JPH07111471B2 - Period trip monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention measures the reactor power from the neutron flux in the starting system region and the intermediate system region in the reactor pressure vessel, The present invention relates to a period trip monitoring device that generates a control rod pull-out prevention signal or a scrum signal when a transient phenomenon such as an abnormal increase in the average output or local output of the above is shown.

(Prior Art) In general, the neutron flux level in a reactor is in a wide measurement range (for example, in a boiling water reactor, an 11-digit measurement range).
Therefore, it is technically difficult to measure with one measuring means. For this reason, conventionally, three measuring means are used in combination.

The first measurement means is in the low neutron flux range (start-up region), in which the reactor power is proportional to the count rate,
The neutron flux level is measured by calculating the count rate by counting the low-range 6 digits by the pulse measurement method. The second measuring means is based on the intermediate neutron flux range (intermediate region). In this region, the reactor power is proportional to the root mean square value of the fluctuation components of the output signal, and the Campbell method is used for the measurement.
That is, it is measured by the square of the effective value of the AC component of the detector output signal. The third measuring means is based on the high neutron flux range (output region), in which the direct current from the detector is measured, paying attention to the fact that the reactor output is proportional to the direct current.

In recent years, a wide-area measurement device has been developed that measures the pulse measurement method and the Campbell method as the same measurement device, and measures the start-up region and the intermediate region collectively as one measurement region (start-up intermediate region). It became possible to do.

In addition, the handling method when the above-mentioned measuring means is used as a safety system of a nuclear reactor is also different. Generally, the time T until the output becomes e (base of natural logarithm) times is defined as a period and is used as an index of output change. In the start-up intermediate region, this period is monitored, and when this value exceeds a certain value, a control rod withdrawal prevention signal or a reactor emergency stop (hereinafter referred to as scrum) signal is output.

On the other hand, in the output region, the scrum signal is output when the output instruction value exceeds a fixed value, for example, 120% of the rated output. Here, a sudden increase in output is prevented in the intermediate start-up region, and safety is ensured by monitoring the output region so that the rated output is not exceeded.

Next, a period trip monitoring device used in the activation intermediate area is shown. The safety device used in the output area is not directly related to the present invention and will not be described in detail.

FIG. 1 is a block diagram of a conventional period trip monitoring device in an activation intermediate area.

The period trip monitoring device is a wide area measuring device 9 for measuring the reactor output in the intermediate start-up region, and a control rod system monitoring device 10a for outputting a control rod withdrawal prevention signal according to the reactor output signal from the wide area measuring device 9, And a scrum monitoring device 10b that outputs a scrum signal.

The wide area measurement device 9 includes a neutron flux detector 1 such as each split counter installed in the reactor, and a wide area amplifier 2.
And a wide area processing circuit 3 and a switch 4.

Of these, the wide-area amplifier 2 has a pulse amplifier into which the output signal of the neutron detector 1 is separated into frequency bands and a high frequency component is input, and a Campbell system amplifier into which an intermediate frequency component is input. Further, the wide area processing circuit 3 discriminates the output of the pulse amplifier, measures the counting rate, outputs a starting signal, and a start output processing circuit, and squares the output signal of the Campbell amplifier, smoothes it, and outputs it as an intermediate signal. And an intermediate output processing circuit. Further, the switch 4 passes the intermediate signal when the count rate of the activation signal is equal to or more than the preset value, and conversely passes the activation signal when the activation signal is less than the preset value.

On the other hand, the control rod system monitoring device 10a outputs the reactor output signal φ _o from the wide area measurement device 9 to the control rod system signal φ _a through the control rod system amplifier 5a and the control rod system low pass filter 6a.
The reactor output signal φ _o and the control rod system signal φ _a are compared by the comparator 7a, and when the reactor output signal φ _{o is} larger than the control rod system signal φ _a , the control rod pull-out prevention signal is output. Further, scrum system monitoring apparatus 10b, a reactor power signal phi _o from the wide area measurement device 9 and scram system signal phi _b through scram system amplifier 5b and scram system low pass filter 6b, the reactor power signal phi _o and scram system signal φ _b is compared by the comparator 7b, and when the reactor signal φ _o is larger than the scrum system signal φ _b , the scrum signal is output.

Here, the relationship between the reactor output signal φ _o , the control rod system signal φ _a, and the scrum system signal φ _b is expressed by the following equation.

