Patent Number: 
Section: claims

1. A neutron monitoring method comprising the steps of counting negative pulse signals output from a neutron detector that outputs negative pulse signals upon detecting neutron flux, counting positive pulse signals output from the neutron detector, and subtracting pulse count from said negative pulse count per unit time so as to measure the neutrons. 2. A neutron monitoring system comprising a neutron detector that outputs negative pulse signals upon detecting neutron flux, a first pulse count rate measurement means provided with the pulse signals output from said neutron detector for counting the negative pulses per unit time (negative pulse count rate), a second pulse count rate measurement means provided with the output pulse signals from said neutron detector for counting the positive pulses per unit time, and a pulse count correction means for subtracting the pulse count of said second pulse count rate measurement means from the pulse count of said first pulse count rate measurement means. 3. A neutron monitoring system comprising a neutron detector that outputs negative pulse signals upon detecting neutron flux, a first pulse height discrimination means provided with the pulse signals output from said neutron detector for discriminating whether the pulse height in the negative side is equal to or greater than a preset level or not; a second pulse height discrimination means provided with the pulse signals output from said neutron detector for discriminating whether the pulse height in the positive side is equal to or greater than a preset level or not; a first pulse count rate measurement means provided with pulse signals discriminated by said first pulse height discrimination means for counting the negative pulses per unit time; a second pulse count rate measurement means provided with pulse signals discriminated by said second pulse height discrimination means for counting the positive pulses per unit time; and a pulse count correction means for subtracting the pulse count of said second pulse count rate measurement means from the pulse count of said first pulse count rate measurement means. 4. A neutron monitoring system comprising a neutron detector that outputs negative current pulse signals upon detecting neutron flux; a pre-amplifier for converting and amplifying current pulse signals output from said neutron detector into voltage pulse signals; a digital pulse count rate measurement means provided with said voltage pulse signals amplified by said pre-amplifier for counting the negative pulses and the positive pulses per unit time respectively; and a pulse count correction means for subtracting the positive pulse count from the negative pulse count counted by said digital pulse count rate measurement means. 5. A neutron monitoring system comprising a neutron detector that outputs negative current pulse signals upon detecting neutron flux; a pre-amplifier for converting and amplifying current pulse signals output from said neutron detector into voltage pulse signals; a negative pulse height discrimination means provided with said voltage pulse signals amplified by said pre-amplifier for discriminating whether the negative pulse height level is equal to or greater than a preset level or not; a positive pulse height discrimination means provided with said voltage pulse signals amplified by said pre-amplifier for discriminating whether the positive pulse height level is equal to or greater than a preset level or not; a negative pulse count rate measurement means provided with said negative pulse signals discriminated by said negative pulse height discrimination means for counting negative pulses per unit time; a positive pulse count rate measurement means provided with said positive pulse signals discriminated by said positive pulse height discrimination means for counting positive pulses per unit time; and a pulse count correction means for subtracting the positive pulse count of said positive pulse count rate measurement means from the negative pulse count of said negative pulse count rate measurement means. 6. A neutron monitoring system comprising a neutron detector that outputs negative pulse signals upon detecting neutron flux; a first pulse count rate measurement means provided with the pulse signals output from said neutron detector for counting the negative pulses per unit time; a second pulse count rate measurement means provided with the pulse signals output from said neutron detector for counting the positive pulses per unit time; a pulse count correction means for subtracting the pulse count of said second pulse count rate measurement means from the pulse count of said first pulse count rate measurement means; and a display device for displaying the negative pulse count of said first pulse count rate measurement means, the positive pulse count of said second pulse count rate measurement means, and the corrected pulse count corrected by said pulse count correction means.