alt RWM, United Kingdom
Czech Flag SURAO, Czech Republic
Swiss Flag Nagra, Switzerland

Current programmes for the long-term management of long-lived radioactive waste are focused on underground disposal. Emplacing the waste in deep geological repositories along with multiple engineered barriers is widely accepted as a safe means of isolating it from the biosphere.

Monitoring systems will be necessary to help evaluate the behaviour of repository components, or the impacts of the repository on the environment (IAEA 2001). A monitoring programme is typically divided into the three phases, the so called (1) baseline monitoring, (2) the monitoring during construction and operational until closure and (3) post-closure monitoring (Fig. 1).

Lasmo fig1Fig. 1: The three phases of a typical monitoring programme (after NRC 2003)

The objective of the LArge Scale MOnitoring (LASMO) project is to evaluate existing monitoring techniques in the near and far field of a repository-like environment during both the baseline and operational phase until closure of the repository. The LASMO project is implemented at the Grimsel Test Site (GTS) located in the Swiss Alps. Since its establishment in 1984, the GTS has hosted a wide range of underground research under repository-relevant boundary conditions, allowing LASMO to build upon 30 years' knowledge and experience regarding the local (hydro-)geology, data acquisition, development and testing of equipment, conceptualisation and modelling (Blechschmidt et al. 2008, Kickmaier et al. 2005, McCombie et al. 1995, Vomvoris et al. 2013, 2015). In addition, the project takes advantage of ongoing and planned construction works and related lake drainage of the local hydro power plant, operated by Kraftwerke Oberhasli AG (KWO). These measures may affect the hydraulic and/or rock mechanical conditions around the GTS and are used as analogues for perturbations during repository construction and/or operation, or eventually closure. Hence, the LASMO project provides a unique opportunity for developing, testing and surveying monitoring strategies and techniques at different phases of repository implementation (baseline, construction, operation) at a large scale and under realistic boundary conditions.

The LASMO project is conducted in the framework of Phase VI of the research programme of the Grimsel Test Site. GTS Phase VI runs from January 2003 to 2018 and is dedicated to repository-relevant (i.e. small to large-scale, long-term) in-situ experiments ( Currently (as per 2015), LASMO is a cooperation project with Nagra, SÚRAO and RWM as project partners. The project started in 2013 and is planned to last until 2018.

Fig. 2 illustrates the experimental concept and the timeline of the LASMO project with milestones. The available instrumentation at the GTS and the pre-existing data set on the surrounding geosphere is augmented within the LASMO project by a comprehensive monitoring programme and data acquisition with a focus on rock mass, groundwater and stress characterisation. The extensive monitoring network allows the development of baseline characteristics, and testing the sensitivity of the different monitoring techniques and/or parameters to perturbations that are either of natural (e.g. earthquakes, meteoric events) or manmade origin (e.g. underground excavation, power plant operation). Furthermore, the existing and the collected monitoring data are used to develop and iteratively update geological/structural, hydraulic, hydrochemical and stress models in 3D of the geosphere around the GTS and to the surface.

Milestone 1 reflects the end of the implementation phase, which was largely completed before the emptying of Lake Raeterichsboden in October 2014 (Fig. 2Fig.). Milestones 2 – 4 are the completion of the first status report and annual reports for the years 2016 and 2017, respectively. Milestone 5 will be accomplished with the finalisation of the synthesis report, which is planned for 2018.

Lasmo fig2

Fig. 2: Experimental concept of the LASMO project.

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