Hostname: page-component-78c5997874-j824f Total loading time: 0 Render date: 2024-11-19T06:54:46.175Z Has data issue: false hasContentIssue false
  • English
  • Français

The Behavior of 99Tc in Doped-Glass/Basalt Hydrothermal Interaction Tests

Published online by Cambridge University Press:  25 February 2011

D.G. Coles  and
M. J. Apted
D.G. Coles
Affiliation:
Pacific Northwest Laboratory, P.O. Box 999, Richland, WA 99352
M. J. Apted
Affiliation:
Rockwell Hanford Operations, P.O. Box 800, Richland, WA 99352
Get access

Abstract

The release of polyvalent radionuclides from a nuclear waste repository located in basalt may be sensitively related to the redox potential (Eh) imposed by the basalt. A series of tests are reported here evaluating the effect of basalt on the concentrations of 99Tc released into solution from a borosilicate glass waste form. Crushed PNL 76-68 glass, doped with 0.7 mg 9 99Tc/g glass, was reacted with reference basalt groundwater under oxic hydrothermal conditions in a sampling autoclave, both alone and in the presence of crushed basalt. The steady state fluid concentrations of 99Tc and various stable species were determined from samples obtained at the test conditions of 200 °C, 30 MPa, and a initial solution to solid mass ratio of 10 for both tests.

In the glass + groundwater test, the 99Tc concentration rose rapidly to about 50 mg/L after only 200 hr of run time and remained at a value between 50 and 60 mg/L throughout the duration of the test. For the basalt + glass + groundwater test, the 99Tc concentration rose to an initial value of about 2.5 mg/L. At about 700 hr, the 99Tc concentration began to drop rapidly until a value near the analytical detection limit (approximately 0.005 mg/L) was reached after a test duration of 1,400 hr. It is concluded that the presence of basalt in these hydrothermal experimtents reduces the concentration of 99Tc in solution by nearly four orders of magnitude, probably by control of solution Eh and subsequent precipitation of a solid containing a reduced form of technetium. Reaction mechanisms are discussed that can account for these observations.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 26: Symposium D – Scientific Basis for Nuclear Waste Management VII , 1983 , 129
Copyright
Copyright © Materials Research Society 1984

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. Smith, M.J. et al. , Engineered Barrier Development for a Nuclear Waste Pepository Located in Basalt: An Integration of Current Knowledge, RHO-BWI-ST-7, Rockwell Hanford Operations, Richland, WA (1980).10.2172/6889960Google Scholar
2. Apted, M.J., Overview of Hydrothermal Testing of Waste Package Barrier Materials at the Basalt Waste Isolation Project, RHO-BW-SA-228, Rockwell Hanford Operations, Richland, WA and PNL-4382, Pacific Northwest Laboratory, Richland, WA (1982).Google Scholar
3. Chambre, P.L., Pigford, T.H., and Zavosky, S., Solubility-Limited Dissolution Rate in Groundwater, UCB-NE-4016, University of California, Berkeley, CA (1982).Google Scholar
4. Strachan, D.M., Scientific Basis for Radioactive Waste Management-V, Lutze, W., ed. (Elsevier Science Publishing Co., New York 1982) p 182–191.Google Scholar
5. Bibler, N.E., DP-MS-82-82, Savannah River Laboratory, Aiken, SC (1983).Google Scholar
6. Lasaga, A.C., Rate Laws of Chemical Reactions in: Kinetics of Geochemical Processes, Ribbe, P.H., ed., Mineralogic Society of America, Washington, D.C., 1–68, (1981).Google Scholar
7. Apted, M.J. and Myers, J., RHO-BW-ST-38, Rockwell Hanford Operations, Richland, WA (1982).Google Scholar
8. Westsik, J.H. Jr. and Peters, R.D., in Scientific Basis for Nuclear Waste Management-3 (Plenum Press, New York 1981), 355–362.10.1007/978-1-4684-4040-9_45Google Scholar
9. Shade, J.W. and Clark, R.W., PNL-SA-10755, Pacific Northwest Laboratory, Richland, WA (1983).Google Scholar
10. Pederson, L.R., Buckwalter, C.Q., and McVay, G.L., Nuclear Technology 62, 151–158 (1983).10.13182/NT83-A33214Google Scholar
11. Bradley, D.J., Harvey, C.O., and Turcotte, R.P., PNL-3152, Pacific Northwest Laboratory, Richland, WA (1979).Google Scholar
12. Seyfried, W.E., Gordon, P.C., and Dickson, F.W., Am. Mineralogist 64, 646–649 (1979).Google Scholar
13. Brunauer, S., Emmett, P.H., and Teller, E., Adsorption of Gases in Multimolecular Layers, J. Am. Chem. Soc. 60, 309–319 (1938).10.1021/ja01269a023Google Scholar
14. Jensen, B.S., The Geochemistry of Radionuc1ides with Long Half-Lives, Their Expected Migration Behavior, Report RisΦ-R-430, (RisΦ National Laboratory, Denmark 1980).Google Scholar
15. Bondietti, E.A. and Francis, C.W., Science 203, 1,337–1,340 (1979).10.1126/science.203.4387.1337CrossRefGoogle Scholar
16. Bigoglio, G.,Chatt, A., DePlano, A., and Zorn, F., J. Radioanal. Chem. 79, 153–164 (1983).10.1007/BF02518863Google Scholar
17. Jacobs, G.K. and Apted, M.J., RHO-BW-SA-174, Rockwell Hanford Operations, Richland, WA (1981).Google Scholar