Quintessa Update February 2010 Header Image

Welcome to the February 2010 edition of Quintessa Update, the electronic newsletter of Quintessa Limited.

Postclosure Safety Assessment of Canadian DGR


The Canadian Nuclear Waste Management Organization (NWMO), on behalf of Ontario Power Generation (OPG), is seeking regulatory approval for construction of a proposed Deep Geologic Repository (DGR) for the long-term management of OPG's low and intermediate level radioactive waste on lands adjacent to OPG's Western Waste Management Facility on the Bruce nuclear site in the Municipality of Kincardine, Ontario. Quintessa and its sub-contractors Intera Engineering and SENES Consultants have recently completed a preliminary postclosure assessment of the DGR conceptual design for NWMO. A suite of eight technical reports has been produced and are now available from the NWMO website. They include the Version 1 Postclosure Safety Assessment Report, which provides an overview of the work that has been undertaken. This study will form the basis of the next version of the postclosure safety assessment that will support the final Environmental Impact Statement and Preliminary Safety Report. For more information regarding the preliminary postclosure safety assessment, please contact Richard Little.

Thermo-Hydro-Mechanical Modelling of Bentonite in Project THERESA


The recently completed THERESA project was an international co-operative research project sponsored by the European Commission undertaken between 2007 and 2009. With support from the Swedish nuclear power regulator SSM, Quintessa contributed to the modelling of coupled thermo, hydro and mechanical (THM) processes in bentonite buffers using Quintessa's QPAC general-purpose modelling code. Good comparisons were obtained between calculations and experimental data for the evolution of temperature, saturation, density, relative humidity, stresses and pressures. A new process model was developed that considers the disposition and physical form of water in the bentonite-water-air system, and uses this micro-scale knowledge to model macro-scale emergent phenomena such as swelling and porosity structure changes. For more information please contact Philip Maul.

Potential Interactions between ILW/LLW and HLW/SF in a Co-located Geological Disposal Facility

In June 2008 the UK Government published a 'White Paper' as part of the 'Managing Radioactive Waste Safely' (MRWS) programme to provide a framework for managing the UK's higher activity radioactive wastes. The White Paper identified benefits to disposing all of the UK's higher activity wastes at the same site, and this is currently the preferred option. Quintessa and Galson Sciences have recently undertaken a project for the Nuclear Decommissioning Authority Radioactive Waste Management Directorate (NDA RWMD) to assess the implications of this preferred option for the operational and post-closure performance of a Geological Disposal Facility (GDF).


The GDF is likely to comprise two or more co-located modules, with each module containing specific types of waste with a specific Engineered Barrier System (EBS). The study considered a GDF comprising one module for ILW and some LLW, and a second co-located module for HLW and SF. The potential Thermo-Hydro-Mechanical-Chemical (THMC) interactions between the modules were identified and analysed for a range of potential host rocks and disposal concepts (packaging and EBS). The most significant potential interactions relevant to the current stage of the MRWS programme were analysed in further detail using dimensionless analyses, and 1D and 3D models for an illustrative GDF layout. For more information, please contact George Towler.

Portfolio Selection Tool for AGR Channel Inspections

CHANSELA Screenshot

Quintessa has developed a custom portfolio selection tool, CHANSELA (Channel Selection Assistant), for British Energy, which supports decisions on which selection of channels of Advanced Gas Cooled Reactors (AGRs) should be inspected to support continued safe operation. CHANSELA is able to suggest the combination of channels that will provide the maximal amount of information subject to user-specified constraints, and to compare this with user-defined selections. The software employs some novel concepts, including a genetic algorithm for optimising channel selections, and allows every stage of the process to be documented, providing a clear and transparent audit trail. For more information, please contact Philip Maul.

DECOVALEX-2011: Understanding the Hydro-Mechanical Behaviour of the Ventilation Experiment in Opalinus Clay at Mont Terri

As part of the international DECOVALEX-2011 project Quintessa, in collaboration with the University of Edinburgh (UoE) and UFZ Leipzig, have modelled the micro-tunnel Ventilation Experiment (VE) at the Mont Terri underground laboratory in Opalinus Clay using the QPAC and Rockflow/GeoSys codes, in support of NDA RWMD.

Relative Humidity in the VE Tunnel and Relative Humidity in the VE Tunnel

Significant progress has been made in understanding the coupled Hydro-Mechanical behaviour of the VE and underpinning laboratory experiments, such that the fundamental process set for tunnel-scale drying and wetting appears to be relatively well understood. Further improvements to the predictive power of the models have been gained by coupling the porous medium model with a new prototype model of the distribution of water vapour and air flow in the tunnel itself. The plots of relative humidity in the VE tunnel (left) and water saturation in the host-rock (right) were produced using fully coupled Hydro-Mechanical calculations in QPAC. For more information, please contact Alex Bond.

Treatment of Chemotoxic Species in the Environmental Safety Case for a Geological Disposal Facility

Two reports on the treatment of chemotoxic species in the Environmental Safety Case for a Geological Disposal Facility (GDF) for UK radioactive waste have been produced by Quintessa on behalf of NDA RWMD. The first provides a detailed assessment of the possible release of priority chemotoxic substances from a generic GDF, and quantitatively assesses human exposures and potential associated health risks posed by such releases. The second report includes a literature review on additive and synergistic effects for radiological and chemical toxins and an assessment of the likelihood of these effects occurring as a result of releases from a generic GDF. For further information please contact James Wilson.

Reinventing The Firm

The financial crisis has called into question many of our core assumptions about economic structures, governance and institutions. How can firms be structured so that not only shareholders but employees, the economy and society profit? This question has been addressed in a recent document by the think tank Demos, in which William Davies argues that it is time to bring these models out of the wilderness and into the debate about where capitalism goes next. It presents a wide range of quantitative data alongside three new case studies of employee-owned firms, including Quintessa.