Etalonnage de capteurs de force et de déplacement pour mesures en sodium liquide à partir de la temperature ambiante jusqu’à 350 °c et exemples de résultats

¹ CEA –Centre de Cadarache, DTN/STCP/LIET 13 108 Saint-Paul Lez Durance, France
² PRESCAMEX, 10, rue des Ardennes 77 123 Le Vaudoué, France
³ AREVA NP, 10, rue Juliette Récamier 69 456 Lyon Cedex 06, France
⁴ RBConsultant, 16, rue de la carrière 60 300 Senlis, France

^a jean-louis.portier@cea.fr

Abstract

Special tests have to be performed at high temperatures (up to 350 °C) in liquid sodium in order to qualify numerical model of dynamic behavior of mechanical structures. Accurate measurements have to be taken during these tests, in order to compare the results of the model calculations with what really happens on the structure. Among all the parameters to be measured inside the liquid sodium, the most important are efforts and relative displacements. Unfortunately, no sensors of these types of parameters, able to take measurement in sodium at 350 °C, are available on the market. In addition to that, the sensors which are needed have to be integrated in the tested structure without large modifications of it. Considering all of that, it has been decided to build special sensors. They are of cantilever type and their sensitive devices are high temperature weldable strain gages. The basis of their design and their description are given. Their measurement values have to be confident and for that they have to be metrologically traceable to the International System of units (SI). That is to say that these special sensors have to be calibrated at temperatures up to 350 °C. But no efforts and displacements measurement standards, working up to 350 °C, are available on the market. The calibration technique which is describe in the document is based on the engineering and fabrication of a special high temperature calibration bench working on the differential method for the coupling between the measurements standards and the sensors which has to be calibrated. These ones are inside an oven and the measurement standards are outside it, at ambient temperature. Thanks’ to that, the measurements standards can be simply normal sensors with calibration certificates established by accredited organisms. All the analyses and calculations which demonstrate that the errors coming from the variations of the temperature of the calibration bench stay below the specifications limits are explained. The validation test of this calibration bench which show that the calibration uncertainty is below 0.1 to 0.2% is described. Then the results of the calibrations of the effort and displacement sensors are given. Effort sensor will be able to give measurement results with uncertainties of about 0,6% when they are used at ambient temperature and 1% when they are used at 320 °C. The same figures for the displacement sensors are respectively 1,3% and 1,7%. At the end of the document an example of a useful application of these sensors is given.