HRP RADIATION CORROSION STUDIES: IN-PILE LOOP L-4-11

Abstract

The sixth in-pile loop experiment, L-4-11, was com pleted. The loop operated in-pile for a total of 1109 hr, during which time the LITR energy output was 2175 Mwhr. The main-stream operating temperature was 250 deg C. During this run the loop was drained and then recharged with fresh solution. Based on oxygen data, the corrosion rate for the first 110 hr of operation was 5.0 mpy; for the next 232 hr the rate was 1.7 mpy. For the first 120 hr of operation with the second fuel solution the corrosion rate was 7.2 mpy, and for the remainder of the run the rate was 1.9 mpy. The nickel data gave parallel results. Corrosion specimen of a large variety of zirconium alloys, titanium alloys, and stainless steels, as well as specimen of synthetic sapphire, sintered alumina, platinum, and Incoloy, were included in the experiment. Corrosion rates of most of the zirconium alloys, titanium alloys, and stainless steels were generally consistent with rates observed in the previous in-pile loops. The zirconium alloys Zr-3 (3% Ag), Zr-3 (0.52% Sn, 5.71%, Ti, 40 ppm N/sub 2/), Zr-3 (0.52% Sn, 0.28% Fe, 5.66% Ti, 60 ppm N/sub 2/), Zr-3 (1.4% Fe), and Zr-4 (0.7% Fe, 2.8% Cr) corroded at rates about two to three times those observed for Zircaloy-2 at the same power denity. The zirconium alloy containing 3.84% Al and 2.5% Mn corroded at rates about 10 to 20 times those for Zircaloy-2. The zirconium alloy containing 2% niobium corroded at the same rate as Zircaloy-2 in the core but at a much higher rate, 17 mpy, in the in-line position. However, a zirconium alloy containing 15% riobium corroded at less than one-third the Zircaloy-2 corrosion rates in the core and exhibited rates similar to Zircaloy-2 in the in-line position. Corrosion rates for Incoloy were found to be about the same as those for stainless steel exposed to similar condition. All sintered aluminum oxide specimens in the main stream disintegrated; however, the aluminum oxide bearings in the low temperature region of the pump showed no measurable wear. Synthetic sapphire became cloudy and corroded at a rate of 12 mpy. Platinum was slightly affected in the core. (auth)