Award Date

12-2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Radiochemistry

First Committee Member

Ralf Sudowe, Chair

Second Committee Member

Ken Czerwinski

Third Committee Member

David Vieira

Graduate Faculty Representative

Gary Cerefice

Number of Pages

195

Abstract

Knowledge of low-energy cross sections for stable and unstable nuclei in neutron-, γ- and ion induced reactions is important in both the simulation and radiochemistry diagnosis of nuclear device performance. This dissertation explores extraction chromatography and ion chromatography methods for the intragroup separation of trivalent actinides and lanthanides in support of cross section measurements for isotopes of interest. For trivalent actinides, americium (Am(III)) and curium (Cm(III)), separation is necessary to assist in experiments related to the measurement of neutron capture cross section for 241 Am and the production of 242 m Am/242g Am isomeric ratio. Extraction chromatography resins (TEVA, TRU, DGA(N), Ac, Ln, Ln2, Ln3) were characterized to study the absorption of Am(III) and Cm(III) from different mineral acids (HNO3 , HCl, HBr) in an effort to establish a new separation method. Radiotracers, 241 Am and 244 Cm, were used for characterization of these resins by analysis with liquid scintillation counter. From the seven resins, only two systems (TRU and DGA(N) in HNO3 ) showed any significant difference in the extraction between these trivalent actinides. For those systems, a separation was performed using column chromatography procedures.

In addition to pure acids, extraction of these actinides from different metal nitrate systems (LiNO3 , NaNO3 , KNO3 , Mg(NO3 )2 , Ca(NO3 )2 and Al(NO 3 )3 ) by Aliquat-336 were studied in both extraction chromatography and solvent extraction experiments. Extended x-ray absorption fine structure spectroscopy was used to explore the speciation of Am(III) in four different metal nitrate solutions (all except KNO 3 ) in order to better understand salting-out effects that lead to enhanced extraction of trivalent actinides. Results showed no metal ion dependency on the speciation of Am(III) nitrato complexes. Additionally, for the metal nitrate systems (LiNO3 and Al(NO3 )3 ) that showed the largest difference in extraction between Am(III) and Cm(III), column chromatography methods were investigated for separation.

In trivalent rare earth separations, an ion chromatography method using a cation exchange column was established for separation of a neighboring lanthanide pair, thulium (Tm(III)) and erbium (Er(III)). The focus of this work was to develop a procedure for the separation of few milligram of thulium ( 171 Tm) from an irradiated target of erbium (170 Er) to obtain material for neutron capture cross section measurements on 171 Tm. Ion chromatography studies focused on the optimization of operating parameters for the separation of these lanthanides with respect to flow rate, temperature, complexant and pH. Additionally, a method was established for purification of trivalent lanthanides from complexants to allow for analysis of elution fractions for individual lanthanides using atomic emission spectroscopy. Five different α-hydroxycarboxylic acids were investigated as complexants in an isocratic elution system for the separation of these lanthanides of which only two, α-hydroxyisobutyric acid and α-hydroxy-α-methylbutyric acid, were able to elute lanthanides of the column within a given elution volume.

Keywords

Actinide elements; Americium; Chromatographic analysis; Chromatography; Curium; Erbium; Neutrons – Capture; Rare earth metals; Thulium

Disciplines

Analytical Chemistry | Chemistry | Radiochemistry

File Format

pdf

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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