EXAFS analyses of technetium(I) carbonyl complexes – stability studies in solutions

Seifert, Stefan; Kunstler, Jens-Uwe; Gupta, Antje; Funke, H.; Reich, Tobias; Hennig, Christoph; Roßberg, André; Pietzsch, Hans‐Jürgen; Alberto, Roger; Johannsen, B.

doi:10.1524/ract.2000.88.3-4.239

Cited by 12 publications

(8 citation statements)

References 16 publications

(13 reference statements)

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“…The Hartree-Fock calculation followed by a Møller-Plesset correlation energy correction, truncated at secondorder (MP2) yielded the second lowest total energy, spent only 17% longer CPU time than the HFB method. It also produced Tc-C and Tc-O bond lengths closest to those determined with EXAFS by Seifer et al 10,11 Therefore, we adopted the MP2/ CEP-121G method exclusively.…”

Section: Resultsmentioning

confidence: 94%

“…Only few compounds formed by lower oxidation-state Tc were investigated for the same purpose owing to the lack of suitable Tc precursors. Although technetium carbonyls, such as Tc 2 (CO) 10 , have long been known, unfortunately, they have to be synthesized at a high temperature and under a high pressure. The situation was entirely changed by Alberto and his co-workers.…”

Section: Introductionmentioning

confidence: 99%

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The structure, energy and stability of components formed in the preparation of fac-[99mTc(CO)3(H2O)3]+

Wang

Liu

et al. 2003

Phys. Chem. Chem. Phys.

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The geometry and total molecular energy of ten species in the system [Tc(CO) i (H 2 O) 6Ài ] + (i ¼ 0-6) are calculated by using ab initio MO method at the MP2/CEP-121G level. Their formation free energies are estimated in the sequence [Tc(HThe computation results of relative composition for various CO-to-H 2 O concentration ratios indicate that fac-[Tc(CO) 3 (H 2 O) 3 ] + is the dominant species when the pressure of CO is 0.1 MPa as experimentally observed, and preparation of some of the other species is also possible in controlled conditions.

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Section: Resultsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

The structure, energy and stability of components formed in the preparation of fac-[99mTc(CO)3(H2O)3]+

Wang

Liu

et al. 2003

Phys. Chem. Chem. Phys.

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“…The first task will provide an enhanced set of fundamental binding data relevant to speciation of non-pertechnetate alkaline soluble Tc in Hanford tank waste. It is known that the Tc(I) tricarbonyl moiety can complex with various mono-and polydentate organic molecules (Alberto et al 1998;Seifert et al 2000). The Hanford tanks contain a variety of organic complexants and degradation products.…”

Section: Approach: Examine Chemistry and Stability Of Tc(i) Carbonyl Complexesmentioning

confidence: 99%

Preliminary Assessment of the Low-Temperature Waste Form Technology Coupled With Technetium Removal

Brown¹,

Wilmarth²,

Westsik³

et al. 2014

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The U.S. Department of Energy Office of Environmental Management (EM) is engaging the national laboratories to provide the scientific and technological rigor to support EM program and project planning, technology development and deployment, project execution, and assessment of program outcomes. As an early demonstration of this new responsibility, Pacific Northwest National Laboratory (PNNL) and Savannah River National Laboratory (SRNL) have been chartered to implement a science and technology program addressing low-temperature waste forms for immobilization of DOE aqueous waste streams, including technetium removal as an implementing technology. As a first step, the laboratories examined the technical risks and uncertainties associated with the Cast Stone waste immobilization projects at Hanford. Science and technology needs were identified for work associated with 1) conducting performance assessments and risk assessments of waste form and disposal system performance, and 2) technetium chemistry in tank wastes and separations of technetium from waste processing streams. Technical approaches to address the science and technology needs were identified and an initial sequencing priority was suggested. The following table summarizes the most significant science and technology needs and associated approaches to address those needs. These approaches and priorities will be further refined and developed as strong integrated teams of researchers from national laboratories, contractors, industry, and academia are brought together to provide the best science and technology solutions.Implementation of a science and technology program that addresses these needs by pursuing the identified approaches will have immediate benefits to DOE in reducing risks and uncertainties associated with near-term decisions regarding supplemental immobilization at Hanford. Longer term, the work has the potential for cost savings and for providing a strong technical foundation for future performance assessments at Hanford and across the DOE complex.

