JPS58106493A - 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] (g) Technical Field of the Invention The present invention is directed to a forced circulation boiling water nuclear reactor that prevents the stability of the reactor output or the flow stability of the coolant from being impaired. Reactor stability control system.

2) Technical background of the invention and its problems Boiling water nuclear reactors are designed to maintain the inherent stability of the reactor under various expected operating conditions. Channel hydraulic stability and core stability can be considered as reactor-specific stability. In the former case, vibrations in the coolant flow impede heat transfer to the moderator;
This also examines the thermal and hydraulic stability within the channel that causes fluctuations in the reactor output, and the latter considers the stability due to the reactivity feedback effect of the entire reactor. To evaluate these stability levels, the width reduction ratio is used in the design of boiling water reactors. That is, the second overshoot of the response to a minute step-like human force change is defined as the ratio of the deviation to the final settling of the '14/oats (-shoot). The width reduction ratio (referred to as the limit standard) that must be maintained under all operating conditions, and the design margin that is expected to ensure good stability during operation during operation. The width reduction ratio (referred to as the operational design basis) is defined as unfavorable.The width reduction ratio of channel hydraulic stability is defined as /
, 0 , 0.3, and the width reduction ratio in core stability is i,
o, o, rs.

These stability deteriorates as the coolant flow rate decreases and as the output decreases, the reduction ratio increases. Considering channel stability, the lower the coolant flow rate and the higher the output, the larger the void volume ratio becomes, and the ratio of λ phase pressure loss (pressure loss) to single phase pressure loss (pressure loss) becomes larger. deteriorates channel hydraulic stability. Furthermore, if the void volume ratio is large, the void reactivity coefficient will have a large negative value, and the core stability will also deteriorate.

In the prior art, operating conditions are attached to limit the operation under the above-mentioned unstable conditions. Figure 1 is an operating state diagram showing the relationship between reactor coolant flow rate (relative to rated) and reactor output (% of rated). These are seven examples of coolant flow 1 and reactor power conditions. The conventional technology added restrictions to prevent operation outside this range, and was a passive measure that merely provided a fence.

3) Purpose of the Invention In recent years, there has been a technological trend of improving nuclear reactor design technology and expanding nuclear couplant operability. Therefore, in response to the generalization of electronic and computer technology in recent years, we are monitoring nuclear reactors by making full use of equipment configuration and computer application technology, and are not simply restricting them as in the past, but when approaching unstable operating conditions. This system is designed to detect this situation and proactively take measures to prevent it from becoming even more unstable, thereby improving safety performance with higher reliability, reducing the burden on operators, and reducing operational constraints. It is an object of the present invention to improve the operational performance of a nuclear reactor, such as by reducing the

lI) Structure of the Invention The present invention provides a forced circulation type boiling type nuclear reactor equipped with a selective control rod insertion device, reactor power instrumentation based on reactor side base signals, in-reactor coolant flow side instrumentation, and control rod position detection device. In the reactor, a signal indicating the safety level of the stability of the reactor output and the flow stability of the coating material is calculated based on the signals transmitted from the reactor power instrumentation and the in-reactor coolant flow instrumentation, and this is A safety monitoring device that sends out a safety level display signal, a safety level setting device that compares the signal level of a preset signal and the above safety level display signal and outputs a safety maintenance signal based on the difference, and a safety maintenance signal. In response to this, a selected control rod insertion or stop signal is issued.
A selective control rod insertion control device that performs a preset selective control rod insertion, and a selective control rod that indicates that the selective control rod has been inserted for a preset insertion amount based on a control rod position signal from a control rod position detection device. It consists of a selection control rod insertion confirmation device that transmits an insertion attraction signal.

Embodiment of the Invention An embodiment of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a reactor pressure vessel of a boiling water reactor, and the reactor pressure vessel 10 has an in-core instrumentation system or an in-core meter for instrumenting the reactor output. Pipe mounting/
2 and a reactor coolant raw stone instrumentation 3 for measuring the flow rate of the coolant flowing into the reactor core are installed, respectively.

In-core instrumentation 7.2 is reactor power instrumentation/! connected to the stability monitoring device/7 of the reactor stability control device/6 via i;
The in-core instrumentation signal /g is input to the reactor output splitter /S, and a reactor output signal /9 corresponding to this input signal is output,
This reactor output signal/? and is input to the stability monitoring device/7. This monitoring device/7 has a reactor coolant flow meter/
,? The coolant flow rate signal -〇 is input.

