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Title: Distribution and Solubility of Radionuclides and Neutron Absorbers in Waste forms for Disposition of Plutonium Ash and Scraps, Excess Plutonium, and Miscellaneous Spent Nuclear Fuels

Abstract

Successful immobilization of actinides (Am, Cm, Th, Pu, Np, etc.) in crystalline and amorphous host matrixes with appropriate neutron absorbers (B, Hf, Gd, etc.) requires sound scientific knowledge of the local chemical environments of both the actinides (An) and the neutron absorbers and their interaction with the host matrixes. This understanding leads to a more systematic and efficient approach to predicting solubilities than the strictly empirical approach now used. The goals of this ongoing research are to determine solubility limits of representative actinides (Pu and U) and neutron absorbers (Hf and Gd) in crystalline and amorphous matrixes and to determine solution mechanisms of these species in the two types of systems. Actinides and neutron absorbers in amorphous systems have been studied at PNNL in collaboration with LBNL and University of Michigan and in crystalline systems at ANSTO. We believe that we are in a position to understand the chemical systematics of silicate melts so that the solubility of actinides, neutron absorbers, and, we would suggest, other metal species in glass no longer must be determined empirically but can be calculated from a set of equilibrium constants in a fashion similar to aqueous systems.

Authors:
Publication Date:
Research Org.:
Pacific Northwest National Lab., Richland, WA (US)
Sponsoring Org.:
USDOE Office of Environmental Management (EM) (US)
OSTI Identifier:
831154
Report Number(s):
EMSP-60387-2000
R&D Project: EMSP 60387; TRN: US0405642
DOE Contract Number:
FG07-97ER45672; FG07-64ER45676
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jun 2000
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 54 ENVIRONMENTAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACTINIDES; ANSTO; DISTRIBUTION; GLASS; NEUTRON ABSORBERS; NUCLEAR FUELS; PLUTONIUM; RADIOISOTOPES; SILICATES; SOLUBILITY; WASTE FORMS; SPENT FUELS

Citation Formats

Strachan, Denis M. Distribution and Solubility of Radionuclides and Neutron Absorbers in Waste forms for Disposition of Plutonium Ash and Scraps, Excess Plutonium, and Miscellaneous Spent Nuclear Fuels. United States: N. p., 2000. Web. doi:10.2172/831154.
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Strachan, Denis M. Distribution and Solubility of Radionuclides and Neutron Absorbers in Waste forms for Disposition of Plutonium Ash and Scraps, Excess Plutonium, and Miscellaneous Spent Nuclear Fuels. United States. doi:10.2172/831154.
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Strachan, Denis M. Thu . "Distribution and Solubility of Radionuclides and Neutron Absorbers in Waste forms for Disposition of Plutonium Ash and Scraps, Excess Plutonium, and Miscellaneous Spent Nuclear Fuels". United States. doi:10.2172/831154. https://www.osti.gov/servlets/purl/831154.
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@article{osti_831154,
title = {Distribution and Solubility of Radionuclides and Neutron Absorbers in Waste forms for Disposition of Plutonium Ash and Scraps, Excess Plutonium, and Miscellaneous Spent Nuclear Fuels},
author = {Strachan, Denis M.},
abstractNote = {Successful immobilization of actinides (Am, Cm, Th, Pu, Np, etc.) in crystalline and amorphous host matrixes with appropriate neutron absorbers (B, Hf, Gd, etc.) requires sound scientific knowledge of the local chemical environments of both the actinides (An) and the neutron absorbers and their interaction with the host matrixes. This understanding leads to a more systematic and efficient approach to predicting solubilities than the strictly empirical approach now used. The goals of this ongoing research are to determine solubility limits of representative actinides (Pu and U) and neutron absorbers (Hf and Gd) in crystalline and amorphous matrixes and to determine solution mechanisms of these species in the two types of systems. Actinides and neutron absorbers in amorphous systems have been studied at PNNL in collaboration with LBNL and University of Michigan and in crystalline systems at ANSTO. We believe that we are in a position to understand the chemical systematics of silicate melts so that the solubility of actinides, neutron absorbers, and, we would suggest, other metal species in glass no longer must be determined empirically but can be calculated from a set of equilibrium constants in a fashion similar to aqueous systems.},
doi = {10.2172/831154},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2000},
month = {Thu Jun 01 00:00:00 EDT 2000}
}
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DOI:  10.2172/831154
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  • ; ;
    'The objective of this research is to gain a fundamental understanding of the distributions and the solubility limits for actinides Pu and U and rare earth neutron absorbers such as Gd and Hf in waste forms. This will be accomplished by systematically studying the local structural environments of these constituents in representative waste forms such as glass, ceramics, and vitreous ceramics. Basic knowledge of these issues will provide a technical and scientific basis that can be used by the US Department of Energy (DOE), Environment Management (EM) Program in developing, evaluating, and selecting waste forms for the safe disposal ofmore » Pu, spent nuclear fuel, and other transuranic wastes. The work presented here is a summary of the research activity from November 1997 to May 1998. The elucidation of the correlations between the local structural environments of actinides and rare earth neutron absorbers in waste forms as functions of waste form compositions, and waste form processing conditions will also advance basic material science. The work presented here is a summary of the research activity from November 1997 to May 1998. Currently being studied is the effect of the Pu oxidation state on its solubility in borosilicate-based glasses. When glasses are melted in ambient atmosphere, Pu(IV) has been shown to be the dominant oxidation state as determined by ultraviolet-visible-near infrared spectroscopy (UV-VIS-NIR) and x-ray absorption fine structure (XAFS) techniques. However, no literature data are available for glasses containing Pu predominantly as Pu(III) nor the solubility for Pu(III) in the glass. The results of the study demonstrate that in borosilicate glass, Pu(III) is significantly more soluble than Pu(IV). Using x-ray diffraction analysis the solubility of Pu(III) as oxide was determined to be at least 25 mass% in the reduced glass, while it was no greater than 10 mass% in the same glass under oxidizing conditions (glass melting temperature was 1,400 C). The oxidation states of Pu in the glasses were determined by XAFS analysis using the Pu L III edge as shown in Figure 1. Using standard reference XAFS spectra of Pu(IV) and Pu(III), the authors estimated that about 90% of the Pu was present as Pu(IV) in the oxidized glass and about 95% of the Pu was Pu(III) in the reduced glass. In contrast to the redox effect on the solubility limit of Pu, the solubility of U in soda-lime (SL) silicate glass is favored under oxidizing conditions or glass with high Na 2 O concentration. In ambient atmosphere at 1,500 C, the solubility, in terms of UO{sub 3}, is found to be 30 mass% in the baseline glass (SRM 1,830 from NIST) and at least 40 mass% in the baseline glass with additional Na{sub 2}O.'« less

