Klaus Wieczorek

Gesellschaft für Anlagen und Reaktorsicherheit

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Juan Carlos Mayor

Empresa Nacional de Residuos Radiactivos

David Jaeggi

Federal Office of Topography swisstopo

Kristof Schuster

Federal Institute for Geosciences and Natural Resources

Rainer Schuhmann

Institut für Umwelttechnologien (Germany)

Jürgen Hesser

University Hospital Heidelberg

Franz Königer

Institut für Umwelttechnologien (Germany)

Irina Gaus

National Cooperative for the Disposal of Radioactive Waste (Switzerland)

José Luis García-Siñeriz

Abertis Infraestructuras (Spain)

Katja Emmerich

Karlsruhe Institute of Technology

Markus Furche

Federal Institute for Geosciences and Natural Resources

Cooperative Institutions

Federal Institute for Geosciences and Natural Resources

Gesellschaft für Anlagen und Reaktorsicherheit

Centre National de la Recherche Scientifique

Universitat Politècnica de Catalunya

Belgian Nuclear Research Centre

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

International Center for Numerical Methods in Engineering

Federal Office of Topography swisstopo

Karlsruhe Institute of Technology

Direction des énergies

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Excavation damaged zones in rock salt formations

CRC Press eBooks (2017)

Norbert Jockwer Klaus Wieczorek

During an ongoing project which succeeds previous investigations of the excavation damaged zone (EDZ) performed in the Stassfurt halite of the Asse salt mine, the EDZ evolution, especially after cutting off the contour zone, is investigated. Three test locations have been prepared in the floor of an almost 20 year old gallery on the 800-m level of the Asse mine: (1) the drift floor as existing, (2) the new drift floor shortly after removing of a layer of about 1 m thickness of the floor with a continuous miner, (3) the new drift floor 2 years after cutting off the 1-m layer. Subject of investigation are the diffusive and advective gas transport and the advective brine transport very close to the opening. Spreading of the brine is tracked by geoelectric monitoring in order to gain information about permeability anisotropy. Results obtained up to now show that EDZ cut-off is a useful method to improve sealing effectiveness when constructing technical barriers.

10.1201/9781315106502-4

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Citations (1)

Swelling experiments on mudstones

C.L. Zhang Klaus Wieczorek Mingliang Xie

Overburden

Overburden pressure

Effective stress

10.3724/sp.j.1235.2010.00044

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Citations (45)

Gas generation measurements in the Febex project

Norbert Jockwer Klaus Wieczorek

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Analiza mechanizmów wstrząsów górotworu z rejonu stref uskokowych - doświadczenia kopalni „Ziemowit"

Wiadomości Górnicze (2013)

A. Gołda G. Śladowski Klaus Wieczorek

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Doświadczenia związane z wdrażaniem systemu PPV w ramach monitoringu zagrożenia sejsmicznego i tąpaniami w KWK „Ziemowit"

Przegląd Górniczy (2016)

A. Gołda G. Śladowski Klaus Wieczorek

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Large-scale testing of a sandwich shaft-sealing system at the Mont Terri rock laboratory

Safety of Nuclear Waste Disposal (2021)

Klaus Wieczorek Katja Emmerich Rainer Schuhmann Jürgen Hesser Markus Furche

Abstract. Shaft-sealing systems for nuclear waste repositories are constructed to limit fluid inflow from the adjacent rock during the early stage after closure of the repository and to delay the release of possibly contaminated fluids from the repository at later stages. Current German concepts of shaft seals contain the hydraulic sandwich sealing system as a component of the lower seal in host rock (Kudla and Herold, 2021). The KIT-developed sandwich sealing system consists of alternating sealing segments (DS) of bentonite and equipotential segments (ES) that are characterized by a high hydraulic conductivity. Within the ES, fluid is evenly distributed over the cross section of the seal. Water bypassing the seal via the excavation-damaged zone or penetrating the seal inhomogeneously is contained, and a more homogeneous hydration and swelling of the DS is obtained. The functionality of such a system was proven in laboratory and semi-technical-scale experiments (Schuhmann et al., 2009). After a joint international pre-project (Emmerich et al., 2019) dedicated to the planning of a large-scale in situ test that demonstrates the feasibility and effectiveness of the sandwich shaft-sealing system in interaction with the host rock, the large-scale experiment was launched at the Mont Terri rock laboratory in July 2019 with partners from Germany, Switzerland, Spain, UK, and Canada. It consists of two experimental shafts of 1.18 m diameter and 10–12.6 m depth, constructed using a core drilling technique with a custom-made drill rig in a new niche in the sandy facies of the Opalinus Clay. The seal in shaft 1 consists of four DS (calcigel) of 1 m thickness and five ES (fine-grained quartz sand), each 30 cm thick (Fig. 1). Shaft sinking began in August 2020 and was completed in November 2020. In the following months, the sealing system and instrumentation of shaft 1 were installed. The sealing system is saturated from a pressure chamber located at the shaft bottom via an inclined lateral feeding borehole. Hydration of the system started in May 2021. Shaft 2 will host a slightly modified system emplaced 1–1.5 years later, in order to integrate experience obtained during the early operation phase of shaft 1. In contrast to shaft 1, the excavation-damaged zone around shaft 2 will have had time to develop. The seals and the surrounding rock are intensely monitored. Measurements in the rock (geophysics, pore pressure, and total stress) were started between August 2019 and March 2020. Characterization of the excavation-damaged zone along the wall of shaft 1 was performed by geophysical and surface packer measurements prior to seal emplacement. Measurements inside the shaft comprise water content, relative humidity, and temperature, pore pressure, stress, and displacements. The in situ work is backed by laboratory testing and model simulation. Data and experience obtained to date will be presented. The sandwich experiment is funded by the German Federal Ministry for Economic Affairs and Energy under contract 02E11799.

