Jerome Bucher | Lawrence Berkeley National Laboratory (original) (raw)

Papers by Jerome Bucher

The solubilit~_es of crystalline Nd(OH} 3 and Am(OH} 3 \tere measured at 25 ~ lo C in aqueous sol... more The solubilit~_es of crystalline Nd(OH} 3 and Am(OH} 3 \tere measured at 25 ~ lo C in aqueous solutions of 0.1 M NaCl0 4 under argon as a function of pH by determination of the solution concentrations of Ndand Ant. Prior to use in-the solubility measurements, the solid materials were characterized through their x-ray.-powder patterns. Analyses~:of the.solubility data with the computer code MlNEQL a 11 ov1ed estimates of the sol ubi 1 i ty product constants, KslO' and the second and third hydrolysis constants, K 12 and K 13 , for Nd 3 + and Am 3 +. Upper limits for the fourth hydrolysis constants \tere also estimated. For Ud, they are: 1 og KslQ ~ 16.0 ~ .2, log K 12 •-15.8 ~ .s. log K 13 =-23.9 ~ .2 and log: K 14 <-34. For Am, they are: log KslO = 15 •. 9-~-.4, log K 12 This report was done with support from the Department of Energy. Any conclusions or opinions expressed in this report represent solely those of the author(s) and not necessarily those of The Regents of the University of California, the Lawrence Berkeley Laboratory or the Department of Energy. Reference to a company or product name does not imply approval or recommendation of the product by the University of California or the U.S. Department of Energy to the exclusion of others that may be suitable.

The Journal of Physical Chemistry A, 2001

The radiation chemistry of pertechnetate has been examined in highly alkaline solution. In the pr... more The radiation chemistry of pertechnetate has been examined in highly alkaline solution. In the presence of selected, organic Oscavengers, radiolysis reduces TcO 4

Organometallics, 1999

The crystal structures of [Cp′′ 2 UF] 2 and [Cp q 2 UO] 2 are reported, where Cp′′ is 1,3-(Me 3-S... more The crystal structures of [Cp′′ 2 UF] 2 and [Cp q 2 UO] 2 are reported, where Cp′′ is 1,3-(Me 3-Si) 2 C 5 H 3 and Cp q is 1,3-(Me 3 C) 2 C 5 H 3. Both complexes have idealized C 2h symmetry, and their U‚‚‚U distances are 3.85 and 3.39 Å, respectively. The X-ray absorption spectra of several uranium metallocene complexes, and the numerical results from fitting the EXAFS spectra, are reported. For [Cp q 2 UF] 2 , the U‚‚‚U distance was found by EXAFS to be similar to that in [Cp′′ 2 UF] 2 , implying that [Cp q 2 UF] 2 is dimeric. A structural model is advanced that correlates the U‚‚‚U distance with the orientation of the cyclopentadienyl rings; the orientation is due to a subtle combination of steric repulsions between ligands on the same metal center and between ligands on adjacent metal centers.

Inorganic Chemistry, 1995

Environmental Science & Technology, 2005

Cementitious waste forms (CWFs) are an important component of the strategy to immobilize high-lev... more Cementitious waste forms (CWFs) are an important component of the strategy to immobilize high-level nuclear waste resulting from plutonium production by the U.S. Department of Energy (DOE). Technetium (9 9 Tc) is an abundant fission product of particular concern in CWFs due to the high solubility and mobility of pertechnetate, TcO 4

Chemistry of Materials, 2001

The microstructure, physical characteristics, corrosion behavior, and reactivity of zerovalent ir... more The microstructure, physical characteristics, corrosion behavior, and reactivity of zerovalent iron nanoparticles synthesized on a support (primarily a nonporous, hydrophobic polymer resin) were studied. The remediation of groundwater by zerovalent iron in in situ permeable reactive barriers relies on the redox reaction between metallic iron and a reducible contaminant. Decreasing the size of the iron particles and dispersing them on a support increases the specific surface area of the iron, as well as the ratio of surface to bulk iron atoms, and should thereby increase both the reaction rate and the fraction of iron atoms available for the reaction. Borohydride reduction of aqueous ferrous sulfate gives supported iron nanoparticles, 10-30 nm in diameter, which consist of 85% zerovalent iron by weight. These materials ("ferragels") are stable in air and have corrosion behavior comparable to iron filings. Interestingly, the presence or absence of a support, as well as the boron remaining from the borohydride reduction process, influences the electrochemical corrosion rate of the composite materials. Supported and unsupported zerovalent iron nanoparticles are superior to iron filings in both terms of initial rates of reduction and total moles of contaminants (Cr(VI), Pb(II), TcO 4-) reduced per mole of iron. The enhanced reactivity and passive corrosion behavior of these materials should make them good candidates for use in permeable reactive barriers.

Radiochimica Acta

ABSTRACT

The chemistry of technetium in certain high-level nuclear waste (HLW) tanks at the Hanford Site c... more The chemistry of technetium in certain high-level nuclear waste (HLW) tanks at the Hanford Site complicates the treatment and vitrification of HLW. A major problem is the presence, in certain tanks, of unidentified, lower-valent technetium species, which are difficult to remove from the waste by current separation processes. Radiolytic reduction of TcO4- in alkaline solutions containing selected organic compounds, approximating the conditions in HLW, was investigated to determine the classes of compounds that can be formed under these conditions. Insoluble TcO2 x xH2O is the primary radiolysis product with the majority of organic compounds investigated, including citrate, dibutyl phosphate, and aminopolycarboxylates. X-ray absorption fine structure (XAFS) measurements show that TcO2 x xH2O has a one-dimensional chain structure consisting of edge-sharing TcO6 octahedra with bridging oxide and trans water ligands. When diols, such as ethylene glycol, are present, only soluble, Tc(IV) alkoxide compounds are produced. The XAFS and UV-visible spectra of these compounds provide evidence for a binuclear structure similar to (H2EDTA)2Tc2(mu-O)2. The properties of the Tc(IV) alkoxide complexes were determined and are consistent with those observed for the soluble, lower-valent technetium complexes that complicate the treatment of HLW at the Hanford site.

