DISSOLUTION OF 3013-DE SAMPLE 10-16

Taylor-Pashow, K.

Savannah River Site (S.C.)

关键词: Flammability;    Solubility;    Nitric Acid;    Tungsten;    Chlorides;   

DOI  :  10.2172/1017425
RP-ID  :  SRNL-STI-2011-00222
RP-ID  :  DE-AC09-08SR22470
RP-ID  :  1017425

美国|英语

来源: UNT Digital Library

【 摘 要 】

The HB-Line Facility has a long-term mission to dissolve and disposition legacy fissile materials. HB-Line dissolves plutonium dioxide (PuO{sub 2}) from K-Area parting support of the 3013 Destructive Examination (DE) program. The PuO{sub 2}-bearing solids originate from a variety of unit operations and processing facilities, but all of the material is assumed to be high-fired (i.e., calcined in air for a minimum of two hours at {ge} 750 C). The Savannah River National Laboratory (SRNL) conducted dissolution flowsheet studies on 3013 DE Sample 10-16 (can R610826), which contains weapons-grade plutonium (Pu) as the fissile material. The dissolution flowsheet study was performed for 4 hours at 108 C on unwashed material using 12 M nitric acid (HNO{sub 3}) containing 0.20 M potassium fluoride (KF). After 4 hours at 108 C, the {sup 239}Pu Equivalent concentration was 32.5 g/L (gamma, 5.0% uncertainty). The insoluble residue comprised 9.88 wt % of the initial bulk weight, and contained 5.31-5.95 wt % of the initial Pu. The residue contained Pu in the highest concentration, followed by tungsten (W). Analyses detected 2,770 mg/L chloride (Cl{sup -}) in the final dissolver solution (3.28 wt %), which is significantly lower than the amount of Cl{sup -} detected by prompt gamma (9.86 wt %) and the 3013 DE Surveillance program (14.7 wt %). A low bias in chloride measurement is anticipated due to volatilization during the experiment. Gas generation studies found approximately 60 mL of gas per gram of sample produced during the first 30 minutes of dissolution. Little to no gas was produced after the first 30 minutes. Hydrogen gas (H{sub 2}) was not detected in the sample. Based on detection limits and accounting for dilution, the generated gas contained < 0.12 vol % H{sub 2}, which is well below the 4.0 vol % flammability limit for H{sub 2} in air. Filtration of the dissolver solution occurred readily. When aluminum nitrate nonahydrate (ANN) was added to the filtered dissolver solution at a 3:1 Al:F molar ratio, and stored at room temperature for 24 hours, the solution filtered approximately 6 times slower than when filtered 30 minutes after ANN addition, requiring 6 minutes to complete compared to 55 seconds for the first filtration. It is likely that the ambient-temperature solubility for ANN was exceeded. A 4-hour dissolution time at a temperature of 108 C in 12 M HNO{sub 3}/0.2 M KF is recommended for dissolution of this material.