In the present paper, some peculiarities concerning the core dynamics behavior of solid fuelled Accelerator Driven Systems (ADS) have been investigated. In particular, two classical kinds of accidental transients, induced either by a reactivity insertion or by a coolant flow reduction, have been considered. Moreover, specific transients for ADS have been preliminarily analyzed, like those induced by unintentional variations of accelerator beam current. The present results have been obtained for an 80 MW Energy Amplifier prototype, fuelled by U/Pu mixed oxides and cooled by a molten Lead-Bismuth alloy. Such a prototype has been proposed in Italy in the frame of a cooperation among different research institutions and a national company.