Diederik Jacques

SCK CEN - Belgian Nuclear Research Centre | SCK CEN · Expert Group for Waste and Disposal

Core Ideas A community effort is needed to move soil modeling forward. Establishing an international soil modeling consortium is key in this respect. There is a need to better integrate existing knowledge in soil models. Integration of data and models is a key challenge in soil modeling. The remarkable complexity of soil and its importance to a wi...

This paper provides a comprehensive overview of existing experimental and modelling approaches to determine effective diffusion coefficients of water saturated ordinary Portland cement-based materials. A dataset for diffusivity obtained from different experimental techniques have been presented for cement paste, mortar and concrete. For cement past...

Abstract: HPx is a multicomponent reactive transport model which uses HYDRUS as the flow and transport solver and PHREEQC-3 as the biogeochemical solver. Some recent adaptations have significantly increased the flexibility of the software for different environmental and engineering applications. This paper gives an overview of the most significant...

Because of its solid structure, low permeability, slow diffusion and good chemical retention for many radionuclides, cementitious materials are often used for conditioning radioactive waste and are omnipresent in many radioactive waste disposal facility concepts as engineered barriers. Cementitious materials are not in geochemical equilibrium with...

The Strategic Research Agenda (SRA; https://www.ejp-eurad.eu/publications/eurad-sra ) of the European Joint Programme on Radioactive Waste Management (EURAD; https://www.ejp-eurad.eu/ ) describes the scientific and technical domains and sub-domains and knowledge management needs of common interest between EURAD participant organizations. Theme numb...

A deep geological repository is considered an appropriate option for disposal of radioactive waste containing long-lived radionuclides. Engineered barriers’ degradation and radionuclide transport strongly depend on the conditions in the repository. This work presents the assessment of the geochemical evolution in a radioactive long-lived intermedia...

This opinion paper describes the major coupled T(Thermal)-H(Hydro)-M(Mechanical)-C(Chemical) processes in geological repository systems and the frontier of related model development. Particular focus is made on the analysis of existing approaches and open research questions with respect to the further development of coupled codes and models for rea...

This study aims to comprehensively investigate the evolution of microstructure, mechanical strength, and their correlation in alkali-activated slag (AAS) mortars, designed for application in the immobilization of liquid radioactive waste, under accelerated carbonation conditions (1% CO 2 , 20 • C and 60% RH). To gain insights into the underlying mi...

Towards the development of net-zero carbon concrete and the wider application of geopolymers, understanding the durability of geopolymers has become essential. However, knowledge on the evolution of microstructure and transport properties of the materials under aggressive conditions due to their interaction with external chemicals is limited. There...

The HYDRUS codes have become standard tools for addressing many soil, agricultural, environmental, and hydrological problems requiring the evaluation of various subsurface physical, chemical, and biological processes. There are now many thousands of HYDRUS users worldwide, with thousands of applications of the HYDRUS models appearing in the peer‐re...

This paper presents a numerical study to investigate delayed ettringite formation (DEF) that may pose a long-term durability risk by altering the microstructure with consequent swelling leading to cracking. A chemo–thermal model is used to predict the evolution and distribution of temperature and hydration phases in a wide range of blended cements....

Digitalization and Artificial Intelligence is the fastest emerging paradigms in engineering and natural science applications. As an example data-driven and physics-inspired machine learning methods have been developed and evaluated to accelerate numerical simulations; evaluating their usability for applications related to the radioactive waste mana...

Engineered barrier systems in a geological disposal system contain many cementitious components. A strong geochemical interaction is expected between these repository components and the surrounding host rock, since cement is not at equilibrium under relevant disposal conditions and thus will evolve with time. Thermodynamic modelling is a useful ap...

Data science (digitalisation and artificial intelligence) became more than an important facilitator for many domains in fundamental and applied sciences as well as industry and is disrupting the way of research already to a large extent. Originally, data sciences were viewed to be well-suited, especially, for data-intensive applications such as ima...

Components of the so-called “multiple-barrier system” from the waste form to the biosphere include a combination of waste containers, engineered barriers, and natural barriers. The Engineered Barrier System (EBS) is crucial for containment and isolation in a radioactive waste disposal system. The number, types, and assigned safety functions of the...

The Maldegem Formation (Bartonian, Eocene) occurs in the subsoil of the East Flanders, Belgium and consists of alternating layers of clay and loamy sands. Specifically, the ~10 m thick clay layer known as Zomergem Member is investigated as potential barrier for containment of highly acidic plume from the historical crude oil treatment. In this...

This paper investigates the synergistic interaction between carbonation and microcracks in hardened cement pastes. Ordinary Portland cement pastes with three different water/cement ratios of 0.4, 0.5 and 0.6, hydrated for 28 days with crack apertures ranging from 10 to 150 μm were subjected to accelerated carbonation in a climate chamber that contr...

Thanks to the recent progress of technology, the fields of artificial intelligence (AI) and machine learning methods (ML) are growing at a very fast pace. The EURAD (European Joint Programme on Radioactive Waste Management) community has recently started using ML for a) accelerating numerical simulations, b) improving the efficiency of multiscale a...

