Hydrolysis of late-washed, irradiated tetraphenylborate slurry simulants I: Phenylboric acid hydrolysis kinetics Page: 9 of 54
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Westinghouse Savannah River Company WSRC-TR-95-0099
Savannah River Technology Center Revision 0
Keywords: DWPF, Salt Process Cell,
Retention Period: R aa
Reference: Activity No. DWPT-94-0013
TTR No.: HLW/DWPF/TTR-940021
August 21, 1996
To: L. F. Landon, 704-1T
From: J. C. Marek, 704-T C
Hydrolysis of Late-Washed, Irradiated Tetraphenylborate -
Slurry Simulants I: Phenylboric Acid Hydrolysis Kinetics (U)
Data from nineteen bench-scale precipitate hydrolysis experiments were analyzed to determine
the kinetics of phenylboric acid (PBA) reactions at 90 *C during precipitate hydrolysis
processing of late-washed, irradiated tetraphenylborate slurry simulants. The data for
phenylboric acid disappearance were modeled as a first order, irreversible chemical reaction
assuming batch reactor kinetics. Resultant rate constants and initial phenylboric acid
concentrations are reported with 95% confidence limits. Projected rates of benzene generation
immediately after the precipitate transfer are also reported. The results allow prediction of rates
of benzene evolution from phenylboric acid hydrolysis. The results also provide conservative
estimates of reaction times for complete conversion of phenylboric acid at 90 *C.
The late-washed, irradiated feeds used in this study cover a wide range of conditions, including
gamma irradiation doses of 1.9 E+08 rads, 2.0 E+08 rads, 3.0 E+08 rads, and 5.1 E+08 rads,
mercury concentrations of 0 and 3150 mg/L, nitrite concentrations of from < 14 mg/L to
> 900 mg/L, and layup irradiation doses after the late washing operation of 0 and 4.6 E+07 rads.
Hydrolysis operating conditions covered precipitate feedrates of 32 - 51 gpm (scaled to a 3,600
gallon batch), acidities ranging from 0.2 to 0.36 M, and copper catalyst concentrations ranging
from 400 to 1200 ppm. The copper and acidity concentrations extend considerably beyond the
recommended process operating parameters (0.25 0.05 M acidity, 950 100 ppm copper).
The maximum observed rate constant for phenylboric acid disappearance within the range of
recommended process operating parameters was 2.52 0.44 hrf at the 95% confidence level.
The minimum observed rate constant for phenylboric acid disappearance within the range of
recommended process operating parameters with feeds containing mercury was 1.26 0.09 hrd
at the 95% confidence level. Mercury increases the rate of phenylboric acid hydrolysis based on
results from comparison runs with and without mercury. Assuming complete conversion of the
phenylboric acid to benzene, the average benzene generation rate at 90 *C immediately after the
precipitate transfer was 8.8 0.9 g/hr-L at the 95% confidence level. The phenylboric acid
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Marek, J.C. Hydrolysis of late-washed, irradiated tetraphenylborate slurry simulants I: Phenylboric acid hydrolysis kinetics, report, February 10, 2000; South Carolina. (https://digital.library.unt.edu/ark:/67531/metadc705729/m1/9/: accessed May 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.