t-WISE-BASED MULTI-FAULT INJECTION TECHNIQUE FOR THE VERIFICATION OF SAFETY CRITICAL I&C SYSTEMS

One well-known method for the verification and certification of NPP I&C and other safety critical systems is the fault injection technique (FIT). FIT is based on a design fault injection and vulnerability injection into the software code and the field-programmable gate array (FPGA) design or a physical fault injection into hardware modules. The requirements for FIT for safety critical applications are described in detail in the standard NUREG/CR-7151. In addition to the injection of single faults, NUREG/CR-7151 recommends employing a multi-fault injection technique (MFIT). The application of MFIT increases the verification time, but it has the potential to significantly improve the quality of the system. This paper reviews different MFITs for FPGAand software-oriented systems, with special consideration to NPP I&C systems. To increase the effectiveness of the fault injection, an MFIT procedure that applies the t-wise combinatorial method is proposed. This method allows combinations of multiple faults to be found and provides full coverage of all combinations of any t-types of faults with a minimum number of checks. While the t-wise method is well known in software testing, to the best of our knowledge, this is its first application to the fault injection. Different types of coverage are considered. A case study of MFIT is considered based on a project of FPGA-based modules for NPP I&C systems.