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Hafnium Hydroxide Complexation and Solubility: the Impact of Hydrolysis Reactions on the Disposition of Weapons-Grade Plutonium

Published online by Cambridge University Press:  10 February 2011

G. Cerefice ,
M. Draye ,
K. Noyes  and
K. Czerwinski
G. Cerefice
Affiliation:
Nuclear Engineering Department, Massachusetts Institute of Technology, Cambridge, MA
M. Draye
Affiliation:
Nuclear Engineering Department, Massachusetts Institute of Technology, Cambridge, MA
K. Noyes
Affiliation:
Nuclear Engineering Department, Massachusetts Institute of Technology, Cambridge, MA
K. Czerwinski
Affiliation:
primary contact: Bldg. 24–210, 77 Mass. Ave., Cambridge, MA. 02139kczer@mit.edu
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Abstract

The stability constants for the complexation of hafnium by hydroxide ions is investigated by potentiometric titration over a range of ionic strengths (1m = 0.1 to 6.6 molal). The stability constants are determined from the titration data using the HYPERQUAD suite of programs. The stability constants at infinite dilution are determined using the Specific Ion Interaction Theory from the stability constants determined by titration. The results are shown with the error given as 2 standard deviations.

log β11 (Hf(OH)3+) = 13.84 ± 0.54 log β12 (Hf(OH)22+) = 25.71 ± 0.39 log β13 (Hf(OH)3+) = 36.24 ± 0.88 log β14 (Hf(OH)40) = 45.52 ± 0.80

The solubility product of Hf(OH)4 (s) is determined in 0.1 M NaC1O4 by measuring the total hafnium in solution that is in equilibrium with an excess of hafnium hydroxide solid under an argon atmosphere. The total Hf concentration is determined by ICP-AES. The solubility product is determined using the stability constants measured for the H f hydrolysis products in 0.1 M NaClO4. The precipitate examined is confirmed to be a hydroxide by IR spectroscopy. For Hf(OH)4 (s) in 0.1 M NaC1O4, the solubility product is log Ksp (Hf(OH)4 (s)) = −51.8 ± 0.5

The solubility and stability constants determined are used, along with literature values for plutonium solubility and complexation constants, to examine the behavior of hafnium and plutonium under the conditions expected at Yucca Mountain.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 1025
Copyright
Copyright © Materials Research Society 1999

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References

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