Consorzio RFX, Padova, Italy
ITER Organization, St. Paul lez Durance, France
F4E, Barcelona, Spain
MITICA, the prototype of the ITER heating neutral beam injector, will use an extensive computer-based safety system (MS) to provide occupational safety. The MS will integrate all personnel safety aspects. After a detailed risk analysis to identify the possible hazards and associated risks, we determined the safety instrumented functions (SIFs), needed to mitigate safety risks, and the associated Safety Integrity Levels (SIL), as prescribed in the IEC 61508 technical standard on functional safety of electrical/electronic/programmable electronic safety-related systems. Finally, we verified the SIFs versus the required SIL. We identified 53 SIFs, 3 of which allocated to SIL2, 23 to SIL1, and the others without SIL. Based on the system analysis, we defined the MS architecture, also considering the following design criteria: - Using IEC 61508 and IEC 61511 (Safety instrumented systems for the process industry) as guidelines; - Using system hardware to allow up to SIL3 SIFs; - Using certified software tools to allow programming up to SIL3 SIFs. The SIL3 requirement derives from the need to minimize the share of the hw/sw failure probability, thus allowing maximum share to sensors and actuators. The paper presents the requirements for the MITICA safety systems and the system design to meet them. Due to the required system reliability and availability, the hardware architecture is fully redundant. Given the requirement to choose proven solutions, the system implementation adopts industrial components.
