Selective complexation of f-elements Partitioning & Transmutation

Transcription

1 Selective complexation of f-elements Partitioning & Transmutation Antje Bremer, Andreas Geist, Petra J. Panak 1 KIT Universität des Landes Baden-Württemberg und nationales Forschungszentrum in der Helmholtz-Gemeinschaft

2 Partitioning & Transmutation Strategy Long-term radiotoxicity and heat load of used nuclear fuel governed by transuranium elements (TRU = Np, Pu, Am, Cm) Radiotoxicity [Sv/t HM ] Total Fission Products Minor Actinides (Np, Am, Cm) Plutonium nat. U Time after discharge [y] Due to Cm partitioning Due to Am partitioning Due to interim storage time 2

3 Partitioning & Transmutation Strategy Basic idea behind the partitioning and transmutation strategy separate and Transuranium elements destroy chemical separation processes actinide separations neutron-induced nuclear reactions recycle as fuel 3

4 Actinide Separation Here: hydrometallurgical separation by liquid-liquid extraction liquid-liquid extraction organic phase aqueous phase = FP = TRU (Np, Pu, Am, Cm) = extractant M n+ aq + n A aq + L org MA n L org 4

5 Actinide Separation European strategy Used Nuclear Fuel U, Pu, Np, Am, Cm Ln, Fission Products PUREX U, Pu, Np Am, Cm Ln, Fission Products DIAMEX Am, Cm Ln SANEX Am, Cm other Fission Products Lanthanides 5

6 SANEX Process Extracting Agents An(III) / Ln(III) separation very challenging due to chemical similarity Only viable using soft (N or S) donor extractants BTP KIT-INE Thiophosphinic acid FZ Jülich Z. Kolarik et al., Solvent Extr. Ion Exch. 1999, 17, G. Modolo et al., Solvent Extr. Ion Exch. 1999, 17,

7 SANEX Process Extracting Agents npr-btp npr-btp Am(III) Distribution ratio: D M = [M(III)] org M(III) aq D M(III) Eu(III) 10 2 SF Am(III)/Eu(III) Separation factor: SF Am/Eu = D Am D Eu SF Am/Eu [HNO 3 ] ini [mol/l] 10 1 organic phase: n-pr-btp in kerosene/1-octanol aqueous phase: HNO 3 N. L. Banik et al., Inorg. Chem. Commun. 2013, 29,

8 SANEX Process Extracting Agents npr-btp Cm(III) Cf(III) npr-btp 10 1 Np(III) Ho(III) 10 0 D M(III) La(III) 120 Pm(III) Nd(III) 116 Gd(III) 112 Y(III) 108 Lu(III) 104 organic phase: n-pr-btp in kerosene/1-octanol aqueous phase: HNO 3 or HNO 3 + NH 4 NO 3 r M(III) [pm] (CN = 9) An(III) separated from all Ln(III) and Y(III) N. L. Banik et al., Inorg. Chem. Commun. 2013, 29,

9 SANEX Process Extracting Agents Requirements for the extractants High selectivity Extraction from nitric acid solutions Fast extraction kinetics Good solubility in organic solvents Chemical and radiation stability CHON principle Easy synthesis 9

10 SANEX Process Extracting Agents Requirements for the extractants High selectivity Extraction from nitric acid solutions Fast extraction kinetics Good solubility in organic solvents Chemical and radiation stability CHON principle Easy synthesis npr-btp ( ) 10

11 SANEX Process Extracting Agents Developments CyMe 4 -BTP npr-btp BTBPs BTPhens 11

12 SANEX Process Extracting Agents Current European reference molecule for the SANEX process Very good selectivity Chemically stable Drawbacks: Low solubility Slow extraction kinetics CyMe 4 -BTBP Nevertheless: successful hot counter-current test at ITU 12

13 Selectivity of N-Donor Ligands Molecular reason for selectivity of BTP/BTBP ligands not fully understood Analytical approach detailed investigations of BTP/BTBP ligands multi-method strategy Extraction studies NMR Computational chemistry ESI-TOF-MS TRLFS X-ray methods EXAFS XANES XRD XPS RIXS 13

14 Selectivity of N-Donor Ligands Molecular reason for selectivity of BTP/BTBP ligands not fully understood Analytical approach detailed investigations of BTP/BTBP ligands multi-method strategy Extraction studies NMR Computational chemistry ESI-TOF-MS TRLFS X-ray methods EXAFS XANES XRD XPS RIXS 14