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“…Furthermore, recent research has shown that such substitutions for the water molecules in the Tc(I) tricarbonyl moiety can be a facile process (Lukens et al 2006a;Seifert et al 2000;Lukens et al 2004;Alberto et al 1998;Helm 2008). It is worth noting here that the possibility of replacing a carbonyl with a linear nitrosyl ligand to generate the neutral complex [(NO)(CO) 2 Tc(H 2 O) 3 ] or a similar derivative such as noted above is also a plausible candidate based on the available technetium XANES and EXAFS data.…”

Section: Sy 103mentioning

confidence: 99%

Development of a Chemistry-Based, Predictive Method for Determining the Amount of Non-Pertechnetate Technetium in the Hanford Tanks: FY 2012 Progress Report

Rapko¹,

Bryan²,

Bryant³

et al. 2013

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Executive SummaryThis report describes investigations directed toward understanding the extent of the presence of highly alkaline soluble, non-pertechnetate technetium (n-Tc) in the Hanford Tank supernatants. The goals of this report are to: a) present a review of the available literature relevant to the speciation of technetium in the Hanford tank supernatants, b) attempt to establish a chemically logical correlation between available Hanford tank measurements and the presence of supernatant soluble n-Tc, c) use existing measurement data to estimate the amount of n-Tc in the Hanford tank supernatants, and d) report on any likely, processfriendly methods to eventually sequester soluble n-Tc from Hanford tank supernatants.The work described herein follows on a substantial literature developed in the 1990s and early 2000s that first identified the problem of the presence of n-Tc and led to a tentative identification of the species in at least two Hanford tank waste supernatants. This project attempted to correlate chemically relevant indicators for which quality-valid data exists in the TWINS database suitable for eventual extrapolation to as-yet untested tank supernatants. In addition, two other tangential tasks were undertaken. First, a model was developed that expanded upon a previously published model by Lukens et al. (2001), for the rate of reduction of pertechnetate by radiolysis and inorganic chemical-based processes. Using information obtained from TWINS, this model was applied to the Hanford tank supernatants to identify the rate of pertechnetate reduction in the various Hanford tank supernatants. Second, one proposed species for n-Tc, the complex [(CO) 3 Tc(H 2 O) 3 ] + , was prepared, and initial studies into its spectroscopic signature and chemical stability were performed.From this work, the only acceptable chemically based correlations with data from the TWINS database were that the fraction of n-Tc present negatively correlates with either of two, closely related variables: total dose experienced in the tank, and 137 Cs concentration in the tank supernatants. The observed inverse correlation is counterintuitive, but a possible explanation is discussed. However, the correlation should lend some insight as to which tanks might be tested to further validate and enhance the predictive value of this correlation.As noted above, chemical data, radiolysis constants and known chemical rate constants for the reaction of water radiolysis products with inorganic Hanford tank waste supernatant constituents were used to evaluate the relative rates of pertechnetate reduction in the Hanford tank supernatants. These results are summarized in the report. Interestingly, the reduction rate for pertechnetate is greatest in two tanks, AZ-101 and AZ-102, where the presence of n-Tc is not detected. However, this reduction only concerns the rate of pertechnetate reduction; the speciation of the reduced product is not addressed. Consequently, reduction of pertechnetate to the poorly alkaline-soluble technetium dioxide could ...

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EXAFS analyses of technetium(I) carbonyl complexes – stability studies in solutions

Cited by 12 publications

References 16 publications

The structure, energy and stability of components formed in the preparation of fac-[99mTc(CO)3(H2O)3]+

The structure, energy and stability of components formed in the preparation of fac-[99mTc(CO)3(H2O)3]+

Preliminary Assessment of the Low-Temperature Waste Form Technology Coupled With Technetium Removal

Development of a Chemistry-Based, Predictive Method for Determining the Amount of Non-Pertechnetate Technetium in the Hanford Tanks: FY 2012 Progress Report

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