Development of a computerized Safety Shutdown System test facility

The Special Safety Systems in CANDU Nuclear Generating Stations include two diverse and fully independent emergency Shutdown Systems, SDS1 and SDS2. Computers have been introduced into SDS1 and SDS2 in the three CANDU 600 MWe plants operating in Canada and Korea since 1982 to provide the trip decision function. Following this experience, the design of completely computerized systems for next CANDU plant, Darlington NGS 'A', is in progress and due for installation in late 1985. A significant feature of this system is a computerized test facility, which performs all required routine testing of Shutdown System components to verify the availability of the systems. This facility is comprised of an appropriate test language and real-time Test Interpreter. The software provides the capability to exercise the separate trip-function computers, process instrumentation and control logic. The test language developed resembles a simplified high-level programming language which has been tailored for this specific application. It features instructions to handle digital and analog I/O, perform simple mathematical calculations and provide annunciation and data logging capabilities. The language is designed such that the test programs are readable by the operator since they replace the written procedures previously used by the operations staff. This paper describes the features of the test language, its applications to testing of Shutdown Systems in an operating plant and the hardware configuration employed. Other applications of this facility are also mentioned