Nuclear decommissioning missions involve the use of electronic equipment for various purposes (monitoring, inspection, remote operation, etc) in harsh environments, such as ionizing radiation. However, the Total Ionizing Dose (TID) can produce electrical and functional degradation and even total failure in electronic systems. Hence, these systems must be qualified to know their tolerance to these conditions and their availability during their mission. Some test methodologies (MIL-STD-1019 method 883, ESCC standard 22900, JEDEC standard JEP133C 1/10) are well known to characterize electronic devices under ionizing radiation. But they only focus on elementary components such as semiconductors and transistors. However, nowadays, there is no system-level testing methodology. The CASIMIR project proposes to develop test procedures for evaluating electronic devices in a nuclear environment representative of D&D worksites. In this communication, we will present the first steps of a system-level qualification methodology for various devices (camera, SD cards, sensors, microcomputer...) based on Commercial-Off-The-Shelf (COTS) components subjected to TID. We will also present the PRESERVE platform (X-rays and 60Co) used to carry out these experiments. Finally, we outline the next steps in the implementation of a system-level qualification methodology for electronic devices in the irradiating environment of D&D worksites