SALOME is a free software that provides a generic platform for Pre and Post-Processing for numerical simulation. It is based on an open and flexible architecture made of reusable components available as free software. It is open-source (LGPL), and you can download both the source code and the executables from their website.
The SALOME simulation platform, developed jointly with the CEA and a number of industrial and academic partners, gives access to the fine degree of modelling required. Its design allows for detailed representation of all physical phenomena (mechanical, thermo-hydraulic, neutronic) and their interaction. It provides a common environment (meshing, display, supervision of calculations) which significantly increases the productivity of studies. This technology is providing the basis for new tools developed for nuclear engineering.