Flowsheet acidic waste

Figure 3. Conceptual flowsheet for actinide partitioning from ICPP acidic waste...

Fig. 1. Schematic flowsheet of uranium processing (acid leach and ion exchange) operation. Numbers refer to the numbers that appear in the boxes on the flowsheet. Operations (3), (6), (9), and (11) may be done by thickening or filtration. Most often, thickeners are used, followed by filters. The pH of the leach slurry <4) is elevated to reduce its corrosive effect and to improve the ion-exchange operation on the uranium liquor subsequently separated, In tile ion exchange operation (7), resin contained in closed columns is alternately loaded with uranium and then eluted. The resin adsorbs the complex anions, such as UC fSO 4-. in which the uranium is present in the leach solution. Ammonium nitrate is nsed for elution, obtained by recycling the uranium filtrate liquor after pH adjustment. Iron adsoibed with the uranium is eluted with it. Iron separation operation (8) is needed inasmuch as the iron hydroxide slurry is heavily contaminated with calcium sulfate and coprecipitated uranium salts. Therefore, the slurry is recycled to the watering stage (3). Washed solids from 1,6). the waste barren liquor from (7), and the uranium filtrate from (11) are combined. The pH is elevated to 7.5 by adding lime slurry before the mixture is pumped to the tailings disposal area. (Rio Algom Mines Limited, Toronto)...

Law, J.D., Herbst, R.S., Todd, T.A. 2002. Integrated AMP-PAN, TRUEX, and SREX testing. II. Flowsheet testing for separation of radionuclides from actual acidic radioactive waste. Sep. Sci. Technol. 37 (6) 1353-1373. 

Herbst, R.S., Law, J.D., Todd, T.A. et al. 2002. Universal solvent extraction (UNEX) flowsheet testing for the removal of cesium, strontium, and actinides elements from radioactive, acidic dissolved waste. Solvent Extr. IonExch. 20 (4—5) 429 445. 

FIGURE 4.3 Flowsheet of cesium process for extraction of cesium from acidic high-activity level waste with MC8 (0.062 M) diluted in the mixture TBP (1.5 M)/TPH. 

Although solvent samples have been observed for approximately one year without any solids formation, work was completed to define a new solvent composition that was thermodynamically stable with respect to solids formation and to expand the operating temperature with respect to third-phase formation.109 Chemical and physical data as a function of solvent component concentrations were collected. The data included BC6 solubility cesium distribution ratio under extraction, scrub, and strip conditions flowsheet robustness temperature range of third-phase formation dispersion numbers for the solvent against waste simulant, scrub and strip acids, and sodium hydroxide wash solutions solvent density viscosity and surface and interfacial tension. These data were mapped against a set of predefined performance criteria. The composition of 0.007 M BC6, 0.75 M l-(2,2,3,3-tetrafluoropropoxy)-3-(4-.sw-butylphenoxy)-2-propanol, and 0.003 M TOA in the diluent Isopar L provided the best match between the measured properties and the performance criteria. 

Simulated solutions of Russian waste and INL (Idaho National Laboratory, USA) waste were used as feed solutions. Extraction of cesium was 98.4%, and of strontium, 98.1%. A problem with low solubility of the crown ethers (<180 mg/L for all type of solutions) was shown in the tests. The authors pointed out the main positive features of the proposed flowsheet a salt-free strip product with very low nitric acid concentration (<0.1 M), possibility to extract both cesium and strontium, and low losses of extractants. A last step in the modification of this solvent was the addition of polyalkylphosphonitrilic acid to the mixture of crown ethers.65 Positive results were obtained for extraction of not only Cs and Sr, but also MAs from simulated HLW. 

Pilot-plant work has been performed for the Savannah River Laboratory and for Battelle s PNL to develop fluidized-bed process flowsheets for solidifying neutralized AEG waste and for acid Purex waste. A Purex waste, partially neutralized and containing 2M Na (type PW-6), will... 

Mclsaac, L. D., Baker, J. D., Krupa, J. F., Meikrantz, D. H., and Schroeder, N. C., "Flowsheet Development Work at the Idaho Chemical Processing Plant for the Partitioning of Actinides from Acidic Nuclear Waste," Actinide Separations Symposium, ACS Pacific Chemical Conference, Honolulu,... 

Flowsheet Development Work at the Idaho Chemical Processing Plant for the Partitioning of Actinides from Acidic Nuclear Waste... 

Because of the great variety of aqueous waste streams and differences in process flow arrangements in different plants, there is no standard flowsheet for processing aqueous wastes from the PUREX process. Figure 14.15 depicts the principal steps in one possible scheme for concentrating the wastes and recovering water and nitric acid from them. Low-level, low-acid, low-salt wastes are neutralized, if necessary, and concentrated in a simple flash or vapor-compression evaporator to produce LLW concentrates and waste sufficiently decontaminated for return to process. 

Flowsheet for demonstration of the UNEX process. (Data from Law, S. Herbst, T. Todd, V. Romanovskiy, V. Barbain, V. Esimantovskiy, I. Smirnov, and B.N. Zaitsev, 2001. The universal solvent extraction (UNEX) process 11. Flowsheet development and demonstration of the UNEX process for the separation of cesium, strontium, and actinides from actual acidic radioactive waste. Solvent Extraction and Ion Exchange 19(l) 23-36.)... 

In outline, reprocessing was based on disassembly of the fuel assemblies to individual pins, single pin cropping, dissolution in nitric acid and operation of a Purex-type flowsheet in a chemical separation plant equipped with pulsed mixer settlers. The modified dissolver cell and solvent extraction plant were recommissioned late in 1979 and were tested in reprocessing of the final batches of DFR fuel. The new head-end facility, to disassemble the PFR fuel assemblies and to crop the pins, and the new waste treatment facilities were commissioned in 1980 reprocessing of the first batches of PFR fuel began later that year. 

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