Where i = a, b φ _o (t): input signal to control rod system or scrum system monitoring device 10 _i φ _i (t): signal that has passed through amplifier 5i and low-pass filter 6i (φ _{a in} FIG. 5) And φ _b ) G _i : the gain of the amplifier 5i λ _i : the reciprocal of the time constant of the low-pass filter 6i (1) is solved analytically when the neutron flux rises at the period τ _i. Given in.

(Φ _o (t) = φ _o (0) e ^{t / τ} i) Furthermore, by utilizing the fact that φ _i = φ _{o at} t = ∞, RC _i = (G _i −1) · τ _i …… (3) Then, the relation between the time constant RC _i of the low-pass filter 6 _i and the gain G _i is given. Therefore, when RC _i and G _i are set in this monitoring device 10i, a period τ _i is given, and when it is desired to output a control rod withdrawal prevention signal or a scrum signal at a certain period (for example, 10 seconds), the corresponding RC _i Set the combination of G _i and G _i .

For example, if RC _i = 40 seconds and G _i = 5 seconds, τ _i = 10 seconds from trip setting period τ _i (3), and if the reactor output rises in a period shorter than 10 seconds, the trip signal will be changed. Emit. Fig. 6 shows an example of the response when the neutron flux of the reactor rises in the period of 9 seconds with the control rod withdrawal prevention period of 20 seconds and the scrum setting period of 10 seconds. Code 30
Indicates the reactor output signal φ _o of the switching device 4 shown in FIG. 5, and reference numeral 31 indicates the scrum system signal φ after passing through the scrum system amplifier 5b and the scrum system low-pass filter 6b, which are components of the scrum monitoring device 10b. indicates _b, reference numeral 32 denotes a component in which the control rod system amplifier 5a, the control rod system signal phi _a after passing through the control rod system low pass filter 6a of the control rod system monitoring device 10a. A control rod pull-out prevention signal is generated at the intersection 33, and a trip signal such as a scrum system signal is generated at the intersection 34.

However, in the period trip monitoring device, a trip signal cannot be generated for a neutron flux increase (reactor output increase) of a period that is equal to or greater than the control rod withdrawal prevention setting or the scrum setting period.

Fig. 7 shows a response example when the control rod withdrawal prevention setting period τ _i is 20 seconds, the low-pass filter time constant RC _i is 40 seconds, and the neutron flux rises in period 20 seconds under the conditions from the amplifier gain G _i. . Reference numeral 30 indicates the reactor output signal φ _o of the switch 47 shown in FIG. 5, and reference numeral 32 indicates the control rod system signal φ _a .

From FIG. 7, it can be seen that the reactor output signal φ _o does not intersect with the control rod system signal φ _a , that is, the control rod withdrawal is prevented and increases with time. As described above, in the conventional period trip monitoring device, the control rod withdrawal prevention signal or the scrum signal cannot be generated by the period when the neutron flux output of the period that is equal to or higher than the trip setting period is increased. Therefore, the fuel enthalpy was increased and the fuel integrity was impaired.

The present invention has been made in consideration of such points,
Control rod withdrawal prevention setting or scrum setting Increase in neutron flux of period or more, that is, even when reactor output increase rate is not large but reactor output increase continues for a long time, output increase is appropriately prevented It is an object of the present invention to provide a period trip monitoring device that can be used.

[Structure of Invention]

(Means for Solving Problems) The present invention is a wide-area measurement in which a neutron detector, a wide-area amplifier, a wide-area processing circuit, and a switch installed in a nuclear reactor are sequentially connected to generate a reactor output signal. And a control unit for converting the reactor output signal into a control rod system signal through a control rod system amplifier and a control rod system low-pass filter, and outputting a control rod pull-out prevention signal when the reactor output signal is larger than the control rod system signal. A rod system monitoring device, and a scrum monitoring device that outputs the scrum signal when the reactor output signal is a scrum system signal through a scrum system amplifier and a scrum system low-pass filter and the reactor output signal is larger than the scrum system signal. A period trip monitoring device comprising: a wide area measuring device, wherein the reactor output signal is supplied to a timer system amplifier and a timer system low pass filter. A timer system signal smaller than the control system signal and the scrum system signal through a filter, and a timer monitoring device that operates a timer when the reactor output signal is larger than the timer system signal is connected to the timer monitoring device. The present invention is characterized in that a timer and a comparator that outputs a control rod pull-out prevention signal when the operating time of the timer exceeds a predetermined time are sequentially connected.

