Speciation, Dissolution, and Redox Reactions of Chromium Relevant to Pretreatment and Separation of High-Level Tank Wastes

Rai, Dhapat ; Rao, Linfeng

Pacific Northwest National Laboratory (U.S.)

关键词: Leaching;    Removal;    Oxidizers;    12 Management Of Radioactive Wastes, And Non-Radioactive Wastes From Nuclear Facilities;    Hydroxides;   

DOI  :  10.2172/895843
RP-ID  :  ERSD-95018-2006
RP-ID  :  None
RP-ID  :  895843

美国|英语

来源: UNT Digital Library

【 摘 要 】

Chromium, one of the problematic elements in tank sludges, is considered the most important constituent in defining the total volume of high-level radioactive waste (HLW) glass. Current sludge-washing processes (e.g. caustic leaching, 3 M NaOH) are not effective in removing Cr. Such inefficient removal would result in the production of an unacceptably large volume of HLW glass and thus a tremendous increase in the cost of waste disposal. This proposed research seeks to develop fundamental data for chromium (Cr) reactions that are not currently available but are essential for developing effective methodologies for removing Cr form high-level waste (HLW). Our objectives are to study (1) the dissolution of several solid phases (e.g., CrOOH, Cr2O3(c), Cr(OH)3, and Fe and Cr, binary hydroxides, identified to be important from sludge leaching studies) in highly alkaline solutions and in the presence of other electrolytes (e.g., carbonate, phosphate, sulfate, nitrite), and (2) the effect of the nature of Cr solid phases and aqueous species on their redox reactivity with a variety of potential oxidants (H2O2, persulfate, hypochlorite, etc.). This information will provide critical support for developing enhanced pretreatment strategies for removing Cr from HLW and will achieve a major cost reduction in HLW disposal.