CHARACTERIZATION AND ACTUAL WASTE TEST WITH TANK 5F SAMPLES
The initial phase of bulk waste removal operations was recently completed in Tank 5F. Video inspection of the tank indicates several mounds of sludge still remain in the tank. Additionally, a mound of white solids was observed under Riser 5. In support of chemical cleaning and heel removal programs, samples of the sludge and the mound of white solids were obtained from the tank for characterization and testing. A core sample of the sludge and Super Snapper sample of the white solids were characterized. A supernate dip sample from Tank 7F was also characterized. A portion of the sludge was used in two tank cleaning tests using oxalic acid at 50 C and 75 C. The filtered oxalic acid from the tank cleaning tests was subsequently neutralized by addition to a simulated Tank 7F supernate. Solids and liquid samples from the tank cleaning test and neutralization test were characterized. A separate report documents the results of the gas generation from the tank cleaning test using oxalic acid and Tank 5F sludge. The characterization results for the Tank 5F sludge sample (FTF-05-06-55) appear quite good with respect to the tight precision of the sample replicates, good results for the glass standards, and minimal contamination found in the blanks and glass standards. The aqua regia and sodium peroxide fusion data also show good agreement between the two dissolution methods. Iron dominates the sludge composition with other major contributors being uranium, manganese, nickel, sodium, aluminum, and silicon. The low sodium value for the sludge reflects the absence of supernate present in the sample due to the core sampler employed for obtaining the sample. The XRD and CSEM results for the Super Snapper salt sample (i.e., white solids) from Tank 5F (FTF-05-07-1) indicate the material contains hydrated sodium carbonate and bicarbonate salts along with some aluminum hydroxide. These compounds likely precipitated from the supernate in the tank. A solubility test showed the material to be water-soluble consistent with the determined composition. The analytical data for the solid residues filtered from the oxalic acid solution and filtered oxalic acid indicate a large portion of the Tank 5F sludge used in the tank cleaning test dissolved into the oxalic acid. The results of a material balance calculation indicate a high percentage of the iron, uranium, sodium, and aluminum dissolved during both tests. Approximately half of the manganese, a small portion of the plutonium, and essentially none of the nickel dissolved during the tank cleaning tests. Additionally, the results show slightly higher dissolution of the sludge in the 75 C test compared to the 50 C test however, the amount of sludge dissolution gained by using the higher temperature remains small. Some uncertainty remains with respect to the amount of plutonium dissolved in the tank cleaning test. The neutralization of the filtered oxalic acid solutions from the cleaning test produced a large volume of solids ({approx}2X the original sludge mass after filtration and air drying). A large portion of the increase in solids could be attributed to the formation of sodium oxalate. The data from analysis of the solid residues filtered from the neutralization tests and the filtrate obtained indicate most of the iron, uranium, manganese, and a large portion of the aluminum precipitated during the neutralization tests. The data for the 50 C test and the 75 C test show good agreement with the exception of the amount of aluminum precipitated from the neutralization. The slower addition rate of the oxalic acid filtrate to the simulated Tank 7F supernate in the 75 C test might account for the smaller amount of aluminum precipitated and differences in the particle size/morphology and composition of the particulates. Some evidence of uranium separation from other sludge elements appears in the 75 C data. Data collected from the tank cleaning and neutralization tests indicates most of the uranium dissolved during the cleaning test with oxalic acid along with the iron, aluminum, and sodium in the sludge. During the neutralization of the oxalic acid, the majority of the uranium precipitates from solution along with the iron and other typical sludge elements. The CSEM results of the 75 C neutralization test provide some evidence of uranium separation from other sludge elements. However, the CSEM analysis looked at a very small amount of sample, which might not be representative of the bulk material and the sludge sample also showed areas of high uranium concentration. Additionally, how the test results will scale to the full-scale neutralization in a waste tank remains uncertain. The analysis of the oxalic acid filtrates indicates that only a small portion of the plutonium dissolved during the tank cleaning test. However, the analytical data from the solid residues filtered from the cleaning test contradict the solution data and indicate approximately half of the plutonium dissolved.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC09-96SR18500
- OSTI ID:
- 921675
- Report Number(s):
- WSRC-STI-2007-00192-R1; TRN: US0802133
- Country of Publication:
- United States
- Language:
- English
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