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EXTRACTANT SEPARATION IN DIAMEX-SANEX PROCESS

GLOBAL 2007, Boise, September 9-13, 2007. EXTRACTANT SEPARATION IN DIAMEX-SANEX PROCESS. X. HERES, E. AMEIL, I. MARTINEZ, P. BARON, C. HILL Radiochemistry & Processes Department CEA Marcoule. OUTLINE. Context, objectives, principles Choice of extractant in the organic phase

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EXTRACTANT SEPARATION IN DIAMEX-SANEX PROCESS

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  1. GLOBAL 2007, Boise, September 9-13, 2007 EXTRACTANT SEPARATION IN DIAMEX-SANEX PROCESS X. HERES, E. AMEIL, I. MARTINEZ, P. BARON, C. HILL Radiochemistry & Processes Department CEA Marcoule GLOBAL 2007, Boise, September 9-13, 2007

  2. OUTLINE • Context, objectives, principles • Choice of extractant in the organic phase • Choice of reagents in the aqueous phase • Batch validation • Conclusion, Outlook GLOBAL 2007, Boise, September 9-13, 2007

  3. CEA and LLRN recovery: general flowsheet Spent fuel I Uranium and Plutonium PUREX Tc Np Cs AdditionalSeparations Am Fission Products Cm GLOBAL 2007, Boise, September 9-13, 2007

  4. Two step strategy DIAMEX SANEX Am, Cm Ln Fission Products One step strategy DIAMEX-SANEX Am, Cm Fission Products Advanced partitioning strategy in CEA Spent Fuel PUREX U, Pu, Np Demonstrative test performed in 2005 (Atalante CEA): More than 99.9% of purified Am, Cm recovered Optimization: DIAMEX-SANEX, a “one cycle strategy” process GLOBAL 2007, Boise, September 9-13, 2007

  5. DIAMEX-SANEX From PUREX Selective strip. Ln strip. Extr. Ln FP An Objectives - Principles • Objective: • Selective recovery of An(III) in one single extraction cycle after PUREX process • Principles: • Co-extraction of An(III) and Ln(III) by DIAMEX type Process • An(III) selective stripping using an aqueous complexing agent GLOBAL 2007, Boise, September 9-13, 2007

  6. Difficulties - Resolutions • Difficulty Aqueous An selective complexants are efficient only at low acidity • Two extractants in solvent, efficient in two distinct acidity ranges • Malonamide to extract An, Ln from PUREX raffinate (high acidity) • Acidic extractant to keep Ln in the organic phase at low acidity. • Other difficulty Acidic extractant extract some fission products at high acidity • Extractant separation to recycle them selectively GLOBAL 2007, Boise, September 9-13, 2007

  7. DIAMEX-SANEX without extractant separation Solvent treatment DMDOHEMA HDEHP HTP DMDOHEMA HDEHP HTP EXTRACTION Mo STRIPPING FEED HNO3 > 3 M base Citric acid pH 3 Mo + Pd + Ru F.P. (except Ln,Y,Mo,Zr,Ru) DMDOHEMA HDEHP HTP Ln STRIPPING An STRIPPING Zr,Fe STRIPPING HNO3 + Oxalic acid HEDTA + citric pH 3 Am + Cm HNO3 1 M Ln + Y Zr + Fe GLOBAL 2007, Boise, September 9-13, 2007

  8. DIAMEX-SANEX with extractant separation DMDOHEMA HTP EXTRACTION / SRUBBING (DIAMEX process) DMDOHEMA Solvent treatment F.P. (except Ln+Y) FEED HNO3 >3M HNO3 HEDTA. oxalic acid HNO3 0.5M DMDOHEMA HTP Acidic extractant HTP Extractant separation Ln STRIPPING An STRIPPING pH > 5 DTPA or HEDTA Glycolic acid pH 3 Am + Cm HNO3 0.5-1M Ln + Y GLOBAL 2007, Boise, September 9-13, 2007

  9. Choice of acidic extractant (1) • More then 30 dialkylphosphoric acid synthesized and studied • Choice of HDHP (di-n-hexyl phosphoric acid) because of: • Good lipophilic properties:DHDHP > 20 at pH < 3,5 with An stripping solution (DTPA / glycolic acid)(with concentrated Ln DHDHP  6-9  (Ln(DHP)n more soluble but not a drawback for the process since aqueous outflow should contain few Ln) • Good Ln/An selectivity and Ln extraction properties:DLn > 2 and SF(Ln/An) > 20 pH > 2 with DTPA/glycolic acid solution (cations at nominal concentrations, UOX3 fuel for example) GLOBAL 2007, Boise, September 9-13, 2007

