scholarly journals Bentonite clay barriers in nuclear waste repositories

2020 ◽  
Vol 205 ◽  
pp. 01003
Author(s):  
Lyesse Laloui ◽  
Alessio Ferrari ◽  
Jose A. Bosch
Keyword(s):  
Nuclear Waste ◽  
Constitutive Models ◽  
Bentonite Clay ◽  
In Situ Experiment ◽  
Future Prediction ◽  
Bentonite Clays ◽  
High Level ◽  
Waste Repositories ◽  
Clay Barriers

Deep disposal of high-level radioactive waste is the preferred solution worldwide for the long-term disposal of nuclear waste. This concept involves a series of geological and engineered barriers that provide isolation of the waste from the biosphere. Most designs involve bentonite clays as seals in different forms. During the operation of the repository, the bentonite will be subjected to a series of complex thermo-hydro-mechanical phenomena that will interact with each other. Predicting the long-term safety of geological repositories thus involve a rigorous analysis of these multi-physical processes. This paper presents a review of recent numerical approaches and analyses that have aimed to improve the understanding of processes that will take place in clay barriers over the lifetime of nuclear waste repositories. The understanding of bentonite behavior from laboratory experiments under relevant conditions is analyzed. Constitutive models that attempt to predict such behavior are presented, focusing on the stress-strain model ACMEG-TS. These models are implemented in the finite element code Lagamine which allows for the study of real scale tests. Two application cases are presented: the performance of a clay barrier according to the Swiss design, and a model of the FEEBX in situ experiment, which was modelled after a real repository under natural conditions. Overall, the relevant processes are well captured quantitatively by the models, allowing for the establishment of sound basis for future prediction and long-term design of the final underground repositories.

Predicting Pu Concentrations in Solutions Contacting Geologic Materials

1981 ◽  
Vol 6 ◽  
Author(s):  
Richard G. Strickert ◽  
Dhanpat Rai
Keyword(s):  
Nuclear Waste ◽  
Safety Assessment ◽  
High Level Waste ◽  
Stable Phase ◽  
Borosilicate Glasses ◽  
Geologic Materials ◽  
Solid Phases ◽  
High Level ◽  
Waste Repositories

ABSTRACTKnowledge of Pu solid phases present in nuclear wastes is important for predicting the geochemical behavior of Pu. Thermodynamic data and experimental measurements using discrete Pu compounds, Pu-doped borosilicate glasses (simulating a high-level waste form), and Pu contaminated sediments suggest that PuO2(c) is very stable and is expected to be present in the repository. The solubility of the stable phase, such as PuO2(c), can be used to predict the maximum Pu concentration in solutions for long-term safety assessment of nuclear waste repositories.

Environmental Remediation of High-Level Nuclear Waste in Geological Repository: Modified Computer Code Creates Ultimate Benchmark in Natural Systems

2010 ◽  
Author(s):  
Geoffrey J. Peter
Keyword(s):  
Nuclear Waste ◽  
Environmental Remediation ◽  
Computer Code ◽  
Nuclear Waste Repository ◽  
Natural Systems ◽  
Permanent Storage ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Waste Repositories

Isolation of high-level nuclear waste in permanent geological repositories has been a major concern for over 30 years due to the migration of dissolved radio nuclides reaching the water table (10,000-year compliance period) as water moves through the repository and the surrounding area. Repositories based on mathematical models allow for long-term geological phenomena and involve many approximations; however, experimental verification of long-term processes is impossible. Countries must determine if geological disposal is adequate for permanent storage. Many countries have extensively studied different aspects of safely confining the highly radioactive waste in an underground repository based on the unique geological composition at their selected repository location. This paper discusses two computer codes developed by various countries to study the coupled thermal, mechanical, and chemical process in these environments, and the migration of radionuclide. Further, this paper presents the results of a case study of the Magma-hydrothermal (MH) computer code, modified by the author, applied to nuclear waste repository analysis. The MH code verified by simulating natural systems thus, creating the ultimate benchmark. This approach based on processes similar to those expected near waste repositories currently occurring in natural systems.

scholarly journals A multiple-code simulation study of the long-term EDZ evolution of geological nuclear waste repositories

2008 ◽  
Vol 57 (6) ◽  
pp. 1313-1324 ◽  
Author(s):  
Jonny Rutqvist ◽  
Ann Bäckström ◽  
Masakazu Chijimatsu ◽  
Xia-Ting Feng ◽  
Peng-Zhi Pan ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Simulation Study ◽  
Multiple Code ◽  
Waste Repositories

Comparison of Granite, Tuff, and Basalt as Geologic Media for Long-Term Storage of High-Level Nuclear Waste

1990 ◽  
Vol 212 ◽  
Author(s):  
D. E. Grandstaff ◽  
V. J. Grassi ◽  
A. C. Lee ◽  
G. C. Ulmer
Keyword(s):  
Nuclear Waste ◽  
Nuclear Waste Repository ◽  
Long Term Storage ◽  
Hydrothermal Experiments ◽  
Ion Activity ◽  
Activity Ratios ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Term Storage

ABSTRACTSystematic differences in pH, cation/proton ion activity ratios, and redox have been observed between solutions produced in rock-water hydrothermal experiments with tuff, granite, and basalt. Stable pH values in tuff-water experiments may be as much as 1.5 pH units more acidic than basalt-water experiments at the same temperature and ionic strength. Redox (log fO2) values in 300°C tuff experiments are 4–7 orders of magnitude more oxidizing than basalt experiments and ca. 4 log units more oxidizing than the magnetite-hematite buffer. Such fluid differences could significantly affect the performance of a high-level nuclear waste repository and should be considered in repository design and siting.

scholarly journals A Critical Review of the Recent Improvements in Minimizing Nuclear Waste by Innovative Gas-Cooled Reactors

2008 ◽  
Vol 2008 ◽  
pp. 1-18 ◽  
Author(s):  
E. Bomboni ◽  
N. Cerullo ◽  
G. Lomonaco ◽  
V. Romanello
Keyword(s):  
Nuclear Waste ◽  
Critical Review ◽  
Simplified Models ◽  
Geological Disposal ◽  
Fuel Cycles ◽  
Multiple Recycling ◽  
High Level ◽  
Coupling Current ◽  
The University

This paper presents a critical review of the recent improvements in minimizing nuclear waste in terms of quantities, long-term activities, and radiotoxicities by innovative GCRs, with particular emphasis to the results obtained at the University of Pisa. Regarding these last items, in the frame of some EU projects (GCFR, PUMA, and RAPHAEL), we analyzed symbiotic fuel cycles coupling current LWRs with HTRs, finally closing the cycle by GCFRs. Particularly, we analyzed fertile-free and Pu-Th-based fuel in HTR: we improved plutonium exploitation also by optimizing Pu/Th ratios in the fuel loaded in an HTR. Then, we chose GCFRs to burn residual MA. We have started the calculations on simplified models, but we ended them using more “realistic” models of the reactors. In addition, we have added the GCFR multiple recycling option usingkeffcalculations for all the reactors. As a conclusion, we can state that, coupling HTR with GCFR, the geological disposal issues concerning high-level radiotoxicity of MA can be considerably reduced.

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