Am and Cm Absorption Studies on TEVA Resin from Metal Nitrate Matrices Narek Gharibyan1, Ashlee Crable1, Steffen Happel2, Ralf Sudowe1 1University of Nevada, Las Vegas 2Triskem International, Bruz, France Glenn T. Seaborg Award for Nuclear Chemistry: Symposium in Honor of Kenton J. Moody 237th ACS Meeting Salt Lake City, Utah

Outline Overview Experimental Design Results Conclusion Future Work Project introduction Objectives TEVA resin & previous results Experimental Design Results k’ value LiNO3, NaNO3, KNO3, Mg(NO3)2, Ca(NO3)2 and Al(NO3)3 Metal and nitrate effects Summary Conclusion Future Work Acknowledgement

Neutron Capture Cross-Section for 241Am Project Goal: neutron capture cross-section and isomeric ratio determination for: In collaboration with LANL and UCB 141 y (n,γ) IT 241Am 16.02 h β- 242Am 162.8 d 242Cm

Neutron Capture Cross-Section for 241Am Decay scheme of 241Pu Major interest from NNSA and weapons laboratories Weapons grade plutonium Contains ~0.5% 241Pu (0.65 %1; 0.54 %2) 1Keegan, R.P., Gehrke, R.J., Applied Radiation and Isotopes 59, 137-143 (2003) 2Condit, R.H., Plutonium Dispersal in Fires: Summary of What is Known. 1993, Lawrence Livermore National Laboratory

Group Objective Development of efficient separation method for separating milligram quantities of Am from trace amounts of Cm Overlapping interest with the fuel cycle and nuclear forensics

Am/Cm Separation Oxidation of Am(III) to Am(V) or Am(VI) to enhance separation Highly dependent on stability of the higher oxidation states Reduction due to acid matrix or organic solvents Separation without oxidation of Am Some of the current methods: Tertiary pyridine resin with nitric acid-methanol system Cation exchange with HIB system Extraction chromatography: high molecular weight quaternary ammonium nitrate (Aliquat-336 nitrate) LiNO3 system Separation factor3 of 2.7 at 3.6 M Separation factor4 of >105 at 3.6 M 3Horwitz, E.P., Bloomquist, C.A.A., Orlandini, K.A., Henderson, D.J., Radiochim. Acta 8, 127-132 (1967) 4Borkowski, M., Fuks, L., Nukleonika 33, 10-12, 275-79 (1988)

Trialkyl, methylammonium nitrate Resin - TEVA TEVA resin from Eichrom Active component: high molecular weight quaternary ammonium nitrate (or chloride) R R N + NO3- R CH3 R = C8H17 and C10H21 Trialkyl, methylammonium nitrate

Previous Results - TEVA

Primary Objective What effects do metals have on absorption properties of Am and Cm in nitrate matrices? Li+, Na+, K+, Ca2+, Mg2+ and Al3+

Experimental Design Preconditioning resin ~100 mg of resin 2.000 mL of specific NO3- solution Mix for 1 hour Addition of Am-241 or Cm-244 stock solution 0.500 mL stock solution added (in 0.01 M HNO3) Filtration and activity determination 1.3 mL aliquot filtered using PTFE filter 1.000 mL analyzed with LSC Example: 2.00 M LiNO3 – 0.002 M HNO3 *For statistical purposes, five trials were performed at each condition

Results Absorption expressed in terms of k’ values, number of free column volumes to peak maximum5 k’ value can be determined from Dw Dependent on the resin (correction factor)6 Resin Correction Factor (F) TEVA 0.526 5Horwitz, E.P., Chiarizia, R., Dietz, M.L., Solvent Extr. Ion Exch. 10, 313-336 (1992) 6Eichrom Website: “Extraction Chromatography of Actinides and Selected Fission Products: Principles and Achievement of Selectivity” August 2008

Results – TEVA from LiNO3 Highest SF 2.57 @ 3.75 M *Error bars show standard deviation from five measurements

Results – TEVA from NaNO3 Highest SF 2.36 @ 6.00 M

Results – TEVA from KNO3 Highest SF -

Results – TEVA from Mg(NO3)2 Highest SF 2.39 @ 2.00 M

Results – TEVA from Ca(NO3)2 Highest SF 2.49 @ 2.00 M

Results – TEVA from Al(NO3)3 Highest SF 2.67 @ 1.60 M

Results – Am on TEVA: [Metal Nitrate] [X(NO3)Y]

Results – Am on TEVA: [Nitrate]

Results – Cm on TEVA: [Nitrate]

Summary Extraction species are anionic Am and Cm nitrato species Am(NO3)4- and Cm(NO3)4- Formation of anionic species evident >2.00 M nitrate k’ value for Am and Cm increase at higher nitrate concentrations Higher absorption for Am compared to Cm, SF~2.5 From literature, SF of 2.7 (Horwitz) and >105 (Borkowski)

Summary Cation effects: two groups Group #A (Li+, Mg2+, Al3+): metal cation radius7 (pm) 67-90 Group #B (Na+, Ca2+): metal cation radius7 (pm) 114-116 7Wulfsberg, G. Principles of Descriptive Chemistry; Brooks/Cole Publishing, Monterey, CA, 1987, p. 25

Conclusion Two different possible mechanism for understanding metal cation effect on Am/Cm absorption to TEVA resin: 1. More nitrates interact with larger cation Effectively reducing the nitrate concentration in solution, reduces the formation of anionic actinide nitrato complexes at given nitrate concentration 2. Larger cations prevent interaction with active sites on the resin Larger cations more effectively shield the anionic actinide nitrato species from binding to the active sites on the resin By formation of secondary positive layer (positive) around the anionic species

Future Work Repeat Li and Na systems with solvent extraction method Aliquat-336 available from Sigma-Aldrich Should provide information on whether or not cations shield extraction species from active sites on the resin Dynamic column studies with TEVA resin Reproduce results from batch experiments

Acknowledgements Ralf Sudowe David Vieira (LANL) Heino Nitsche (UCB/LBNL) Chris Klug Tom O’Dou Trevor Low UNLV Radiochemistry Group Funding for this work was provided by the DOE under contract DE-FG52- 06NA27480 through subcontract SA5709-11122 with UC Berkeley

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