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WALKER, DARREL. FLASH POINT OF CSSX SOLVENT. United States: N. p., 2006. Web. doi:10.2172/882726.
WALKER, DARREL. FLASH POINT OF CSSX SOLVENT. United States. doi:10.2172/882726.
WALKER, DARREL. Wed . "FLASH POINT OF CSSX SOLVENT". United States. doi:10.2172/882726.
author = {WALKER, DARREL},
abstractNote = {},
doi = {10.2172/882726},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2006},
month = {Wed Mar 01 00:00:00 EST 2006}

Technical Report:

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  • The results of the present study have validated an equal-volume blending strategy for upgrading freshly prepared CSSX solvent to a blended solvent functionally equivalent to NG-CSSX solvent. It is shown that blending fresh CSSX solvent as currently used in MCU with an equal volume of an NG-CSSX solvent concentrate of appropriate composition yields a blended solvent composition (46.5 mM of MaxCalix, 3.5 mM of BOBCalixC6, 0.5 M of Cs-7SB, 3 mM of guanidine suppressor, and 1.5 mM of TOA in Isopar L) that exhibits equivalent batch ESS performance to that of the NG-CSSX solvent containing 50 mM of MaxCalix, 0.5more » M of Cs-7SB, and 3 mM of guanidine suppressor in Isopar L. The solvent blend composition is robust to third-phase formation. Results also show that a blend containing up to 60% v/v of CSSX solvent could be accommodated with minimal risk. Extraction and density data for the effect of solvent concentration mimicking diluent evaporation or over-dilution of the equal-volume blended solvent are also given, providing input for setting operational limits. Given that the experiments employed all pristine chemicals, the results do not qualify a blended solvent starting with actual used MCU solvent, which can be expected to have undergone some degree of degradation. Consequently, further work should be considered to evaluate this risk and implement appropriate remediation if needed.« less
  • The purpose of this investigation was to determine whether nitrated organic compounds could be formed during operation of the Caustic-Side Solvent Extraction (CSSX) process, and whether such compounds would present a safety concern. The CSSX process was developed to remove cesium from alkaline high-level salt waste stored at the US Department of Energy Savannah River Site (SRS). The solvent is composed of the cesium extractant calix[4]arene-bis-(4-tert-octylbenzo-crown-6) (BOBCalixC6), a fluorinated alcohol phase modifier, tri-n-octylamine (TOA), and an isoparaffinic diluent (Iospar{reg_sign}). During the CSSX process, the solvent is expected to be exposed to high concentrations of nitrate and nitrite dissolved in themore » alkaline waste feed. The solvent will also be exposed to dilute (50 mM) nitric acid solutions containing low concentrations of nitrite during scrubbing, followed by stripping with 1 mM nitric acid. The solvent is expected to last for one year of plant operation, and the temperatures the solvent may experience during the process could range from as low as 15 C to as high as 35 C. Excursions from standard process conditions could result in the solvent experiencing higher temperatures, as well as concentrations of nitrate, nitrite, and most importantly nitric acid, that exceed normal operating conditions. Accordingly, conditions may exist where nitration reactions involving the solvent components, possibly leading to other chemical reactions stemming from nitration reactions, could occur. To model such nitration reactions, the solvent was exposed to the types of nitrate- and nitrite-containing solutions that might be expected to be encountered during the process (even under off-normal conditions), as a function of time, temperature, and concentration of nitrate, nitrite, and nitric acid. The experiments conducted as part of this report were designed to examine the more specific effect that high nitrite concentrations could have on forming nitrated organics. The present set of results supplement those obtained from earlier experiments conducted in FY 2001 in which nitration effects due to nitric acid alone and an average nitrite-containing alkaline simulant were examined.« less
  • In this work, solvent recovery from aqueous CSSX process raffinate effluent was tested using the process diluent (Isopar{reg_sign}L). A model was developed to obtain stage efficiency for the diluent contact stages. The model was used to fit experimental data from a 19.8-hr solvent recovery test. Diluent-in-aqueous entrainment was measured during the test. Vacuum distillation was used to concentrate the solvent components, BOBCalixC6 and modifier, in the diluent used in solvent recovery. Using the results, a feasibility study was performed to compare the annual cost of lost solvent under each of four solvent recovery options. These options were decanter tank, centrifuge,more » two-stage diluent contact using centrifugal contactor, and no solvent recovery action.« less
  • The effects on phase separation and emulsion formation of variables present in the caustic washing of solvent in the caustic-side solvent extraction process have been investigated. The evaluation program was performed in two experiments; results of the first experiment were used to determine conditions for the second test. In the first experiment, the effects of solvent degradation product concentrations (4-sec-butylphenol and dioctylamine), wash solution NaOH concentration, and solvent-to-wash solution volume ratio (O:A) on phase separation were examined. Phase separation performance was quantified in terms of the dimensionless dispersion number, which is also a variable used in the prediction of centrifugalmore » contactor performance by computational means. In the second experiment, phase separation performance in a 5-cm centrifugal contactor was investigated as a function of contactor speed, aqueous-phase NaOH concentration, and solvent-to-wash volume ratio. Separation performance was quantified in terms of the maximum throughput that could be achieved without resulting in >1% contamination of either effluent phase with the opposing phase. Results of the first experiment indicated that none of the variables considered affected phase separation performance at a 95% significance level and that dioctylamine concentration was the only single factor that affected phase separation at a 90% significance level. The results do indicate 90% significance for interaction effects between NaOH concentration and O:A and between NaOH concentration and 4-sec-butylphenol concentration. However, none of the dispersion numbers obtained were inconsistent with values obtained in previous studies of CSSX solvent formulations. Results of contactor performance tests indicated that acceptable phase separation was achieved at relatively high throughputs over a range of O:A ratios and wash solution NaOH concentrations. Emulsion formation during contactor operation was observed only under off-normal conditions. Taken together, the results of the work described in this report indicate that from the perspective of phase separation efficiency, CSSX solvent washing can be performed over a range of conditions. Consequently, contaminant removal considerations should not be affected by hydraulic performance concerns in the selection of parameters for solvent treatment.« less
  • The solvent was loaded with {sup 137}Cs and subsamples were stored on a shaker table while in contact with the extract, scrub, or strip aqueous phases. Evidence of solvent degradation was evaluated at exposure times of 0, 20, 54, and 83 days. This resulted in estimated solvent doses ranging up to 1.24 Mrad, equivalent to the dose expected to be received during 16.5 years of operation at the plant proposed for the Savannah River Site. The break times and distribution of cesium of the batch samples remained constant within experimental error; in addition, no third-phase formation was observed. The solventmore » concentrations of calix[4]arene-bis-(tert-octylbenzo-crown-6) and 1-(2,2,3,3-tetra-fluoroproproxy)-3-(4-sec-butylphenoxy)-2-propanol remained constant within experimental error. Solvent degradation with irradiation was evidenced by a decrease in the trioctylamine (TOA) concentration in the solvent and an increase in the solvent concentration of the degradation product 4-sec-butylphenol. No decline in extraction or scrubbing performance of the irradiated solvents was observed. The stripping performance of the solvent was seriously impaired with irradiation; however, a mild caustic wash and replenishment of the TOA concentration restored the ability to strip the irradiated solvent.« less