[en] Purpose: To detect the counterflow state of a recirculation pump as a differential pressure, and after confirming the detection result, and operation circuit is switched, whereby the fluid flow in the core can be accurately detected even at a time when one recirculation pump is stopped. Method: A method of measuring the fluid flow in the core of a bwr type reactor by seeking the total flow of fluid flows of jet pumps belonging to A and B loops so as to obtain the fluid flow in the core of the reactor, which method is characterized by subtracting the flow of the stopped loop jet pump from that of the sound loop jet pump in accordance with the compatible establishment of a pump stop condition and such a condition that the differential pressure of the flow generator of the jet pump of the stopped loop is less than the predetermined value at a time when one loop is tripped. (Nakamura, S.)

[en] Purpose: To keep a water level constant in a reactor core in the abnormal state of a nuclear power plant by controlling a cooling system turbine upon separation of a bwr type reactor. Constitution: When a nuclear power plant is separated and the supply of feedwater is interrupted, since the feedwater level in the reactor is lowered, RCIC system, that is, a reactor separation cooling system is automatically started to introduce vapor from a main vapor pipe to the RCIC turbine, and a pump is drived to feedwater from a condensate storage tank to the reactor. A water level signal from a reactor water level detector and a flow rate signal from a flow rate detector and a flow rate generator of the pump are inputted and calculated in a flow rate controller, based on which the opening degree of a turbine regulation valve is adjusted. This can change the flow rate in the vapor to control the revolutional number of the turbine thereby keeping the reactor water level constant. (Horiuchi, T.)

[en] Purpose: To automatically control reactor heating while keeping the condition of temperature rising rate by determining the deviations based on the reactor water temperature, the aimed temperature and the aimed temperature rising rate and operating control rods. Constitution: Actual temperature in the reactor is measured by a temperature detector and compared with a value from a setter to determine the temperature deviation. While on the other hand, the rising rate for the measured temperature is calculated in a differentiator and compared with a value from a setter to determine the deviation, which is passed through an integrator to calculate the deviation for the temperature rising rate. The signals for the temperature deviation and the temperature rising rate deviation are selected in a lower value preference circuit and the operation amount for the control rod is judged in a control rod operation judging section depending on the deviation amount. The control rod to be operated is determined in a sequence control section for the selection of control rod. The control rod selected and the direction of the operation are displayed on a display and the selected control rod is automatically driven by a control rod drives to thereby carry our reactor heating. (Furukawa, Y.)

[en] Purpose: To enable continual retention of water level in a nuclear reactor to specified value. Method: When a water level in a reactor reaches a predetermined high-water-level setting point or low-water-level setting point, drain amount necessary for returning to an ordinary water level and drain amount necessary for maintaining the water level are calculated by a computer, the opening-degree of a drain control valve is calculated with a deviation between the drain amount thus calculated and the drain amount actually measured, thereby always maintaining the water level at the specified range. (Yoshihara, H.)

[en] Purpose: To provide a water level measuring system so that a reactor water level detecting signal can be corrected in correspondence to a recirculation flow, thereby to carry out a correct water level detection in a wide range of the reactor. Method: According to the operation record of a precursor reactor, the ratio Δh of the lowering of the water level due to the recirculation flow is lowered in proportion to the ratiowith respect to the rated differential pressure of the recirculation flow. Accordingly, the flow of recirculation pump is measured by an elbow differential pressure generator utilizing an elbow of a pipe, and the measured value is multiplied by a gain by a ratio setter, and therefter, an addition computation is carried out by an adder for correcting the signal from a water level detector. When the signal from the water level detector is corrected in this manner, the influence of the lowering of the water level due to the recirculation flow can be removed, and an interlocker predetermined in the defined water level can be actuated, thus the influence of the dynamic pressure due to the recirculation flow acting on the instrumental pipe line detecting the reactor water level can be removed effectively. (Yoshino, Y.)

[en] Purpose: To improve the reactor safety by determining the setting value for the protecting operation on the safety side. Constitution: Flowrate for each of pumps is calculated in a first reactor core flowrate computing device based on the Q-H characteristics of the pump by using a pump deck differential pressure detector and a internal pump motor rotational number detector. Separately, the reactor core flowrate is calculated in a second reactor core flowrate computing device based on the previously calibrated differential pressure-reactor core flowrate curve by using a reactor core grid plate differential pressure detector. The lower value of the two is outputted through a lower value preference circuit to an APRM signal processing device to provide a setting signal for the APRM scram setting value and APRM control rod extraction inhibitive setting value. If the difference between the two reactor core flowrates is increased, it is judged as the abnormality in the measuring system to issue an large deviation information. (Sekiya, K.)

[en] Purpose: To enable to obtain the output of compensation signals for boric acid removal and injection rate accurately corresponding to the actual position of control rods in a heavy water moderated BWR type reactor. Constitution: A time in which a power conditioning control rod reaches from a reference position to an upper or lower limit position is measured and a predetermined compensation signal for borid acid removal and injection is outputted only when the time is longer than a predetermined time. Further, the time in which the signal is being outputted is set such that it is not longer than a predetermined time. Thus, if the control rod reaches the upper or lower limit position by the reactivity applied in a transient manner, no compensation signal is outputted. Further, if the control rod does not return within a predetermined of time after the generation of the compensation signal, it is juged abnormal and the controlling operation is interrupted at that point. In this way, increase of the abnormal power rise or power down can be avoided. (Ikeda, J.)

[en] Purpose: To enable optimul and automatic control of the water level in a reactor even when a feedwater control system is operated in a manual mode, such as, at the start, stop and the recovery operation after a scram of the reactor. Constitution: A water level control device for a nuclear reactor is composed of a computer and an analog memory, plant signals from a reactor water level detector, a reactor pressure detector, a feedwater pump discharge pressure detector and a drain water flow rate detector are collected, and the openings of the feedwater control valve and the drain control valve are calculated. Further, the openings of the feedwater control valve and the drain control valve are controlled based on the calculated result, and the water level in the reactor is properly maintained. At this time a communication valve to a condenser remains opened. (Sekiya, K.)

No abstract available

No abstract available