Authors:E. Patera, D. Hobart, A. Meijer, and R. Rundberg
The understanding and prediction of radionuclide migration within the geosphere of a high-level radioactive waste repository requires knowledge of chemical and physical processes. In this paper, we present an overview of the investigations being performed at Los Alamos National Laboratory for the site characterization activites of the Yucca Mountain Project. The areas of investigation include: the determination of solubility concentration limits and chemical speciation for fission products and actinides; the collection of sorption data and understanding of sorption mechanisms; and the transport mechanism of advection, diffusion, and dispersion.
Authors:J. Schwantes, W. Taylor, R. Rundberg, and D. Vieira
Approximately one curie of 171Tm (T1/2 = 1.92a) has been produced and purified for the purpose of making a nuclear target for the first measurements of its neutron
capture cross section. Target preparation consisted of three key steps: (1) material production; (2) separation and purification;
and (3) electrodeposition onto a suitable backing material. Approximately 1.5 mg of the target material (at the time of separation)
was produced by irradiating ca. 250 mg of its stable enriched 170Er lanthanide neighbour with neutrons at the ILL reactor in France. This production method resulted in a “difficult-to-separate”
1:167 mixture of near-neighboring lanthanides, Tm and Er. Separation and purification was accomplished using high-performance
liquid chromatography (HPLC), with a proprietary cation-exchange column (Dionex, CS-3) and alpha-hydroxyisobutyric acid (α-HIB)
eluent. This technique yielded a final product of ∼95% purity with respect to Tm. A portion (20 μg) of the Tm was electrodeposited
onto thin Be foil and delivered to the Los Alamos Neutron Science Center (LANSCE) for preliminary analysis of its neutron
capture cross section using the Detector for Advanced Neutron Capture Experiments (DANCE). This paper discusses the major
hurdles associated with the separation and purification step, including scale-up issues related to the use of HPLC for material
separation and purification of the target material from α-HIB and 4-(2-pyridylazo)resorcinol (PAR) colorant.
Authors:E. Bond, T. Bredeweg, J. FitzPatrick, M. Jandel, R. Rundberg, A. Slemmons, and D. Vieira
In this paper, we describe the separation chemistry and electrodepositions conducted for the preparation of 241Am, 243Am and 233U targets used for cross-section measurements at DANCE. Thick, adherent deposits were prepared using molecular plating from
isopropyl alcohol solutions. Improved yields and thicknesses were observed for 241Am electrodeposition after the material was purified using TRU resin from Eichrom. Similarly, 233U deposits were improved after purification with an anion exchange column in 9 M HBr followed by purification using UTEVA
resin from Eichrom.
Authors:G. G. Miller, P. Z. Rogers, P. Palmer, D. Dry, R. Rundberg, M. Fowler, and J. Wilhelmy
The neutron capture behavior of certain radioactive rare earth nuclides, among them 171Tm and 151Sm, is of interest for astrophysical reasons and for the interpretation of radiochemical data from underground nuclear tests. In order to measure neutron capture excitation functions for these radionuclides, targets were produced that met stringent requirements. This paper describes the purification chemistry and target preparation methods that were employed in order to deliver appropriate samples for study.
Authors:E. Bond, S. Glover, D. Vieira, R. Rundberg, G. Belier, V. Meot, D. Hynek, Y. Jansen, J. Becker, and R. Macri
This paper describes the preparation of samples for an experiment to measure the cross-section for 235U(n,n′)235mU in a fast fission spectrum of neutrons provided by a fast pulsed reactor/critical assembly. Samples of 235mU have been prepared for the calibration of the internal conversion electron detector that is used for the 235mU measurement. Two methods are described for the preparation of 235mU. The first method used a U-Pu chemical separation based on anion-exchange chromatography and the second method used an alpha
recoil collection method. Thin, uniform samples of 235mU+235U were prepared for the experiment using electrodeposition.