Description: Canister SS-9 was filled with high-level phosphate ceramic waste material in March 1969. Following 1.2 years water storage at 50/sup 0/C, 3.5 years hot air storage at 400 to 500/sup 0/C, and 10 months water storage at 50/sup 0/C, the canister failed. The canister has three visible cracks, one of which is 13 in. long. It was concluded from metallography that failure was due to stress-assisted intergranular attack enhanced by metal sensitization during the hot air storage period, and a high chloride ion concentration in the canister storage water. Cores were taken from Canister SS-9 and the leach rate of the material in deionized water was determined to be 5.1 x 10/sup -4/ g/cm/sup 2/-day for the first day. Averaged over 90 days, the material leach rate was 3.1 x 10/sup -5/ g/cm/sup 2/-day. Since it was known that the failure occurred sometime between quarterly canister storage water sampling periods, these leach rates were used to calculate an effective waste surface area presented by the canister cracks. Thus, the leach rates for the first day and the average for 90 days represent the extremes that could have occurred. The effective waste surface area contacted via the canister cracks was calculated to be between 1 and 20 m/sup 2/. Based on the calculated effective surface area and the above leach rates of the phosphate ceramic material, 6.1 g of waste were dissolved per day. This is related to the activity of the canister as follows: Curies of /sup 137/Cs in Canister SS-9 (corrected to May 1977) = 1.78 x 10/sup 4/; Curies of /sup 137/Cs leached in one day, based on above leach rates = 5.5 x 10/sup -1/; Percent of total cesium in canister = 3.1 x 10/sup -3/; Curies of /sup 137/Cs leached in one day based on averaged ...
Date: November 1, 1977
Creator: Bradley, D.J.
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Partner: UNT Libraries Government Documents Department