JPS61225503A - Controller for feedwater of nuclear reactor - 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 feed water control device that controls a nuclear reactor feed water pump and maintains a constant water level in the reactor.

[Technical Background of the Invention] In general, for boiling water reactors, a reactor standard water level that is necessary for stable operation of the reactor is determined, and this reactor standard water level is determined in any operating state of the reactor. The deviation of the reactor water level from the water level must be within the permissible range, in case.

If the reactor water level deviates from this allowable range, the reactor power must be reduced or the reactor must be shut down, and maintaining the reactor water level at the standard value is extremely important in boiling water reactors. It is. On the other hand, the reactor water level is subject to constant fluctuations due to the change in the flow rate of steam flowing out from the reactor to the turbine depending on the reactor output. Must be controlled. A reactor feed water control device is provided for this purpose.1 Usually, by changing the rotational speed of the reactor feed water pump or the opening degree of the flow rate adjustment valve provided at the outlet of the reactor feed water pump, Controls the flow rate of water supplied to the reactor.

Fig. 4 shows an example of this, in which 1 is a reactor 92, a water supply pump for feeding water into the reactor, and 3 is a flow rate adjustment valve provided at the outlet of the water supply pump 2 to adjust the water supply flow rate. , 4 is a water level setting device that provides a water level reference signal, 5 is a water level detector that detects the reactor water level, and 6 is a water level reference signal L1 from the water level setting device 4 and a water level signal L2 from the water level detector 5.
a first computing unit that inputs and computes a water level deviation signal;
7 is a water level controller that inputs a water level deviation signal and calculates a flow rate command signal [, 4; 8 is a flow rate detector that detects the flow rate of the water supply pump; 9 is a pump flow rate signal from the flow rate detector 8; and the flow rate controller output signal L7, and if the pump flow rate is low, select the flow rate controller output signal, and if the pump flow rate is not low, select the pump flow rate signal, and select the selection signal L.
8 is a switching contact that outputs, 10 is a flow rate command signal from a water level controller 7, and 4 is a switching contact output signal. a second computing unit that inputs and computes a flow rate deviation signal LG.

Reference numeral 11 denotes a flow rate controller which inputs the flow rate deviation signal L6 and drives the flow rate regulating valve 3, and calculates the flow rate controller output signal L7.

FIG. 5 is a block diagram showing the operation of the above configuration,
G1 (S) is a transfer function representing the water level controller 7, G2 (S
) is a transfer function representing the flow rate controller 11, G, (s) is a transfer function representing the flow rate regulating valve 3, and G4 (S) is a transfer function representing the nuclear reactor 1. At this time, the pump flow rate is not low (that is, the switching contact 9 does not indicate the pump flow rate signal).

), then the transfer characteristic from the water level reference signal Li (S) to the flow rate control deviation signal Li (S) is expressed by the following equation.

Normally, the water level controller 7 is expressed as a proportional gain, the flow rate regulating valve 3 is O-type (i.e., 11111G3(S) = finite), the reactor 1 is expressed as an integral characteristic, and the flow rate controller 11 usually includes an integral element. , and for a step-like change in L (S), by using the final value theorem of Laplace transform, the steady value of LG becomes =O (3). Therefore, the flow rate command signal is 4 and the pump flow rate signal is output.
match, and the flow rate of the water supply pump 2 is controlled by the water level controller 7. However, when the water supply pump 2 is stopped, the flow rate signal is always output regardless of the opening degree of the flow rate adjustment valve 3.
= O, and the flow rate command signal does not match L6≠0...
(4), that is, since the flow rate controller 11 includes an integrator, the flow rate controller 11 is saturated according to the above equation (4), and the opening degree of the flow rate regulating valve 3 is always in a fully open state. There is.

On the other hand, in a general atomic coupler plant, a plurality of water supply pumps are installed, and normal water supply control is performed using some of these pumps (for example, 2 out of 4 pumps).