The 1st European Joint Programme on geological disposal of radioactive waste was initiated in June 2019. In this framework, the work described in this contribution is included in WP2 – ACED (Assessment of Chemical Evolution of ILW and HLW Disposal Cells). The broad scope of this WP is the assessment of the chemical evolution at the disposal cell sc...

We accelerate reactive transport (RT) simulation by replacing the geochemical solver in the RT code by a surrogate model or emulator, considering either a trained deep neural network (DNN) or a k-nearest neighbor (kNN) regressor. We focus on 2D leaching of hardened cement paste under diffusive or advective-dispersive transport conditions, a solid s...

In many parts of the world, major regional drinking water resources are represented by saturated/unsaturated systems. While the groundwater of deep aquifer systems are not likely to show significant anthropogenic contamination (i.e. from mining, oil and gas installations, legacy sites, geothermal energy reservoirs, phosphate and nuclear industry) s...

Carbonation of alkali activated materials is one of the main deteriorations affecting their durability. However, current understanding of the structural alteration of these materials exposed to an environment inducing carbonation at the nano/micro scale remains limited. This study examined the evolution of phase assemblages of alkali activated slag...

Changes in pollutant concentrations in environmental media occur both from pollutant transport in water or air and from local processes, such as adsorption, degradation, precipitation, straining, and so on. The terms “fate and transport” and “transport and fate” reflect the coupling of moving with the carrier media and biogeochemical processes desc...

Carbonation of alkali activated materials is one of the main deteriorations affecting their durability. However, current understanding in structural alteration of these materials exposed to an environment inducing carbonation at nano/micro scale remains limited. This study examined the evolution of phase assemblages of alkali activated slag mortars...

Soil contains the largest terrestrial pool of organic matter, and the cycling of organic carbon in soils plays a crucial role in controlling atmospheric carbon dioxide (CO2) and global climate change. Although considerable progress has been made in previous modeling studies on the fate of soil organic matter (SOM), only a few models used a process-...

This study investigates how reactive transport (RT) simulation can be accelerated by replacing the geochemical solver the RT code by a surrogate model or emulator, considering either a trained deep neural network (DNN) or a k-nearest neighbor (kNN) regressor. We focus on 2D leaching of hardened cement paste under diffusive or advective-dispersive t...

We present vec2pix, a deep neural network designed to predict categorical or continuous 2D subsurface property fields from one-dimensional measurement data (e.g., time series), thereby offering an alternative approach to solve inverse problems. The performance of the method is investigated through two types of synthetic inverse problems: (a) a cros...

Modeling of the land surface water‐, energy‐, and carbon balance provides insight into the behavior of the Earth System, under current and future conditions. Currently, there exists a substantial variability between model outputs, for a range of model types, whereby differences between model input parameters could be an important reason. For large‐...

Development and Improvement Of NUmerical methods and Tools for modelling coupled processes (DONUT) Workpackage in the European Joint Programme on Radioactive Waste Management (EURAD)

The 1st European Joint Programme on geological disposal of radioactive waste (EURAD) co-founded by the Horizon 2020 European programme was initiated in June 2019. Main activities within EURAD consist on R&D and strategic studies aiming at developing and consolidating Scientific and Technical knowledge of repository concepts as well as addressing sa...

Many environments to which concrete is exposed are highly aggressive due to various chemical components. In such environments, concrete is subjected to processes of chemical degradation, among which carbonation is one of the most frequently seen degradation processes. Though, the influence of saturation degree (or relative humidity - RH) of the spe...

Modelling of combined dissolution-precipitation at the pore scale requires the conceptualization of mineral precipitation and crystal growth, the formation of a protective diffusive layer by precipitants and slow reaction kinetics that are all coupled with alterations of the microstructure. In this work, we propose an improved approach for handling...

Redox potential (Eh) measurements are widely used as indicators of the dominant reduction-oxidation reactions occurring underground. Yet, Eh data are mostly used in qualitative terms, as actual values cannot be used to distinguish uniquely the dominant redox processes at a sampling point, and should therefore be combined with a detailed geochemical...

Suction cups are widely used in agricultural and environmental research and monitoring under the hypothesis that the sample chemistry represents the soil pore water solute composition around the cup location. The objective of this study was to analyze the sampling procedures that lead to the most representative sample for soil aqueous phase composi...

Shale weathering was characterized and quantified in a lysimeter and modelling study that jointly considered the flow, transport, gas diffusion and reactivity processes induced by exposure to the atmosphere of a recently excavated shale. In this mechanically disaggregated shale presenting preferential pathways for water and a hydraulic conductivity...

We present vec2pix, a deep neural network designed to predict categorical or continuous 2D subsurface property fields from one-dimensional measurement data (e.g., time series), thereby, offering a new way to solve inverse problems. The method's capabilities are investigated through two types of synthetic inverse problems: (a) a crosshole ground pen...

Microstructure strongly influences flow and transport properties of porous media. Flow and transport simulations within porous media, therefore, requires accurate three-dimensional (3D) models of the pore and solid phase structure. To date, no imaging method can resolve all relevant heterogeneities from the nano- to the centimeter scale within comp...

