JPS5896283A - Reactor stability control 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 l) Technical Field of the Invention The present invention relates to a boiling water temperature nuclear reactor that constantly monitors and controls the stability of reactor output or the stability of coolant flow so that these are not impaired. Regarding safety control devices.

f) Technical background of the invention and its problems Boiling water fox reactors are designed so that the inherent stability of the reactor is not impaired under various expected operating conditions.

Channel hydraulic stability and core stability are examined as the unique stability characteristics of nuclear reactors. Channel Hydraulic Stability and Cooling Consider the thermo-hydraulic stability in channels where oscillations in the flow rate impede heat transfer to the moderator, thereby causing pulsations in the reactor power. It is something. Core stability refers to the stability of the entire reactor due to the reactivity feedback effect. The annihilation ratio is used to evaluate the stability of these reactors in the design of boiling water reactors. That is, the first overshade in response to a minute step-like input change is defined by the ratio of the deviation of the first overshade to the final set value. The design also takes into account the reduction width ratios (referred to as limit criteria) to be met under all operating conditions expected during plant operation, and the design considerations to ensure good stability characteristics in actual operation. As a margin, an annihilation ratio (referred to as an operational design standard) is defined, beyond which it is undesirable. The annihilation ratio of channel hydraulic stability is /, 0.0.1, respectively, and that of core stability #i
/, 0.0.1! It is.

The lower the coolant flow rate or the higher the output, the larger the attenuation ratio becomes, and the stability becomes worse. Considering channel stability, the lower the coolant flow rate or the higher the output, the larger the void volume ratio becomes, and the ratio of co-phase pressure drop to single-phase pressure drop becomes larger, which worsens channel stability. Furthermore, if the void volume ratio is large, the made reaction coefficient becomes large with a negative value, which deteriorates core stability.

In the conventional technology, operating conditions are set to prevent operation under the above-mentioned unstable conditions.

Figure 1 is an operating state diagram showing the relationship between reactor coolant flow rate and reactor power (both expressed as percentages of rated power). The shaded range in the figure is an example of conditions for the reactor coolant flow rate and reactor output that are allowable during normal operation. This system in the prior art was only a negative measure.

J) Purpose of the Invention The main purpose of the present invention is to provide a reactor stability control system for a nuclear reactor that corresponds to the recent technical trends of improving nuclear reactor design technology and expanding nuclear couplant operability. .

In addition, in response to the generalization of electronic technology and computer technology in recent years, another purpose is to monitor unstable operation by monitoring equipment configuration and computer application technology, rather than restricting operating conditions as in conventional technology. Once the reactor approaches the area, it actively prevents it from approaching the unstable condition any further, reducing the burden on operators, easing operational constraints, and improving reactor operational performance. It is an object of the present invention to provide a nuclear reactor stability control device for a nuclear reactor that can improve safety performance by preventing the occurrence of such problems.

DESCRIPTION OF THE INVENTION The present invention provides an emergency insertion device for all control rods, a device for inserting control rods selected in advance, a warning device for operators, a reactor output instrumentation based on in-reactor instrumentation signals, and an in-reactor coolant flow instrumentation. In a forced circulation type boiling water reactor with , the signal level of the reactor output signal emitted from the reactor power instrumentation is compared with the signal level of the stability allowable output signal, and when the former signal level exceeds the latter signal level, a stability maintenance signal is issued. The stability setting device outputs signals, and the stability maintenance signal outputs control rod withdrawal prevention, selected control rod insertion, all control rod insertion, alarm, and recirculation flow rate change signals, and controls all or some of these operations. and a stability control device that performs the combination.

j) Embodiments of the Invention Figure 1 is a chart showing the region where the unstable condition (the annihilation ratio exceeds /, 0) is expressed in terms of reactor output and reactor coolant flow rate. An embodiment of the present invention will be described below with reference to FIG.

In Fig. 2, the reactor pressure aS of the boiling edema reactor according to the code /#f main power plant 11IK is shown, and the reactor pressure aS in this pressure vessel l is shown.
A reactor core is constructed by combining and installing fuel assemblies, etc. (not shown). Reactor coolant is supplied into the reactor core by the operation of a reactor coolant circulation pump J. This reactor coolant tank is supplied to the peripheral area inside the reactor pressure vessel l by the operation of the water supply pump j, and the supplied coolant 41Fi
It is supplied to the lower plenum by the pump operation of the circulation pump 3 and then guided into the core a.

