Welcome to the Spring 2008 edition of Quintessa Update, the electronic newsletter of Quintessa Limited


THERESA Thermo-Hydro-Mechanical Modelling

THM Results Quintessa recently hosted the second Work Package 4 meeting for the EC THERESA project, which is focussed on the simulation of Thermal-Hydro-Mechanical (THM) and Chemical processes in clay buffers and host rock in order to improve understanding for radioactive waste disposal safety cases. Three benchmark cases based on THM laboratory experiments are being modelled in the present phase of the project. For example, the figure shows a comparison of Quintessa's modelling results using the QPAC multi-physics code with experimental data for the time-dependent relative humidity in resaturating bentonite. For more information, please contact Alex Bond.

Performance Assessment (PA) Methodology for CO2 Storage

PA tool By linking together two existing software tools, Quintessa has developed a methodology for use in the PA of CO2 storage. These tools are: (1) TESLA, providing an environment for constructing decision trees, propagating evidence and recording the logic underlying a decision; and (2) an online database of Features, Events and Processes (FEPs), which can be accessed directly from the decision tree.

The TESLA decision trees represent a hierarchy of hypotheses supported by independent numerical representations of evidence. The evidence for and against a hypothesis being correct may correspond to quantitative or qualitative information and is propagated through the tree using Evidence Support Logic (ESL). For more information please contact Richard Metcalfe.

Releases from Potential UK Underground Gas Storage Facilities

Underground gas storage The British Geological Survey (BGS) has recently undertaken a project for the Health and Safety Executive (HSE), to examine the potential for leakage of natural gas from Underground Gas Storage (UGS) in salt caverns and depleted oil/gas reservoirs. Quintessa was sub-contracted by BGS to support this project by developing leakage scenarios and carrying out simple scoping calculations to evaluate the likely significance of leakage. The BGS component of the work is reported in HSE RR605, which provides context, background and data for the work reported by Quintessa in HSE RR606. For more information please contact Sarah Watson.

Swedish Regulatory Review of SR-Can

Review of SR-Can The regulatory authorities in Sweden, SKI and SSI, have recently published a review of SKB's SR-Can safety assessment for the development of a final spent nuclear fuel repository. Quintessa staff supported the review process, with David Savage acting as chair of the EBS review group (published as SKI Report 2008:10), and Mike Egan as secretary for the methodology review group (published as SSI Report 2008:05 / SKI Report 2008:15). In addition, Quintessa has continued to provide support to SKI through independent assessment calculations relating to a range of technical issues raised by the safety assessment (published as SKI Report 2008:12). For more information, please contact Philip Maul.


Discovalex logo Quintessa and the University of Edinburgh have recently been awarded a contract from NDA-RWMD to participate in the international DECOVALEX-2011 project. DECOVALEX-2011 aims to improve understanding of THMC coupled processes and apply this to the performance assessment of radioactive waste disposal facilities. One of the ways in which these aims are being addressed is by modelling experiments performed in Opalinus Clay at the Mont Terri underground laboratory. Quintessa will be using the multi-physics QPAC code for these modelling studies, while Edinburgh University will be applying Rockflow/GeoSys.


Alex Bond from Quintessa and Chris McDermott from Edinburgh University attended the inaugural meeting of DECOVALEX-2011 hosted by NDA-RWMD in the elegant surroundings of Magdalen College, Oxford. This meeting brought together 28 delegates from Canada, China, the Czech Republic, Finland, France, Japan, Korea, Spain, Sweden and the USA. For more information, please contact Alex Bond.

New Faces

Kiyoshi Fujisaki James Wilson Quintessa's Warrington office is pleased to welcome James Wilson who has carried out research into the effects of iron on the stability of bentonite barriers and has been involved with public health protection issues including contaminated land risk assessment and chemical incident management. Also, Quintessa Japan is pleased to welcome Kiyoshi Fujisaki who has spent several years in research, development and assessment of the long-term behaviour of engineered barriers for the geological disposal of HLW.

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