SU1429818A1 - Method of monitoring the process of boiling of sodium in nuclear reactor active zone - Google Patents

Abstract

The invention relates to a measuring tech- nique and can be used on power and experimental nuclear reactors with commetallic heating fluid to monitor the development of the boiling process in the core of the nuclear reactor. The chain of the invention is the determination of the stage of sodium evaporation. The tech- nical solution is based on the imbalance of time intervals by the occurrence of a sodium boiling signal by measuring the amplitude of oscillations of the neutron flux in the frequency band, which is characteristic of the boiling sodium. The method has a higher perforation and is more sensitive than the prototype. 1 silt

Description

j The invention relates to a measurement technique and can be used on energy and experimental nuclear-cooled nuclear reactors for. ontrol for the development of the boiling process in the core of a nuclear reactor.

 The purpose of the invention is the determination of sodium evaporation, the method of controlling the process of boiling the atom in the nuclear zone of the JTOpa nuclear reaction is carried out as follows. The measured neutron current is filtered from the background noise jconponent of the normal operation, editor, in the frequency band from 0.3 to i50 Hz. Then the level of the signal at each time point is determined using the measuring system. In the period when there is no boiling, the admissible level of fluctuations of the signal level is determined. They set the setting a little more than the acceptable level of the scope of the stake; After the measured signal at this level is exceeded, a sodium boiling signal is formed. After the coolant boils are fixed, the time when the ANP of the measured signal becomes less than the setpoint is determined, and at this point the time begins. If the time before the appearance of a new boiling point signal is not less than 1 s and not more than 20 s, then a signal is formed that begins the stage of evaporation of sodium from the core package. Otherwise, it is stated that there is no extension of the coolant.

The drawing shows a block diagram of a device implementing the proposed method.

The device contains a neutron flux detector 1, a matching device 2, the input of which is connected to a non-Gtron flux detector 1, and an output to the input of a bandpass filter 3, and an amplitude discriminator 4, the input of which is connected to the output of a bandpass filter 3s device 5 for measuring the time absence of a signal, input which is connected to the output of an amp lit. of discriminator L, the comparing device 6, one of the inputs of which is connected to the output of the device 5 for measuring the time of the absence of a boiling signal, setpoint 7 of the boundary values of th interval.

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The transceiver of which is connected to the second input of the comparison device 6, and the indicator BS which input is connected to the output of the comparison device 6.

The pa6oTaet device is as follows.

At the moment of boiling of sodium in the package, the resulting volume of vapor mbdliruet neutron flux, the changes of which are recorded by the detector 1 neutron flux. Fluctuations of the neutron flux corresponding to the stage of development of boiling cause the corresponding oscillations of the electric current at the output of the detector of the ron flux, which are selected by the band-pass filter 3. The matching device 2 provides electrical matching between the output of the neutron detector 1 and the input of the band-pass filter 2. Signal from the output the bandpass filter 3 is fed through the amplitude discriminator 4 to the device 5 for measuring the time of the absence of the boiling signal at the time of the intersection of the amplitude of the measured signal from the filter output 3 setpoint. According to the signal corresponding to the intersection of the setpoint from the value when the amplitude of the signal at the output of the bandpass filter 3 is above a predetermined level, to the value when the amplitude of the signal at the output of the bandpass filter is below the setpoint level, the boiling time absence signal that starts countdown no signal about boiling. The signal corresponding to the torque above or the set level, the device 5 for measuring the time of the absence of the boiling signal is turned off, and the time measured by this device enters the input of the comparing device 6, which compares its value with the values of the time interval corresponding to sodium evaporation , the values of which come from the setpoint generator 7 of the boundary values of the time interval, the boundary values in the setting unit 7, the boundary values of the time interval are set on the basis of the experiment research data, experimentally, for a given package design. The signal obtained as a result of the comparison by the comparator device 6 enters the indicator 8, which signals to the operator that there is a stage of evaporation of sodium from the bag in the core of the nuclear reactor.

A positive effect in the implementation of the proposed method is achieved due to the fact that the state when only sodium vapor is in the core package is periodically replaced by the process of a new portion of liquid sodium getting inside the bag, which boils in the process of evaporation and formation of steam volume modulates the neutron flux accordingly. Since couples. The newly evaporating sodium prevented for some time the ingress of a new portion of liquid sodium, the modulation of the neutron flux by a change in the volume of steam at the fixed frequencies is absent and the signal about the boiling of sodium disappears. Then, as the sodium vapor pressure decreases, due to their release from the bag through the outlet windows of the bag, conditions are created to get 1n inside the bag of the new batch of sodium and the process is repeated. So with boiling experiments

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sodium inside the core package at the BN-350 reactor was observed bursts of the amplitude of oscillations of the neutron flux, the state of one to three oscillations with a time interval between them from 8 to 15 s.

Claims (1)

Invention Formula The method of controlling the sodium boiling process in the core of a nuclear reactor, which consists in measuring the amplitude of oscillations of the neutron flux in the frequency band, is characteristic of the sodium boiling process, and generating a boiling signal when the measured signal exceeds the threshold value, characterized in that evaporation of sodium, measure the time interval between the loss of the boiling signal and the noftsjieHH of the boiling signal and, if the measured value of the no boiling point in the range from} to 20 s is found, form a signal There is a stage of evaporation of sodium from the core package. five five