Overview on material relocation phenomena in liquid metal fast reactors as consequence of core disruption

During core destruction of liquid metal cooled reactors materials relocation and their reactivity feedback effects determine the course of the resulting nuclear power excursion. The objective of the analysis of these relocation phenomena is twofold: 1. Evaluation whether the resulting power excursion might lead to a mechanical loading of the reactor vessel and roof structures which exceed load limits being able to violate the integrity of these structures; 2. Determination of resulting core materials distribution within the reactor vessel after achievement of permanent subcriticality for analysis of their long term in-place coolability. Dependinh on the core states established during the different phases of core destruction, different phenomena determine the materials relocation and their reactivity feedbacks. A qualitative overview of the most important material relocation phenomena and their impact on reactivity feedbacks is given. Specific aspects of fuel relocation phenomena in the initiation phase and in the late transition phase are discussed