Study results confirm that waterfowl are consuming seeds from a variety of agronomically important weed species, including Palmer amaranth, which can remain viable after passage through digestive tracts and have potential to be dispersed over long distances by waterfowl. © 2017 Society of Chemical Industry.

Chloride (Cl -) salt processing in strong acids is used to recycle plutonium (Pu) from pyrochemical residues. The Savannah River National Laboratory (SRNL) is studying the potential application of nitrogen dioxide (NO 2 ) gas to effectively convert dissolved pyrochemical salt solutions to chloride-free solutions and improve recovery operations. An NO 2 sparge has been shown to effectively remove Cl -from solutions containing 6-8 M acid (H + ) and up to 5 M Cl -. Chloride removal occurs as a result of the competition of at least two reactions, one which is acid-dependent. Below 4 M H + , NO 2 reacts with Cl -to produce nitrosyl chloride (ClNO).Between 6 M and 8 M H + , the reaction of hydrochloric acid (HCl) with nitric acid (HNO 3 ), facilitated by the presence of NO 2 , strongly affects the rate of Cl -removal. The effect of heating the acidic Cl -salt solution without pre-heating the NO 2 gas has minimal effect on Cl -removal rates when the contact times between NO 2 and the salt solution are on the order of seconds.

The H-Canyon facility will be used to dissolve Pu metal for subsequent purification and conversion to plutonium dioxide (PuO 2) using Phase II of HB-Line. To support the new mission, the development of a Pu metal dissolution flowsheet which utilizes concentrated (8-10 M) nitric acid (HNO 3) solutions containing potassium fluoride (KF) is required. Dissolution of Pu metal in concentrated HNO 3 is desired to eliminate the need to adjust the solution acidity prior to purification by anion exchange. The preferred flowsheet would use 8-10 M HNO 3 , 0.015-0.07 M KF, and 0.5-1.0 g/L Gd to dissolve the Pu up to 6.75 g/L. An alternate flowsheet would use 8-10 M HNO 3 , 0.1-0.2 M KF, and 1-2 g/L B to dissolve the Pu. The targeted average Pu metal dissolution rate is 20 mg/min-cm 2 , which is sufficient to dissolve a "standard" 2250-g Pu metal button in 24 h. Plutonium metal dissolution rate measurements showed that if Gd is used as the nuclear poison, the optimum dissolution conditions occur in 10 M HNO 3 , 0.04-0.05 M KF, and 0.5-1.0 g/L Gd at 112 to 116 C (boiling). These conditions will result in an estimated Pu metal dissolution rate of ~11-15 mg/min-cm 2 and will result in dissolution times of 36-48 h for standard buttons. The recommended minimum and maximum KF concentrations are 0.03 M and 0.07 M, respectively. The maximum KF concentration is dictated by a potential room-temperature Pu-Gd-F precipitation issue at low Pu concentrations. Testing at 8-10 M HNO 3 , 0.1-0.2 M KF, and 1-2 g/L B demonstrated that ~20-35 mg/min-cm 2 Pu metal dissolution rates can be achieved at 112 to 116 C (boiling). The concentration of B in solution did not have a significant effect on dissolution rate. The data also indicate that lower KF concentrations would yield dissolution rates for B comparable to those observed with Gd at the same HNO 3 concentration and dissolution temperature. The low-temperature Pu precipitation issue associated with the use of Gd does not occur for dissolution with B; however, the B concentration must be maintained below the H 3 BO 3 solubility limit and the KF concentration must not exceed the value where B precipitates as KBF 4. To confirm that the optimal conditions identified by the dissolution rate measurements can be used to dissolve Pu metal up to 6.75 g/L in the presence of representative concentrations of Fe and Gd or B, a series of experiments was performed to demonstrate the flowsheets. In three of the five experiments, the offgas generation rate during the dissolution was measured and samples were analyzed for hydrogen gas (H 2). The use of 10 M HNO 3 containing 0.03-0.05 M KF, 0.5-1.0 g/L Gd, and 1.9 g/L Fe resulted in complete dissolution of the metal in 2.0-3.5 h. When B was used as the neutron poison, 10 M HNO 3 solutions containing 0.05-0.1 M KF, 1.9 g/L Fe, and 1 g/L B resulted in complete dissolution of the metal in 0.75-2.0 h. All experiments were performed using a dissolution temperature of 100 C. No residues were observed following the dissolutions in either the Gd or B system. Dissolut...

Researchers at the Savannah River Technology Center (SRTC) successfully demonstrated the Caustic-Side Solvent Extraction (CSSX) process flow sheet using a 33-stage, 2-cm centrifugal contactor apparatus in two 24-hour tests using actual high level waste. The CSSX process for removal of cesium from alkaline solutions is the reference process for decontamination of high level waste (HLW) at the Savannah River Site (SRS). The solvent consists of a calix [4]arene-crown-6 extractant (BOBCalix), an alkylphenoxy alcohol modifier, and trioctylamine (TOA) dissolved in an inert hydrocarbon matrix (Isopar ® L). Previously, we demonstrated the solvent extraction process with actual SRS HLW supernatant solution using a non-optimized solvent formulation. Following that test, the solvent system was optimized to enhance extractant solubility in the diluent by increasing the modifier concentration. We now report results of two tests with the new and optimized solvent. The first test used a composite of supernatant solutions from two waste tanks and the second test used a solution derived from dissolved salt cake. Test results showed that the CSSX process using the optimized solvent reduces 137 Cs in HLW supernatant solutions to concentrations below the waste acceptance criterion (WAC) of 45 nCi/g for disposal as low-level waste (called "Saltstone"). Waste decontamination factors as high as three million were achieved during testing. Test durations exceeded 24 hours of uninterrupted operation and demonstrated hydraulic stability of the contactor array while operating with the optimized solvent. Carryover of organic solvent in aqueous streams (and aqueous in organic streams) was found to be less than 1%. The concentration factor (i.e., the ratio of the cesium concentration in the strip raffinate to the concentration in the waste) averaged approximately 13 during both tests, slightly below the process requirement of 15. Uncertainties in process flow rate measurement and control prevented the test from achieving the target of 15.

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