Modelling engineered barriers for spent nuclear fuel repository using a double-structure model for pellets

Abstract

This paper describes an experimental programme and the corresponding modelling in order to characterise the hydromechanical (HM) behaviour of pellets. At least two levels of porosity can be distinguished in the pellets: microporosity and macroporosity. In general, the microstructure is associated with the active clay minerals, while the macrostructure accounts for the larger-scale structure of the material. In pellets, this concept can be somewhat different as a pellet arrangement creates a large-scale macropore structure. The Barcelona expansive model is proposed to reproduce the material response through infiltration and oedometer tests. In addition to expansive model parameters, a set of hydraulic laws considering the double-structure phenomenon is necessary to perform HM analysis. This paper also describes the effect of macroporosity on the intrinsic permeability changes. To illustrate the general objectives of this research, a full-scale thermohydromechanical calculation has been done to show the capabilities of the approach. The Barcelona basic model (for clays) and Barcelona expansive model (for pellets) have been used in this full-scale calculation.

Modelling of oedometer tests on pellet-powder bentonite mixtures to support mock-up test analysis

“…Some parameters have been obtained from experimental results on the mixture, such as the saturated elastoplastic compressibility parameter ߣሺͲሻ (in terms of void ratio), and the saturated pre-consolidation (yield) stress ‫‬ ‫כ‬ [13]. Parameters not directly obtained from experimental results were taken from [14].…”

The Modeling of Laboratory Experiments with COMSOL Multiphysics Using Simplified Hydromechanical Model

“…A broad range of aspects related to thermo-hydro-mechanicalchemical processes was investigated in numerous studies focusing on high temperature effect [13,14], liquid/gas flow properties [15][16][17], mechanical [18,19] or chemical [20,21] aspects. While much research has been conducted on compacted bentonite material, comparativelyfewer investigations have been performed on other forms of bentonite (granular [22], pellets of different sizes and forms [23][24][25][26], pellet-powder mixtures [6,[27][28][29]).…”

Applications of the new thermo-hydro-mechanical-chemical coupled code ‘Thebes’

“…This topic has been the focus of many research groups (e.g. Olivella et al, 1996;Rutqvist et al, 2001;Collin et al, 2002;Seetharam et al, 2007;Sánchez et al, 2017;Jacinto and Ledesma, 2017;Abed and Sołowski, 2017;Ahmad, 2017;Toprak et al, 2018;Rodriguez-Dono et al, 2018;Villar et al, 2018).…”