Patent Number: 
Section: claims

1. A power monitoring system comprising:a plurality of local power range monitoring devices, each of the local power range monitoring devices having a plurality of local power channels to obtain local neutron distribution in a nuclear reactor core;an averaged power range monitoring device that receives power output signals from the plurality of the local power range monitoring devices and obtains an average output power signal of the reactor core as a whole; andan oscillation power range monitoring device including an oscillation power range monitoring mechanism that receives power output signals from the local power range monitoring devices and monitors power oscillations of the reactor core, whereinthe output signals from the local power range monitoring devices to the averaged power range monitoring device and the output signals from the local power range monitoring devices to the oscillation power range monitoring device are independent, whereineach of the local power range monitoring devices has a function to transmit to the oscillation power range monitoring device, breakdown or exclusion signals of the local power range monitoring device itself and of any of the local power channels connected to the local power range monitoring device,when the breakdown or exclusion signal of one or more of the local power channels is generated, the oscillation power range monitoring device excludes only the one or more local power channels corresponding to the breakdown or exclusion signal or signals,when the breakdown or exclusion signal of one or more of the local power range monitoring devices is generated, the oscillation power range monitoring device excludes all local power channels corresponding to the one or more local power range monitoring devices, andvariables that are changed according to a type of fuel of the reactor core are set by hardware switches on a board that comprises part of the oscillation power range monitoring mechanism, the hardware switches comprising a combination of electrical contacts that are positioned such that the variables cannot be changed without stopping the oscillation power range monitoring mechanism. 2. The power monitoring system according to claim 1, wherein,the variables that are changed according to the type of fuel of the reactor core are stored in an element whose internal state cannot be changed by operation of the oscillation power range monitoring mechanism. 3. The power monitoring system according to claim 1, whereinthe oscillation power range monitoring mechanism has a transmission section that transmits output signals not having input signals in a one-way direction, and the transmission section transmits the output signals to a state display section that displays state of power oscillations. 4. The power monitoring system according to claim 1, whereinthe oscillation power range monitoring mechanism has a transmission section that transmits output signals not having input signals in a one-way direction, and the transmission section transmits the output signals to a history recording device that records a predetermined period of time of past history. 5. The power monitoring system according to claim 4, whereinthe history recording device includes: a determination means that makes a determination as to whether data is normally received; and a determination result transmission means that transmits a determination result of the determination means to the transmission section, wherein transmission of data from another oscillation power range monitoring mechanism to the transmission section is limited to one-way transmission. 6. The power monitoring system according to claim 4, whereinthe transmission section and the history recording device are electrically isolated. 7. The power monitoring system according to claim 1, wherein at least one variable that is changed according to the type of fuel of the reactor core is selected from the group consisting of a peak determination amplitude value, a trough determination amplitude value, a multiplication factor determination value, a trip determination amplitude value, an oscillation interval minimum determination value, and an oscillation interval maximum determination value.