1. 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. 2 OUTLINE Context, objectives, principles Choice of extractant in the organic phase Choice of reagents in the aqueous phase Batch validation Conclusion, Outlook

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

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

5. 5 GLOBAL 2007, Boise, September 9-13, 2007 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 Extr. Selective strip. From PUREX DIAMEX-SANEX Ln strip. AnFP Ln

6. 6 GLOBAL 2007, Boise, September 9-13, 2007 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

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

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

9. 9 GLOBAL 2007, Boise, September 9-13, 2007 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: D HDHP > 20 at pH < 3,5 with An stripping solution (DTPA / glycolic acid) (with concentrated Ln D HDHP  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: D Ln > 2 and SF(Ln/An) > 20 pH > 2 with DTPA/glycolic acid solution (cations at nominal concentrations, UOX3 fuel for example)

10. 10 GLOBAL 2007, Boise, September 9-13, 2007 Choice of acidic extractant (2)  Hydrolytic and radiolytic stability better than DMDOHEMA Several studies and hot tests have shown that DMDOHEMA is suitable for a nuclear process  No precipitate or gel with Ln in organic phase A 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  Choice of HDHP (di-n-hexyl phosphoric acid) because of:

11. 11 GLOBAL 2007, Boise, September 9-13, 2007 Biphasic systems studied for DMDOHEMA/HDHP separation Organic phase Aqueous solutions DMDOHEMA (0.6-0.65M) HDHP (0.08-0.15M) Citric acid (0.3-0.6M) Glycolic acid (0.3-1M) Tartaric acid (0.3-1M) 1 carboxylic acid 1 'CHON' Base TMAOH Hydrazine TBAOH Ammonium carbonate (NH 4 ) 2 CO 3 +

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

13. 13 GLOBAL 2007, Boise, September 9-13, 2007 Effect of the base on HDHP stripping efficiency 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) Organic phase HDHP 0.14M DMDOHEMA 0.6M in HTP Aqueous phases citric acid 0.3-0.6M pH ini 5-6 (fitted with the 'CHON' base) % of HDHP in the aqueous phase after one extraction (  100% of DMDOHEMA remained in the organic phase)

14. 14 GLOBAL 2007, Boise, September 9-13, 2007 Effect of the carboxylic acid % of HDHP in the aqueous phase after one extraction (  100% of DMDOHEMA remained in the organic phase) Organic phase HDHP 0.14M DMDOHEMA 0.6M in HTP Aqueous phases citric acid 0.3-0.6M pH ini 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)

15. 15 GLOBAL 2007, Boise, September 9-13, 2007 Experiments to validate extractant separation A D D A D A A D D A D A D D D A A D D D A A HNO 3 A A After shaking More than 95% HDHP stripped after two extractions More than 90% of HDHP recovered in the organic phase after one extraction

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

17. 17 GLOBAL 2007, Boise, September 9-13, 2007 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…

18. 18 GLOBAL 2007, Boise, September 9-13, 2007 DIAMEX-SANEX: 3 steps to recover An(III) pH 4321-2 log(D An ) log(D Ln ) 1 2 3 4 pH area for efficient selective An stripping 0 312 An+Ln COEXT. Ln STRIPPING An STRIPPING DIAMIDE (DIAMEX) Acidic extractant DMDOHEMA