To address some to the issues with microprocessor based instrumentation and control (I&C) systems in the nuclear power industry, some vendors have turned to field programmable gate array (FPGA) based applications. An FPGA is a type of programmable logic device that uses simple and transparent internal structures. In many types of FPGAs, the program cannot be modified in the field; therefore, they can be robust and secure. The verification of FPGA logic channels is normally much simpler and more affordable than in the case of a software implementation. FPGA vendors also tend to offer longer term support of their products as compared to microprocessor vendors. Furthermore, FPGA-based applications are more resilient to obsolescence due to the portability of the development tools (e.g., hardware description languages) between different versions of FPGA chips produced by either the same or different manufacturers. A number of IAEA workshops starting in 2007 have been held to discuss the issues related to the design, qualification, implementation, licensing, and operation of this new digital I&C technology. To date, there have been seven workshops and interest continues to grow. Some reports, guidance and standards are currently available; however, there is a need for additional guidance and standards that are more comprehensive and match the way designers are proposing to use these devices in nuclear power plant applications. Regulators, utilities, and vendors need clearer and more consistent definitions to help support regulatory reviews and to establish appropriately aligned expectations amongst all parties. This paper will discuss the development of regulatory guidance by the U.S. Nuclear Regulatory Commission to address this need.
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