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Title: Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides.

Abstract

The United States is now re-assessing its nuclear waste disposal policy and re-evaluating the option of moving away from the current once-through open fuel cycle to a closed fuel cycle. In a closed fuel cycle, used fuels will be reprocessed and useful components such as uranium or transuranics will be recovered for reuse. During this process, a variety of waste streams will be generated. Immobilizing these waste streams into appropriate waste forms for either interim storage or long-term disposal is technically challenging. Highly volatile or soluble radionuclides such as iodine ({sup 129}I) and technetium ({sup 99}Tc) are particularly problematic, because both have long half-lives and can exist as gaseous or anionic species that are highly soluble and poorly sorbed by natural materials. Under the support of Sandia National Laboratories (SNL) Laboratory-Directed Research & Development (LDRD), we have developed a suite of inorganic nanocomposite materials (SNL-NCP) that can effectively entrap various radionuclides, especially for {sup 129}I and {sup 99}Tc. In particular, these materials have high sorption capabilities for iodine gas. After the sorption of radionuclides, these materials can be directly converted into nanostructured waste forms. This new generation of waste forms incorporates radionuclides as nano-scale inclusions in a host matrix andmore » thus effectively relaxes the constraint of crystal structure on waste loadings. Therefore, the new waste forms have an unprecedented flexibility to accommodate a wide range of radionuclides with high waste loadings and low leaching rates. Specifically, we have developed a general route for synthesizing nanoporous metal oxides from inexpensive inorganic precursors. More than 300 materials have been synthesized and characterized with x-ray diffraction (XRD), BET surface area measurements, and transmission electron microscope (TEM). The sorption capabilities of the synthesized materials have been quantified by using stable isotopes I and Re as analogs to {sup 129}I and {sup 99}Tc. The results have confirmed our original finding that nanoporous Al oxide and its derivatives have high I sorption capabilities due to the combined effects of surface chemistry and nanopore confinement. We have developed a suite of techniques for the fixation of radionuclides in metal oxide nanopores. The key to this fixation is to chemically convert a target radionuclide into a less volatile or soluble form. We have developed a technique to convert a radionuclide-loaded nanoporous material into a durable glass-ceramic waste form through calcination. We have shown that mixing a radionuclide-loaded getter material with a Na-silicate solution can effectively seal the nanopores in the material, thus enhancing radionuclide retention during waste form formation. Our leaching tests have demonstrated the existence of an optimal vitrification temperature for the enhancement of waste form durability. Our work also indicates that silver may not be needed for I immobilization and encapsulation.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
USDOE
OSTI Identifier:
990070
Report Number(s):
SAND2010-5901
TRN: US1007365
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; 36 MATERIALS SCIENCE; CALCINATION; CHEMISTRY; CRYSTAL STRUCTURE; ELECTRON MICROSCOPES; ENCAPSULATION; FUEL CYCLE; IODINE 129; LEACHING; OXIDES; RADIOACTIVE WASTES; RADIOISOTOPES; SORPTION; STABLE ISOTOPES; SURFACE AREA; TECHNETIUM 99; URANIUM; VITRIFICATION; WASTE FORMS; WASTE STORAGE; X-RAY DIFFRACTION; Nuclear facilities-Waste disposal.; Transuranic wastes (TRU)-Storage.; Transuranic elements-Analysis-Technological innovations.; Nuclear waste repositories.