On the other hand, the reactor stability control device/l is the stability monitoring device/l.
7. Stability setting device 2λ, selection control rod insertion confirmation device, 23
and a selection control rod insertion confirmation device review. Stability monitoring device/7 has reactor coolant flow metering/? and the reactor power instrumentation/S corresponding to the in-core tIl signal J5 which is also the output of the in-core instrumentation/S.
An output signal t of the reactor output from is input at the same time, and a stability display signal J is output to the stability setting device λU. These 42 stability setters can be used for stability maintenance signal or stop signal,
27 is output to the selection control rod insertion control device, 23. Insert selective control rod; Mo1” control device-5? is selection it+I ll
1ll 4ii (Insert signal Yug to control rod drive controller H
The control rod drive control device 29 outputs a control rod drive control signal 30 to all control rod drives 1 and 1, and the operation of this control rod drive mechanism 3/ causes the control rods 3λ to move to the core part/l. It is taken in and taken out.

On the other hand, a control rod position detection device 33 is connected to the control rod drive 1, ? The control rod position signal 3B of the control rod 32 detected at j is input to the selected control rod confirmation device 21I. The selective control rod insertion completion signal 3 from the selective secondary rod confirmation device J is input to the stability monitoring device/7.

In addition, if the stability monitoring device is used, the stability display signal 8 transmitted from "/7" is the coolant flow rate signal 20 and the reactor output signal /9.
A numerical value indicating the degree of low fluorescence (e.g. attenuation ratio) as a function of
Obtain by calculating. The safety level setting device varnish has a setting signal 7da0 that determines the upper limit of the stability set in advance, and when the setting signal yo and the stability display signal yo are exceeded, a stability maintenance signal 2A is transmitted.

The selection control rod insertion control device 3 receives the stability maintenance signal λt and transmits a selection control rod insertion signal 2g, and the control rod drive control device 3, which received this signal, uses the auxiliary signal of the selection control rod. Control rod drive 1 allows insertion only to a preset amount of insertion.
31 will insert the control rod by the insertion amount.

F-? It is expressed as a function of (X, Y).

X indicates the signal level of the flow rate signal UO, Y indicates the signal level of the output signal/9, and F indicates the signal level of the stability display signal.
Specifically, it may be a function type. Alternatively, intermediate values may be interpolated by storing numerical values in a memory element or the like. As an example of the stability display signal, FIG. 2 shows an example of the stability reduction ratio, the total flow 1, and the output analyzed using the detailed design code. This gives an example of the function F(X,Y).

Further, an example of the setting level of the setting signal G0 is shown in Fig. AA (line attenuation ratio O0).

Now, as described above, the selected control rod is inserted by the preset auxiliary signals l/, / by the stability maintenance signal roller. In addition, in the case of a boiling water reactor, the control rod position detection device 3S has a device that transmits the control rod position signal 3A.
When the control rod is inserted by a preset insertion amount, the selected control rod insertion confirmation device 2 issues a selected control rod insertion completion signal 3. This selected control rod insertion end signal 37
Then, the stability monitoring device recalculates the stability based on the reactor output signal /9 at that time, the coolant flow l, and the signal J, and sends the stability display signal 5. Then, the signal level is compared with the signal level of the setting signal 3 which determines the lower limit of stability set in advance, and when the signal level of the stability maintenance signal is lower than the signal level of the setting signal 3, further selective control rod insertion is prohibited. Send a stop signal 27 to prohibit. Conversely, if the signal level of the stability display signal 2S is still higher than the setting signal yorz, the stability maintenance signal 26 is sent again and the selected control rod is fully reinserted.

That is, (1) A parameter indicating the degree of constant stability, such as the attenuation ratio, is calculated based on the output and flow rate.

(j) Set operating permissible parameters.

(3) If the parameter in (1) above exceeds the operating permissible parameter, selectively insert the control rod.

(ri) After inserting a certain amount, recalculate the stability parameter again.

α) If the recalculated value falls below the operation permissible parameter, stop selective control rod insertion, and if it does not fall below, select control rod insertion again.

This action is repeated.

The above effects can be summarized as follows.

