OSIRIS REACTOR - Centre de Cadarache - CEA

28EXPERIMENTAL DEVICESCEA••• NUCLEAR ENERGY AUTHORITY measurements of the dimensions of samples: sensors of the LVDT type to measure the lengthening of fuel sheaths,or off-line strain gauges for on-line measurements of the diametrical strain of materials or fuels, measurements of the mechanical stress applied to samples when loading, the stress being created by systems of bellowsusing a pressure controlled outside the irradiation devices, the measurement of the release of fission gases in fuels under irradiation, using a backpressure sensor installed at the endof the fuel rods.Temperaturemeasurementin a CHOUCA deviceThe temperature ofthe experimental load duringthe irradiation is an importantparameter that conditions the qualityof the experiment.This is particularly true for studiesrelated to the behaviour underflux of materials with mechanicalproperties sensitive to irradiationtemperatures.The example below illustratesthe change in temperaturesmeasured near pressurizedcylindrical test specimensirradiated in a CHOUCA device.The upper part of the firstfigure shows the change duringan irradiation cycle ofthe temperatures measuredby 2 thermocouples nearthe same test specimen.The lower part of the figurehighlights the influence ofthe axial variation of gammaheating on the temperatures.The second figure illustratesthe stability of the temperaturesmeasured during a cycle.Temperature (°C)Temperature (°C)Temperature (°C)History file of the temperatures measured by thethermocouples installed in the sample holder.Irradiation time (H)Monitoring of temperaturefor one cylindrical sampleIrradiation time (H)Thermocoupleused for regulationMonitoring for another sampleLocal temperature stability.Irradiation time (H)