Abstract: A method for sterilizing by X-rays an assembly containing a single-use device intended to receive a biopharmaceutical fluid, comprising: placing a plurality of dosimeters, repeatedly passing the assembly in front of the X-ray radiation window, according to a first face then according to a second face of the assembly, at several irradiation power-time pairs (PTi), followed by mapping the radiation dose; and —determining an optimum power-time pair (PTopt) for which the mapping reveals that all dosimeters have recorded a radiation dose above a minimum sterility dose (Dmin), and for which the dosimeter associated with a fragile element of the single-use device records a radiation dose below a maximum dose (Dmax) defined as being the dose from which the X-ray irradiation deteriorates the fragile element.