(Operation) When the reactor output signal becomes larger than the timer system signal, the timer operates, and the control rod withdrawal signal is issued from the comparator when the timer operating time has exceeded the specified time. Therefore, even when the reactor power increases at a period larger than the control rod pull-out prevention setting period or the scrum design period, it is possible to appropriately prevent the sudden increase in the reactor output.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 are views showing an embodiment of a period trip monitoring device according to the present invention. The same parts as those of the conventional device are designated by the same reference numerals, and detailed description thereof will be omitted.

The period trip monitoring device includes a neutron flux detector 1, a wide area amplifier 2, and a wide area processing circuit 3 installed in a reactor.
And a switching device 4 are provided, and a control rod system monitoring device 10a and a scrum system monitoring device 10b are connected to the wide area measuring device 9.

Further, the wide area measuring device 9 includes a timer system amplifier 12, a timer system low-pass filter 13, a comparator 14, a timer ON generator 15,
And a timer system monitoring device 11 including a timer OFF generator 16
Is also connected to the timer monitoring device 11.
17 and the comparator 18 are sequentially connected.

The timer system monitoring device 11 converts the reactor output signal φ _o from the wide area measurement device 9 into a timer system signal φ _t through the timer system amplifier 12 and the timer system low-pass filter 13, and outputs the reactor output signal φ _o and the timer system signal φ _t. When the reactor output signal φ _o is larger than the timer system signal φ _t, the timer 17 is operated via the timer ON generator 15 by comparing the above with the above. On the other hand, when the reactor output signal φ _o is less than the timer system signal φ _t , the timer 17 is stopped via the timer OFF generator 16.

Further, the elapsed operation time T _ON of the timer 17 is compared with a preset route time T _set by the comparator 18, and the elapsed operation time T _{ON is}
When is longer than the set elapsed time T _set , a control rod pull-out prevention signal is output.

Next, the operation of this embodiment having such a configuration will be described.

Also in this embodiment, the signal φ _t after passing through the timer system amplifier 12 and the timer system low-pass filter 13 is the reactor output signal φ _o from the wide area measurement device and the above-mentioned equation (1),
The relationship between the expressions (2) and (3) is established.

Therefore, the setting period for starting the timer operation can be set by determining the gain of the timer system amplifier 12 and the time constant of the timer system low-pass filter 13, respectively. Further, the scrum setting period and the control rod withdrawal prevention setting period can be set in the same manner as in the conventional device.

For example, FIGS. 2 to 4 show response examples when the scrum setting period is set to 10 seconds, the control rod withdrawal prevention setting period is set to 20 seconds, and the timer setting period is set to 25 seconds.

Here, FIG. 2 is a response example in which the output of neutron flux is increased in period 9 seconds, FIG. 3 is an example of response in which the output of neutron is increased in period 15 seconds, and FIG. It is a response example when the output rises in seconds.

2 to 4, reference numeral 20 indicates a reactor output signal φ _o output by the wide area measuring device 9, and reference numeral 21 indicates a scrum system signal φ _b that has passed through the scrum system amplifier 5b and the scrum system low pass filter 6b. are shown, reference numeral 22 denotes a control rod system signal phi _a after passing through the control rod system amplifiers 5a and the control rod system low pass filter 6a, reference numeral 23 is a timer-based amplifier 12
And the timer system signal φ _t after passing through the timer system low-pass filter 13.

Fig. 2 shows an example of response when the reactor output signal φ _o rises at period 9 seconds. The timer operation starts at intersection 24 (T ₁ ), and the control rod withdrawal prevention signal occurs at intersection 25 (T ₂ ),
A scrum signal is generated at intersection 26 (T ₃ ).

Of these, when the timer starts and when the scrum signal is generated from T _1.
Time T ₃ -T1 to T ₃ is set elapsed time in the comparator 18
It is shorter than T _set . Therefore, in the case shown in FIG. 2, the control pull-out prevention signal is not generated from the comparator 18.

