Reactor protection system design using application specific integrated circuits
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Implementing reactor protection systems (RPS) or other engineering safeguard systems with application specific integrated circuits (ASICs) offers significant advantages over conventional analog or software based RPSs. Conventional analog RPSs suffer from setpoints drifts and large numbers of discrete analog electronics, hardware logic, and relays which reduce reliability because of the large number of potential failures of components or interconnections. To resolve problems associated with conventional discrete RPSs and proposed software based RPS systems, a hybrid analog and digital RPS system implemented with custom ASICs is proposed. The actual design of the ASIC RPS resembles a software based RPS but the programmable software portion of each channel is implemented in a fixed digital logic design including any input variable computations. Set point drifts are zero as in proposed software systems, but the verification and validation of the computations is made easier since the computational logic an be exhaustively tested. The functionality is assured fixed because there can be no future changes to the ASIC without redesign and fabrication. Subtle error conditions caused by out of order evaluation or time dependent evaluation of system variables against protection criteria are eliminated by implementing all evaluation computations in parallel for simultaneous results. On- chipmore » redundancy within each RPS channel and continuous self-testing of all channels provided enhanced assurance that a particular channel is available and faults are identified as soon as possible for corrective actions. The use of highly integrated ASICs to implement channel electronics rather than the use of discrete electronics greatly reduces the total number of components and interconnections in the RPS to further increase system reliability. A prototype ASIC RPS channel design and the design environment used for ASIC RPS systems design is discussed.« less