Patent Number: 
Section: claims

1. An out-of-core nuclear instrumentation device comprising:a detector signal-processing circuit that converts neutron flux leaking from a nuclear reactor vessel into a current value and performs a measurement processing on the neutron flux, the neutron flux being detected by a neutron detector disposed outside the nuclear reactor vessel,wherein the detector signal-processing circuit comprises:a current/voltage conversion part that converts the current value into a voltage value,a variable gain amplification part that amplifies the voltage value with a variable gain by a digital-to-analog (D/A) converter,a measurement range selection part that is provided in the current/voltage conversion part or the variable gain amplification part and selects a measurement range according to the current value,a temperature measurement unit that measures a temperature of the measurement range selection part,a temperature compensation part that outputs a gain compensation value to the D/A converter based on the temperature, anda selective adjustment control part that adjusts and controls a gain of the D/A converter with selective control of the measurement range and the gain compensation value. 2. The out-of-core nuclear instrumentation device according to claim 1,wherein the measurement range selection part comprises a current level response-use resistance circuit in which a plurality of serial bodies in which resistors and switches are connected in series are connected in parallel. 3. The out-of-core nuclear instrumentation device according to claim 1,wherein the measurement range selection part comprises a second D/A converter capable of selecting a gain according to the measurement range. 4. The out-of-core nuclear instrumentation device according to claim 3, further comprising:a constant temperature control part that performs constant temperature control in order to keep the variable gain amplification part at a constant temperature. 5. The out-of-core nuclear instrumentation device according to claim 1, further comprising:a fixed gain amplification part that is connected with the variable gain amplification part in series and amplifies an output of the variable gain amplification part with a fixed gain. 6. The out-of-core nuclear instrumentation device according to claim 2, further comprising:a fixed gain amplification part that is connected with the variable gain amplification part in series and amplifies an output of the variable gain amplification part with a fixed gain. 7. The out-of-core nuclear instrumentation device according to claim 3, further comprising:a fixed gain amplification part that is connected with the variable gain amplification part in series and amplifies an output of the variable gain amplification part with a fixed gain. 8. The out-of-core nuclear instrumentation device according to claim 4, further comprising:a fixed gain amplification part that is connected with the variable gain amplification part in series and amplifies an output of the variable gain amplification part with a fixed gain.