The remaining feedwater pumps are for backup purposes and are normally stopped, but in the event of a malfunction of the normal water supply pump, or if there is a possibility that the reactor water level deviates from the permissible range and drops rapidly, it will be automatically started. , designed to supply water. However, as mentioned above, if the flow rate controller 11 is saturated when the pump is stopped, the flow rate of the automatically started water supply pump is 100% or a value close to it.
For a certain period of time until the saturation of No. 1 is eliminated, the water will flow in an uncontrolled state, and on the contrary, it will become supercharged water, causing the reactor water level to rise rapidly and deviate from the permissible range.

Therefore, even when the water supply pump 2 is stopped.

The switching contact 9 is provided to prevent the flow rate controller 11 from becoming saturated. In the case of pump flow rate paper, the switching contact 9 selects the flow rate controller output signal L1, so the transfer characteristic from the flow rate command signal L4 to the flow rate controller output signal L7 is as follows. Therefore, from the final value theorem of Laplace transform and equation (2), in steady state, L, = L,
(5), the flow rate controller 11 is not saturated even when the water supply pump is stopped, and the flow rate controller output signal L7 is maintained at the same value as the flow rate command signal L4. It turns out.

[Problems with the background art] However, this is only a characteristic during steady state;
When the switching contact 9 is switched, the flow rate controller output signal L7 and the pump flow rate signal are output, and unless they match, the flow rate deviation signal L6 becomes L4 when the pump flow rate is not low and when it is low, respectively, as shown in FIG. -L, and L4-L, resulting in a flow deviation signal and a bump. This is because the switching contact 9 switches between the flow rate controller output signal L7 and the pump flow rate signal, and if there is a deviation between the two, that deviation is output as a variation through the flow rate controller 11. A bump occurs in the flow controller output signal L7.

On the other hand, the flow rate controller output signal L7 and the pump flow rate signal L5 usually do not match because the characteristic between the opening degree of the flow rate regulating valve 3 and the flow rate has nonlinearity. For this reason, in the conventional configuration, a bump always occurs when the switching contact 9 is switched, and the flow rate of water supplied to the reactor fluctuates, resulting in fluctuations in the reactor water level, and deviations from the reactor reference water level are not allowed. There was a risk of deviating from the specified range.

[Object of the Invention] An object of the present invention is to eliminate fluctuations in reactor water level and provide a stable reactor water supply control device by performing bumpless switching between a pump flow rate signal and a flow rate controller output. .

[Summary of the Invention] Therefore, the present invention is characterized in that a correction signal is calculated from the pump flow rate signal and the flow rate controller output signal, and the correction signal is added to the flow rate deviation signal at the time of switching.

[Embodiments of the Invention] The present invention will be described below based on an embodiment shown in FIG. FIG. 1 is a block diagram of a nuclear reactor feed water control system showing one embodiment of the present invention. In the figure, the same reference numerals as in Fig. 4 indicate the same or equivalent parts, and the difference from Fig. 4 is as follows: pump flow rate signal L5 + flow rate controller output signal L7 - switching contact output signal, ×2... (6), the output signal L9 of the third calculator 12 is input to the first-order lag circuit 14 via the contact 13, and the first-order lag circuit 14 The output signal Lxa
This is the point where the signal is input to the second arithmetic unit 10 via the contact 15 as a correction signal.

Figure 2 shows the movements of the contacts 13 and 15. In the steady state, the contact 13 is closed and the contact 15 is open, and when the switching contact 9 operates (that is, the pump flow rate is "low" →
Contact 13 is open only for a certain period of time (tl) from "not low" or "not low" to "low").

Contact 15 is closed. Therefore, in a steady state, the flow rate deviation signal L6 input to the flow rate controller 11 is unchanged from the configuration shown in FIG. 4, and the control operation is also the same.

On the other hand, for a certain period of time (tl) after the switching contact 9 operates, the output signal of the first-order delay circuit 14 is the same. is input to the second adder 10 via the contact 15, so the first-order lag circuit output signal L1° is added to the flow rate deviation signal L6.

