Reactor trip on turbine trip inhibit control system for nuclear power generating system

摘要

1474959 Nuclear power plant COMBUSTION ENG Inc 26 July 1974 [31 July 1973] 33207/74 Heading G6C Nuclear power plant (Fig. 1) in which a bypass system 48 is operative to divert working medium from passing to a turbine 34 under turbine load-shedding conditions, and in which a protective system 46 is operative to shut-down the reactor in such conditions, comprises means to inhibit reactor shutdown in such conditions if it is established that the by-pass system 48 can divert sufficient of the working medium as to enable the reactor to continue operating safely. The plant is such that normally a certain percentage of shed turbine load can be tolerated without shut-down being necessary (e.g. up to 15% of the shed load can be accommodated by continued operation of the reactor but at higher power). The by-pass system comprises valves 52 (Fig. 2) which, when in an automatic mode A, provide availability signals 76 from which individual capacity signals 80 are derived by multiplication of the signals 76 by weighting factors K1, K2, K3, K4 (these correspond to the capacity of each valve, in terms of the percentage of reactor power that can be diverted thereby), and subsequently a total capacity signal 84 is formed at 82. At 86 the signal 84 is increased by a bias signal 88 representing the aforementioned ability of the plant to accommodate a certain proportion of the shed load without reactor shut-down occurring, to give a capability signal 90 which is compared at 98 with a reactor power signal 94 (derived from neutron flux probe 96). If the resultant signal is positive, a binary "1" signal 104 is generated and forms an inhibit signal 72 applied to the protective system 46 to prevent reactor shut-down resulting from the loadshedding (although shut-down can still result from other causes). Thus, 100% turbine loadshedding can be managed, without reactor shut-down, if the by-pass system has the capacity to divert 85% of the shed load. In a modification (Fig. 3, not shown) condenser availability (to receive working medium from the by-pass system) is also taken into account in the generation of the inhibit signal.