Hostname: page-component-84b7d79bbc-dwq4g Total loading time: 0 Render date: 2024-07-28T06:35:50.518Z Has data issue: false hasContentIssue false
  • English
  • Français

Revised Eh-pH Diagrams (25 C, One Bar) for Uranium and Transuranic Elements: Application to Radioactive Waste Studies

Published online by Cambridge University Press:  21 February 2011

D. G. Brookins
D. G. Brookins*
Affiliation:
Dept. of Geology, University of New Mexico, Albuquerque, NM 87131
Get access

Abstract

Eh-pH diagrams are useful for comparing the probable geochemical behavior of many elements including U and the transuranics Np, Pu, Am. Revised Eh-pH diagrams have been constructed for U, Np, Pu and Am at 25 C, 1 bar conditions. These diagrams, based on new and revised thermodynamic data, include aqueous and solid species in the generic system M-C-O-H. The species M(OH)− is considered herein, although it's existence has not been verified.

Aqueous U(VI) species are dominated by below pH 5 and by carbonate complexes at higher pH. U(IV) species include important fields of UO2, and U(OH)4. If Si is present, USiO4 may be important. U3O8, occurs between the U(IV) and U(VI) species.

Np(IV) solid species are problematic. NpO2 covers a wide range of Eh-pH, but its precursors, NpO. (OH)2 and Np(OH)4 cover more restrictive Eh-pH ranges with more important. This increases potential for radionuclide migration. Np(V, VI) carbonate complexes are important only at high Eh.

Pu(IV) species are dominated by PuO2, but Pu(OH)4 does not occupy as much Eh-pH space, being replaced in large part by . With carbonate present, Pu(III) species also replace part of the Pu(OH)4 field, and Pu2 (CO3)3 becomes important. Pu(VI) carbonate complexess occur only at high Eh.

Am(III) species dominate Eh-pH space in the system Am-C-O-H, with Am2 (CO3)3 a major phase. Under carbonate-poor conditions, Am(OH) 3 is important. AmO2 occurs at high Eh, pH, and at high Eh and very high pH.

The importance of the M(OH)4 precursors to MO2 species is the enhanced possibility of radionuclide migration from buried spent fuel rods, even under reducing condtions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 125: Symposium N – Materials Stability and Environmental Degradation , 1988 , 161
Copyright
Copyright © Materials Research Society 1988

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

[1] Brookins, D.G., Eh-pH Diagrams for Geochemistry (Springer-Verlag Pubs., Heidelberg, in press 1988).CrossRefGoogle Scholar
[2] OECD (Org. Econ. Cooperation Development), tabulation of thermodynamic data (1985)Google Scholar
[3] Garrels, R.M. and Christ, C.L., Solutions, Minerals and Equilibria (Harper and Row Pubs., New York, 1965), 453 p.Google Scholar
[4] Pourbaix, M., Atlas of Electrochemical Equilibria (Pergamon Press, Oxford; 1966), 645 p.Google Scholar
[5] Verink, E.D., J. Educ. Modules Mat. Sci. Engg. 1, 535 (1979).Google Scholar
[6] Brookins, D.G., Geochemical Aspects of Radioactive Waste Disposal (Springer-Verlag Pubs., Heidelberg, 1984), 345 p.CrossRefGoogle Scholar
[7] Brookins, D.G., DOE Report BFEC-029-E, 1979, 454 p.Google Scholar
[8] Langmuir, D., Geochim. Cosmochim. Acta 42, 547 (1979).CrossRefGoogle Scholar
[9] Brookins, D.G., Ed., The Geological Disposal of High Level Radioactive Wastes, (Theophrastus Publications, Athens; 1987), 535–544.Google Scholar
[10] Brookins, D.G., Rocky Mountain Assoc. Geol. Gdbk. 77, 337.Google Scholar
[11] Tripathi, V., Ph. D. dissertation, Stanford Univ. (1984), 434 p.Google Scholar
[12] Brookins, D.G., DOE Report, ORNL-TM-10501 (1987), 178 p.Google Scholar
[13] Ryan, J.L., Rai, D., Polyhedron 2 (1983), 947.CrossRefGoogle Scholar
[14] Rai, D., Ryan, J.L., Inorg. Chem. 24 (1985), 247.CrossRefGoogle Scholar
[15] Rai, D., Radiochim. Acta 35 (1984), 97.CrossRefGoogle Scholar
[16] Wagman, D., et al., J. Phys.. Chem. Ref. Data, suppl. 2, 11 (1982), 392 p.Google Scholar