw power level. In general, stainless steel corrosion results from these experiments were comparable to those observed in other in-pile loop experiments. Corrosion was confined primarily to the core areas and was power-density dependent. Some variations in attack, both positive and negative, with velocity of solution flow past specimens have been observed in other experiments, but there was no apparent effect of varying velocities in the range 10 to 40 fps on either the core-channel or in- line channel specimens in the present experiments. The coreannulus steel specimens in L-2-15 corroded at rates very much greater than those in the channel. This difference may have resulted, in part, from the differences in velocities, however, it may have also been a result of galvanic actton between the steel annulus specimens and adjacent platinum specimens. In previous 250 deg C experiments the occurrence of a change in the stainless steel corrosion rate was correlated with a decrease in acidity and/or increase in the nickel concentration. The results for the oxygen consumption rates on steel during radiation exposure in the present experiments varied with radiation time in a manner qualitatively similar to that observed at the lower temperature. However, the concentration of excess acid in the present experiments probably remained fairly constant throughout the radiation exposures, and correlations similar to those obtained at the lower temperature could not be established. The acid concentration in the 280 deg C experiments was greater than the concentrations prevailing when corrosion rate changes occurred in the 250 deg C experiments. The difference in acid tolerance is probably a result of the increased temperature, since a similar beneficial effect of temperature occurs out-ofpile No overall correlation has been established for the various factors found to have influenced steel corrosion in previous experiments. Results of the present experiments provide additional evidence in support of previous findings but do not further their interpretation. Zircaloy-2 corrosion results from both loops have been discussed and correlated elsewhere in terms of the 280 deg C relationship between the corrosion rate R (mils per year, mpy), power density P (w/ml), and uranium sorption factor alpha : 1/R = 2.23/P alpha + 1/40. The data from these experiments obey this relationship. (This is only a portion of the Author abstract.)
Research Organization:
Oak Ridge National Lab., Tenn.
DOE Contract Number:
W-7405-ENG-26
NSA Number:
NSA-17-027750
OSTI ID:
4704064
Report Number(s):
ORNL-3099
Country of Publication:
United States
Language:
English