[en] Thin films present matter in the transition from 3D (bulk) to 2D and 1D environment, i.e. from solid state to molecules and atoms. The decreasing bonding has a profound influence on the electronic structure, and leads to a direct interrelation between electronic and geometric structure. Thin films are excellent candidates for model systems for studying surface reactivity of nuclear systems (important in assessment of waste stability) and 5f localization-delocalization in actinides systems (solid state physical research). We will discuss preparation of actinide thin films (from Th to Am) and the use of photoemission spectroscopy for studying their electronic structure and chemical state. We will compare the metals with compounds of increasing degree of ionicity (carbides, nitrides, hydrides, oxides) and discuss the relation between 5f bonding and chemical environment. We will address the study of dilute actinide compounds (U/Au, U/Pd, U/Ag, Pu/Si) and off-stoichiometric systems, where the electronic structure is determined by the competition between isolation in a matrix and local bonding. We will then focus our attention on surface reactivity and the use of thin films in the study of surface corrosion reactions in waste systems. Structural aspects of thin films and their possible implications in surface reactions will also be addressed. (author)