Chelant screening and refinement tests - Phase I, Task 2. Topical progress report, December 1993--June 1994 Page: 16 of 236
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the metal surface. Thus, the vast majority of information available on cleaning and
decontamination using chelants does not specifically apply to the removal of actinides.
The approach taken in this program was to build on the chemical cleaning expertise
acquired by Babcock & Wilcox during the development and qualification of the Electric Power
Research Institute/Steam Generator Owners Group (EPRI/SGOG) chemical cleaning process
(Reference 3). The mechanism of the technology proposed for development was similar to that
of the referenced process, and entails the formation of stable complexes between the chelant and
contaminant species. Metal ions possess reactive sites at which the activity of the metal is
centered. To inhibit the reaction of a metal ion, it is necessary to introduce a material which
forms a stable complex with metal ions, and thus, blocks the reactive sites of the metal ion.
When used appropriately, chelating agents can effectively stabilize a metal ion in solution.
Stabilization of the metal ion in solution also shifts the metal to ion equilibrium and allows
chelating solutions to continuously promote dissolution of metals into the solution phase
(Reference 4). Chelating agents have been successfully used for a number of years in the
chemical cleaning industry for deposit dissolution.
The generic goal of this program is to develop a solvent capable of selectively chelating
uranium and other actinides. This selectivity is required to eliminate the potential for the
chelating capacity of the solvent to be exhausted by metallic species, such as iron, which might
be present in overpowering quantities. A second requirement of the process is the ability to
control corrosion of the base metal. In cases where materials are surface contaminated only,
and reuse of the equipment is a possibility, corrosion should be controlled at a low rate.
However, in cases where contamination has migrated into the grain boundaries of the base metal,
a more aggressive solvent is required, to corrode away base metal and expose the radioactive
species for removal.
The specific goal of this task was to first perform laboratory screening tests to identify
the best solvents for the selective chelation of uranium. The best solvents from the screening
test program were then carried forward into the refinement phase of this task. The specific
objective of the refinement tests was to optimize the solvent application parameters and to define
the process application sequence for the subsequent bench and pilot plant tests.
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Chelant screening and refinement tests - Phase I, Task 2. Topical progress report, December 1993--June 1994, report, July 1, 1995; United States. (https://digital.library.unt.edu/ark:/67531/metadc680875/m1/16/: accessed April 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.