Gas Generation and Migration

We provide an integrated package, based on laboratory, modelling and assessment studies, to address problems created by generation of gas in deep geological repositories and the implications for the short and long-term safety of the repository. We offer:

prediction of quantities and generation rates of gas arising from metals and organic materials, based upon waste inventory, repository design and the predicted ambient conditions (the GAMMON code);
calculation of gas migration through fractured or porous rocks containing liquids (the techSIM, CapFracBundle and PORES codes);
assessment of the consequences for repository performance of gas generation and migration;
assessment of consequences (radiological, toxicological, flammability) of release of gas to biosphere (GAS2/RIMERS);
design and execution of experimental programmes to provide key data, e.g., on gas production from corrosion or biodegradation;
development/tailoring of models
coordination of large multi-partner projects, for example the Europe-wide PROGRESS initiative sponsored by the CEC
internationally-recognised expertise on the effects of gas on repository safety NEA concerted action.

A recent review of the research into gas migration carried out predominantly by ourselves for United Kingdom Nirex Limited is provided in:

W.R. Rodwell, T.R. Lineham and M.P. Gardiner, Gas Migration in the Geosphere: Review of the Work Undertaken by the Nirex Safety Assessment Research Programme, AEA Technology Report AEAT/R/ENV/0295, 2000.

We have been carrying out a programme of research into the modelling of gas migration in highly compacted and water-saturated bentonite on behalf of a consortium of radioactive waste disposal agencies (the GAMBIT Club). Results from the first two phases of this work have been published:

P.J. Nash, B.T. Swift, M. Goodfield and W.R. Rodwell, Modelling Gas Migration in Compacted Bentonite, Posiva Report 98-08, Helsinki, 1998.

B.T. Swift, A.R. Hoch, and W.R. Rodwell, Modelling Gas Migration in Compacted Bentonite: GAMBIT Club Phase 2 Final Report, Posiva Report 2001-02, 2001.

A further example of recent research work carried out ourselves in relation to gas migration from underground radioactive waste disposal facilities is provided by an investigation of approaches to modelling gas migration through single rough fractures:

R.F. McCarthy, P.J. Nash, and W.R. Rodwell, Two-Phase Flow in a Variable Aperture Fracture, AEA Technology Report AEAT/R/ENV/0173, 2000.

R.F. McCarthy, B.T. Swift, and W.R. Rodwell, Further Development of a Single Fracture Gas Migration Model, AEA Technology Report AEAT/ERRA-0324, 2001.

This service provides an essential understanding of the effects that may be associated with gas generation and migration, in terms of both the gases themselves and their effect on other exposure pathways The codes used to calculate two-phase flow (gas and oil or water) enable prediction of how underground reservoirs of oil and natural gas will behave.

GAS2/RIMERS is used to evaluate the radiological impact of radioactive gases released into the biosphere. Close

GAMMON (GAs generation from Microbial degradation and Metal corrosiON) is a computer program developed by ourselves on behalf of Nirex for modelling this gas generation. GAMMON models generation of gases from the coupled processes of anaerobic corrosion of metals (generating H2) microbial degradation of cellulosic wastes (generating CO2 and CH4). As well as the bulk gases, small quantities of radioactive gases may also be formed. In a repository for low- and intermediate-level waste, the principal radioactive gases formed are likely to be the 3H- and 14C-substituted isomers of the major bulk gases. For these radioactive gases, GAMMON can calculate generation rates as a function of time from a variety of sources. Close

PORES was originally developed in the oil industry to simulate flow of three fluid phases and is used to model the movement of gas and water through porous media. Close

CapFracBundle is used to address the displacement of water by gas from a porous medium represented as a bundle of parallel capillaries or fractures. Close

techSIM has been developed by ourselves as a three-dimensional multi-phase oil reservoir simulator. It can model gas flow as a free phase in a single or multi-phase system and as a dissolved species in a liquid phase. Different effects can be represented in a properly coupled fashion. Geological and geometric features can be modelled in more detail than in simpler idealised models. The following may be included in a techSIM model: coupling of repository pressure rise and gas flux; gas compressibility; gas solubility in the water phase; spatial variability of geological properties; detailed geometry of the repository. Output from techSIM can include the variation with time of average pressure in a pre-defined region of the model, for example the repository, and the flow of each fluid phase between different regions of the model. Close

We coordinated, edited and provided a substantial technical contribution to the recent EC/NEA instigated current status report on gas migration and two phase flow. The resulting report is:

W.R. Rodwell, A.W. Harris, S.T. Horseman, Ph. Lalieux, W. Müller, L. Ortiz Amaya, and K. Pruess, Gas Migration through Engineered and Geological Barriers for a Deep Repository for Radioactive Waste. A Joint EC/NEA Status Report published by the European Commission, European Commission Report EUR 19122 EN, 1999.

A brief summary of the conclusions of this work was provided in:

W.R. Rodwell, B. Haijtink, and P. Lalieux, The Impact of Gas on the Safety of Underground Waste Repositories, NEA Newsletter 17(2), 18-20, 1999.

We also coordinated and contributed to the EC 4th framework PROGRESS project on gas generation and migration in relation to radioactive waste disposal. This work was described in the final PROGRESS project report:

W.R. Rodwell (ed.), Research into Gas Generation and Migration in Radioactive Waste Repository Systems (PROGRESS Project): Final Report, European Commission Report EUR 19133 EN, 2000.

Last updated:: 07-Mar-2003