Metropol

European Commission Directorate-General For The Information Society And Media Directorate-General For Research And Innovation

Description

A computer code for the simulation of transport of contaminants with groundwater
Nuclear energy and safety

Informations

• Publié par: EUROPEAN-COMMISSION-DIRECTORATE-GENERAL-FOR-THE-INFORMATION-SOCIETY-AND-MEDIA-DI
• Nombre de lectures: 13
• EAN13: 928261896
• Langue: English

Extrait

ICommission of the European Communities
Metropol:
A computer code for the simulation
of transport of contaminants
with groundwater
F. J. Sauter, S. M. Hassanizadeh, A. Leijnse,
P. Glasbergen, A. F. M. Slot
RIVM
POPO BoxBox 11
3720 BA Bilthoven
The Netherlands
FinalFinal report
This work was carried out under cost-sharing Contract No FI1W/0081-NL
with the European Atomic Energy Community, in the framework of its
thirdthird R&DR&D programmeprogramme onon 'Management andand storagestorage ofof radioactiveradioactive waste'waste'
(1985-89),(1985-89), PartPart A,A, TaskTask 44 'Geological'Geological disposaldisposal studies'studies'
Directorate-General
Science, Research andand Development
1990 EUR 13073 enPublished by the
COMMISSIONCOMMISSION OFOF THETHE EUROPEANEUROPEAN COMMUNITIESCOMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
L-2920 Luxembourg
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of the is responsible for the use which might be made of
the following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1990
ISBN 92-826-1896-X Catalogue number: CD-NA-13073-EN-C
©© ECSC-EEC-EAEC, BrusselsBrussels Luxembourg,Luxembourg, 19901990
Printed in FranceCONTENTS
PagePage
1. INTRODUCTION 1
2. THE METROPOL PACKAGE 3
3. THE BASIC EQUATIONS 5
4. MESHMESH GENERATION 8
5. NUMERICAL METHODS 10
6. VELOCITY CALCULATIONS 11
7.7. PARTICLEPARTICLE TRACKINGTRACKING 1212
8. POST PROCESSING 13
9. TESTING AND VALIDATION 14
10. APPLICATIONS 19
11.11. REFERENCES 2020
IIIIII1.1. INTRODUCTION
Final disposal of nuclear waste has recently become an environmental issue
in many countries all over the world. In The Netherlands, several disposal
alternatives have been considered. Amongst these, disposal in a salt
formation hashas turnedturned outout toto bebe oneone ofof thethe mostmost promisingpromising possibilities.possibilities.
Safety assessment studies will be carried out in all phases of the process
of selection of geological formation and site, and site characterization.
From the evaluation of possible release scenarios in a rock- salt- specific
safety evaluation for NE Netherlands it became obvious that in almost all
casescases groundwatergroundwater actsacts asas thethe mainmain transporttransport mechanismmechanism leachingleaching nuclidesnuclides
from its containment and transporting them to the biosphere (Onshore
Disposal Committee, 1989). Events considered in one of the most important
scenarios studied are: the ingress of water via a permeable connection from
the overburden into the mined cavities, and subsequent outflow of brine
contaminatedcontaminated withwith dissolveddissolved radionuclidesradionuclides backback toto thethe aquiferaquifer system.system. TheThe
outflow is caused by converging of the mined galleries after complete
filling-up of the remaining space in the post-closure period. A second
important combination of events is: combined diapirism and subrosion of
salt domes by groundwater untili the disposal area is exposed, followed by
dissolutiondissolution ofof radionuclides. ForFor aa completecomplete overviewoverview ofof allall scenarios oneone
is referred to Onshore Disposal Committee (1989) . The events mentioned
above all have one feature in common : high-density (brine) flow is
involved and radionuclides might migrate with groundwater of variable
density,density, duedue toto mixingmixing ofof brinebrine withwith lessless salinesaline water.water.
For the investigation of radionuclide migration in the geosphere under
these conditions a numerical model specifically developed for this problem
is essential. Many requirements need to be met in any geosphere transport
modelling, such as the ability to handle a large number of dissolved
speciesspecies andand toto taketake intointo accountaccount phenomenaphenomena suchsuch asas rock-rock- typetype -specific-specific
geochemical properties, radioactive decay and density variation. This could
