A modelling study of the effect of rock alteration on the redistribution of uranium
- Japan Atomic Energy Research Institute, Ibaraki (Japan)
A modelling study was carried out to understand the effect of rock alteration on uranium radionuclide concentrations in rocks, in the vicinity of the Koongarra ore deposit, Australia. The one-dimensional, advection-dispersion-sorption model considers two important factors resulting from the process, mechanism and rate of chlorite weathering, one type of rock alteration that has occurred over a million-year period; (a) the changes in this distribution coefficients of uranium and thorium over time, and (b) that in rock porosity. The distribution coefficient and rock porosity at a given time, are expressed as average values of those of the coexisting minerals. By assuming a Darcy velocity of 0.9 m/y and an initial uranium concentration in the groundwater of 0.5 ppm, similar to present-day values, we were able to derive, from the finite-element modelling, uranium concentrations in the rock which are in good agreement with observed values. The calculated values of {sup 230}Th,{sup 234}U activity ratios show a similar trend to those observed, although more experimental data are necessary to confirm the similarity. However, in the absence of the rock alteration, the calculated results did not agree with those observed. The present study suggests that rock alteration should be included in models used to predict uranium migration over long-geologic timescales.
- OSTI ID:
- 62243
- Report Number(s):
- CONF-921101-Vol.294; TRN: 95:002922-0059
- Resource Relation:
- Conference: 16. Materials Research Society (MRS) fall meeting, Boston, MA (United States), 30 Nov - 5 Dec 1992; Other Information: PBD: 1993; Related Information: Is Part Of Scientific basis for nuclear waste management XVI; Interrante, C.G. [ed.] [Nuclear Regulatory Commission, Washington, DC (United States)]; Pabalan, R.T. [ed.] [Southwest Research Inst., San Antonio, TX (United States)]; PB: 959 p.
- Country of Publication:
- United States
- Language:
- English
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