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Title: Phase chemistry and radionuclide retention from simulated tank sludges

Abstract

Decommissioning high level nuclear waste tanks will leave small amounts of residual sludge clinging to the walls and floor of the structures. The permissible amount of material left in the tanks depends on the radionuclide release characteristics of the sludge. At present, no systematic process exists for assessing how much of the remaining inventory will migrate, and which radioisotopes will remain relatively fixed. Working with actual sludges is both dangerous and prohibitively expensive. Consequently, methods were developed for preparing sludge simulants and doping them with nonradioactive surrogates for several radionuclides and RCRA metals of concern in actual sludges. The phase chemistry of these mixes was found to be a reasonable match for the main phases in actual sludges. Preliminary surrogate release characteristics for these sludges were assessed by lowering the ionic strength and pH of the sludges in the manner that would occur if normal groundwater gained access to a decommissioned tank. Most of the Se, Cs and Tc in the sludges will be released into the first pulse of groundwater passing through the sludge. A significant fraction of the other surrogates will be retained indefinitely by the sludges. This prolonged sequestration results from a combination coprecipitated and sorbed intomore » or onto relatively insoluble phases such as apatite, hydrous oxides of Fe, Al, Bi and rare earth oxides and phosphates. The coprecipitated fraction cannot be released until the host phase dissolves or recrystallizes. The sorbed fraction can be released by ion exchange processes as the pore fluid chemistry changes. However, these releases can be predicted based on a knowledge of the fluid composition and the surface chemistry of the solids. In this regard, the behavior of the hydrous iron oxide component of most sludges will probably play a dominant role for many cationic radionuclides while the hydrous aluminum oxides may be more important in governing anion releases.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
756116
Report Number(s):
SAND2000-1266C
TRN: US0003650
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: American Chemical Society, New Orleans, LA (US), 08/22/1999--08/26/1999; Other Information: PBD: 19 May 2000
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; RADIOACTIVE WASTE STORAGE; HIGH-LEVEL RADIOACTIVE WASTES; STORAGE FACILITIES; DECOMMISSIONING; SLUDGES; SIMULATION; PHASE STUDIES; WATER INFLUX; RADIONUCLIDE MIGRATION; IRON OXIDES; ALUMINIUM OXIDES; SORPTIVE PROPERTIES

Citation Formats

KRUMHANSL,JAMES L., LIU,J., ARTHUR,SARA E., HUTCHERSON,SHEILA K., QIAN,MORRIS, and ANDERSON,HOWARD L. Phase chemistry and radionuclide retention from simulated tank sludges. United States: N. p., 2000. Web.
KRUMHANSL,JAMES L., LIU,J., ARTHUR,SARA E., HUTCHERSON,SHEILA K., QIAN,MORRIS, & ANDERSON,HOWARD L. Phase chemistry and radionuclide retention from simulated tank sludges. United States.
KRUMHANSL,JAMES L., LIU,J., ARTHUR,SARA E., HUTCHERSON,SHEILA K., QIAN,MORRIS, and ANDERSON,HOWARD L. Fri . "Phase chemistry and radionuclide retention from simulated tank sludges". United States. https://www.osti.gov/servlets/purl/756116.
@article{osti_756116,
title = {Phase chemistry and radionuclide retention from simulated tank sludges},
author = {KRUMHANSL,JAMES L. and LIU,J. and ARTHUR,SARA E. and HUTCHERSON,SHEILA K. and QIAN,MORRIS and ANDERSON,HOWARD L.},
abstractNote = {Decommissioning high level nuclear waste tanks will leave small amounts of residual sludge clinging to the walls and floor of the structures. The permissible amount of material left in the tanks depends on the radionuclide release characteristics of the sludge. At present, no systematic process exists for assessing how much of the remaining inventory will migrate, and which radioisotopes will remain relatively fixed. Working with actual sludges is both dangerous and prohibitively expensive. Consequently, methods were developed for preparing sludge simulants and doping them with nonradioactive surrogates for several radionuclides and RCRA metals of concern in actual sludges. The phase chemistry of these mixes was found to be a reasonable match for the main phases in actual sludges. Preliminary surrogate release characteristics for these sludges were assessed by lowering the ionic strength and pH of the sludges in the manner that would occur if normal groundwater gained access to a decommissioned tank. Most of the Se, Cs and Tc in the sludges will be released into the first pulse of groundwater passing through the sludge. A significant fraction of the other surrogates will be retained indefinitely by the sludges. This prolonged sequestration results from a combination coprecipitated and sorbed into or onto relatively insoluble phases such as apatite, hydrous oxides of Fe, Al, Bi and rare earth oxides and phosphates. The coprecipitated fraction cannot be released until the host phase dissolves or recrystallizes. The sorbed fraction can be released by ion exchange processes as the pore fluid chemistry changes. However, these releases can be predicted based on a knowledge of the fluid composition and the surface chemistry of the solids. In this regard, the behavior of the hydrous iron oxide component of most sludges will probably play a dominant role for many cationic radionuclides while the hydrous aluminum oxides may be more important in governing anion releases.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2000},
month = {5}
}

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