Core stability will be explained using a stability attenuation ratio as an example of a stability display signal. The curve shown by a-a' in Figure 3 corresponds to curve A in the unstable region in Figure 1, and is the boundary line of the region where the market reduction ratio exceeds 0 and becomes unstable. . The curve indicated by b-b' is a contour line that satisfies the conditions for the attenuation ratios o and g, which are the set levels of the set signal shown in FIG. When the width reduction ratio approaches and exceeds O and S under operating conditions, a selective control rod insertion signal is activated, and a preselected control rod is inserted by a preset insertion amount. In Figure 3, operation is performed under the condition of coolant flow rate and reactor output shown at point A, the width reduction ratio is O, S, the selected control rod is inserted by the stability maintenance signal, and the flow rate output condition is set to B.
This shows that stability is maintained well. In this case, the width reduction ratio at point B is about 0.2.

In addition, the shaded area partitioned by curves A and B in Fig. 9 indicates combinations of reactor coolant flow 1゜ and reactor power for which unstable conditions (spanning ratio exceeds 80) are established. Among these, the unstable region A indicates instability due to the stability of the reactor core, and the other unstable region B indicates instability due to the hydraulic stability of the fuel channel.

FIG. S is a graph showing the relationship between the reactor output and the coolant flow rate, and the shaded area in the figure shows the allowable operating range that can guarantee safe operation of the reactor. In FIG. 7, the symbol ys is a main steam pipe equipped with a main steam isolation valve 6, and the symbol 7 is a water supply pipe equipped with a water supply pump. Symantei 9 is a reactor coolant forced circulation pump,
The symbol SO is a steam/water separator.

6) Effects of the Invention As described above, according to the present invention, the operating state can be controlled while monitoring the stability during operation of the nuclear reactor, and the stability can be prevented from approaching an unstable condition. In other words, it is controlled to maintain the most stable conditions at all times, ensuring that the inherent stability of the reactor is not impaired, reducing the burden on reactor operators, and ensuring safe operation of the reactor. Further improvement can be expected.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing an example of a function for setting the signal level of the stability display signal used in the reactor stability control rack-4 according to the present invention. , FIG. 3 is a graph illustrating the operating state of a nuclear reactor when the present invention is implemented, FIG. 9 is a graph showing a region where unstable conditions of the reactor hold, and FIG. It is a graph showing a driving tolerance range. 10...Reactor pressure vessel, //...Reactor core, 7.2
... In-reactor instrumentation, /3 ... Reactor coolant flow rate instrumentation, /
! r... Reactor power instrumentation, /B... Reactor stability control device, /7... Stability monitoring device, /Z... In-reactor instrumentation signal, 19... Reactor power Signal, -〇... Coolant flow rate signal, 〃... Stability setting device 1.23... Selective control rod insertion control device, Koku... Selective control rod insertion confirmation device, 2S... Stability Display signal, Kootsu... Stability maintenance signal, 27... Stop signal, -g... Selected control rod insertion signal, 29... Control rod drive control device, 30... Control rod drive control signal , 3/... control rod drive mechanism, 32...
Control rod, 39...Control rod position detection device, 3O...Control rod @ position signal, 37...Selected control rod insertion end signal, Gθ, DA3...Setting signal.

Claims (1)

[Claims] In a forced circulation boiling water reactor equipped with a 1-selection control rod insertion device, reactor output instrumentation based on in-reactor instrumentation signals, in-reactor coolant flow metering, and control rod position detection device, A signal level indicating the degree of stability of the reactor power or coolant flow is calculated as a function of the output signal emitted from the reactor power instrumentation and the w-force signal emitted from the in-reactor coolant flow instrumentation. a stability monitoring device that transmits a stability display signal; a stability setting device that compares a preset signal level with the signal level of the stability display signal and outputs a stability maintenance signal corresponding to the difference; A selective control rod insertion control device that issues a selected control rod insertion or stop signal based on a sex retention signal and inserts a selected control rod selected in advance, and a control rod position detection device that receives a position signal of the selected control rod and inserts the selected control rod. A reactor stability control device comprising a selective control rod insertion confirmation device that transmits a complete selective control rod insertion signal when only a preset insertion tube is inserted. Insertion end signal selection The control rod insertion end signal is sent to the stability monitoring device, and the stability monitoring device again calculates and transmits a stability display signal from the nuclear power output signal and coolant flow rate signal at that time. The nuclear reactor stability control device according to claim 1, characterized in that the same subsequent operations are repeated. 3. In the C-th and subsequent operations of the repeated operations, the signal level of the stability display signal is When the signal level falls below the stability lower limit setting signal set in the stability setting device, a stop signal is sent to the selective control rod insertion control device to prohibit insertion of any more selected control rods. A nuclear reactor stability control device according to claim 1.