JPS58187895A - Reactor operation monitoring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a nuclear reactor operation monitoring system that automatically operates a control rod drive control device to maintain reactor stability.

[Technical background of the invention]

Boiling water reactors are designed so that the inherent stability of the reactor is not compromised over a variety of anticipated operating conditions. Channel stability can be considered as one criterion for evaluating the inherent stability of a nuclear reactor. This is due to thermal-hydraulic conditions that impair reactor stability, such as oscillations in the coolant flow in the reactor core that impede the transfer of heat to the coolant and thereby oscillate reactor power. It examines events.

As a standard for stability evaluation, the width reduction ratio is used in boiling water reactors. This is expressed as the ratio of the deviation of the first overshoot of the response from the final set value to the deviation of the second overshoot from the final set value when a small step-like input change occurs. be. The width reduction ratio has a design limit standard that must be observed under all operating conditions expected during reactor operation, and an operating standard that allows for a margin to ensure good stability characteristics during actual operation. Furthermore, the reduction ratio includes a reduction ratio for channel stability (channel hydraulic stability) and a reduction ratio for core stability. The reduction ratio for channel stability is determined by the coolant flow rate, and the limit criterion is 1.0,
The operating standard is 0.5, the reduction ratio for core stability is determined by the core output, and the limit standard is 1.
0, driving standard is 0.25. The smaller the coolant flow cap and the higher the core power, the higher the detour rate becomes, and the ratio of two-phase pressure loss to single-phase pressure loss becomes larger. The width attenuation ratio becomes large and the channel stability deteriorates.

In general, the reduction ratio for channel stability is greatly influenced by the power distribution of all the fuel channels that make up the reactor core. This power distribution includes a radial power distribution and an axial power distribution. FIG. 1 shows the channel stability reduction ratio with respect to the radial peak coefficient, and as is clear from the figure, in the radial output distribution, the larger the radial peak coefficient, the worse the channel stability becomes.

In addition, in the axial output distribution, the phase stability where the peak position is downward becomes worse. This is because if the peak position is located below, voids 9 will occur early in the coolant flowing from the lower end of the core, increasing the pressure loss in the two-phase portion.

Figure 2 shows the relationship between core coolant flow M (flow ratio to rated) and reactor power (output ratio to rated), assuming a constant radial peak coefficient, and shows the range shown by diagonal lines. is the range of allowable coolant flow rate and reactor power during normal operation.

Further, FIG. 3 shows a region where unstable conditions are satisfied based on the relationship between output and flow rate, and the shaded area is the unstable region.

[Problems with background technology]

Conventionally, when operating a nuclear reactor, operating conditions have been restricted to prevent stability from deteriorating, that is, from reaching unstable conditions.

Therefore, the burden on the operator is heavy, and this improvement has been discounted.

[Purpose of the invention]

An object of the present invention is to provide a nuclear reactor operation monitoring device that can reduce the burden on operators during reactor operation, alleviate all operational constraints, and improve reliability and safety.

[Summary of the invention]

The reactor operation monitoring device according to the present invention detects the axial power distribution signal of the reactor core and the core power output based on the power detection signal sent from the in-core instrumentation corresponding to an outstanding number of fuel channels that divide the reactor core in the radial direction. an arithmetic circuit that outputs a signal, an auxiliary arithmetic circuit that inputs the flow signal sent from the core flow I instrumentation and the axial power distribution signal and outputs a core output signal, and each of the fuel channels. The axial power distribution signal, the core output signal, and the core current signal, which are provided corresponding to each case, are input, and when these signals deviate from the stability setting range preset to maintain reactor stability, A stability setting device for the number of aircraft that outputs a stability loss signal according to the situation, and a control system to restore reactor stability by inputting the stability loss signal output from one of the stability setting devices. Stick drive &! 1 and a stability recovery device that operates the control device.

[Embodiments of the invention]

FIG. 4 shows an embodiment of the present invention, in which numeral 1 indicates a nuclear reactor pressure vessel. Inside the pressure vessel 1, a core 4 is constructed by loading a core support 2 with a large number of fuel assemblies 3. and the lower plenum 6. Cooling water 7 is housed inside the reactor pressure vessel 1, and a steam separator 8 and a steam dryer 9 are housed in the upper part of the pressure vessel 1. Further, a main steam piping 1o is connected to the peripheral wall soil portion of the pressure vessel 1, and a main steam isolation valve 11 is inserted into the main steam piping 10. Further, a water supply pipe 13 for supplying water into the upper glenum 5 from a water supply pump f12 is connected to the peripheral wall of the pressure vessel 1.

