In a nuclear reactor, gamma-rays are ubiquitous and arise from fissions, decays following activation of fission products or from capture processes occurring in fuel or in reactor components. Gamma-rays have a major contribution to the heating of the reactor structures and to the surrounding dose rate. Accurately characterising the gamma field in nuclear reactors is therefore of strong interest for core operation and safety concerns. Zero power research reactors, such as the CROCUS reactor facility, offer the possibility to measure gamma rays in a pure neutronic environment, allowing for validation experiments of computed spectra, dose estimates, burn up calculations, prompt to delayed gamma ratios and reactor noise measurements.