MRS Proceedings, 1994

XANES (X-ray Absorption Near Edge Spectroscopy) has been employed to evaluate the efficacy of a p... more XANES (X-ray Absorption Near Edge Spectroscopy) has been employed to evaluate the efficacy of a process designed to encapsulate and reduce TcO4- in cement matrices, thereby immobilizing Tc. The oxidation state of Se following bioremediation of Se by bacteria has also been determined by XANES. The XANES measurements were performed at the Stanford Synchrotron Radiation Laboratory (SSRL) and the National Synchrotron Light Source (NSLS) at the respective K edges of Tc (21.0 keV) and Se (12.7 keV). Comparison of the XANES spectra of Tc in untreated cement to Tc in slag treated cement and to the chemical shifts of reference materials, shows that the oxidation state of Tc is the same in both cements. Thus, the addition of a reducing agent to the cement formulation does not significantly reduce the TcO4-. The common soil bacterium, Bacillus subtilis, is known to incorporate Se on or within the cell wall when exposed to a Se(IV) solution. The Se XANES spectra of B. subtilis, as well as bacil...

Advanced Engineering Materials, 2009

Synchrotron radiation techniques represent powerful tools to characterize materials down to the n... more Synchrotron radiation techniques represent powerful tools to characterize materials down to the nanometer level. This paper presents a survey of the state-of-the-art synchrotron-based techniques which are particularly well-suited for investigating materials properties. Complementary X-ray absorption techniques such as extended X-ray absorption fine structure (EXAFS), X-ray magnetic circular dichroism (XMCD), photoemission electron microscopy (PEEM) are used to address the individual local atomic structure and magnetic moments in Fe–Cr model systems. The formation of atomic clusters/precipitates in such systems is also investigated by means of scanning transmission X-ray microscopy (STXM). Such advanced analytical techniques can not only offer valuable structural and magnetic information on such systems, they can also serve for validating computational calculations performed at different time and length scales which can help improve materials lifetime predictions.

The Journal of Physical Chemistry

The use of slope analysis for interpreting extraction data is usually coupled with the assumption... more The use of slope analysis for interpreting extraction data is usually coupled with the assumption that the activity coefficients of the new chemical species that yield the changes in slope are ideal. This assumption is shown to be wrong in several extraction systems that are described. In particular, the phenomenon of "backbending" in certain tertiary ammonium salt systems is completely inexplicable under such an assumption, and incorrect extractant coordination numbers are obtained for trioctylphosphine oxide-strong acid species in poor solvents. As a result of this assumption literature values for aggregation numbers determined for alkylammonium salts in poor solvents may be too large.

Analytical Chemistry, 1978

Several universal buffer solutions, variably composed of 3-5 mM potassium acetate, potassium dihy... more Several universal buffer solutions, variably composed of 3-5 mM potassium acetate, potassium dihydrogen phosphate, ethylenediammonium dichloride, and Borax, were examined as a convenient and reliable method for calibrating a glass electrode to read true hydrogen ion concentration. From the results of 19 titrations, 25 'C, pH 2 to 12, I , 0.05 to 0.20 M (KCI), pH meter (adjusted with NBS pH, 4.008 and 6.865 buffers) readings, pH,, using a Beckman 39501 combination electrode, can be converted to -log [H'], p[H], by pH, = 1' + S'p[H] where 1' = 0.2269 -1.9491+ 7.75612, d1') = 0.019 pH and S' = 0.9657 + 0.47521 -1.53212, ci(S') = computer program was coded to calculate A' and S'for any titration in the range 0 to 40 O C and 0 to 0.3 M (KCI), and for any Combination of the four buffer components. A microcomputer-controlled automatic titrator, programmed in BASIC, was used to collect the potentiometric data. 0.0022. At 1 0 . 1 M PH, = 0.110 -k 0.998p[H]. A FORTRAN

Inorg Chem, 1999

The authors have used EXAFS spectroscopy to investigate the inner sphere coordination of trivalen... more The authors have used EXAFS spectroscopy to investigate the inner sphere coordination of trivalent lanthanide (Ln) and actinide (An) ions in aqueous solutions as a function of increasing chloride concentrations. At low chloride concentration, the hydration numbers and corresponding Ln,An-O bond lengths are as follows: La{sup 3+}, N = 9.2, R = 2.54â«; Ce{sup 3+}, N = 9.3, R =

The objective of this program is to identify and obtain appropriate thermodynamic testing data on... more The objective of this program is to identify and obtain appropriate thermodynamic testing data on the solubilities of compounds and on the solution complexes of important waste radionuclides which are likely to form in the salt repository. Information on the chemical behavior of the waste radionuclides is important for site selection and characterization, and is necessary for demonstrating that the

Thermochemical data on the solubilities of compounds and solution complexes of the waste radionuc... more Thermochemical data on the solubilities of compounds and solution complexes of the waste radionuclides likely to form in the natural systems are required to adequately assess and predict the ability of the storage site to meet established site characteristics and standards for rates of release of radioactive materials set by the US Nuclear Regulatory Commission. Taken as a group, the