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Title: Uncertainty in the reactive transport model response to analkaline perturbation in a clay formation

Abstract

The mineral alteration in the concrete barrier and in the clay formation around long-lived intermediate-level radioactive waste in the French deep geological disposal concept is evaluated using numerical modeling. There are concerns that the mineralogical composition of the surrounded clay will not be stable under the high alkaline pore fluid conditions caused by concrete (pH {approx} 12). Conversely, the infiltration of CO{sub 2}-rich groundwater from the clay formation into initially unsaturated concrete, at the high temperature (T {approx} 70 C) produced from the decay of radionuclides, could cause carbonation, thereby potentially affecting critical performance functions of this barrier. This could also lead to significant changes in porosity, which would affect aqueous diffusive transport of long-lived radionuclides. All these processes are therefore intimately coupled and advanced reactive transport models are required for long-term performance assessment. The uncertainty in predictions of these models is one major question that must be answered. A mass-transfer model response to an alkaline perturbation in clay with standard model values is first simulated using the two-phase non-isothermal reactive transport code TOUGHREACT. The selection of input parameters is thereafter designed to sample uncertainties in a wide range of physico-chemical processes without making a priori assumptions about the relativemore » importance of different feedbacks. This 'base-case' simulation is perturbed by setting a parameter to a minimum, intermediate or maximum value or by switching on/off a process. This sensitivity analysis is conducted using grid computing facilities of BRGM (http://iggi.imag.fr). Our evaluation of the preliminary results suggests that the resaturation and the heating of the near-field will be of long enough duration to cause a limited carbonation through all the width of the concrete barrier. Another prediction is the possibility of self-sealing at the concrete/clay interface. Further research is however required to discuss the effect of such evolution on the desirable performance function of both barriers.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
COLLABORATION -BRGM/France
OSTI Identifier:
926308
Report Number(s):
LBNL-63403
R&D Project: 0; BnR: YN0100000; TRN: US0802537
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Conference
Resource Relation:
Conference: TOUGH2 Symposium, Berkeley, CA,03/17/2006
Country of Publication:
United States
Language:
English
Subject:
54; CLAYS; CONCRETES; DECAY; EVALUATION; FORECASTING; HEATING; INTERMEDIATE-LEVEL RADIOACTIVE WASTES; MASS TRANSFER; PERFORMANCE; POROSITY; RADIOISOTOPES; SENSITIVITY ANALYSIS; SIMULATION; STANDARD MODEL; TRANSPORT

Citation Formats

Burnol, A, Blanc, P, Xu, T, Spycher, N, and Gaucher, E C. Uncertainty in the reactive transport model response to analkaline perturbation in a clay formation. United States: N. p., 2006. Web.
Burnol, A, Blanc, P, Xu, T, Spycher, N, & Gaucher, E C. Uncertainty in the reactive transport model response to analkaline perturbation in a clay formation. United States.
Burnol, A, Blanc, P, Xu, T, Spycher, N, and Gaucher, E C. 2006. "Uncertainty in the reactive transport model response to analkaline perturbation in a clay formation". United States. https://www.osti.gov/servlets/purl/926308.
@article{osti_926308,
title = {Uncertainty in the reactive transport model response to analkaline perturbation in a clay formation},
author = {Burnol, A and Blanc, P and Xu, T and Spycher, N and Gaucher, E C},
abstractNote = {The mineral alteration in the concrete barrier and in the clay formation around long-lived intermediate-level radioactive waste in the French deep geological disposal concept is evaluated using numerical modeling. There are concerns that the mineralogical composition of the surrounded clay will not be stable under the high alkaline pore fluid conditions caused by concrete (pH {approx} 12). Conversely, the infiltration of CO{sub 2}-rich groundwater from the clay formation into initially unsaturated concrete, at the high temperature (T {approx} 70 C) produced from the decay of radionuclides, could cause carbonation, thereby potentially affecting critical performance functions of this barrier. This could also lead to significant changes in porosity, which would affect aqueous diffusive transport of long-lived radionuclides. All these processes are therefore intimately coupled and advanced reactive transport models are required for long-term performance assessment. The uncertainty in predictions of these models is one major question that must be answered. A mass-transfer model response to an alkaline perturbation in clay with standard model values is first simulated using the two-phase non-isothermal reactive transport code TOUGHREACT. The selection of input parameters is thereafter designed to sample uncertainties in a wide range of physico-chemical processes without making a priori assumptions about the relative importance of different feedbacks. This 'base-case' simulation is perturbed by setting a parameter to a minimum, intermediate or maximum value or by switching on/off a process. This sensitivity analysis is conducted using grid computing facilities of BRGM (http://iggi.imag.fr). Our evaluation of the preliminary results suggests that the resaturation and the heating of the near-field will be of long enough duration to cause a limited carbonation through all the width of the concrete barrier. Another prediction is the possibility of self-sealing at the concrete/clay interface. Further research is however required to discuss the effect of such evolution on the desirable performance function of both barriers.},
doi = {},
url = {https://www.osti.gov/biblio/926308}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}

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