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Radiochemistry Ph.D. program at the University of Nevada, Las Vegas

Radiochemistry Ph.D. program at the University of Nevada, Las Vegas. ¡Ken Czerwinski! Harry Reid Center and Department of Chemistry University of Nevada, Las Vegas. Outline. Overview of UNLV Program Education Research Capabilities Current Projects Technetium Chemistry

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Radiochemistry Ph.D. program at the University of Nevada, Las Vegas

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  1. Radiochemistry Ph.D. program at the University of Nevada, Las Vegas ¡Ken Czerwinski! Harry Reid Center and Department of Chemistry University of Nevada, Las Vegas

  2. Outline • Overview of UNLV Program • Education • Research • Capabilities • Current Projects • Technetium Chemistry • US reactors produce 2 tons of 99Tc annually • Compound synthesis • Waste form chemistry

  3. UNLV Radiochemistry Labs

  4. Ph.D. Radiochemistry Program • Developed by Health Physics Department • Chemistry and Health Physics core • Required courses in nuclear chemistry, radiochemistry, laboratory • Initiated Fall 04 • Currently 10 graduate students • Research opportunities for undergraduates, visiting students, and visiting researchers • Need to develop next generation of radiochemists • Nuclear Waste Treatment • Homeland Security • Environmental Radiochemistry • Information available at radchem.nevada.edu

  5. Research Program Concepts • Chemistry based analysis of actinides and radionuclides • Interested in chemical species • Program unified by • investigations of chemical behavior • thermodynamics • kinetics • utilization of laboratory studies, site observations, and modeling • incorporation of results into codes • Compare laboratory results to observations • Research coupled with education program • Provide undergraduate and graduate students with actinide research opportunities

  6. Experimental Techniques • Evaluate change of actinide species under different conditions • Spectroscopy • XAFS, UV-Visible, Laser, NMR, EELS • Radiochemical separation and detection • Thermal methods • TGA, DSC • Scattering • Powder XRD • Analytical • ICP-AES, ICP-MS • Microscopy • SEM, TEM

  7. Modern research facilities at UNLV • 3 laboratories (HRC) and counting room (Health Physics) • Ability to work with actinides and fission products • Can work with macro amounts of material • Adding three more radiochemistry laboratories at HRC

  8. Personnel • Two professors in Radiochemistry • Professor Ken Czerwinski, Chemistry • Professor Ralf Sudowe, Health Physics • Separations • Heavy element chemistry, environmental chemistry • New radiochemistry hire in chemistry • New organometallic professor • Tc chemistry • Senior scientists in nuclear science program • Dr. Thomas Hartmann • Solid phase analysis

  9. Student opportunities in Ph.D. program • Research intensive program • Graduate students perform research in the 1st year • 60 credits beyond undergraduate degree • 4 core courses • Nuclear, radiochemistry, detectors, laboratory • Other courses based on research interests • Laboratory research • Opportunities at National Laboratories • Program offers full support for graduate students • Stipends, tuition, insurance, fees, travel

  10. Current Research Projects in Radiochemistry Program • Materials and solid phases • Oxide and nitride fuel research • Recent NERI on actinide nitride synthesis • TRISO Fuels • Repository and reprocessing chemistry • Actinides in ZrO2-MgO • Used as basis of 244Pu targetry for element 114 synthesis • Separations • Fundamental chemistry of U and Pu in the tributylphosphate-nitrate-dodecane system • Electrochemical separations of Am and Cm from the lanthanides • Pursuing new direction in room temperature ionic liquids • Rapid and automated separations for radionuclide analysis • Separation of radionuclides from drinking water • Environmental behavior • Interaction of Bacteria with Actinide Containing Mixed Waste • Fate and Transport of Radionuclides at Yucca Mountain • Include impact of bacteria • Identification of radionuclides in the environment • Pu speciation and behavior at the Nevada Test Site and BOMARC site • Synthesis and structure • Novel Tc compounds • Funding from DOE-NE, EMSP, DOE-Science, DOE-NSO, DARPA

  11. Synthesis and Characterization of Quadruple-Bonded Technetium Dimers Frederic Poineau, Ken Czerwinski, Al Sattelberger Harry Reid Center University of Nevada, Las Vegas Steve Conradson, LANL

