Technical Report NTB 86-22

Code verification of the groundwater flow Model FEM 301HYDROCOIN – Level 1 – Case 2 and Case 6

The FEM301 code allows modelling steady-state flow of groundwater circulation in saturated media in 1, 2 or 3 dimensions. FEM301 has been used in the project Gewähr which summarises the safety analyses for final disposal of radioactive wastes in Switzerland. In order to check the accuracy of the results of FEM301, Nagra participates in the international HYDROCOIN project which comprises 24 teams from 10 different countries, the aim being to compare the results of different calculation codes. This report describes the work that has been done in this connection with the FEM301 code. Two cases are presented. The first is a two-dimensional model of a fractured rock mass. A quantitative comparison of FEM301 with 2 different models (GWHRT and STOKES) shows good agreement. The second case is a three-dimensional model of a sedimentary basin presenting marked contrasts in the hydraulic conductivities. A qualitative comparison has been carried out with the models SWENT, FE3DGW and CFEST. A detailed quantitative comparison must be published in the frame of the final report of HYDROCOIN – Level 1.