The coolant guided to the reactor core is heated and boiled while passing through the reactor core, and is guided to the upper plenum via the steam separator 6. The heated coolant vapor guided to the upper plenum 7 is then taken out from the main steam pipe t via the main steam isolation valve d,
It is adapted to drive a turbine of a generator (not shown).

Condensate (coolant) that drives the turbine and whose temperature has been lowered in a condenser (not shown) is returned to the reactor pressure vessel l by the operation of the reactor feed water pump j.

On the other hand, a reactor coolant flow meter (device) is installed at the lower part of the reactor core in the reactor pressure vessel l, and this flow meter 13 is a reactor stability control device i.

electrically connected to. Reactor stability control device 10Fi
, stability monitoring value//, stability setting device/-, and stability control device 13. The stability monitoring device is a reactor coolant flow meter! Input the flow rate signal 16 from
A stability allowable output signal 17 is output to the stability setting device l.

Furthermore, input the reactor output signal/1 to the stability setting device l. The reactor output signal /l is a signal that the in-core instrumentation signal - which is the output from the in-reactor instrumentation X, is input to the reactor power instrumentation and output from there.

The stability setter I receives the stability allowable output signal 17 and the reactor output signal /1 and outputs a stability maintenance signal 24I to the stability control device 13.

Stability control device 13 alarm alarm ko to alarm signal, control rod withdrawal prevention control device core to control rod withdrawal prevention signal ko, selective control rod insertion device knob to selection control rod insertion signal JO, control rod emergency insertion device A full control rod insertion signal JJ is output to J/. The control command signal S from each of the above-mentioned device cores, cots, and J/ is input to the control rod drive device Jj, and a control rod drive signal J6 is output. The control rod drive signal 34 is input to the control rod drive device, and the control rods are driven.

In addition, in FIG. 3, reference numeral 1 is a control rod drive device that controls the insertion and removal of control rods 1I10 inserted into the core of the nuclear reactor.

Next, the operation of the present invention will be explained.

The nuclear reactor stability control device IO of the present invention is configured as described above, but these can be configured by an electric computer.

An example of an equation for the stability monitoring device// to calculate the stability allowable output signal 16 using the flow rate signal 16 from the reactor coolant flow meter/j is・X+1. (X is the reactor coolant flow rate, and y#i is the stability allowable output signal, each expressed as a rated percentage.) However, the reactor differential pressure, jet pump flow rate, and recirculation pump flow rate may be directly taken as the core flow signal. Further, the reactor coolant flow rate may be selected as these calculation equations. The following figure shows the stability allowable output signal level expressed by a function expressed by a linear equation of the recirculation drive flow rate, taking a jet pump type boiling water reactor as an example.

In the case of a quadratic equation, it is expressed as Y-muX"+lX+C (x,
The definition of y is the same as for the linear equation). - If the following formula is used, the stability can be determined by setting the stability allowable output signal close to the condition where stability is considered to be actually impaired (the unstable area explained by the diagonal line in Figure 3), so the operation The range of possibilities expands.

Next, the stability allowable output signal 17 level calculated by the stability monitoring device // and the level of the reactor output signal /l generated from the reactor output signal u by the reactor internal instrumentation (device) 27 are compared by a stability setter, and as a result, when the latter signal level exceeds the former signal level, a stability maintaining signal evaluation is issued. The stability control device/J is activated by receiving this stability maintenance signal 2da, and transmits a control rod withdrawal prevention signal, a selected control rod insertion signal Jθ, a full control insertion signal Jθ, and an alarm signal. .

The control rod withdrawal prevention control device J7 is activated by the signal X and prohibits withdrawal of the control rod after the signal d is issued. signal a
The operation of the selective control rod insertion device by OK causes only the preselected control rods to be fully inserted into the reactor core. Signal 3 activates the control rod emergency insertion device J/ to quickly fully insert all control rods.

The alarm signal activates the alarm, alerting the operator to approaching operating conditions that may compromise stability.

4) Modification of the invention As a modification of the invention, as shown in FIG. Ko, selection control rod insertion signal 30. Set separately for all three control rod insertion signals. By doing this, an emergency shutdown of the reactor will not occur, and the power level will be limited to warning the operators and preventing the control rods from being withdrawn, and if unstable conditions approach, the selected control rods will be activated. In addition, if unstable conditions are approached, the reactor will be scrammed, resulting in unnecessary shutdown of the plant.