Citation Formats

Rodriguez, Mark Andrew, Bencoe, Denise Nora, Brinker, C Jeffrey, Murphy, Andrew Wilson, Holt, Kathleen Caroline, Turnham, Rigney, Kruichak, Jessica Nicole, Tellez, Hernesto, Miller, Andy, Xiong, Yongliang, Pohl, Phillip Isabio, Ockwig, Nathan W, Wang, Yifeng, and Gao, Huizhen. Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides.. United States: N. p., 2010. Web. doi:10.2172/990070.
Rodriguez, Mark Andrew, Bencoe, Denise Nora, Brinker, C Jeffrey, Murphy, Andrew Wilson, Holt, Kathleen Caroline, Turnham, Rigney, Kruichak, Jessica Nicole, Tellez, Hernesto, Miller, Andy, Xiong, Yongliang, Pohl, Phillip Isabio, Ockwig, Nathan W, Wang, Yifeng, & Gao, Huizhen. Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides.. United States. doi:10.2172/990070.
Rodriguez, Mark Andrew, Bencoe, Denise Nora, Brinker, C Jeffrey, Murphy, Andrew Wilson, Holt, Kathleen Caroline, Turnham, Rigney, Kruichak, Jessica Nicole, Tellez, Hernesto, Miller, Andy, Xiong, Yongliang, Pohl, Phillip Isabio, Ockwig, Nathan W, Wang, Yifeng, and Gao, Huizhen. Wed . "Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides.". United States. doi:10.2172/990070. https://www.osti.gov/servlets/purl/990070.
@article{osti_990070,
title = {Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides.},
author = {Rodriguez, Mark Andrew and Bencoe, Denise Nora and Brinker, C Jeffrey and Murphy, Andrew Wilson and Holt, Kathleen Caroline and Turnham, Rigney and Kruichak, Jessica Nicole and Tellez, Hernesto and Miller, Andy and Xiong, Yongliang and Pohl, Phillip Isabio and Ockwig, Nathan W and Wang, Yifeng and Gao, Huizhen},
abstractNote = {The United States is now re-assessing its nuclear waste disposal policy and re-evaluating the option of moving away from the current once-through open fuel cycle to a closed fuel cycle. In a closed fuel cycle, used fuels will be reprocessed and useful components such as uranium or transuranics will be recovered for reuse. During this process, a variety of waste streams will be generated. Immobilizing these waste streams into appropriate waste forms for either interim storage or long-term disposal is technically challenging. Highly volatile or soluble radionuclides such as iodine ({sup 129}I) and technetium ({sup 99}Tc) are particularly problematic, because both have long half-lives and can exist as gaseous or anionic species that are highly soluble and poorly sorbed by natural materials. Under the support of Sandia National Laboratories (SNL) Laboratory-Directed Research & Development (LDRD), we have developed a suite of inorganic nanocomposite materials (SNL-NCP) that can effectively entrap various radionuclides, especially for {sup 129}I and {sup 99}Tc. In particular, these materials have high sorption capabilities for iodine gas. After the sorption of radionuclides, these materials can be directly converted into nanostructured waste forms. This new generation of waste forms incorporates radionuclides as nano-scale inclusions in a host matrix and thus effectively relaxes the constraint of crystal structure on waste loadings. Therefore, the new waste forms have an unprecedented flexibility to accommodate a wide range of radionuclides with high waste loadings and low leaching rates. Specifically, we have developed a general route for synthesizing nanoporous metal oxides from inexpensive inorganic precursors. More than 300 materials have been synthesized and characterized with x-ray diffraction (XRD), BET surface area measurements, and transmission electron microscope (TEM). The sorption capabilities of the synthesized materials have been quantified by using stable isotopes I and Re as analogs to {sup 129}I and {sup 99}Tc. The results have confirmed our original finding that nanoporous Al oxide and its derivatives have high I sorption capabilities due to the combined effects of surface chemistry and nanopore confinement. We have developed a suite of techniques for the fixation of radionuclides in metal oxide nanopores. The key to this fixation is to chemically convert a target radionuclide into a less volatile or soluble form. We have developed a technique to convert a radionuclide-loaded nanoporous material into a durable glass-ceramic waste form through calcination. We have shown that mixing a radionuclide-loaded getter material with a Na-silicate solution can effectively seal the nanopores in the material, thus enhancing radionuclide retention during waste form formation. Our leaching tests have demonstrated the existence of an optimal vitrification temperature for the enhancement of waste form durability. Our work also indicates that silver may not be needed for I immobilization and encapsulation.},
doi = {10.2172/990070},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2010},
month = {9}
}

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