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Am and Cm Absorption Studies on TEVA Resin from Metal Nitrate Matrices
Narek Gharibyan1, Ashlee Crable1, Steffen Happel2, Ralf Sudowe1
1University of Nevada, Las Vegas2Triskem 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
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
241Am
242Cm
IT
242Am β-
(n,γ) 141 y
16.02 h
162.8 d
Project Goal: neutron capture cross-section and isomeric ratio determination for:
In collaboration with LANL and UCB
Neutron Capture Cross-Section for 241Am
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
Decay scheme of 241Pu
Major interest from NNSA and weapons laboratories Weapons grade plutonium
Contains ~0.5% 241Pu (0.65 %1; 0.54 %2)
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)
Resin - TEVA
TEVA resin from Eichrom Active component: high
molecular weight quaternary ammonium nitrate (or chloride)
N + NO3-
R
CH3
R
R
R = C8H17 and C10H21
Trialkyl, methylammonium nitrate
Previous Results - TEVA
0
2
4
6
8
10
0.01 0.1 1 101
AmCm
k'
[HNO3]
0
5
10
15
20
25
2.75 3.00 3.25 3.50 3.75 4.00 4.25
AmCm
k'
[LiNO3]
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) Mix for 1 hour
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
FDk
AAA
v
A
m
AD
w
sor
s
s
r
rw
'Correction Factor (F)Resin
0.526TEVA
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
-50
0
50
100
150
200
250
0.00 1.00 2.00 3.00 4.00 5.00 6.00
AmCm
k'
LiNO3
*Error bars show standard deviation from five measurements
Highest SF2.57 @ 3.75 M
Results – TEVA from NaNO3
-2
0
2
4
6
8
10
12
14
0.00 1.00 2.00 3.00 4.00 5.00 6.00
AmCm
k'
NaNO3
Highest SF2.36 @ 6.00 M
Results – TEVA from KNO3
0
2
4
6
8
10
0.00 0.50 1.00 1.50 2.00
AmCm
k'
KNO3
Highest SF-
Results – TEVA from Mg(NO3)2
-50
0
50
100
150
200
250
300
0.00 0.50 1.00 1.50 2.00 2.50 3.00
AmCm
k'
Mg(NO3)2
Highest SF2.39 @ 2.00 M
Results – TEVA from Ca(NO3)2
-10
0
10
20
30
40
50
60
0.00 1.00 2.00 3.00 4.00
AmCm
k'
Ca(NO3)2
Highest SF2.49 @ 2.00 M
Results – TEVA from Al(NO3)3
-10
0
10
20
30
40
50
60
70
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
AmCm
k'
Al(NO3)3
Highest SF2.67 @ 1.60 M
Results – Am on TEVA: [Metal Nitrate]
-50
0
50
100
150
200
250
300
0.00 1.00 2.00 3.00 4.00 5.00 6.00
k'
X(NO3)Y
LiNO3
LiNO3
NaNO3
Ca(NO3)2
Mg(NO3)2
Al(NO3)3
KNO3
[X(NO3)Y]
Results – Am on TEVA: [Nitrate]
0.1
1
10
100
1000
0.00 2.00 4.00 6.00 8.00
Am (Li)Am (Na)Am (Al)Am (Mg)Am (Ca)
k'
[NO3
-]
1
10
100
1000
0.00 2.00 4.00 6.00 8.00
Am (Li)Am (Na)Am (Al)Am (Mg)Am (Ca)
k'
[NO3
-]
Results – Cm on TEVA: [Nitrate]
0.1
1
10
100
1000
0.00 2.00 4.00 6.00 8.00
Cm (Li)Cm (Na)Cm (Al)Cm (Mg)Cm (Ca)
k'
[NO3
-]
1
10
100
1000
0.00 2.00 4.00 6.00 8.00
Cm (Li)Cm (Na)Cm (Al)Cm (Mg)Cm (Ca)
k'
[NO3
-]
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
Questions?