Then, the cooling water 7 is heated and boiled by the heat generated by the nuclear reaction of the uranium fuel in the fuel assembly s, and is separated into steam and water by the steam-water separator 8, and then sent to the steam dryer 9. The steam is then dried and sent through the main steam piping 10'.1 to a turbine (not shown) for driving the 11 steam generators. After driving the turbine there, a water purifier (not shown)
The water flows into the reactor pressure vessel 1 and is then supplied to the reactor pressure vessel 1 again by the water supply pump 12 through the water supply pipe 13.

Furthermore, control rods 14 containing neutron absorbing material between the fuel assemblies 3 are inserted into the core 4 from below. These control rods 14 are individually driven up and down by a control rod drive mechanism 15 provided at the bottom of the reactor pressure vessel 1, and are configured to control the output in the reactor core 4. There is. In addition, the control rod drive mechanism 15.
... are controlled by the control rod drive control device 16.

At the top of the core support 2, jets 17 for forced coolant circulation are supported around the core 4, and are used to send cooling water 7 in the upper plenum 5 to the lower plenum 6. Like mfJX, it is. The core 4 is provided with in-core gauge devices 8 corresponding to each of a plurality of fuel channels divided in the radial direction, and
A core current meter device 9 is provided for detecting the coolant flow nt in the reactor. Then, the output detection signals a... from each of the in-core measuring devices 8... are sent to the reactor output detection circuit 20, and based on the core output signal output from this device @20, the operator needs to It is configured to allow you to perform various operations.

In the figure, reference numeral 1 indicates a reactor operation monitoring device installed outside the reactor pressure vessel 1, which is configured as follows.

In the figure, 22 is an arithmetic circuit, a zsd reactor stability auxiliary arithmetic circuit.

The arithmetic circuit 22 outputs an auxiliary signal cf large input regarding the core power distribution from the reactor power instrumentation circuit 2°, an axial power distribution signal d, and a core output signal e.

Further, the reactor stability auxiliary calculation circuit 23 uses the axial power distribution signal d from the j calculation circuit 22 and the core flow meter device 9.
The flow rate signal f for each fuel channel is inputted, and the flow rate signal gk ratio is outputted.

In the figure, 24... is a stability setting device provided correspondingly to each fuel channel, and this is the stability monitoring path 25.
and a stability setting circuit 26.

The stability monitoring circuit 25 inputs the axial power distribution signal d from the arithmetic circuit 22 and the core flow rate signal g from the reactor stability auxiliary arithmetic circuit 23, and calculates the function of the axial power distribution and the core flow rate. The fuel assembly stability limit output is determined, and a fuel assembly stability limit output signal hi is output. An example of this functional formula is as follows.

(1) - In the case of the following formula...Y=AX+
B However, X is the book indicated by the core flow flit rating,
Y indicates the fuel assembly stability limit output in rated chi, and corresponds to (1) in FIG.

(2) In the case of quadratic formula...Y=AX2+B
The line X corresponds to the broken line curves (2) in FIG. 5 and FIG. 6. Figure 5 shows the relationship between core flow jlt (rated %) and reactor radial power (rated %), and Figure 6 shows the relationship between reactor axial power and the width reduction ratio for channel stability. It is a figure showing related money.

In the case of the quadratic equation, it is possible to set the stable allowable output signal level by approaching the unstable region shown in the shaded area in Figures 3, 5, and 6, so the - The operable area is expanded.

Here, when the axial position of the fuel channel is t-2, the axial output coefficient H is expressed as H=F(Z). Therefore, based on the conventional average power coefficient H=F (Z), the limit power pl that causes channel oscillation can be determined for a specific core flow tx. Further, when the stability limit output for an arbitrary output coefficient H is defined as P, a new limit output rlt can be obtained as the PZPo total Po coefficient from Y'=p/p -Y (where Y=AX+B).

In addition, the limit output Y can be calculated directly from the core flow rate X and the axial position 2.
It may be seven as in finding lf. Further, the limit output Y may be obtained not only from a functional equation such as a linear equation or a quadratic equation, but also from a numerical table prepared in advance.

The stability setting circuit 26 inputs the fuel assembly stability limit output signal from the stability monitoring circuit 25 and the core output signal e from the calculation path 22, and compares their signal levels. When the core output signal exceeds the fuel assembly stability limit output signal hl, a stability loss signal corresponding to the state, that is, a control rod withdrawal prevention signal i1, a selected control rod insertion signal j, or an all control rod insertion signal ki is output. At the same time,
It is configured to output an operator alarm signal t.

In addition, 27 in Fig. 4 is a reactor stability recovery installation, and this device 27 includes a control rod withdrawal prevention circuit 28 and a selective control rod insertion circuit 2.
◎ The control rod withdrawal prevention circuit 28 is composed of the control rod emergency insertion circuit 3o and the control rod emergency insertion circuit 3o.
4 When control rod withdrawal prevention signal i is output, from then on,
The control rod drive control device 16 is operated so that the control rods 14... are not pulled out.

