Behaviour of fuel pins presenting a cladding rupture

The objective is to follow by different techniques (fission gas analysis, delayed neutron detection (DND), γ scanning and neutroradiography examinations) the evolution of failed fuel (U, Pu)O2 pins during irradiation in a sodium loop at a temperature of 400 to 5000C, in a thermal or epithermal neutron flux and at a power between 20 and 55 kW.m-1 the pins being pre-irradiated between 0 and 12% FIMA and from 50 to 140 dpas. The signals coming from stable fission gases allow to detect fuel over-heatings, while the kinetics of emission of the short half lived radioactive gases are controlled by the inlet and outlet displacements of sodium through the pin; at last, the secondary ruptures are revealed by the evolution of DND signals and the locations of compounds -as fuel-caesium- are followed by γ spectrometry