Integrated AMP-PAN, TRUEX, and SREX Flowsheet Test to Remove Cesium, Surrogate Actinide Elements, and Strontium from INEEL Tank Waste Using Sorbent Columns and Centrifugal Contactors

Abstract

Three unit operations for the removal of selected fission products, actinides, and RCRA metals (mercury and lead) have been successfully integrated and tested for extended run times with simulated INEEL acidic tank waste. The unit operations were ion exchange for Cs removal, followed by TRUEX solvent extraction for Eu (actinide surrogate), Hg, and Re (Tc surrogate) removal, and subsequent SREX solvent extraction for Sr and Pb removal.Approximately 45 L of simulated INTEC tank waste was first processed through three ion exchange columns in series for selective Cs removal. The columns were packed with a composite ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) sorbent. The ion exchange system was operated continuously for ~34 hours at 22 bed volumes per hour in the first two columns. The first two columns were each sized at a bed volume of 60 cm 3 and were operated to 100% breakthrough. The experimental breakthrough data were in excellent agreement with modeling predictions based on data obtained with much smaller (1.5 cm 3 ) columns. The third column (220 cm 3 ) was used for polishing and Cs removal after breakthrough of the up-stream columns. The Cs removal was >99.83% in the ion exchange system without interference from other species.Most of the effluent from the ion exchange (IX) system was immediately processed through a TRUEX solvent extraction flowsheet to remove europium (americium surrogate), mercury and rhenium (technetium surrogate) from the simulated waste. The TRUEX flowsheet test was performed utilizing 23 stages of 3.3 cm centrifugal contactors. The TRUEX test was operated a total of 71.3 hours and processed ~41 L of the IX effluent using 1.5 L of TRUEX solvent with constant solvent recycle. The TRUEX solvent was recycled through the flowsheet an estimated 17 times. Greater than 99.999% of the Eu, 96.3% of the Hg, and 56% of the Re were extracted from the simulated feed and recovered in the strip and wash streams. Minor operational problems were encountered in the solvent wash section, where Hg precipitated as HgO; the problem did not require shutdown of the system. Flooding was never observed during the experiment. Over the course of the test, there was no detectable build-up of any components in the TRUEX solvent.The raffinate from the TRUEX test was stored and subsequently processed several weeks later through a SREX solvent extraction flowsheet to remove strontium, lead, and Re (Tc surrogate) from the simulated waste. The SREX flowsheet test was performed using the same centrifugal contactors used in the TRUEX test after reconfiguration and the addition of 3 stages. Approximately 51 L of TRUEX raffinate was processed through the system during 77.9 hours of continuous operation with 1.5 L of SREX solvent and continuous solvent recycle. The SREX solvent was recycled through the system an estimated 45 times without measurable build-up of any components in the solvent. Approximately 99.9% of the Sr, >99.89% of the Pb, and >96.4% of the Re were extracted from the aqueous feed to the SRE...

The Effect of Gamma Irradiation on the Ion Exchange Properties of Caesium-Selective Ammonium Phosphomolybdate-Polyacrylonitrile (AMP-PAN) Composites under Spent Fuel Recycling Conditions

“…This level of irradiation thus has little or no effect on the ion exchange properties of both AMP and AMP-PAN. K d values for Cs + at both concentrations tested remained above 10,000 after 24 h. Under the conditions we tested, both AMP and AMP-PAN follow pseudo-second-order absorption kinetics adhering to the Langmuir isotherm, mirroring previous results [20,30,36]. We have thus demonstrated the efficacy of AMP-PAN as a Cs ion exchange composite under the Cs + concentrations and acidity of spent fuel dissolver conditions following exposure to significant levels of gamma radiation.…”

A Reliable Hybrid Adsorbent for Efficient Radioactive Cesium Accumulation from Contaminated Wastewater

“…Moreover, incomplete removal, high cost and considerable disposal of toxic waste resulting from such processes have significantly hindered the application of these methods. Various ion-exchange resins such as hollow Prussian blue, zeolite, ammonium molybdophosphate-polyacrylonitrile (AMP-PAN), potassium-nickel hexacyanoferrate-polyacrylonitrile (KNiFC-PAN), metal hexacyanoferrate and polyphenol rich have also been investigated for removing Cs from liquid wastewater 13 14 15 16 17 18 19 20 21 22 23 . However; highly selective materials are always welcome to remove the Cs from the liquid wastewater.…”