The present article describes the preliminary design studies for an oncoming experimental programme at the CROCUS facility. CROCUS is a teaching and research zero-power reactor operated by the Laboratory for Reactor Physics and Systems Behaviour (LRS) at the Swiss Federal Institute of Technology (EPFL). The PETALE experimental programme (Programme d’Etude en Transmission de l’Acier Lourd et ses Eléments) continues the nuclear data validation efforts required for modelling GEN-III PWR reactors with heavy steel reflectors. PETALE, within the framework of the VEP (Venus-Eole-Proteus) collaboration, extends the results of the reflector experiments carried out in the CEA E (PERLE programme) and IPEN/MB-01 reactors. The 56Fe inelastic scattering cross section and its resonant behaviour will be studied. The validation will also be expanded to Ni and Cr isotopes. The water reflector will be replaced successively by sheets of stainless steel alloy and pure metals – iron, nickel, and chromium. Scattering cross sections at around 1 MeV will thus be studied separately. Data will be extracted from two sources: the measured neutron flux attenuation using adequate dosimetry and possibly fission chambers in the metal reflector, and from the criticality effects of these reflectors. PETALE will also be used with nuclear data adjustment methods. The nuclear data adjustment community is interested in integral experiments that are predominantly sensitive to a specific reaction. This is because compensation effects, or spurious adjustments, may occur when the adjustments are performed using global integral parameters like keff and reactivity. Separated and elemental integral experiments, like PETALE, allow limiting compensation effects in the adjusted nuclear data. This article presents the design of the experimental setup. A parametric study has been carried out with MCNPX for assessing the optimal configuration and the feasibility of the experiments. This study is the first step towards optimising the global sensitivity of the experiments over the reactions in the energy range of interest, thus assessing the measurements’ target uncertainties, and preparing further use of the programme results.