OSIRIS REACTOR - Centre de Cadarache - CEA

EXPERIMENTAL DEVICESNUCLEAR ENERGY AUTHORITY ••• CEA25This system reduces the dimensions of the flowlines to the shielded compartment where the systems required to condition thecoolant are located (pressurizer, pumps, exchangers etc.) and thus make them flexible to authorize movements in the reactor pool.An electric heating element placed at the head of loop and an exchanger in the reactor pool control the thermics of the system.Instrumentation: The power released by the experimental load during irradiation is measured in real time by a heat balance produced by meansof the flux, pressure and temperature sensors, as well as by a neutron balance carried out using collectrons. The detection of break in the clad of a fuel rod is provided by the measurementof the gamma activity conveyed in the water of the loop, together withthe measurement of delayed neutrons.Power rampsThe power ramps located inthe ISABELLE 1 loop are designedto simulate the power transients,whether normal or incidental,in PWRs. They are used toimprove our understanding ofthe mechanisms of the interactionbetween the pellet and the sheathof a fuel rod and replyto the industrial issue of increasingthe manoeuvrability of PWRs.The variation in power is obtainedby displacing the loopperpendicular to the core ofthe reactor, and slaving thedisplacement to the neutron power. The control of the chemistry of the water used in the installation is ensuredby a conditioning plant. It is controlled by analysing the water samples thatare taken during reactor operation at various points of the circuit. The ISABELLE 1 loop is also equipped with a sensor of the type LVDT to continuouslymonitor the lengthening of the fuel element during variations in power.Neutron beam photographyof the inter-pellet distance(with break of fuelelement sheath).Distribution of inter-pellet luminance 10/11Before rampAfter rampDisplacement along the longitudinal axisBefore rampAfter rampThe changes in the variousparameters are monitoredthroughout the experiment.Relative lengthening of the fuel rodRelative powerUnités arbitrairesactivité gamma relativeposition du système de déplacementCote (mm)Gamma spectrometry: axial distribution of activity beforeand after ramp (with break in fuel element sheath).activité neutronique relativeFine characterization of fuel by non-destructivetesting is also carried out.