Inflow

10.5194/sand-1-133-2021

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Mont Terri Project - Heater experiment : rock and bentonite thermo-hydro-mechanical (THM) processes in the near field of a thermal source for development of deep underground high level radioactive waste repositories

I. Goebel H.-J. Alheid Kaufhold Michael Naumann Th. Pletsch

Bentonite

High-level waste

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Design of a pilot plant to analyse sealing systems based on rock salt bricks

CRC Press eBooks (2015)

Francis D. Hansen Till Popp Klaus Wieczorek D. Stührenberg

Disregarding the real cylindrical geometry of a shaft sealing element, a rough estimation of the initial porosity of the sealing system depending on block size and joint thickness can be calculated by equation (4) assuming a cubic geometry.

Salt lake

10.1201/b18393-24

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EBS Behaviour Immediately After Repository Closure in a Clay Host Rock: The HE-E Experiment (Mont Terri URL)

ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management, Parts A and B (2011)

Irina Gaus Klaus Wieczorek Juan Carlos Mayor Thomas Trick Jose ́-Luis Garcia` Sin ̃eriz

The evolution of the engineered barrier system (EBS) of geological repositories for radioactive waste has been the subject of many research programmes during the last decade. The emphasis of the research activities was on the elaboration of a detailed understanding of the complex thermo-hydro-mechanical-chemical processes, which are expected to evolve in the early post closure period in the near field. It is important to understand the coupled THM-C processes and their evolution occurring in the EBS during the early post-closure phase so it can be confirmed that the safety functions will be fulfilled. Especially, it needs to be ensured that interactions during the resaturation phase (heat pulse, gas generation, non-uniform water uptake from the host rock) do not affect the performance of the EBS in terms of its safety-relevant parameters (e.g. swelling pressure, hydraulic conductivity, diffusivity). The 7th Framework PEBS project (Long Term Performance of Engineered Barrier Systems) aims at providing in depth process understanding for constraining the conceptual and parametric uncertainties in the context of long-term safety assessment. As part of the PEBS project a series of laboratory and URL experiments are envisaged to describe the EBS behaviour after repository closure when resaturation is taking place. In this paper the very early post-closure period is targeted when the EBS is subjected to high temperatures and unsaturated conditions with a low but increasing moisture content. So far the detailed thermo-hydraulic behaviour of a bentonite EBS in a clay host rock has not been evaluated at a large scale in response to temperatures of up to 140°C at the canister surface, produced by HLW (and spent fuel), as anticipated in some of the designs considered. Furthermore, earlier THM experiments have shown that upscaling of thermal conductivity and its dependency on water content and/or humidity from the laboratory scale to a field scale needs further attention. This early post-closure thermal behaviour will be elucidated by the HE-E experiment, a 1:2 scale heating experiment setup at the Mont Terri rock laboratory, that started in June 2011. It will characterise in detail the thermal conductivity at a large scale in both pure bentonite as well as a bentonite-sand mixture, and in the Opalinus Clay host rock. The HE-E experiment is especially designed as a model validation experiment at the large scale and a modelling programme was launched in parallel to the different experimental steps. Scoping calculations were run to help the experimental design and prediction exercises taking the final design into account are foreseen. Calibration and prediction/validation will follow making use of the obtained THM dataset. This benchmarking of THM process models and codes should enhance confidence in the predictive capability of the recently developed numerical tools. It is the ultimate aim to be able to extrapolate the key parameters that might influence the fulfilment of the safety functions defined for the long term steady state.

Closure (psychology)

Shrinkage

10.1115/icem2011-59288

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INFLUENCE OF MINING ACTIVITY ON THE INTEGRITY OF SALT FORMATIONS AS CANDIDATE HOST ROCKS FOR NUCLEAR REPOSITORIES

Klaus Wieczorek R. Miehe T. Rothfuchs Cezar‐Ioan Trifu V. Shumila

The opening, operation and post-closure of a nuclear waste repository in a saliferous system require an in-depth understanding of the stress redistribution within this system. While the stress is released in rock salt by creep, the stiffer anhydrite layers tend to store higher loads that create fracture conditions. Thus, natural joints or newly developed fractures in the anhydrite can become pathways for brines affecting the long-term safety of the repository. To investigate the effect of large-scale stress redistribution on the anhydrite in response to mining, advantage is taken of the underground environment offered by the Bernburg mine in Germany. The roomand-pillar mining conditions induce a more intense loading than expected for a normal repository. A microseismic array composed of 16 three-component accelerometers is employed to monitor the fracture occurrence within a region of 160 x 160 x 100 m over a period of four years as the mining approaches. The analysis includes an examination of the seismic event locations, frequency, event clustering, and source mechanism. As expected, the seismic activity increased as the mining works came closer. More than 1700 seismic events that occurred during nonworking days have been recorded and located. No significant fractures are observed at the interface between the rock salt and the anhydrite, but several roughly parallel band-like structures within the 35 m thick anhydrite layer exhibit high seismic activity. The source mechanism is mostly thrust-like, with few pure-shear events. From an overlying drift, a 59 m long borehole is drilled into the center of the most active seismic cluster. An inspection with a borehole camera shows two brine-bearing joints exposed at approximately 10 and 15 m depth below the rock salt/anhydrite interface, respectively. These observations match closely the fractures derived from event locations. Furthermore, the hydraulic integrity of the anhydrite is investigated through permeability tests. Brine injection results in the borehole show significantly increased permeability in the joint region (2·10 -15 m 2 ), which does not appear to affect the integrity of the anhydrite above the joint (permeability below

Anhydrite

Microseism

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