This paper presents a detailed comparison between 3 methods for emulating CPU-intensive reactive transport models (RTMs): Gaussian processes (GPs), polynomial chaos expansion (PCE), and deep neural networks (DNNs). State-of-the-art open source libraries are used for each emulation method while the CPU-time incurred by one forward run of the conside...

Understanding the dissolution of nuclear waste glass in hyper-alkaline conditions is critical to predicting its safe disposal in cement-dominated disposal conditions. In this work, solution data from the early-stage SON68 glass dissolution in a KOH solution (pH 13.5 and 30 °C) were interpreted with models based on silicon (Si) diffusion controlled...

Global probabilistic inversion within the latent space learned by a Generative Adversarial Network (GAN) has been recently demonstrated. Compared to inversion on the original model space, using the latent space of a trained GAN can offer the following benefits: (1) the generated model proposals are geostatistically consistent with the prescribed pr...

In regional hydrogeological models groundwater – surface water interaction is generally represented with a Cauchy boundary condition, in which a conductance parameter governs the exchange flux rate. In some models, the conductance is controlled by the streambed properties, since it has generally a lower hydraulic conductivity than the aquifer. Howe...

Simulation of dissolution processes with a pore-scale reactive transport model increases insight in coupled chemical-physical-transport processes. However, modelling of dissolution process often requires a large number of time steps especially when the buffering capacity of solid phases is high. In this work we analyze the interplay between solid b...

The objective of this study is to quantify the contributions of microstructure and molecular size of diffusing species to tortuosity, constrictivity and effective diffusivity. The microstructural effect is simulated with different intact, leached or carbonated cement pastes with varying water to cement ratios and limestone replacement filler replac...

This paper presents an overview of a research program at the Belgian Nuclear Research Centre (SCK•CEN) concerning long-term durability of cementitious materials.The need for this research originates from the Belgian nuclear waste disposal concept, which proposes ordinary portland cement as the candidate binder for engineered barriers. Three main de...

In regions with intensive agriculture nitrate is one of the most relevant contaminants in groundwater. Denitrification reduces elevated nitrate concentrations in many aquifers, yet the denitrification potential is limited by the concentration of available electron donors. The aim of this work was to study the denitrification potential and its limit...

This paper presents a detailed comparison between 3 methods for emulating CPU-intensive reactive transport models (RTMs): Gaussian processes (GP), polynomial chaos expansion (PCE) and deep neural networks (DNNs). Besides direct emulation of the simulated uranium concentration time series, replacing the original RTM by its emulator is also investiga...

This work aims at understanding of carbonation process in unsaturated fractured cementitious materials, which influences significantly the material properties. Dissolution of cement hydration products (portlandite (CH), C-S-H) and precipitation of calcium carbonate cause changes in surface geometry. On the other hand, geometry determines the amount...

The problem of calcium leaching kinetics of ordinary Portland cement based mortars is revisited via a mesoscale approach. Based on state-of-the-art lattice-Boltzmann technique, a comprehensive suite of leaching analysis is undertaken to address a number of open questions such as (i) the competing effects of interface transition zone (ITZ) and aggre...

In this paper, we present and analyze a novel global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who performed the experiments or they...

Core Ideas Cation exchange (CE) on illite, a main sorption process for Cs ⁺ , is driven by Cs ⁺ concentration. Undefined CE and surface complexation on OM are main sorption processes for Sr ²⁺ . ¹³⁷ Cs ⁺ migrated only into shallow depths of a few centimeters after 3 yr. ⁹⁰ Sr ²⁺ migrated into deeper layers of the soil due to competitive sorption....

In this paper, we present and analyze a global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database, for the first time. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who performed the exper...

The paper presents an evaluation of the combined use of the HYDRUS and SWI2 packages for MODFLOW as a potential tool for modeling recharge in coastal aquifers subject to saltwater intrusion. The HYDRUS package for MODFLOW solves numerically the one-dimensional form of the Richards equation describing water flow in variablysaturated media. The code...

In this paper, a newly developed lattice Boltzmann method based reactive transport model to simulate changes in microstructure of ordinary Portland cement paste due to calcium leaching is presented. The model takes three-dimensional digitized cement paste microstructure as input and is capable to capture an evolution of microstructure due to leachi...

The role of capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These m...

Download Abstract In this paper, we present and analyze a global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database, for the first time. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who...

Probabilistic inversion within a multiple-point statistics framework is often computationally prohibitive for high-dimensional problems. To partly address this, we introduce and evaluate a new training-image based inversion approach for complex geologic media. Our approach relies on a deep neural network of the generative adversarial network (GAN)...

Nuclear power, to most of us, is mystic and somehow scary, and despite its drawbacks, is still playing an important role in the world wide energy supply. However concrete, without mystery as the most widely used materials in construction, is used as a major constituent for nuclear facilities such as radioactive waste repositories and nuclear power...

We provide a brief overview of the HYDRUS models and their add-on modules, and to demonstrate possible applications of the software to the subsurface fate and transport of chemicals involved in coal seam gas extraction and water management operations.