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Title: Technetium, Iodine, and Chromium Adsorption/Desorption Kd Values for Vadose Zone Pore Water, ILAW Glass, and Cast Stone Leachates Contacting an IDF Sand Sequence

Abstract

Performance and risk assessments of immobilized low-activity waste (ILAW) at the Integrated Disposal Facility (IDF) have shown that risks to groundwater are quite sensitive to adsorption-desorption interactions occurring in the near- and far-field environment. These interactions between the underlying sediments and the contaminants present in the leachates that descend from the buried glass, secondary waste grouts, and potentially Cast Stone low-activity waste packages have been represented in these assessments using the contaminant distribution coefficient (Kd) construct. Some contaminants (99Tc, 129I, and Cr) present in significant quantities in these wastes have low Kd values and tend to drive risk to public health and the environment. Relatively small changes in the Kd value can cause relatively large changes in the retardation factor. Thus, even relatively small uncertainty in the Kd value can result in a relatively large uncertainty in the risk determined through performance assessment modeling. The purpose of this study is to further reduce the uncertainty in Kd values for 99Tc, iodine (iodide and iodate), and Cr (chromate; CrO42-) by conducting systematic adsorption-desorption experiments using actual sand-dominated Hanford formation sediments from beneath the IDF and solutions that closely mimic Hanford vadose zone pore water and leachates from Cast Stone and ILAWmore » glass waste forms. Twenty-four batch and 21 flow-through column experiments were conducted, yielding 261 Kd measurements for these key contaminants, and contributing to our understanding for predicting transport from wastes disposed to the IDF. While the batch Kd methodology is not well-suited for measuring Kd values for non-sorbing species (as noted by the U.S. Environmental Protection Agency), the batch Kd results presented here are not wholly inconsistent with the column Kd results, and could be used for sensitivity purposes. Results from the column experiments are consistent with the best estimate and lower range of Kd values reported by Krupka et al. and Cantrell et al.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1373020
Report Number(s):
PNNL-24683
830403000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES

Citation Formats

Last, George V., Snyder, Michelle M.V., Um, Wooyong, Stephenson, John R., Leavy, Ian I., Strickland, Christopher E., Bacon, Diana H., Qafoku, Nikolla, and Serne, R. Jeffrey. Technetium, Iodine, and Chromium Adsorption/Desorption Kd Values for Vadose Zone Pore Water, ILAW Glass, and Cast Stone Leachates Contacting an IDF Sand Sequence. United States: N. p., 2015. Web. doi:10.2172/1373020.
Last, George V., Snyder, Michelle M.V., Um, Wooyong, Stephenson, John R., Leavy, Ian I., Strickland, Christopher E., Bacon, Diana H., Qafoku, Nikolla, & Serne, R. Jeffrey. Technetium, Iodine, and Chromium Adsorption/Desorption Kd Values for Vadose Zone Pore Water, ILAW Glass, and Cast Stone Leachates Contacting an IDF Sand Sequence. United States. doi:10.2172/1373020.
Last, George V., Snyder, Michelle M.V., Um, Wooyong, Stephenson, John R., Leavy, Ian I., Strickland, Christopher E., Bacon, Diana H., Qafoku, Nikolla, and Serne, R. Jeffrey. Sun . "Technetium, Iodine, and Chromium Adsorption/Desorption Kd Values for Vadose Zone Pore Water, ILAW Glass, and Cast Stone Leachates Contacting an IDF Sand Sequence". United States. doi:10.2172/1373020. https://www.osti.gov/servlets/purl/1373020.
@article{osti_1373020,
title = {Technetium, Iodine, and Chromium Adsorption/Desorption Kd Values for Vadose Zone Pore Water, ILAW Glass, and Cast Stone Leachates Contacting an IDF Sand Sequence},
author = {Last, George V. and Snyder, Michelle M.V. and Um, Wooyong and Stephenson, John R. and Leavy, Ian I. and Strickland, Christopher E. and Bacon, Diana H. and Qafoku, Nikolla and Serne, R. Jeffrey},
abstractNote = {Performance and risk assessments of immobilized low-activity waste (ILAW) at the Integrated Disposal Facility (IDF) have shown that risks to groundwater are quite sensitive to adsorption-desorption interactions occurring in the near- and far-field environment. These interactions between the underlying sediments and the contaminants present in the leachates that descend from the buried glass, secondary waste grouts, and potentially Cast Stone low-activity waste packages have been represented in these assessments using the contaminant distribution coefficient (Kd) construct. Some contaminants (99Tc, 129I, and Cr) present in significant quantities in these wastes have low Kd values and tend to drive risk to public health and the environment. Relatively small changes in the Kd value can cause relatively large changes in the retardation factor. Thus, even relatively small uncertainty in the Kd value can result in a relatively large uncertainty in the risk determined through performance assessment modeling. The purpose of this study is to further reduce the uncertainty in Kd values for 99Tc, iodine (iodide and iodate), and Cr (chromate; CrO42-) by conducting systematic adsorption-desorption experiments using actual sand-dominated Hanford formation sediments from beneath the IDF and solutions that closely mimic Hanford vadose zone pore water and leachates from Cast Stone and ILAW glass waste forms. Twenty-four batch and 21 flow-through column experiments were conducted, yielding 261 Kd measurements for these key contaminants, and contributing to our understanding for predicting transport from wastes disposed to the IDF. While the batch Kd methodology is not well-suited for measuring Kd values for non-sorbing species (as noted by the U.S. Environmental Protection Agency), the batch Kd results presented here are not wholly inconsistent with the column Kd results, and could be used for sensitivity purposes. Results from the column experiments are consistent with the best estimate and lower range of Kd values reported by Krupka et al. and Cantrell et al.},
doi = {10.2172/1373020},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2015},
month = {11}
}

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