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DEVELOPMENT OF THE CHEMTARD COUPLED CHEMICAL TRANSPORT CODE

Objective

IN ORDER TO EVALUATE THE LONG-TERM PERFORMANCE OF A GEOLOGICAL REPOSITORY, PREDICTIONS NEED TO BE MADE OF THE LIKELY EXTENT AND RATE OF RADIONUCLIDE TRANSPORT FOLLOWING CONTACT WITH GROUNDWATER. SEVERAL CHEMICAL TRANSPORT SIMULATORS HAVE BEEN WRITTEN FOR THIS PURPOSE AND DURING PREVIOUS DEVELOPMENT WORK THE LAWRENCE BERKELEY CODE CHEMTRN WAS SUBSTANTIALLY MODIFIED AND ENHANCED. THE ENHANCED CODE IS CALLED CHEMTARD (CHEMICAL TRANSPORT ADSORPTION REDOX AND DECAY) AND ALLOWS THE TREATMENT OF AQUEOUS COMPLEXATION, TRANSPORT BY ADVECTION AND/OR DIFFUSION, REVERSIBLE PRECIPITATION-DISSOLUTION, RADIOACTIVE DECAY AND SORPTION BY ION-EXCHANGE OR SURFACE COMPLEXATION. IT MAY BE USED EITHER AS A STAND-ALONE COUPLED TRANSPORT PROGRAM, OR AS PART OF AN INTEGRATED RADIOLOGICAL ASSESSMENT METHODOLOGY.
AS WITH OTHER PROGRAMS CAPABLE OF SIMULATING REACTIVE CHEMICAL TRANSPORT, NUMERICAL PROBLEMS MAY BE ENCOUNTERED WITH CHEMTARD OWING TO UNFAVOURABLE COMBINATIONS OF PARAMETER VALUES. SUCH DIFFICULTIES ARE COMPOUNDED BY THE LONG RUN TIMES REQUIRED FOR ALL BUT THE SIMPLEST SIMULATIONS.
THIS CONTRACT AIMS TO ADDRESS THE ABOVE IN ORDER THAT THE CODE ENTER EFFICIENT ROUTINE USE. THE OBJECTIVES ARE AS FOLLOWS:
1) ENHANCEMENT OF NUMERICAL METHODS
2) DEVELOPMENT AND TESTING OF COMPONENT MODELS
3) IMPROVEMENT OF CODE DOCUMENTATION.

1. THE MODULAR STRUCTURE OF CHEMTARD IS TO BE IMPROVED AND A SEPARATE EXECUTIVE ROUTINE WILL BE CONSTRUCTED. MEANS OF INCREASING THE EFFICIENCY OF THE EXISTING NEWTON-RAPHSON PROCEDURE AND REASONS FOR CONVERGENCE FAILURE WILL BE EXPLORED.
2. THE FUNCTIONAL SCOPE OF THE CODE WILL BE EXTENDED TO COVER TRANSPORT BY PURE DIFFUSION. CURRENT METHODS OF TREATING OXIDATION-REDUCTION AND MINERAL PRECIPITATION WILL BE IMPROVED, THE LATTER TO PERMIT SUPERSATURATION OF SOLIDS.
3. INTERACTIVE SOFTWARE WILL BE WRITTEN TO FACILITATE CONSTRUCTION OF INPUT FILES TOGETHER WITH A GRAPHICS PACKAGE TO DISPLAY CHEMTARD OUTPUT. COMPREHENSIVE DOCUMENTATION WILL ACCOMPANY THE DEVELOPED CODE.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Atkins Wootton Jeffreys Consultants Ltd
Address
Woodcote Grove Ashley Road
KT18 5BW Epsom
United Kingdom

Participants (1)

École Nationale Supérieure des Mines de Paris
France
Address
60 Boulevard Saint-michel
75272 Paris