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Title: Conceptual Model of Subsurface Processes for Iodine at the Hanford Site

Abstract

Currently, there are large dilute 129I groundwater plumes at Hanford, including a groundwater plume in the 200-UP-1 operable unit (OU) located within the Central Plateau of the Hanford Site. The interim record of decision for the 200-UP-1 OU requires that the U.S. Department of Energy evaluate potential treatment options for 129I through further technology evaluation. The approach to the evaluation was defined in the 129I technology evaluation plan and includes an update to the conceptual model (CM) for the plume, as required by the 200 UP 1 remedial design/remedial action work plan. This report describes an updated CM of subsurface processes that affect 129I behavior in the subsurface. This CM was developed to address identified data gaps and to provide input for fate and transport modeling needed to support the remedy evaluation. A significant advancement from previous the CM for the 200-UP-1 OU is recognition of the multiple iodine species in the subsurface and the biogeochemical processes that control their fate and transport. The CM was developed to incorporate the current information from samples of 200 West Area groundwater (including samples within the 200-UP-1 OU) that show iodine is present as a mix of iodide, iodate, and organo-I species, withmore » iodate being the predominant species. Confirmation of iodine species distribution in the plume is recommended to help validate this CM basis. Plume behavior is affected by differential transport of iodine species due to their different sorption characteristics. This CM describes behavior for radioiodine ( 129I) and non-radioactive iodine ( 127I) because both isotopes have the same geochemical behavior. Non-radioactive iodine ( 127I) concentrations are estimated to be 1000 times higher than radioiodine ( 129I) in Hanford Site Central Plateau groundwater. This ratio has important implications for remedial strategies because remedies cannot specifically treat 129I without also targeting 127I. A network of biogeochemical processes controls the fate and transport behavior of iodine in the subsurface. A primary element of the effort to update the iodine CM was to quantify these processes and identify which are of importance at the Hanford Site, in particular for the 200-UP-1 OU.« less

Authors:
ORCiD logo [1];  [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:
1491498
Report Number(s):
PNNL-28053Rev1.0
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English

Citation Formats

Qafoku, Nikolla P., Bagwell, Christopher E., Lawter, Amanda R., Truex, Michael J., Szecsody, James E., Qafoku, Odeta, Kovarik, Libor, Zhong, Lirong, Mitroshkov, Alexandre V., and Freedman, Vicky L. Conceptual Model of Subsurface Processes for Iodine at the Hanford Site. United States: N. p., 2018. Web. doi:10.2172/1491498.
Qafoku, Nikolla P., Bagwell, Christopher E., Lawter, Amanda R., Truex, Michael J., Szecsody, James E., Qafoku, Odeta, Kovarik, Libor, Zhong, Lirong, Mitroshkov, Alexandre V., & Freedman, Vicky L. Conceptual Model of Subsurface Processes for Iodine at the Hanford Site. United States. doi:10.2172/1491498.
Qafoku, Nikolla P., Bagwell, Christopher E., Lawter, Amanda R., Truex, Michael J., Szecsody, James E., Qafoku, Odeta, Kovarik, Libor, Zhong, Lirong, Mitroshkov, Alexandre V., and Freedman, Vicky L. Sun . "Conceptual Model of Subsurface Processes for Iodine at the Hanford Site". United States. doi:10.2172/1491498. https://www.osti.gov/servlets/purl/1491498.
@article{osti_1491498,
title = {Conceptual Model of Subsurface Processes for Iodine at the Hanford Site},
author = {Qafoku, Nikolla P. and Bagwell, Christopher E. and Lawter, Amanda R. and Truex, Michael J. and Szecsody, James E. and Qafoku, Odeta and Kovarik, Libor and Zhong, Lirong and Mitroshkov, Alexandre V. and Freedman, Vicky L.},
abstractNote = {Currently, there are large dilute 129I groundwater plumes at Hanford, including a groundwater plume in the 200-UP-1 operable unit (OU) located within the Central Plateau of the Hanford Site. The interim record of decision for the 200-UP-1 OU requires that the U.S. Department of Energy evaluate potential treatment options for 129I through further technology evaluation. The approach to the evaluation was defined in the 129I technology evaluation plan and includes an update to the conceptual model (CM) for the plume, as required by the 200 UP 1 remedial design/remedial action work plan. This report describes an updated CM of subsurface processes that affect 129I behavior in the subsurface. This CM was developed to address identified data gaps and to provide input for fate and transport modeling needed to support the remedy evaluation. A significant advancement from previous the CM for the 200-UP-1 OU is recognition of the multiple iodine species in the subsurface and the biogeochemical processes that control their fate and transport. The CM was developed to incorporate the current information from samples of 200 West Area groundwater (including samples within the 200-UP-1 OU) that show iodine is present as a mix of iodide, iodate, and organo-I species, with iodate being the predominant species. Confirmation of iodine species distribution in the plume is recommended to help validate this CM basis. Plume behavior is affected by differential transport of iodine species due to their different sorption characteristics. This CM describes behavior for radioiodine (129I) and non-radioactive iodine (127I) because both isotopes have the same geochemical behavior. Non-radioactive iodine (127I) concentrations are estimated to be 1000 times higher than radioiodine (129I) in Hanford Site Central Plateau groundwater. This ratio has important implications for remedial strategies because remedies cannot specifically treat 129I without also targeting 127I. A network of biogeochemical processes controls the fate and transport behavior of iodine in the subsurface. A primary element of the effort to update the iodine CM was to quantify these processes and identify which are of importance at the Hanford Site, in particular for the 200-UP-1 OU.},
doi = {10.2172/1491498},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {11}
}