Patent Number: 058752218
Section: claims

1. In a boiling-water reactor with a reactor core, a method of monitoring the reactor core for an unstable state caused by a local oscillation of a physical variable, the method which comprises: a) disposing a plurality of sensors each in a plurality of regions of a reactor core and measuring with the sensors a physical variable which is subject to local oscillations; combining output signals of the sensors into a given number of region channels and assigning to each region channel a region and the sensors disposed in the region for generating a region signal;  b) combining the region channels into a given number of system channels and generating a system signal; and  c) assigning the system signals to an output channel and generating an output signal in the output channel;  d) setting, with monitoring stages and selection stages, an alarm output signal in each output channel if a monitoring criterion is satisfied in at least a predefined number of the system channels over a plurality of oscillation periods in a minimum number Nmp of the respective system channel;  e) connecting the sensors such that an output signal of each sensor influences only a single region signal, and each region signal influences only a single system signal; and  f) forming the region signals of each system channel from the output signals of those sensors which are located in regions distributed over a cross section of the reactor core in such a way that the regions which are respectively adjacent to such a region contain sensors, the output signals of which are assigned to region channels of other system channels.  a system selection stage, a plurality of region selection stages connected to said system selection stage, a given number of region monitoring stages connected to each said region selection stage, and a sensor stage connected to each said region monitoring stage with a plurality of sensors strategically disposed in regions of a reactor core of a boiling water reactor, wherein  a) measured signals supplied by said sensors to a respective said region monitoring stage are combined into a region signal for the physical variable; each said region signal is monitored in the respective said region monitoring stage in accordance with a monitoring criterion, and a region signal containing a region monitoring signal is output by each region monitoring stage;  b) each region signal is connected to at least one of said region selection stages, and said region selection stages forming respective system monitoring signals from a predefined minimum number of region monitoring signals; and  c) said region selections stages each outputting a respective system monitoring signal to said system selection stage, and said system selection stage outputting an output monitoring signal according to a predefined minimum number of systems. 2. In a boiling-water reactor having a reactor core, a device for monitoring the reactor core with respect to local oscillations of a physical variable causing an unstable state of the reactor, which comprises: