Patent Number: 
Section: claims

1. A core monitoring system comprising:a core thermal limit value monitoring device that outputs a signal to a control unit of a nuclear reactor as a result of monitoring a thermal state value of a nuclear reactor core received from a local power range monitor,the device comprising: three or more signal input processing units each configured to receive a signal output from the local power range monitor, the signal representing a state of the core that has been divided into three or more regions to be monitored, each of the signal processing units includinga calculating unit configured to calculate thermal state values of a subset of the regions to be monitored, the thermal state values being calculated based on the signal received by the signal input processing unit to determine whether signal output to the control unit is necessary;a synchronization processing unit configured to output a signal-output stop signal and a signal-output stop cancellation signal to synchronization processing units of other signal input processing units; andan output processing unit, anda control unit of a nuclear reactor, whereinif a first calculating unit of a first signal input processing unit has determined that signal output to the control unit is necessary, and a first synchronization processing unit of the first signal input processing unit has not received a signal-output stop signal from a synchronization processing unit of one of the other signal input processing units, the first synchronization processing unit is configured to transmit the signal-output stop signal to synchronization processing units of the other signal input processing units, and a first output processing unit of the first signal input processing unit is configured to output a signal to the control unit representing calculation results of the first calculating unit,if the first calculating unit has determined that signal output to the control unit is necessary, and the first synchronization processing unit has received a signal-output stop signal from a synchronization processing unit of one of the other signal input processing units, the first calculating unit is configured to not transmit the signal-output stop signal or the signal-output stop cancellation signal to the synchronization processing units of the other signal input processing units,if the first calculating unit has determined that signal output to the control unit is not necessary, the first synchronization processing unit is configured to determine whether the signal-output stop signal has been transmitted to the synchronization processing units of the other signal input processing units, and if the synchronization processing units of the other signal input processing units have received the signal-output stop signal, the first synchronization unit is configured to transmit the signal-output stop cancellation signal to the synchronization processing units of the other signal input processing units, andthe control unit is configured to control a power level of the nuclear reactor based on the signal output by the core thermal limit value monitoring device to the control unit. 2. The core monitoring system according to claim 1, whereinthe core thermal limit value monitoring device further comprises a region definition information storage unit configured to store a plurality of patterns, each pattern including a combination of region numbers in the regions to be monitored and assigned calculation processing numbers, and each signal input processing unit further comprises:a setting unit configured to assign one of the patterns stored in the region definition information storage unit to the calculating unit of the signal input processing unit;a region definition information table configured to store the assigned pattern; anda reading unit configured to output information from the region definition information table to the calculating unit of the signal input processing unit, the information identifying the subset of regions for which the calculating unit calculates thermal state values. 3. The core monitoring system according to claim 1, further comprising:a core performance calculating device configured to calculate a distribution of power in the core. 4. A core monitoring method comprising:a core thermal limit value monitoring method that uses a computer including three or more CPUs to output a signal to a control unit of a nuclear reactor as a result of monitoring a thermal state value of a nuclear reactor core, based on a local power range monitor, the core thermal limit value monitoring method comprising:a signal inputting step in which the CPUs each receive a signal output from the local power range monitor, the signal representing a state of the core that has been divided into three or more regions to be monitored;a calculating step in which the CPUs each calculate thermal state values of the regions to be monitored based on the received signal to determine whether signal output to the control unit is necessary;if a CPU has determined that signal output to the control unit is necessary, and the CPU has not received a signal-output stop signal from one of the other CPUs, the CPU performs a signal transmitting step of transmitting a signal output stop signal to the other CPUs and an outputting step of outputting a signal representing calculation results from the calculation step to the control unit;if the CPU has determined that signal output to the control unit is necessary, and the CPU has received a signal-output stop signal from one of the other CPUs, the CPU does not perform the signal transmitting step;if the CPU has determined that signal output to the control unit is not necessary, the CPU performs a determination step of determining whether the signal-output stop signal has been transmitted to the other CPUs, and if the other CPUs have received the signal-output stop signal, the CPU performs a signal cancellation step of transmitting a signal-output stop cancellation signal to the other CPUs; andcontrolling a power level of the nuclear reactor based on the signal output to the control unit by the computer including three or more CPUs.