SUMMARY OF RUNS D-77 THROUGH D-93. RATE OF OXIDATION OF CHROMIUM(III) IN DILUTE URANYL SULFATE SOLUTION IN THE PRESENCE OF RUTHENIUM

The rate of oxidation of chromium(III) to chromium(VI), catalyzed by ruthenium, was determined at various temperatures and oxygen concentrations. The rate at 300 deg C was too rapid for measurement by aliquot sampling. In the temperature range of 225 to 275 deg C, oxidation was rapid and the rate increased with oxygen concentration. A linear dependence of initial oxidation rate on the reciprocal of chromium(VI) concentration suggested that a rate-controlling step in the reaction mechanism may be desorption of chromium(VI) from the ruthenium catalyst. The activation energy calculated for the reaction is 19 kcal/mole. (auth

QUARTERLY REPORT OF THE SOLUTION CORROSION GROUP FOR THE PERIOD ENDING JANUARY 31, 1958

The corrosion rate was determined and tabulated for stainless steels, nickel alloys, carbon steels, Zircaloy-2, and niobium in boiler water containing various concentrations of oxygen. The corrosion resistance of stainless steels and nickel alloys was compared with the resistance of the austenitic stainless steels in uranyl sulfate at 200 to 295 deg C. Additional loop runs with UO/sub 3/ --Li/sub 2/CO/sub 3/ --CO/sub 2/ so lution have confirmed previous data with regard to its nonaggressive nature to carbon steel. The corrosion of 347 stainless steel was investigated in 0.04M uranyl sulfate containing 0.04M beryllium sulfate and 0.006M copper sulfate, in 0.075M beryllium sulfate, and in 0.75M beryllium sulfate containing 0.25M dissolved uranium trioxide. centration to 0.03M or decreasing the uranium concentration to 0.02M in simulated HRT fuel solution (0.04M uranyl sulfate, 0.02M sulfuric acid, and 0.005M copper sulfate) has no significant effect on the solution stability or corrosiveness of the solution. The effect of varying the oxygen concentration between 250 and 2800 ppm in 0.17M uranyl sulfate at 250 deg C on the corrosion rate of 347 stainless steel was found to be negligible in the absence of added Cr/sup 4+/. The corrosion rate of 347 stainless steel in dilute sulfuric acid solutions was determined at 250 deg C. Metallographic examinations have been made of stainless steels and titanium alloys stressed to 76% of their room temperature yield strengths and exposed 19,364 hr to the vapor phase above the HRT solution at 300 deg C. The effect of preformed films on the stress-corrosion cracking of 347 stainless steel in boiling and aerated HRT core solutions containing 50 ppm of chloride was studied as a function of the prefilming time. The effect of HRT core solution components either singly or in combination on the stress corrosion of 347 stalnless steel was examined. In order to determine the susceptibility of 347 stainless steel to cracking in chloride-containing distilled water in the absence of oxygen, tests were run at 300 deg C in solutions containing 100 ppm chloride at adjusted pH values of 2.8, 6.5, and 10.5. Other stainless steels and nickel alloys were subjected to stress corrosion cracking tests at 300 deg C in distilled water with 100 ppm chioride at various pH levels. In general, the higher the nickel content, the more resistant the alloy was to cracking. The corrosion behavior of electroless nickel plate on carbon steel was excellent in distilled water at 300 deg C at adjusted pH levels of 2.5, 7.5, and 10.5. The corrosion of Incoloy, AM-350 stainless steel, Stellites 1, 3, and 98M2, and Rexalloy 33 in HRT core solution was studied. (For preceding period see CF-57-10- 80.) (J.S.R.