ENHANCED DISTRIBUTED RECOVERY BLOCKS FOR NUCLEAR REACTOR CONTROL AND SAFETY FUNCTIONS

DESPITE THE PRESSING NEED, THERE IS CURRENTLY NO WIDELY ACCEPTED AND LICENSED DIGITAL SYSTEM FOR REPLACEMENT OF AGING ANALOG REACTOR SAFETY AND PROTECTION HARDWARE. THE PRIMARY OBSTACLE HAS BEEN THE LACK OF A CREDIBLE IMPLEMENTATION OF SOFTWARE FAULT TOLERANCE SUPPORTED BY AN APPROPRIATE SYSTEM ARCHITECTURE. THIS RESEARCH WILL DEVELOPAND TEST AN INNOVATIVE CONSTRUCT IN SOFTWARE FAULT TOLERANCECALLED ENHANCED DISTRIBUTED RECOVERY BLOCK (EDRB) AS A MEANSOF OVERCOMING THIS OBSTACLE. EDRB IS DESIGNED FOR A NETWORK OF MICROCOMPUTERS CONTROLLING HIGHLY CRITICAL FUNCTIONS SUCH AS THE SAFETY ACTUATION SYSTEM OF A PWR (PRESSURIZED WATER REACTOR). THIS NETWORK ARCHITECTURE ALLOWS THE SYSTEM TO BE IMPLEMENTED AS AN ENSEMBLE OF RELATIVELY SIMPLE AND TESTABLE FUNCTIONAL SUBUNITS THAT ARE ISOLATED FROM EACH OTHER BOTH PHYSICALLY AND LOGICALLY. THEISOLATION LARGELY ELIMINATES UNANTICIPATED INTERACTIONS AND MAKES THE DESIGN MUCH EASIER TO VERIFY, ANALYZE, AND CERTIFYTHAN THE CENTRALIZED ARCHITECTURES CURRENTLY USED BY SEVERAL REACTOR VENDORS. EDRB IS A VERY BROAD, SOFTWARE-IMPLEMENTED, FAULT-TOLERANT MECHANISM FOR SUCH A NETWORK. THROUGH EDRB COMPUTERS DETECT FAILURES IN OTHER UNITS AND EFFECT A RECOVERY ON THE APPLICATION SOFTWARE, SYSTEM SOFTWARE, OR HARDWARE LEVEL.