MEASUREMENT AND PREDICTION OF RADIOLYTIC HYDROGEN PRODUCTION IN DEFENSE WASTE PROCESSING SLURRIES AT SAVANNAH RIVER SITE Page: 3 of 16
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WSRC-STI-2006-00114 Rev. 1
Hydrogen production in the HLW storage tanks and in the process tanks in the DWPF is a
concern because of the possible formation of flammable mixtures in the vapor spaces of the tanks.
A previous paper has discussed radiolytic H2 production in the storage tanks and what is being
done to prevent formation of flammable mixtures in those tanks.  This paper discusses
radiolytic H2 production in two DWPF process tanks. The DWPF tanks usually process -30
cubic meters of slurry in these tanks.
To determine the rate of radiolytic H2 production from process slurries in the DWPF,
measurements of radiolytic H2 production were made in the Shielded Cells of Savannah River
National Laboratory (SRNL) using a sample of the slurry from Sludge Batch 3 (SB3) that is
currently being processed by the DWPF. Measurements were made on two types of slurries that
are processed in the DWPF. One was the caustic sludge slurry itself as it would be received by
the DWPF for processing. The other was a slurry that resulted process steps in the DWPF. These
steps include the addition of nitric and formic acids to the slurry. Nitric acid is added to destroy
nitrites and carbonates in the slurry and to adjust the rheology of the slurry. Formic acid is added
to reduce mercury so it can be steam stripped from the slurry. These steps occur in the Sludge
Receipt and Adjustment Tank (SRAT) in the DWPF. To obtain a sample of SRAT slurry for
measuring radiolytic H2 production in Shielded Cells, the DWPF SRAT process was performed
on a sample of SB3 slurry in the Shielded Cells. Measurements of radiolytic H2 production for
the both the sludge slurry and the SRAT slurry were then performed. The results were then
compared to predictions based the radionuclides and chemical compositions of SB3 slurries
coupled with published parameters for the radiation chemical reactions induced by alpha, beta
and gamma radiations on water in the slurries. The predictions were in reasonable agreement
with the results confirming that estimates of the radiolytic production of H2 can be made if the
composition of the slurry in known.
METHODOLOGY AND RESULTS FOR MEASRUREMENTS OF RADIOLYTIC RATE
OF HYDROGEN PRODUCTION IN SB3 SLUDGE AND SRAT SLURRIES
General Description of Experimental Method
Because of the intense radioactivity of the SB3 sample, all the radiolysis tests were performed
remotely in the SRNL Shielded Cells. They were conducted at ambient the temperatures in the
cells (nominally 15-23 C).
For the experiments, an apparatus containing four vessels each equipped with an agitator,
thermocouple, and a connection for a purge line was designed, fabricated and put into one of the
Shielded Cells. For an experiment, each vessel could be attached to an air purge line that passed
out of the back of the cell and flowed through a sampling system of a gas chromatograph (GC)
that was in a radiological hood. The purge line then returned to the cell and vented in the cell.
The vent gas was exhausted with the normal filtered air exhaust from the cell. (In this way the
possibility of contaminated air from the vessels was prevented from exhausting into the back area
of the cells.) The purge rate was usually 10 to 100 standard cubic centimeters per minute (sccm)
from a calibrated mass flow control meter. At set intervals (usually 3 or 30 minutes) small
samples of gas were automatically removed from the purge line by a pumping system in the GC.
The sample was automatically injected into the GC and concentration of H2, in the purge air was
Prior to putting a known amount of SB3 sludge or SRAT slurry into a vessel or performing an
experiment after a slurry was already in a vessel, the slurry was agitated to remove as much of the
PAPER FOR WM'07
Page 2 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/m1/3/: accessed December 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.