English 
Italiano 
The Neutral Beam Test Facility (NBTF) is a research complex that houses the SPIDER experiment, in operation since 2018, and the MITICA experiment in advanced construction. SPIDER is the ITER full-size ion source, while MITICA is the full-scale prototype of the ITER heating neutral beam injector. SPIDER and MITICA share services such as the cooling and the gas and vacuum systems and also share physical spaces, such as the experimental hall, where both experiments are located, the service hall and other common rooms. The NBTF implements conventional personnel and environment safety through independent systems that provide functions such as area segregation (fences, door access keys, limit switches), fire detection and extinguishing, radiation monitoring and access control. Nuclear safety is not required. In addition to specific, independent safety systems, the NBTF requires a central safety system to coordinate all safety actions, implement specific safety functions not covered with the industrial-type systems, supply a unified human machine interface, log safety actions, and provide centralized alarm handling. Due to the different timing of the SPIDER and MITICA experiments, the NBTF safety systems were designed into two separated subsystems, the first one dealing with SPIDER and the common NBTF items, the second one dealing with MITICA. The SPIDER central safety system has been operational since 2021, whereas MITICA safety is under design. The paper presents the process for designing and implementing the safety system using the functional safety technical standards as guidelines. It briefly discusses the risk analysis carried out, the identification of the safety instrumented functions (SIF) and the allocation of the corresponding reliability targets. The paper also presents the implementation of the safety instrumented system, the formal verification of the implemented SIF and the procedure used for testing and validating the system. It also highlights lesson learned to consider in the implementation of the MITICA safety systems and finally summarizes the results achieved.
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