MEASUREMENT AND PREDICTION OF RADIOLYTIC HYDROGEN PRODUCTION IN DEFENSE WASTE PROCESSING SLURRIES AT SAVANNAH RIVER SITE Page: 2 of 16
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WSRC-STI-2006-00114 Rev. 1
MEASUREMENT AND PREDICTION OF RADIOLYTIC HYDROGEN PRODUCTION
IN DEFENSE WASTE PROCESSING SLURRIES AT SAVANNAH RIVER SITE
N. E. Bibler, J. M. Pareizs, T. L. Fellinger, and C. J. Bannochie
Savannah River National Laboratory
Washington Savannah River Co.
Aiken, SC 29808
This paper presents results of measurements and predictions of radiolytic hydrogen production
rates from two actual process slurries in the Defense Waste Processing Facility (DWPF) at
Savannah River Site (SRS). Hydrogen is a flammable gas and its production in nuclear facilities
can be a safety hazard if not mitigated. Measurements were made in the Shielded Cells of
Savannah River National Laboratory (SRNL) using a sample of Sludge Batch 3 (SB3) currently
being processed by the DWPF. Predictions were made using published values for rates of
radiolytic reactions producing H2 in aqueous solutions and the measured radionuclide and
chemical compositions of the two slurries. The agreement between measured and predicted
results for nine experiments ranged from complete agreement to 24% difference. This agreement
indicates that if the composition of the slurry being processed is known, the rate of radiolytic
hydrogen production can be reasonably estimated.
There is an aggressive program at SRS to remove and stabilize the radioactive high level waste
(HLW) sludge slurries that are stored in the large underground tanks at SRS. Each tank can hold
approximately 35 hundred cubic meters of HLW. Currently the DWPF is converting this waste
into a durable borosilicate glass for permanent geologic disposal.
The wastes are stored as caustic sludge slurries. The main components in the insoluble solids in
the caustic slurries are primarily hydrous oxides of Fe, Al, and other elements that were used in
processing operations at SRS. Most of the radionuclides (actinides and U-235 fission products)
are insoluble in caustic and are also in the sludge solids. The supernate of the slurries contain
dissolved NaOH along with soluble nitrate, nitrite, and sulfate salts. The supernate also contains
most of the fission product Cs-137 because it is soluble in caustic.
Hydrogen is continuously produced in the slurries by radiolysis of the water by the beta and alpha
particles and the gamma rays from the radionuclides. In the caustic slurries the precursors of H2
are aqueous electrons (eaq) and H atoms (H).  Based on data from many experimental studies,
the chemical reactions that form H2 are
eag + eag -> H2 + 20H- (1)
H + eag + H20 - H2 + OH- (2)
H + H -> H2 (3)
with Reaction 1 being more important than Reaction 2 and Reaction 2 more important than
Reaction 3. These studies are well summarized in Reference 1.
PAPER FOR WM'07
Page 1 OF 15
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Bibler, N; John Pareizs, J; Terri Fellinger, T & Cj Bannochie, C. MEASUREMENT AND PREDICTION OF RADIOLYTIC HYDROGEN PRODUCTION IN DEFENSE WASTE PROCESSING SLURRIES AT SAVANNAH RIVER SITE, article, January 10, 2007; [Aiken, South Carolina]. (digital.library.unt.edu/ark:/67531/metadc885839/m1/2/: accessed November 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.