15 TRLFS Time Resolved Laser Fluorescence Spectroscopy Information on the inner coordination sphere Identification and quantification of different species Determination of stability constants Low detection limit Non-invasive cuvette with sample Nd:YAG laser (355 nm) Dye laser nm (Cm) shutter optical fiber camera 15

16 TRLFS Fluorescence process Energy excited state excited state Non-radiative relaxation laserpulse excitation complexation emission ground state shift of energy levels shift of emission bands ground state identification of different species Intensity Intensity Wavelength [nm] Wavelength [nm] 16

17 CyMe 4 -BTBP and CyMe 4 -BTPhen BTPhen ligands as enhancements of BTBP ligands conformation cis-locked advantageous for tetradentate coordination positive impact on thermodynamic and kinetic properties (?) CyMe 4 -BTBP CyMe 4 -BTPhen A. Geist et al., Solvent Extr. Ion Exch. 2006, 24, F. W. Lewis et al., J. Am. Chem. Soc. 2011, 133,

18 CyMe 4 -BTBP and CyMe 4 -BTPhen Extraction D M(III) CyMe 4 -BTPhen SF Am/Eu CyMe 4 -BTBP SF Am/Eu [HNO 3 ] aq,ini [mol/l] Am Eu F. W. Lewis et al., J. Am. Chem. Soc. 2011, 133, A. Geist et al., Solvent Extr. Ion Exch. 2006, 24,

19 Complexation of Cm(III) with CyMe 4 -BTPhen Slow complexation kinetics Normalized Intensity nm nm nm time [h:m] 0:00 0:02 0:05 0:10 0:15 0:20 0:30 0:45 1:00 1:30 2:00 4:00 7:30 24:00 28:30 31:30 48:00 52:00 approx. 24 h necessary to reach the equilibrium 1:2-complex [Cm(CyMe 4 -BTPhen) 2 ] Wavelength [nm] Cm(ClO 4 ) 3 in MeOH (+H 2 O), c(hclo 4 ) = 88 mm c(cm(iii)) ini = M, c(btphen) = M 19

20 Complexation of Cm(III) with CyMe 4 -BTPhen Batch experiments Intensity nm nm c(btphen) [M] 0.00 (Int. x50) 9.90E E E E E E E E E E-5 spectra dominated by 1:2- complex even at very low ligand concentrations Wavelength [nm] Cm(ClO 4 ) 3 in MeOH (+H 2 O), c(hclo 4 ) = 88 mm c(cm(iii)) ini = M, c(btphen)= M M 20

21 Complexation of Cm(III) with CyMe 4 -BTPhen Batch experiments Slope analysis and speciation diagram Stability constant log β 02 = 13.8 ± log ([CmBTPhen 2 ]/[Cm] free ) slope = 1.94 ± 0.14 Fraction [%] [Cm(solv.)] 1:2-complex log ([BTPhen] free ) c(btphen) free [M] 21

22 Complexation of Cm(III) with CyMe 4 -BTBP Comparable complexation kinetics Samples equilibrated for 24 h Quantitative analysis Slope analysis: 2.00 ± 0.16 log b 02 = 12.4 ± nm nm 100 [Cm(solv.)] 1:2-complex 80 Normalized Intensity Fraction [%] [Cm(solv.)] 1:2-complex Wavelength [nm] c(btbp) free [M] 22

23 Complexation of Eu(III) with BTPhen and BTBP BTPhen BTBP log β 02 = 11.6 ± 0.3 log β 02 = 11.3 ± nm nm [Eu(solv.)] 1:2-complex [Eu(solv.)] 1:2-complex Normalized Intensity nm nm nm Normalized Intensity nm nm nm nm Wavelength [nm] Wavelength [nm] 23

24 Conclusions Slow complexation kinetics only batch experiments possible log b 02 values BTPhen BTBP Cm(III) Eu(III) Improved complexation behavior 24

25 Conclusions log b 02 values BTPhen BTBP Cm(III) Eu(III) D M(III) [HNO 3 ] aq,ini [mol/l] 25

26 Further project activities Molecular reason for selectivity of BTP/BTBP ligands not fully understood Systematic variation of the molecular structure C5-BPP KIT-INE C5-hemi-BTP Reading HN 4 bipy RG Roesky BTP Et-BDP RG Panak MeN 3 bipy RG Roesky npr-tetrazin RG Panak dmpbipy RG Roesky and many more (BTBPs, BTPhens) 26

27 Thank you for your attention! 27