  12. Fundamental Chemistry of Tc Development of Tc polymer chemistry: • Synthesis and characterization of compound with a Tc-Tc bond  Study of quadruple bonded compound. Use of Tc2X82- as precursor of synthesis. ( complexation, reduction … ) • First study: TcIII2Br82-Br4 -[ Tc≣Tc ]-Br4 •  No structural ( distance Tc-Tc and Tc-Br) and speciation ( UV-Vis) data •  Goal : structural characterization of Tc2Br82- and comparison with Tc2Cl82- • Second study: TcIII2(hpp)4Cl2 •  Tc-hpp compound not synthesized • Preliminary result with Re

  13. Synthetic Route To (n-Bu4N)2Tc2Br8 [Pre-94] TcO2/NH4TcO4 (n-Bu4N)TcO4 I II (n-Bu4N)TcOCl4 III IV (n-Bu4N)2Tc2Cl8 (n-Bu4N)2Tc2Br8

  14. I - Synthesis of (n-Bu4N)TcO4 Starting material not pure ( Mix TcO2/NH4TcO4): 1- Evaporation of mix in NH4OH/H2O2 at 80 ° C 2 - Precipitation in H2O with (n-Bu4N)HSO4 T = 80 ° C, NH4OH / H2O2 (n-Bu4N)HSO4 Starting material (n-Bu4N)TcO4

  15. II - (n-Bu4N)TcO4 (n-Bu4N)TcOCl4 Reduction of Tc(VII) to Tc(V) by 12 M HCl (n-Bu4N)TcO4 + 6 HCl (n-Bu4N)TcOCl4 + Cl2 + 3H2O 12 M HCl T = 0 °C (n-Bu4N)TcO4 (n-Bu4N)TcOCl4

  16. III - (n-Bu4N)TcOCl4  (n-Bu4N)2Tc2Cl8 Reduction (1) Tc(V)  Tc(III) by (n-Bu4N)BH4 in THF and acidification (2) by 12 M HCl in acetone 1- (n-Bu4N)TcOCl4 +4 (n-Bu4N)BH4  Brown intermediate 2- Brown intermediate + HCl  (n-Bu4N)2Tc2Cl8 (n-Bu4N)BH4, THF HCl, acetone (n-Bu4N)2Tc2Cl8 (n-Bu4N)TcOCl4

  17. IV- (n-Bu4N)2Tc2Cl8  (n-Bu4N)2Tc2Br8 Ligand exchange reaction in dichloromethane using HBr gas (n-Bu4N)2Tc2Cl8 + 8 HBr (Bu4N)2Tc2Br8 + 8 HCl Crystallization Dissolution HBr gas T = 30 ° C (n-Bu4N)2Tc2Cl8 (n-Bu4N)2Tc2Br8

  18. Characterization of Tc2Br82- 1- XAS spectroscopy 2- UV-Vis spectroscopy

  19. XAS study ( Stanford synchrotron) - Solid compound mixed with BN - XAS analysis of (n-Bu4N)2Tc2Br8 - Reference compound : (NH4)TcO4 , (n-Bu4N)TcOCl4 and (n-Bu4N)2Tc2Cl8 Sample holder for active material XANES Local geometry and oxidation state EXAFS chemical and structural parameter

  20. EXAFS Fig. FT of (n-Bu4N)2Tc2X8EXAFS spectra. k [ 3, 14 ] Å-1

  21. Results  EXAFS in accordance with the stochiometry Tc2Br82-  Distance Tc-Tc in Tc2Br82- = 2.16 ± 0.02 Å - No influence of X on d Tc-Tc in Tc2X82- - Presence of quadruple bond

  22. XANES: Pre – edge study Kedge : transition 1s  np Orbital Mixing (np +nd) : transition permitted = pre edge Mixing depend of symmetry  Pre-edge study in accordance with symmetry D4H

  23. XANES : Edge absorption study • Fig . Position of edge absorption /Tc(VII) in function of oxidation degree for (n-Bu4N)2Tc2X82- ( X=Cl, Br) , (n-Bu4N)TcOCl4, TcCl62- , [TcCl2(PMe2Ph)2]2 • Position of Tc2Br82- in agreement with oxidation degree III (difference between in Tc2X82- (X=Cl. Br) due to electronegativity of ligand)

  24. UV-Vis study Speciation of Tc2Br82- in CH2Cl2 Interpretation of spectra

  25. Fig. UV-Vis Spectra of Tc2X82- ( X = Cl, Br) in CH2Cl2 [Tc2Cl82-] = 0.826. 10-4 M, [Tc2Br82-] = 0.678.10-4 M  UV-Vis spectra of Tc2Cl82- in agreement with [Cot-81]  UV-Vis spectra of Tc2Br82- present a band around 730 nm.

