Comparison of the Thermal Response of Two Calorimetric Cells Dedicated to Nuclear Heating Measurements During Calibration

Nuclear heating is a key parameter which contributes to the thermal design and the quality of in-pile experiments performed in Material Testing Reactors (MTRs) for the study of nuclear materials and fuels under irradiation. Nuclear heating is typically measured in MTRs by radiometric calorimeters. However, this kind of sensor needs to be improved to accommodate the new experimental conditions inside the channels of the Jules Horowitz Reactor (JHR). In this paper, we study the responses of two non adiabatic differential calorimeter cells having the same geometric design, but different dimensions. These experimental works are carried out during a preliminary out-of-pile procedure for the calibration of these sensors which consists in simulating the heating of the sample by the Joule effect. The influence of the imposed electrical power and of the forced cooling flow is determined on the sensor calibration curves. The more sensitive sensor leads to a quadratic calibration curve. This difference in behavior of the two calorimetric configurations is explained by means of temperature and heat flux measurements performed with a new instrumented jacket.