As another variation, since the reactor pressure vessel due to the in-core instrumentation signal has a large noise component and the signal itself is unstable, an atomic In a boiling water reactor having a signal (TPM) equivalent to the reactor thermal output, the TPM signal is taken as the reactor output signal/l.

7) Effects of the invention FIG. 4 shows the overall effect of the invention from another angle. The relationship between the reduction ratio of channel hydraulic stability and the reactor output is shown in so-called human characters. The shaded area has an opacity ratio of 7.
, is the range in which the unstable condition exceeding 0 is satisfied. The dotted line indicates the extinction ratio of the channel hydraulic stability at the point that provides the stability permissible output signal level shown by the solid line in Figure 3.

a) This dotted line is set below the annihilation ratio/0, where the unstable condition is satisfied. b) If you increase the output from this dotted line (for example, if you increase the output along the natural IIR)
Stability permissible output signal level exceeded. C) From the present invention,
Alarm signal, control rod withdrawal prevention signal 1 selection control rod insertion signal,
All or any of the control rod insertion signals are activated and no further power increase is possible. d) Therefore, it is impossible to approach the region where unstable conditions hold, and unstable reactor operation is impossible.

Core stability is shown in Figure 7, but the content is the same as Figure 4.

In summary, the present invention notifies operators when a nuclear reactor approaches unstable conditions, and at the same time prevents further approach through internal operations, thereby ensuring stable operation and providing wide operational flexibility. It is something to give.

[Brief explanation of drawings]

Fig. 1 is an operating state chart showing the relationship between reactor coolant flow rate and reactor output; Fig. 1 is a chart showing the region where unstable conditions are established in terms of output and flow rate; The configuration diagram showing the embodiment, Figure 1 is a chart of the stability allowable output signal level expressed by the function expressed by the 7th order equation of the recirculation flow rate, and Figure 5 is the same multiple "9 stability allowable output signal level set. Figure 6 is the reactor power and channel hydraulic stability output chart, and Figure 7 is the reactor power and core stability output chart. Reactor core, 3... Reactor coolant circulation pump, D... Reactor coolant, 4... Steam water separator, 7... Upper plenum, 10... Reactor stability control device, / /...stability monitoring device, lco...
Stability setting device, 13... Stability control device, /j...
Reactor coolant flow meter (device), /t...flow signal, 1
7... Stability allowable output signal, /1... Reactor output signal, N... In-reactor instrumentation (equipment), Evaluation... Stability maintenance signal, Correction... Alarm, Mu... ...Alarm signal, core...control rod withdrawal prevention control device, core...control rod withdrawal prevention signal,
Cob...Selective control rod insertion signal, 3o...Selective control rod insertion signal, 31...Control rod emergency insertion device, 3J...
Control rod emergency insertion signal, j! ...control rod drive control device,
36...Control rod drive signal. Figure 6 Single reactor group jJ (%) Figure 7 Atomic lf' Hatake A (%)

Claims (1)

[Claims] l All control rod emergency insertion device, pre-selected control rod insertion device, operator warning device, reactor power needle based on in-reactor instrumentation signals! In a forced circulation type nuclear reactor with I and in-core coolant flow metering, the stability control system calculates the stability allowable output from the flow rate signal emitted from the in-core coolant flow meter and transmits the stability allowable output signal. The stability monitoring device compares the signal level of the reactor output signal emitted from the reactor output signal with the signal level of the stability allowable output signal, and determines that the signal level of the output signal exceeds the signal level of the stability allowable output signal. A stability setting device that sometimes issues a stability maintenance signal, and a stability maintenance signal that outputs a control rod withdrawal prevention signal, selected control rod insertion signal, all control rod insertion signal, alarm signal, and recirculation flow rate change signal, A nuclear reactor comprising a stability control device that operates in combination with rod withdrawal prevention, selective control rod insertion, control rod emergency insertion, operator warning, and recirculation 1aR amount change. Furnace stability control device. 1 Multiple stability allowable output signals can be set, and the control rod withdrawal prevention signal, selected control rod insertion signal, all control rod insertion signal, alarm signal, and recirculation III flow rate change signal can be sent as separate output signals. 2. A reactor stability control system for a nuclear reactor according to claim 1, further comprising a stability setting device capable of controlling the stability of a nuclear reactor.