On the other hand, FIG. 3 shows a response example when the reactor output signal φ _o rises in 15 seconds of the period. The timer starts operating at intersection 24 (T ₁ ), and the control rod pull-out prevention signal is generated at intersection 25 (T ₂ ). Time T ₂ −T ₁ Set elapsed time in comparator 18
It is shorter than T _set, and the control rod pull-out prevention signal is not generated from the comparator 18.

FIG. 4 is an example of a response when the reactor output signal φ _o rises in a period of 21 seconds.

In this case, the reactor output signal φ _o does not intersect with the scrum system signal φ _b 21 after passing through the scrum system low pass filter 6 _b and the control rod system signal φ _a 22 after passing through the control rod system low pass filter 6 _a. However, at a crossing point 24, the timer system signal φ _t after passing through the timer meter low-pass filter 13 intersects with the timer system signal φ _t to start the timer operation (T ₁ ). In this case, the timer 17 operates continuously unless the reactor output signal φ _o becomes less than the timer system signal φ _t . Therefore, the timer start time
At the time T ₄ after the set elapsed time T _set from T _{1, the} control rod pull-out prevention signal is generated from the comparator 18. The value of the reactor output signal φ _o generated by the control rod pull-out prevention signal is shown by reference numeral 27.

As described above, according to the present embodiment, even when the reactor output signal rises in a period larger than the control rod withdrawal prevention setting period, the timer operation start time T ₁ to the set elapsed time T
_At the time T ₄ after the _set , the control rod pull-out prevention signal is generated, so
It is possible to appropriately prevent a rapid increase in reactor power.

〔The invention's effect〕

According to the present invention, even when the reactor power increases at a period larger than the control rod pull-out prevention period or the scrum setting period, it is possible to appropriately prevent the sudden increase in the reactor power. Moreover, since a simple device such as an amplifier, a low-pass filter, and a timer is used without using a differentiating circuit, it is possible to reduce the manufacturing cost.

[Brief description of drawings]

1 to 4 are views showing an embodiment of a period trip monitoring apparatus according to the present invention. FIG. 1 is a block diagram thereof, and FIGS. 2 to 4 are reactor output signals φ _o , control rods. System signal φ _a , scrum system signal φ _b, and timer system signal φ _t
FIG. 5 is a block diagram showing a conventional period trip monitoring device, and FIG. 6 is a response of _a reactor output signal φ _o , a control rod system signal φ _a , and a scrum system signal φ _b of the conventional device. FIG. 7 is a diagram showing an example, and FIG. 7 is a diagram showing a response example when the reactor output is increased in a period which is equal to or greater than the control rod withdrawal prevention setting period of the conventional device. 1 ... Neutron flux detector, 2 ... Wide area amplifier, 3 ... Wide area processing circuit, 4 ... Switching device, 5 ... Amplifier, 6 ... Low-pass filter, 7 ... Comparator, 9 ... Wide area measuring device , 10a
...... Control rod monitor, 10b ...... Scrum monitor, 1
1 ... Timer monitoring device, 12 ... Timer amplifier, 13 ...
… Timer low-pass filter, 14 …… Comparator, 15 …… Timer ON generator, 16 …… Timer OFF generator, 17 …… Timer, 18 …… Comparator, 20 …… Reactor output signal, 21 …… Scrum system signals, 22 …… Control rod system signals, 23 …… Timer system signals.

Claims (1)

[Claims] 1. A neutron detector, a wide area amplifier, a wide area processing circuit, and a switch installed in a nuclear reactor, which are sequentially connected,
A wide area measuring device that outputs a reactor output signal, and the reactor output signal is a control rod system signal through a control rod system amplifier and a control rod system low-pass filter, and is controlled when the reactor output signal is larger than the control rod system signal. A control rod system monitoring device that outputs a rod withdrawal prevention signal, the reactor output signal as a scrum system signal through a scrum system amplifier and a scrum system low-pass filter, and when the reactor output signal is larger than the scrum system signal, the scrum signal A period trip monitoring device comprising: a scram monitoring device for outputting the reactor output signal to the wide area measuring device, the reactor output signal being smaller than the control system signal and the scrum system signal through a timer system amplifier and a timer system low-pass filter. The timer system signal is used, and the reactor output signal is larger than the timer system signal. A timer monitoring device that activates a timer when a threshold is connected is connected to the timer monitoring device, and a comparator that outputs a control rod withdrawal prevention signal when the operating time of the timer exceeds a predetermined time, A period trip monitoring device characterized by being connected.