  10. Choice of acidic extractant (2) • Choice of HDHP (di-n-hexyl phosphoric acid) because of: • Hydrolytic and radiolytic stability better than DMDOHEMASeveral studies and hot tests have shown that DMDOHEMA is suitable for a nuclear process • No precipitate or gel with Ln in organic phaseA lot of dialkylphosphoric acid lead to a precipitate after Ln extraction, as for example the bis(dimethyl1,3)butyl phosphorique HBDMBP, with other behavior similar to HDHP GLOBAL 2007, Boise, September 9-13, 2007

  11. Biphasic systems studied for DMDOHEMA/HDHP separation Organic phase HDHP (0.08-0.15M) DMDOHEMA (0.6-0.65M) Aqueous solutions 1 carboxylic acid Citric acid (0.3-0.6M) Tartaric acid (0.3-1M) Glycolic acid (0.3-1M) + (NH4)2CO3 1 'CHON' Base Ammonium carbonate Hydrazine TBAOH TMAOH GLOBAL 2007, Boise, September 9-13, 2007

  12. Influence of pH on HDHP stripping pH of the aqueous solutions fitting with TMAOH Good stripping of HDHP for pH > 4.5-5 (>pKA of HDHP) with citric/TMAOH aqueous systems (same results for tartaric or glycolic acids) GLOBAL 2007, Boise, September 9-13, 2007

  13. Effect of the base on HDHP stripping efficiency % of HDHP in the aqueous phase after one extraction ( 100% of DMDOHEMA remained in the organic phase) Organic phaseHDHP 0.14M DMDOHEMA 0.6M in HTP Aqueous phasescitric acid 0.3-0.6MpHini 5-6(fitted with the 'CHON' base) The base plays a key role in the stripping of HDHP. TMAOH-TBAOH which contain alkyl chains are the best among the 'CHON' bases studied (lipotropic property) GLOBAL 2007, Boise, September 9-13, 2007

  14. Effect of the carboxylic acid % of HDHP in the aqueous phase after one extraction ( 100% of DMDOHEMA remained in the organic phase) Organic phaseHDHP 0.14M DMDOHEMA 0.6M in HTP Aqueous phasescitric acid 0.3-0.6MpHini 5(fitted with TMAOH) • Suitable performances to strip HDHP in the aqueous phase. • Tartaric seems to be the better choice (efficiency/waste management) but third phases formation at pH 4-5 (accumulation in the process). • Same phenomenon with glycolic acid. • Choice of citric acid (better compromise) GLOBAL 2007, Boise, September 9-13, 2007

  15. A D D A A D D A D D A A D D A D D D D A Experiments to validate extractant separation HNO3 After shaking After shaking A A A A More than 95% HDHP stripped after two extractions More than 90% of HDHP recovered in the organic phase after one extraction After shaking GLOBAL 2007, Boise, September 9-13, 2007

  16. General flowsheet of DIAMEX-SANEX process DMDOHEMA HTP EXTRACTION / SRUBBING (DIAMEX process) DMDOHEMA Solvent treatment F.P. (except Ln+Y) FEED HNO3 >3M HNO3 HEDTA. oxalic acid HNO3 0.5M Acidic extractant + DMDOHEMA HTP Acidic extractant REEXTRACTION DMDOHEMA HTP HNO3 Waste Acidic extractant STRIPPING Ln STRIPPING An STRIPPING DTPA or HEDTA Glycolic acid pH 3 pH buffer solution pH>5 Am + Cm HNO3 0.5-1M Ln + Y GLOBAL 2007, Boise, September 9-13, 2007

  17. Conclusion - Outlook • Extractant separation is a new concept to simplify a process with 2 extractant solvent. • Citric acid and TMAOH are suitable to strip selectively HDHP into an aqueous phase before recycling it in an organic phase by acidification • Inactive and hot tests are planned to validate the whole flowsheet on a surrogate and genuine feed solutions in 2007 and in 2009. • Optimization of the flowsheet are carried out to substitute for TMAOH, not very suitable for waste management… GLOBAL 2007, Boise, September 9-13, 2007

  18. DIAMEX-SANEX: 3 steps to recover An(III) Acidic extractant log(DAn) log(DLn) 4 DIAMIDE (DIAMEX) 3 2 DMDOHEMA pH area for efficient selective An stripping 1 pH 0 4 3 2 1 -1 -2 2 3 1 Ln STRIPPING An STRIPPING An+Ln COEXT. GLOBAL 2007, Boise, September 9-13, 2007

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