Nuclear heating inside an MTR has to be known in order to design and to run irradiation experiments which have to fulfill temperature constraints. An innovative calorimetric system CALMOS has been studied and manufactured for the OSIRIS reactor facility (CEA/Saclay). This device is based on a mobile calorimetric probe which can be inserted in any in-core experimental location and can be moved axially from the bottom of the core up to 1000mm above its mid-plane. This experimental device is made of two parts the probe itself dedicated to measure heating rate and thermal neutron flux, and the handling system moving axially the probe inside and above the core. Advantages brought by this mobile equipment have been already presented. A comprehensive measurement campaign was carried out in 2014 with the first CALMOS-1 calorimeter. However, a thermal limitation imposed on this first version did not allow to go beyond 10W/g and to monitor the nuclear heating up to the 70MW nominal power. The calorimeter gave very good results despite some discrepancies at high heating rates between results deduced from the preliminary calibration and those obtained by the zero method. Based on these results, a new CALMOS-2 calorimeter has been designed both for extending the heating range measurement up to 13W/g and improving the zero method measurement through a 4-wires measurement technique. That was the major difficulty in the calorimetric cell manufacturing (wiring, connections). The new design allows, up to the nominal nuclear heating level, to keep a sufficient margin vs aluminum melting in any point of the calorimetric cell. Based on the CALMOS-1 feedback, CALMOS-2 calorimeter has been designed as an operational measurement device suited to in-core measurement. It is equipped with a programmable system, associated with software driving entirely the cell displacement by a complete automation, the data acquisition and measurements processing. The present paper deals with a comprehensive analysis of all results collected during the 2015 measurement campaign carried out with the new CALMOS-2 system. Advantages of the 4-wires technique for performing the zero method have been evaluated with a comparison between both methods up to a 4 W/g heating level. Thermal flux and nuclear heating measurements have been compared with those obtained with CALMOS-1 in various in-core locations. In addition, a systematic comparison of measured absolute temperatures with those obtained by modeling has been performed. The required input data of the Aluminum thermal conduction coefficient, depending on temperature, has been measured by a specialized laboratory. Many situations have been explored with CALMOS-2 (startup phase, loading of MOLY targets, control rods movements, shutdown). Thermal neutron flux distributions, obtained with the specific SPND, have been compared with those obtained by current devices and with TRIPOLI4 calculations. In addition, taking advantage of the CALMOS-2 heating sensitivity range which covers roughly three decades, the core residual power has been monitored up to three weeks after shutdown. Finally, advantages brought by the complete automation are emphasized. Such evolution permits to extend significantly the scan steps number, improving deeply the profiles definition. Tests have been performed up to an overall 70 hours automatic scanning time for reliability tests. CALMOS-2 becomes a real measurement device well suited to the surveillance and qualification of an MTR reactor. Present results allow us to bring out some interesting prospects to prepare the transfer of this device to the incoming JHR.