1 GLOBAL 2007, Boise, September 9-13, 2007 EXTRACTANT SEPARATION IN DIAMEX-SANEX PROCESS X. HERES,...

GLOBAL 2007, Boise, September 9-13, 2007 1

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


OUTLINE

Context, objectives, principles

Choice of extractant in the organic phase

Choice of reagents in the aqueous phase

Batch validation

Conclusion, Outlook


CEA and LLRN recovery: general flowsheet

Spent fuel

Uranium and

Plutonium

Fission Products

PUREXPUREX

AdditionalSeparationsAdditionalSeparations

Cs

Cm

Am

I

Np

Tc


Advanced partitioning strategy in CEA

Spent Fuel

U, Pu, NpPUREXPUREX

Two step Two step strategystrategyTwo step Two step strategystrategy

Fission Products

DIAMEXDIAMEX Am, CmSANEXSANEX

Ln

One stepOne stepstrategystrategyOne stepOne stepstrategystrategy

Fission Products

Am, CmDIAMEX-SANEXDIAMEX-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


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. FromPUREX

DIAMEX-SANEX

Ln strip.

AnFP

Ln


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 difficultyAcidic extractant extract some fission products at high acidity

Extractant separation to recycle them selectively


DIAMEX-SANEX without extractant separation

HEDTA + citric

pH 3

EXTRACTION

Citric acidpH 3

Ln + Y

Ln STRIPPING

Am + Cm

An STRIPPING

Mo + Pd + Ru

HNO3

1 MZr + Fe

Mo STRIPPING

HNO3 +Oxalic acid

base F.P. (except

Ln,Y,Mo,Zr,Ru)

Zr,Fe STRIPPING

FEEDHNO3 > 3 M

Solvent treatment

DMDOHEMAHDEHP

HTP

DMDOHEMAHDEHP

HTP

DMDOHEMAHDEHP

HTP


DIAMEX-SANEX with extractant separation

DTPA or HEDTA Glycolic acid

pH 3

FEEDHNO3 >3M

EXTRACTION / SRUBBING (DIAMEX process)

F.P. (except Ln+Y)

Ln + Y

Ln STRIPPING

Am + Cm

An STRIPPING

HNO3

0.5-1M

DMDOHEMAHTP

Acidic extractantHTP

HNO3

HEDTA. oxalic acid

HNO3 0.5M

DMDOHEMA HTP

DMDOHEMA Solvent treatment

pH > 5

Extractantseparation


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)


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 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

Choice of HDHP (di-n-hexyl phosphoric acid) because

of:


Biphasic systems studied for DMDOHEMA/HDHP separation

Organic phase

Aqueous solutions

PO

OH

O

O

O

N

O O

N

DMDOHEMA (0.6-0.65M) HDHP (0.08-0.15M)

OH

O

OH

OH O

O

OH

Citric acid(0.3-0.6M)

OH OH

O

Glycolic acid (0.3-1M)

O

OH

OH

OH

O

OH

Tartaric acid(0.3-1M)

1 carboxylic acid

1 'CHON' BaseN

+

CH3

CH3

CH3

CH3

OH

N N

H

HH

H

TMAOH Hydrazine

N+

BuBu

Bu

Bu

OH

TBAOHAmmoniu

m carbonate

(NH4)2CO3

+


Influence of pH on HDHP stripping

0%

20%

40%

60%

80%

100%

120%

1 2 3 4 5 6

Final pH

% F

inal

org

HD

HP

[HDHP]ini=0.08M - CIT 0.6M - O/A=1




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)


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 phasescitric acid 0.3-0.6M

pHini 5-6(fitted with the 'CHON' base)

% of HDHP in the aqueous phase after one extraction ( 100% of DMDOHEMA remained in the organic phase)

HydrazineAmmoniumCarbonate TBAOH

CHON Base

TMAOH0%

10%

20%

30%

40%

50%

60%

70%

80%

90%


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 phasescitric acid 0.3-0.6M

pHini 5(fitted with

TMAOH)

Tartaric AcidCitric Acid

Glycolic Acid

0,3M

0,6M0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

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)


Experiments to validate extractant separation

A

D

DA

D

A

A

D

D

A

D

A

D

D

D

A

A

D

D

D

A

A

HNO3

AA

After shaking

After shaking

After shaking

More than 95% HDHP stripped after two

extractions

More than 90% of HDHP recovered in the organic

phase after one extraction


General flowsheet of DIAMEX-SANEX process

DTPA or HEDTA Glycolic acid

pH 3

FEEDHNO3 >3M

EXTRACTION / SRUBBING (DIAMEX process)

F.P. (except Ln+Y)

Ln + Y

Ln STRIPPING

Am + Cm

An STRIPPING

HNO3

0.5-1MpH buffer solution

pH>5

DMDOHEMAHTP

Acidic extractant+ DMDOHEMA

HTP

HNO3

HEDTA. oxalic acid

Acidic extractant REEXTRACTION

HNO3 0.5M

Acidic extractantSTRIPPING

DMDOHEMA Solvent treatment

DMDOHEMA HTP

WasteHNO3


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…


DIAMEX-SANEX: 3 steps to recover An(III)

pH

4 3 2 1 -1 -2

log(DAn)

log(DLn)

1

2

3

4

pH area for efficient selective An

stripping

0

3 12

An+Ln COEXT.

Ln STRIPPING

An STRIPPING

DIAMIDE (DIAMEX)

Acidic extractant

O

N

O O

N

DMDOHEMA

1 GLOBAL 2007, Boise, September 9-13, 2007 EXTRACTANT SEPARATION IN DIAMEX-SANEX PROCESS X. HERES,...

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Transcript of 1 GLOBAL 2007, Boise, September 9-13, 2007 EXTRACTANT SEPARATION IN DIAMEX-SANEX PROCESS X. HERES,...