Further, the selective control rod insertion circuit 29 inserts only the control rods 14 selected in advance into the reactor core 4 when the selective control rod insertion signal j is output from any of the stability setting circuits 24. Activate control rod drive controller #16.

When the control rod emergency insertion circuit 30 receives the control rod emergency insertion signal k from any of the stability setting circuits 24,
The control rod drive control device 16 is activated so that all control rods 14... are inserted urgently.

Furthermore, when the operator alarm signal t is output, the frog alarm 31 is configured to operate as an alarm to notify the operator that an operating condition that will impair reactor stability is approaching.

With the above configuration, when operating conditions that impair reactor stability are approached, the stability setting circuit 24 outputs a control rod withdrawal prevention signal (a selected control rod insertion signal) according to the condition. etc. is output to the j1 all control rod insertion signal, and the reactor stability recovery device 27 operates the control rod drive control device 16 to prevent control rod withdrawal, selective control rod insertion, all control rod emergency insertion, etc. , the reactor stability is automatically maintained.At the same time, the alarm 31 is activated, so operators can easily know that they are approaching operating conditions that will impair reactor stability. At least one of the control rod withdrawal prevention signal i, selected control rod insertion signal, and all control rod emergency insertion signals can be output. Then, the output will not increase any further, and the region where unstable conditions will no longer be reached will be avoided, making it possible to improve the safety and reliability of nuclear reactor operation.

〔Effect of the invention〕

As described in detail above, the reactor operation monitoring device according to the present invention detects power in the axial direction of the reactor core based on output detection signals sent from the in-core instrumentation corresponding to the joint fuel channels that divide the reactor core in the radial direction. an arithmetic circuit that outputs a power distribution signal and a core output signal; an auxiliary arithmetic circuit that receives the cover signal sent from the core flow rate signal and the axial power distribution signal and outputs a core flow rate signal; The axial power distribution signal, the core output signal, and the reactor core output signal are inputted and the situation is determined when these signals deviate from the stability setting range preset to maintain reactor stability. multiple stability setting devices that output all stability loss signals according to the stability setting device, and control rod drive control to restore reactor stability by inputting the stability loss signal output from any of the stability setting devices. The reactor is equipped with a stability recovery device that activates the device, thereby reducing the burden on operators and easing operational constraints to improve the safety and reliability of reactor operation. can.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the radial power peak coefficient and the channel stability reduction ratio; Figs. 2, 3, and 5 are diagrams showing the relationship between the coolant flow rate and the reactor output; FIG. 4 is a schematic configuration diagram showing one embodiment of the present invention, and FIG. 6 is a diagram showing the relationship between reactor output and width reduction ratio. DESCRIPTION OF SYMBOLS 1... Reactor pressure vessel, 4... Reactor core, 1... Cooling water, 14... Control rod, 15... Control rod drive mechanism, 1
6...Control rod drive control device, JU...Reactor operation monitoring device, 22...Arithmetic circuit, 23...Reactor stability auxiliary calculation circuit, 24...Stability setting device, 25...
Stability monitoring circuit, 26... Stability setting circuit, 27...
・Reactor stability recovery device, d... Axial power distribution signal, e... Core output signal, f... Fluit signal, g...
- Core current signal, h...Fuel assembly stability limit output signal, t...Control rod withdrawal prevention signal, j...Selected control rod insertion signal, k...All control rod insertion signal.

Claims (2)

[Claims] (1) an arithmetic circuit that outputs a core axial power distribution signal and a core output signal based on power detection signals sent from in-core instrumentation corresponding to a plurality of fuel channels that divide the core in the radial direction; an auxiliary calculation circuit that inputs the flow cap signal sent from the core flow meter and the axial power distribution signal and outputs the core output signal; and an auxiliary calculation circuit that is provided corresponding to each of the fuel channels and the axial power distribution signal. ,
When the core output signal and the core flow m signal are input and these signals deviate from the stability setting range preset to maintain full reactor stability, the number of output signals that outputs a loss of stability signal according to the situation is determined. A stability setting circuit, and a stability recovery device that manually operates a control rod drive control device to restore reactor stability by manually receiving stability loss signals output from one of the stability setting devices. A nuclear reactor operation monitoring device characterized by comprising: (2) The stability setting device includes a stability monitoring circuit that inputs the axial power distribution signal and the core output signal and outputs a fuel assembly stability limit output signal, and a stability monitoring circuit that inputs the axial power distribution signal and the core output signal and outputs a fuel assembly stability limit output signal; Claim 1 is characterized by comprising a stability setting circuit which inputs the stability limit output signal and the core output signal and outputs the stability loss signal.
) Nuclear reactor operation monitoring device described in section 2.