Hostname: page-component-586b7cd67f-rcrh6 Total loading time: 0 Render date: 2024-11-29T09:20:46.306Z Has data issue: false hasContentIssue false
  • English
  • Français

Neptunium Speciation in Humic Acid-rich Clay Water upon Interaction With Radioactive Waste Glass Samples

Published online by Cambridge University Press:  11 February 2011

V. Pirlet  and
P. Van Iseghem
V. Pirlet
Affiliation:
Waste and Disposal Department, SCKoCEN (Belgian Nuclear Research Center), Mol, Belgium
P. Van Iseghem
Affiliation:
Waste and Disposal Department, SCKoCEN (Belgian Nuclear Research Center), Mol, Belgium
Get access

Abstract

Organic complexes of actinides are known to occur upon interaction of high level waste glass and Boom Clay which is a potential host rock formation for disposal of high level waste in Belgium. The solubility and mobility of 237Np, one of the most critical radionuclides, can be affected by the high dissolved organic carbon content of the Boom Clay porewater through complexation with the humic substances. The influence of humic substances on the Np behaviour is considered through dissolution tests of Np-doped glasses in Boom Clay water and through fundamental study of the specific interaction between Np(IV) and the humic acids using spectroscopic techniques. High Np(IV) concentrations are found in the glass dissolution tests. These concentrations are higher than what we should expect from the solubility of Np(OH)4, the solubility limiting solid phase predicted under the reducing conditions and pH prevailing in Boom Clay. Studying the specific interaction of Np(IV) with humic acids in Boom Clay porewater, high soluble Np concentrations are also measured and two main tetravalent Np-humate species are observed by UV-Vis spectroscopy. The two species are interpreted in terms of mixed hydroxo-humate complexes, Np(OH)xHA with x = 3 or 4. These species are the most likely species that can form according to the pH working conditions. Using thermodynamic simplified approaches, high complexation constants, i.e. log β131 and log β141 respectively equal to 46 and 51.6, are calculated for these species under the Boom Clay conditions.

Comparing the spectroscopic results of the dissolution tests with the study of the interaction of Np(IV) with humic substances, we can conclude that the complexation of Np(IV) with the humic acids may occur and increases the solubility of Np(OH)4 upon interaction of a Np-doped glass and the Boom Clay porewater.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 757: Symposium II – Scientific Basis for Nuclear Waste Management XXVI , 2002 , II7.1
Copyright
Copyright © Materials Research Society 2003

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] Mallants, D., Marivoet, J., Sillen, X., J. of nuclear materials, 298, 125–135 (2001)Google Scholar
[2] Kim, J.I., Sekine, T., Radiochimica acta, 55, 187–192 (1991)Google Scholar
[3] Moriyama, H., Nakata, Y., Higashi, K., Mat. Res. Soc. Symp. Proc. Vol. 353, 1129–1136 (1995)Google Scholar
[4] Rao, L., Choppin, G.R., Radiochimica acta, 87–95 (1995)Google Scholar
[5] Sakamoto, Y., Nagao, S., Ohnuki, T., Ohashi, A., Sato, S., Ohashi, H., Mat. Res. Soc. Symp. Proc., Vol. 353 (1995)Google Scholar
[6] Moulin, V., Moulin, C., Applied Geochemistry, Vol 10, 573–580 (1995)Google Scholar
[7] Marquardt, C., Herrmann, G., Trautmann, N., Radiochimica Acta 73, 119–125 (1996)Google Scholar
[8] Nash, K.L., Choppin, G.R., J. Inorg. nucl. chem., Vol 42, 1045–1050 (1980)Google Scholar
[9] Choppin, G.R., Nash, K.L., J. Inorg. nucl. chem., Vol 43, 357–359 (1981)Google Scholar
[10] Zuyi, T., Huanxin, G., Radiochimica acta, 65, 121–123 (1994)Google Scholar
[11] Lemmens, K., Aertsens, M., De Cannière, P., Van Iseghem, P., The corrosion of nuclear waste glasses in a clay environment: mechanisms and modelling, R-3092, Final report (1991–1995)Google Scholar
[12] Moulin, C., Wei, J., Van Iseghem, P., Laszak, I., Plancque, G., Moulin, V., Analytical Chimica Acta, 396, 253–261 (1999)Google Scholar
[13] Mikhailov, V.A., “Analytical chemistry of Neptunium”, Edited by Slutzkin, D., Halsted Press, a division of John Wiley & Sons, Inc., New York (1973)Google Scholar
[14] Pirlet, V., Van Iseghem, P., Dierckx, A., Desreux, J.F., J. of alloys and compounds, Vol 271–273, 267–271 (1998)Google Scholar
[15] PAGIS 1988: Performance Assessment of Geological Isolation Systems for Radioactive Waste, report EUR 11775 EN (1988)Google Scholar
[16] Rai, D., Hess, J.N., Felmy, A.R., Moore, D.A., Radiochimica acta 84, 159–169 (1999)Google Scholar
[17] Cachoir, C., accepted for publication in J. of Nucl. Materials Google Scholar
[18] Zeh, P., Kim, J.I., Marquardt, C.M., Artinger, R., Radiochimica acta 87, 23–28 (1999)Google Scholar
[19] Kim, J.I., Radiochimica Acta 52/53, 71 (1991)Google Scholar
[20] Kim, J.I., Zeh, P., Delakowitz, B., Radiochimica acta 58/59, 147 (1992)Google Scholar
[21] Czerwinski, K., Kim, J.I., Mat. Res. Soc. Symp. Proc., Vol 465, 743 (1997)Google Scholar
[22] Pirlet, V., to be published in the doctoral thesis (2003)Google Scholar