  • ; ; ; ...
    The initial goal of this project was to investigate the solubility of radionuclides in glass and other potential waste forms for the purpose of increasing the waste loading in glass and ceramic waste forms. About one year into the project, the project decided to focus on two potential waste forms - glass at PNNL and itianate ceramics at the Australian Nuclear Science and Technology Organisation (ANSTO).

  • ; ; ; ...
    The objective of this research is to develop a basic understanding of the distribution and solubility of radionuclides and neutron absorbers in waste forms and their release from waste forms by studying the local structural environments of these constituents in representative materials.

  • ; ; ; ... - Journal of the American Ceramic Society
    Uranium, plutonium, and several radionuclide surrogates have been examined in a range of glass wasteform materials by x-ray absorption fine structure (XAFS) to improve the understanding of specific effects of glass melt processing conditions on the speciation of the metal ion. The glass melts have been subject to systematic compositional, radionuclide loading, and oxidation reduction potential variations during processing. The speciation of both uranium and plutonium responds to glass melt processing redox conditions and shows trends with increased radionuclide loading. A comparative investigation of the redox properties of plutonium and cerium, a plutonium surrogate, has been completed in a seriesmore » of related glass wasteforms. The observed difference in oxidation states between the two metal ions in these wasteform materials has been successfully interpreted from consideration of the melt glass thermodynamics.« less

  • ; ; ; ...
    Successful immobilization of actinides (Am, Cm, Th, Pu, U, Np, etc.) in crystalline and amorphous host matrices with appropriate neutron absorbers (B, Hf, Gd, etc.) requires sound scientific knowledge of the local chemical environments of both the actinides (An) and the neutron absorbers and their interaction with the host matrices. This understanding leads to a more systematic and efficient approach to predicting solubilities than the strictly empirical approach currently used. The goals of this ongoing research are to determine solubility limits of representative actinides (Pu and U) and neutron absorbers (Hf and Gd) in crystalline and amorphous matrices and tomore » determine solution mechanisms of these species in the two types of systems. Understanding of the chemical systematics of in the two systems will make it possible to calculate the solubility of actinides, neutron absorbers, and, we would suggest, other metal species in glass and ceramic waste form, which have been determined empirically for the past. The research results of the ongoing project will be presented, including solubility of neutron absorbers, Hf(IV) and Gd(III), and local structures of these species in comparison to those of Pu(IV) and Pu(III) in glass. Effect of glass composition, in terms of peralkallinity, Na2O/(Na2O+Al2O3), on dissolution of Hf(IV) and Gd(III)and glass microstructure development will be also presented.« less