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|Título : ||NF-PRO Deliverable 1 of Component 2. State- of-the-art report.|
|Autor : ||de la Cruz, Berta|
Villar, María Victoria
Turrero, María Jesús
Fernández, Ana María
|Palabras clave : ||bentonite|
deep geological repository
|Fecha de publicación : ||26-feb-2021|
|Citación : ||Informe Técnico CIEMAT;CIEMAT/DIAE/54511/07/04|
|Resumen : ||Chapter 1 gives a general view of the different conceptual designs of a Deep
Geological Repository (DGR) in granite, clay and salt formations. It also provides
information on the possibility of retrievability in the different disposal designs.
Chapter 2 is focused on the role and requirements of the different components of the
Engineered Barrier System (EBS), giving special attention to the mineralogical,
chemical and physico-chemical characteristics of the natural bentonitic clay (FEBEX
and MX-80) and ordinary Portland cement.
It also presents a brief review of the mineralogical, chemical and physico-chemical
characteristics of the C-steel and Cu/stainless steel containers, clay barrier and concrete,
the latter being mainly used in clay repositories. The types of pore water, state, location
and quantity of the FEBEX bentonite are reviewed. The chemical composition of the
pore water in the clay barrier is discussed, as well as the techniques to collect the pore
water and the difficulties posed by the small amounts of water collected. The thermohydro-
mechanical properties of the clay barrier are also briefly mentioned.
The hydration stages of concrete are described together with the accompanying
precipitation/dissolution processes of different minerals. The pore water chemistry of
concrete is studied, and the degradation of concrete and its influence on the mobility of
the radionuclides as well as the resulting high pH plume are briefly described.
Chapter 3 gives a general view of the processes that take place during the
hydration/saturation states under thermal gradient. It is organized according to the
chronological order in which the processes may occur. First, the groundwater will flow
through a concrete plug in the case of clay and salt formations causing modifications in
the concrete. The groundwater from the concrete or from the granite will interact with
the bentonite generating a series of geochemical processes in the bentonite. Finally, the
groundwater will reach the canister and corrosion processes will start. The geochemical
processes that take place in a salt formation are also reviewed in this section.
Chapter 4 reviews the pro and cons of the chemical thermodynamic data bases
relevant to nuclear systems. Kinetics is pointed out as being an important uncertainty in
the data bases, since reaction kinetics depend on the environment conditions, making
any extrapolation difficult. Anyway, the development of kinetic data base is in
progress. The most used computer programs to model the near-field geochemical
evolution are mentioned, as well as the main processes and reactions taken into account
in the geochemical modelling. A brief review is given of the thermodynamic of the
main reactions in the near field.
Chapter 5 describes the main chemical processes in each of the considered components
of the EBS (conceptual model); furthermore, a review of the existing numerical models,
and the uncertainties related to present-day models (identification of key chemical
processes, critical concepts and missing parameters) are given. Chapter 6 compiles the known and unknown facts and uncertainties in the host rock/
concrete/ bentonite/ canister interfaces and gives a list of those parameters that should
be studied to broaden the knowledge and understanding of the geochemical processes in
the near field.|
|URI : ||http://documenta.ciemat.es/handle/123456789/1100|
|Aparece en las colecciones: ||Informes de Medio Ambiente|
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