Phase chemistry and radionuclide retention from simulated tank sludges

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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 ... continued below

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14 p.

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KRUMHANSL,JAMES L.; LIU,J.; ARTHUR,SARA E.; HUTCHERSON,SHEILA K.; QIAN,MORRIS & ANDERSON,HOWARD L. May 19, 2000.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA (United States)
    Place of Publication: Albuquerque, New Mexico

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Description

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.

Physical Description

14 p.

Notes

INIS; OSTI as DE00756116

Medium: P; Size: 14 pages

Source

  • American Chemical Society, New Orleans, LA (US), 08/22/1999--08/26/1999

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  • Report No.: SAND2000-1266C
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 756116
  • Archival Resource Key: ark:/67531/metadc711336

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • May 19, 2000

Added to The UNT Digital Library

  • Sept. 12, 2015, 6:31 a.m.

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  • April 7, 2017, 2:37 p.m.

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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, article, May 19, 2000; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc711336/: accessed November 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.