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?