[en] This work has been carried out to analyse different alternatives related to the inner material selection of the Spanish high level waste container for deep geological repository. Its preliminary design considers granitic or clay formations, compacted bentonite sealing, steel corrosion controlled outer wall and glass bed filling of the container. This filling is as relevant as its main role, which is to prevent repository criticality under any foreseen conditions. The present report covers, in first place, the most relevant advances on deep geological storage all around the world, paying special attention on container design solutions. Secondly, having studied carefully the general features of ENRESA preliminary design, the waste forms and all other disposal requirements, a complete and detailed objectives definition is carried out as a selection criterion for candidate materials evaluation and selection. It should be noted that this compilation of demands is significantly deeper and more exhaustive than any other that had been found in literature, including over 20 requirements additionally to another dozen general aspects that could involve improvements in repository performance. Afterwards, eight materials or materials families had been chosen for their potentially interesting properties for geologic disposal. These materials are cast iron or steel, borosilicate glass, spinel, depleted uranium, dehydrated zeolites, hematite, phosphates and olivine. Each one of these candidates (under their possible physical forms) had been examined in detail, using available literature and group experience, and evaluated under each of the previously defined objectives. Finally, some relevant conclusions about candidates suitability are extracted from the previous analysis and all the objectives evaluations for each material are summarized in the form of a few matrices to help in decision making. Some other important aspects related to performance improvement, costs, logistics and manufacturing have also been taken into account and summarized in the same manner. As a short conclusion can be said that either cast iron, borosilicate glass, spinel or depleted uranium look quite promising for the mentioned purpose, that further investigation should be needed on hematite and olivine to be able clarify its suitability for this purpose, specially on certain properties related to its behaviour under irradiation, and that neither dehydrated zeolites nor phosphates are expected to fulfil the desired requirements for this application. (Author)