SOTTOSISTEMA DI AUTOPROVA PER SISTEMA DI PROTEZIONE DI REATTORE NUCLEARE

A self-test system for a nuclear power plant, nuclear reactor protection system is disclosed. Nuclear protection systems are the electronic controls, typically including circuit cards, located intermediate between sensors (as for detecting core overheat) and a control (as for providing rod injection to shut down a reactor). Constant surveillance of the nuclear system protection system is provided by a microprocessor that serially addresses protection system circuit cards and loads them at pre-determined input points with test commands. The addressed cards are thereafter simultaneously activated by a system-wide command. The test command is a pulse which is so short in duration that its affect is transparent to the system and cannot cause overall system operation. The pulse passes through the actuating electrical components to verify, on the real actuating path, the operating integrity of the system. After an appropriate response interval, the output state of the system is recorded in system-wide resident registers. Thereafter, with response data contained in these registers frozen at the recorded state, the output is read. This result is compared with the expected output in computer memory. If correspondence between memory output and register output is found, the next sequential set of test commands is acted upon. If correspondence is not found, a subroutine search is automatically conducted to locate the error. The disclosed self-test subsystem is duplicated in four separate divisions with each division testing one of the four duplicate protection systems. The three remaining and idle divisions constantly monitor the active subsystem's operation. The end result is an overall system which reduces the mean time to discover error, thus minimizing mean time to repair and maximizing protection system availability and safety. The separation of the protection system into four duplicate divisions is not dependent on the disclosed invention and the invention may be applied to protection systems with a different number of divisions.