Opera North (United Kingdom)

With respect to three developments (the widespread use of solid state components as active circuit elements, the acknowledgment that the electronic protective system problem was a switching circuit and logic design problem, and the desire to reduce the probability of reactor shutdown to instrument failures and introduce the two of three coincidence or majority decision concept) system design concepts for reliability enhancement are provided, and system building blocks for a practical realization of these concepts are presented. Although the ideas presented are pointed toward nuclear reactor protective systems, it is felt that the same approaches can be applied to general systems design. (P.C.H.)