JPS57125822A - Detecting apparatus of water level of boiling water type nuclear reactor - Google Patents

Abstract

PURPOSE:To improve the detection capacity, by carrying out a relational operation of only the signal values wherein the difference between two measured value is within the allowable range in all combinations within a range of an allowable error at the normal measuring time among the signals of the plural water level detectors in a nuclear reactor. CONSTITUTION:A signal Sa of a water level detector 1a is inputted into a water level selection signal 10a and Ga is outputted through a measuring range deciding devive 2a and an input switch 3a when the signal Sa is found between the values of the upper limit and lower limit and 0 is outputted when the value is outside of said value, Cb, Gc or 0 is outputted with regard to another water level sensor not shown by the figure in the same way. Signals D1-D3 is outputted by a water level arithmetic device 100 comparing every each two of Ca- Cc and when said output value is smaller than a reference value Ks, G1=(Ga+Gb)/2, G2, G3 are outputted and then, when said output value is larger than the value Ks, G1=0, G2... are outputted. The signals G1-G3 is averaged 7 and averaged signal is inputted into a display device 8. Further, when >=two among Sa-Sc are out of the upper or lower limit of the water level, an alarm is given. Thus, the water level is detected accurately by a redundancy circuit.