Nuclear heating rate measurement in the MIT research reactor using a new compact CALORRE differential calorimeter

This paper presents experimental results obtained thanks to a new compact prototype of CALORRE calorimeter during an irradiation campaign inside the MIT Research Reactor (MITR) in October 2024 within the framework of the CALOR-I research program led by Aix-Marseille University and involving the Nuclear Reactor Laboratory of the MIT and the CEA. The nuclear heating rate was measured for the first time in the MITR. An axial mapping of the nuclear heating rate was realized in 15 axial positions of the in-core water-loop of the MITR (B3 position) by moving the CALORRE differential calorimeter while keeping the reactor in operation (at a reactor power equal to 5 MWth) for a stainless steel (ASI 316L) sample. Moreover, the nuclear heating rate was quantified versus the reactor power at a fixed axial position with and without the displacement of the compact CALORRE calorimeter. The sensor reliability and robustness were studied thanks to calibrations conducted before, during and after the irradiation campaign inside the in-core water-loop with the reactor shut down.