not easily be incorporated into existing models. Therefore, RIVM decided to
develop a new three-dimensional model of groundwater flow. The model,
called METROPOL, which stands for simulation MEthod for the Transport Of
POLlutants,POLlutants, consists ofof aa family ofof packages. TheseThese areare usedused forfor meshmesh
generation, computation of steady- state groundwater flow, simulation of
transient flow, and the solution of coupled flow and transport equations.
Special care has been taken to treat the flow of groundwater containing aSpecialSpecial carecare hashas beenbeen takentaken toto treattreat thethe flowflow ofof groundwatergroundwater containingcontaining aa
highhigh concentrationconcentration solutesolute (e.g.(e.g. salt)salt) correctly. AnotherAnother package simulates
the transport with groundwater of low concentration solutes undergoing
decay and adsorption/desorption. Furthermore, several post-processing
packages (particle tracking, plotting of computed results) are available.
AlthoughAlthough thethe METROPOLMETROPOL codecode isis primarilyprimarily developeddeveloped forfor applicationapplication inin safetysafety
assessments of geologic disposal of radioactive waste, it can also be
applied for other types of hazardous waste. Some recently added features
make the model also applicable for the simulation of groundwater pollution
from sources at the surface.
ThisThis reportreport summarizessummarizes thethe workwork inin thethe fieldfield ofof codecode developmentdevelopment performed
under contract with the Commission of the European Communities. For
detailed information, one is refered to the interim- reports (Sauter, 1987;
Vries and Sauter, 1988; Hassanizadeh et al., 1988).2.2. THETHE METROPOLMETROPOL PACKAGEPACKAGE
METROPOL is a family of three-dimensional groundwater flow models developed
at RIVM. Presently, the package consists of the following programmes:
-- METROMESH :: aa three-dimensional meshmesh generator;generator;
- METROREF : a programme for automatic refinement of the mesh;
- METROPOL- 1: a for modelling steady state groundwater flow with
constant fluid density;
- METR0P0L-2: a programme for modelling transient groundwater flow with
constantconstant fluidfluid density;density;
- METROPOL- 3: a programme for modelling transient groundwater flow and
coupled salt transport with (strongly) varying density;
- METR0P0L-4: a programme for the modelling transient transport of tracers,
including adsorption/desorption and decay;
-- METROPART :: aa postprocessing programme forfor computingcomputing particleparticle
trajectories in a steady state velocity field;
- METROPLOT : a programme for plotting results of
simulations with METROPOL family
METR0P0L-4 is still being extended and modified. A version accounting for
matrixmatrix diffusiondiffusion hashas beenbeen developeddeveloped recently.recently.
Basic characteristics of the METROPOL family are:
- transport takes place in a saturated porous medium;
-- permeability isis anisotropic,anisotropic, although thethe mainmain axesaxes ofof thethe permeability
tensor must coincide with the coordinate system;
- permeability and porosity may vary in space;
- porosity and fluid density are dependent on the pressure;
-- fluidfluid densitydensity isis aa function ofof thethe saltsalt massmass fractionfraction (METROPOL-(METROPOL- 3)3) ;;
- fluid viscosity is a function of the salt mass fraction 3 ) ;;
- the full velocity dependent dispersion tensor is included in the
formulation of the transport equations (METROPOL- 3 and METROPOL- 4) ;
- radioactive decay and production of species is taken into account for
tracers (METR0P0L-4)(METR0P0L-4) ;;
- adsorption/desorption of tracers is taken into account (METR0P0L-4)
a linear adsorption isotherm is assumed with a time- independent
distribution coefficient;-- tracertracer concentration doesdoes notnot influenceinfluence thethe fluidfluid densitydensity (METR0P0L-4) ;;
- matrix- diffus ion can be taken into account (METR0P0L-4) ;
- boundary conditions and sources/sinks are allowed to change in time;
In the following sections , some more information concerning the METROPOL
packagepackage willwill bebe given.given. ForFor aa moremore detaileddetailed description, thethe reader isis
referred to the users manuals (Sauter, 1987).