Functions that can be allocated to cladding during interim storage depend upon the evolution of cladding properties with time. Therefore CEA, in cooperation with EDF and with the support of FRAMATOME and COGEMA, is developing an intensive R&D program on the long term behaviour of spent fuel under interim storage or final disposal conditions. The major aim is to define on a long term creep law and a suitable breaching criterion. The thermal creep under rod internal pressure being condidered as the major mechanism which might lead to cladding breaching in dry storage conditions, a stepwise approach has been developed in which the representative dry interim storage conditions are progressively simulated from more severe conditions. It consists in creep test campaigns on irradiated materials, combined with modelling and microscopy investigations. This paper summarizes the main results obtained during the first step of this program dealing with short creep experiments (10–60 days).