Numerical and experimental calibration of calorimetric sample cell dedicated to nuclear heating measurements

Online nuclear measurements inside experimental channels of MTRs are needed for experimental works (to design set-ups) and for numerical works (input data) in order to better understanding complex phenomena occurring during the accelerated ageing of materials and the irradiation of nuclear fuel. In this paper we focus only on one kind of measurements: nuclear heating performed by means of a radiometric calorimeter. The aims of numerical and experimental works are firstly to optimize the sensor response for new energy deposit ranges and then to miniaturize this sensor for JHR irradiation conditions A first calorimeter, developed previously by the CEA, is studied. It corresponds to a graphite differential calorimeter divided into two twin cells (a reference cell, and a sample one). It is used with a non adiabatic mode or heat flow mode. Experimental calibration of the sample cell is presented. In that case, energy deposit is simulated by Joule effect and the sample cell is inserted into a bath at a regulated temperature and controlled flow. The response of the sensor is shown versus electrical power imposed for two flow regimes (intensive or moderated forced convection). These experimental results are compared to numerical works and improvements are discussed.