Selective partitioning of mercury from co-extracted actinides in a simulated acidic ICPP waste stream Page: 1 of 13
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SELECTIVE PARTITIONING OF MERCURY FROM
CO-EXTRACTED ACTINIDES IN A SIMULATED
ACIDIC ICPP WASTE STREAM' F uJ E IV ED
NOV 2 1' 995
K. N. Brewer, R. S. Herbst, T. J. Tranter, J. D. Law, T. A. ToddO S T I
Lockheed Idaho Technologies Co., Inc.
The TRUEX process is being evaluated at the Idaho Chemical Processing Plant (ICPP) as a
means to partition the actinides from acidic sodium-bearing waste (SBW). The mercury content of
this waste averages 1 g/I. Because the chemistry of mercury has not been extensively evaluated in the
TRUEX process, mercury was singled out as an element of interest. Radioactive mercury, 2"Hg, was
spiked into a simulated solution of SBW containing 1 g/l mercury. Successive extraction batch
contacts with the mercury spiked waste simulant and successive scrubbing and stripping batch
contacts of the mercury loaded TRUEX solvent (0.2 M CMPO-1.4 M TBP in dodecane) show that
mercury will extract into and strip from the solvent. The extraction distribution coefficient for
mercury, as HgCl2, from SBW having a nitric acid concentration of 1.4 M and a chloride
concentration of 0.035 M was found to be 3. The stripping distribution coefficient was found to be
0.5 with 5 M HNO3 and 0.077 with 0.25 M Na2CO3. An experimental flowsheet was designed from
the batch contact tests and tested counter-currently using 5.5 cm centrifugal contactors. Results from
the counter-current test show that mercury can be removed from the acidic mixed SBW simulant and
recovered separately from the actinides.
The Idaho Chemical Processing Plant (ICPP), located at the Idaho National Engineering
Laboratory (INEL) in Southeastern Idaho, is owned by the DOE and currently operated by Lockheed
Idaho Technologies Co., Inc (LITCO). The mission of the ICPP at one time was to reprocess special
DOE and naval fuels. The majority of the reprocessed fuels were either zirconium or aluminum clad.
The headend dissolution completely dissolved the cladding, heavy metals, and fission products. In
order to enhance the dissolution rate of the aluminum clad fuels, mercury was added as a catalyst.
Following uranium recovery via a combination of REDOX and PUREX type processes, the
highly radioactive raffinate streams were sent to temporary underground storage tanks. The liquid
raffinates were eventually solidified by calcining in a fluidized bed operated at 5000C.
During the calcination process, mercury was volatilized and scrubbed out of the off-gas using
nitric acid . The nitric acid scrub solutions, which in essence concentrated the mercury, were sent
back to temporary storage where they were blended with decontamination, solvent wash, and other
solutions, most of which are high in sodium. This waste is referred to as sodium-bearing waste
Unlike the liquid reprocessing raffinates, SBW solutions are not calcinable directly and must
be blended with non-radioactive aluminum nitrate or other first cycle raffinates prior to calcination
(as of November 1993 all raffmates were calcined). Approximately 1.5 million gallons of SBW,
containing a total of 2 metric tons of mercury, are in temporary storage at the ICPP.
If the SBW is eventually blended and calcined, the mercury will most likely report back to
the calciner nitric acid off-gas scrub solution and be sent back to temporary underground storage,
thus resulting in mercury recycle throughout the ICPP waste treatment process.
Due to the growing environmental awareness of the public and DOE laboratories, a safe and
Work performed for the U.S. Department of Energy under Contract No. DE-ACO7-84ID12345.
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Brewer, K.N.; Herbst, R.S. & Tranter, T.J. Selective partitioning of mercury from co-extracted actinides in a simulated acidic ICPP waste stream, article, December 1, 1995; Idaho Falls, Idaho. (https://digital.library.unt.edu/ark:/67531/metadc619350/m1/1/: accessed April 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.