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Title: Speciation, Dissolution, and Redox Reactions of Chromium Relevant to Pretreatment and Separation of High-Level Tank Wastes (First Year of Funding: FY 1998)

Abstract

Chromium, one of the problematic elements in tank sludges, is presently considered to be the most important constituent in defining the total volume of HLW glass to be produced from the Hanford tank wastes. This is because (1) it greatly complicates the vitrification process by forming separate phases in the molten glass and, (2) more importantly, current sludge washing processes are not effective in removing Cr. Inadequate removal of chromium from sludges could result in production of an unacceptably large volume of HLW glass. The removal of Cr from tank sludges is complicated by factors including the complex chemistry of Cr, lack of fundamental data applicable to the HLW chemical systems (high heterogeneity, high ionic strength, high alkalinity and the presence of inorganic and organic ligands, etc.), and the need to avoid processes that may adversely enhance the solubility of Pu and other actinides. Significant gaps exist in the fundamental understanding of Cr chemistry in tank-like environments. Without such data/understanding, these strategies cannot be appropriately evaluated or optimized. The primary objective of the research being carried out under this project is to develop such data/understanding for HLW tank processing. Pacific Northwest and Lawrence Berkeley National Laboratories in collaboration with Washingtonmore » State University are developing fundamental data on the precipitation/dissolution reactions of Cr(III) compounds and the kinetics of oxidation of Cr(III) to Cr(VI) at room and elevated temperatures and under conditions relevant to high-level waste processing. This integrated approach involving measurement of solubility and oxidation rate constants and spectroscopic characterization of aqueous and solid species as a function of ionic strength, alkalinity, redox conditions and temperature will provide thermodynamic and kinetic data. These data are necessary to predict changes in Cr solubility and speciation in response to changes in pretreatment strategies or to develop cost effective tank waste processing technologies that result from reducing the total amount of Cr in processed waste.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab., Richland, WA; Lawrence Berkeley National Lab., Berkeley, CA; Washington State University, Pullman, Washington (US)
Sponsoring Org.:
USDOE Office of Environmental Management (EM) (US)
OSTI Identifier:
833242
Report Number(s):
EMSP-65368-2000
R&D Project: EMSP 65368; TRN: US0406591
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jun 2000
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 54 ENVIRONMENTAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACID NEUTRALIZING CAPACITY; ACTINIDES; CHROMIUM; DISSOLUTION; KINETICS; OXIDATION; REDOX REACTIONS; SLUDGES; SOLUBILITY; TANKS; THERMODYNAMICS; VITRIFICATION; WASTE PROCESSING; WASTES

Citation Formats

Rai, Dhanpat, Rao, Linfeng, Clark, Sue B, and Hess, Nancy J. Speciation, Dissolution, and Redox Reactions of Chromium Relevant to Pretreatment and Separation of High-Level Tank Wastes (First Year of Funding: FY 1998). United States: N. p., 2000. Web. doi:10.2172/833242.
Rai, Dhanpat, Rao, Linfeng, Clark, Sue B, & Hess, Nancy J. Speciation, Dissolution, and Redox Reactions of Chromium Relevant to Pretreatment and Separation of High-Level Tank Wastes (First Year of Funding: FY 1998). United States. doi:10.2172/833242.
Rai, Dhanpat, Rao, Linfeng, Clark, Sue B, and Hess, Nancy J. Thu . "Speciation, Dissolution, and Redox Reactions of Chromium Relevant to Pretreatment and Separation of High-Level Tank Wastes (First Year of Funding: FY 1998)". United States. doi:10.2172/833242. https://www.osti.gov/servlets/purl/833242.
@article{osti_833242,
title = {Speciation, Dissolution, and Redox Reactions of Chromium Relevant to Pretreatment and Separation of High-Level Tank Wastes (First Year of Funding: FY 1998)},
author = {Rai, Dhanpat and Rao, Linfeng and Clark, Sue B and Hess, Nancy J},
abstractNote = {Chromium, one of the problematic elements in tank sludges, is presently considered to be the most important constituent in defining the total volume of HLW glass to be produced from the Hanford tank wastes. This is because (1) it greatly complicates the vitrification process by forming separate phases in the molten glass and, (2) more importantly, current sludge washing processes are not effective in removing Cr. Inadequate removal of chromium from sludges could result in production of an unacceptably large volume of HLW glass. The removal of Cr from tank sludges is complicated by factors including the complex chemistry of Cr, lack of fundamental data applicable to the HLW chemical systems (high heterogeneity, high ionic strength, high alkalinity and the presence of inorganic and organic ligands, etc.), and the need to avoid processes that may adversely enhance the solubility of Pu and other actinides. Significant gaps exist in the fundamental understanding of Cr chemistry in tank-like environments. Without such data/understanding, these strategies cannot be appropriately evaluated or optimized. The primary objective of the research being carried out under this project is to develop such data/understanding for HLW tank processing. Pacific Northwest and Lawrence Berkeley National Laboratories in collaboration with Washington State University are developing fundamental data on the precipitation/dissolution reactions of Cr(III) compounds and the kinetics of oxidation of Cr(III) to Cr(VI) at room and elevated temperatures and under conditions relevant to high-level waste processing. This integrated approach involving measurement of solubility and oxidation rate constants and spectroscopic characterization of aqueous and solid species as a function of ionic strength, alkalinity, redox conditions and temperature will provide thermodynamic and kinetic data. These data are necessary to predict changes in Cr solubility and speciation in response to changes in pretreatment strategies or to develop cost effective tank waste processing technologies that result from reducing the total amount of Cr in processed waste.},
doi = {10.2172/833242},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2000},
month = {6}
}

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