  26. Interpretation of the 730 nm Band • Quadruple bonded compound : • - Metal–Metal bond involves : one s, two p and one d orbital. • Presence of d : Transition d d* ( Ex : Re2X82-, X = Cl, Br) • - d d* transition at low energy OM involved in quadruple bond UV-Vis of Re2X82- ( X=Cl, Br) in CH2Cl2 Tc2Br82- is quadruple bonded must present the d d*  Band at 730 nm assigned to d d*

  27. Results New structural and speciation data on Tc2Br82-: - EXAFS : Tc-Tc = 2.16 Å and Tc-Br = 2.49 Å . - XANES : position of the edge absorption in accordance with an oxidation degree III - UV-Vis : Band 730 nm assigned to the d  d* transition.  Use of (n-Bu4N)2Tc2X8for synthesis of new Tc compound

  28. M2(hpp)4Cl2 ( M = Re,Tc)  Compound with a multiple bond: M26+  Complexation of L-[M-M]-L with hpp ligand.  hpp anion : stabilize the M26+ bond- compound resistant to chemical attack Already synthesized for: Hhpp: 1,3,4,6,7,8-Hexahydro -2H-Pyrimido[1,2-a]Pyrimidine Re2(hpp)4Cl2 [Cot-99]  Preliminary study with Re

  29. SYNTHESIS[Cot-99] Ligand exchange reaction in Hhpp melted under Ar (Bu4N)2Re2Cl8 + 4 Hhpp  Re2hpp4Cl2 + 4HCl + 2 (Bu4N)Cl Hhpp 145° C Re2(hpp)4Cl2 (Bu4N)2Re2Cl8 Air stable and Low solubility

  30. UV-Vis spectroscopy Fig. UV-Vis Spectra of [Re2(hpp)4Cl2]= 5.2.10-5Min CH2Cl2  Spectra of Re2(hpp)4Cl2 exhibits the d d* transition

  31. Electrochemical study Cyclic voltammetry :electro activity domain of Re-hpp system. Fig. CV of [Re2(hpp)4Cl2 ]=0.005M in CH2Cl2. Scan 300 mV.s-1. (Ref = Ag)  System exhibits 3 electro-active species : Re2(hpp)4Cl2, Re2(hpp)4Cl2+ and Re2(hpp)4Cl22+ [Cot-99]

  32. Tc waste form • In UREX+1A • Tc and U extracted into organic phase • UO2TcO7NO3.2TBP • Treatment of organic stream to produce pure U waste • Ease waste disposal • Need to separate Tc from U and create suitable waste form • Anion exchange • Separation of TcO4- from UO22+ • Zr-Tc waste form • Need to form metallic Tc • Pyrolysis/steam reforming of Tc loaded resin

  33. Anion exchange of Tc • Dowex Marathon, Reillex • TGA under Ar to evaluate resin properties • Mass loss above 400º C • Evaluate Tc sorption in batch test • 10 mL of 0.01 M HNO3 • 100 mg resin

  34. Tc sorption 8E-6 M TcO4-, 0.01 M HNO3, 100 mg resin, 10 mL

  35. Sorption results • TcO4- sorbs to resins at different rates • Both suitable • Form metal • Heating under Ar • 450 ºC, then 750 ºC • Reduction in mass, but could not determine if metal formed by XRD • Steam reforming • Increase to 900 ºC with water in Ar gas stream • H2O + C  CO + H2 • Formed metallic Tc

  36. Tc metal

  37. Tc Metal

  38. Results • Sorption of Tc to resin • Able to synthesize metal • Next step • Perform on column with U in solution • Synthesize metal • Make Zr-Tc solid

  39. Program overview • Variety of projects involving actinide chemistry and radiochemistry • Solid phase • Solution phase • Environmental • Synthesis and characterization • Educational program centered on radiochemistry • Opportunity to learn a variety of techniques • Interaction with DOE and international laboratories

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