The safety assessment of nuclear waste disposals needs to predict the migration of radionuclides and chemical species through a geological medium. It is therefore necessary to develop and assess qualified and validated tools that integrate both the transport mechanisms through the geological media and the chemical mechanisms governing the mobility of radionuclides. Such a reactive transport simulation tool has been developed in the context of a numerical software platform. Different component codes are available: PHREEQC and CHESS for the chemical part, CASTEM and MT3D for the transport part. All these components share the same API (Application Programming Interface) and the same GUI (Graphical User Interface). A coupling scheme has already been implemented, qualified and validated on numerous configurations involving aqueous speciation, dissolution-precipitation, sorption, and surface complexation. This work is part of the ALLIANCES project of which the aim is to produce a software platform for the simulation of nuclear waste storage and disposal repository.