The main objective of this project is to develop calculation scheme for the evaluation of gamma heating at any chosen location for both JHR (Jules-Horowitz Reactor) and MARIA reactor. JHR is the future material testing reactor under construction on the Cadarache CEA site (the reactor is going to operate after 2016) and MARIA is an existing Polish reactor having characteristics close to those of JHR. For that purpose both, simulations tools and experimental program, are being developed. Calculations will be carried out with both JHR model and MARIA layout. TRIPOLI4 and APOLLO2 codes will be used for calculations of the gamma heating in reactor cores. Representative calculation scheme for MARIA is needed in view to identify optimal locations for measurements according to JHR needs. The correctness of calculations will be qualified by a comparison with the experimental measurements performed in MARIA reactor. Instrumentation which will be used for these measurements have to be properly calibrated. The main aim of the present paper is to propose a calibration procedure for gamma heating measurements.