FIG. 3 shows the first-order lag circuit output signal. and a characteristic diagram showing changes in the flow rate deviation signal L6. When the pump flow rate is "low" in steady state, L, =L, -L, ...
...(7), and from equation (6), Ll. =l, +t, -Lt X 2=L, -L
, ...(8) Therefore, immediately after the pump flow rate changes from "low" to "not low" and the switching contact 9 operates.

Contact 15 closes, L, =L, -L, +L. =L4 Ls+Ls
Lt=L4-L, ・
...(9), the flow rate deviation signal LG does not change and no bump occurs.

On the other hand, since the contact 13 is open after the switching contact 9 is operated,
Li slowly with a constant time constant (T).

approaches O. Therefore, if tl is made sufficiently large, the flow rate deviation signal L6 will be as follows: LG=L, -L, +L. =L4-L,
・・・・・・After becoming (10), contact 13
is closed, and contact 15 is opened, resulting in the same configuration as the example shown in FIG. Although the case where the pump flow rate is "low" → "not low" has been described above, the same operation occurs in the reverse case.

That is, when the pump flow rate is "not low", L, = L4
-Ls-.-(11) Also, the output signal of the first-order lag circuit 14 is □. is L, , =L, +L7-L, x2=tt-
L, ...- (12) Next, when the pump flow rate is "not low" → immediately after it becomes "low" and the switching contact 9 operates.

L, =L4-L, +L1゜=L4-L, +L, -L
.

= L4-Ls-.-(13) Therefore, the flow rate deviation signal L1 does not change and no bump occurs. After that, L□. gradually decreases to 0, which causes the flow rate deviation signal to rise.
...... (14) and transitions bumplessly from 'L4 LsJ to rL, -L, J.

By the way, in the embodiment described above, the first-order lag circuit 14
The time constant T was set to a constant value, but as is clear from Fig. 3, the larger the time constant T, the slower the change in the flow rate deviation signal L6 becomes. It becomes preferable. However, if the time constant T is increased, the above (
The calculations of equations 8) and (13) will also be delayed, and if the pump flow rate L5 is fluctuating, Ll will not necessarily be calculated. is Ll
. =L, -L, or Ll.

=L, -L, will not be satisfied. Therefore, in such a case, it is not possible to completely prevent bumps when the switching contact 9 operates. So, to solve this problem.

The time constant of the first-order delay circuit 14 may be made variable. In other words, the following problem can be solved.

In this case, if T is changed, t must also be changed, so there is a problem that changing the setting of tl becomes complicated, but this is done by checking the first-order lag circuit output signal L1° with a comparator. It can be solved by That is, lti. 1×ε (ε is a small positive value) ・・・・
A comparator is provided to detect when (16) is reached, and after the switching contact 9 operates, the contact 13 is opened and the contact 15 is closed until the comparator operates. In this way, tl is automatically determined by T, so the above problem is solved.

[Effects of the Invention] As described above, according to the present invention, when the pump flow rate changes, the first-order lag circuit output signal is added to the flow rate deviation signal as a correction signal for a certain period of time, so that feedback is sent to the flow rate controller. Switching between the pump flow rate signal and the flow rate controller output signal can be performed bumplessly, and there is no fluctuation in the reactor feed water flow rate, and the reactor water level is stably controlled.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a reactor feed water control system showing one embodiment of the present invention, Fig. 2 is a timing chart showing the operation of Fig. 1, Fig. 3 is a characteristic diagram of Fig. 1, and Fig. 4 is FIG. 5 is a block diagram of a conventional reactor water supply control system, FIG. 5 is a block diagram of FIG. 4, and FIG. 6 is a characteristic diagram of FIG. 4. l... Nuclear reactor, 2... Water supply pump, 3... Flow rate adjustment valve, 4... Water level setter, 5... Water level detector, 6...
...First arithmetic unit. 7...Water level controller, 8...Flow rate detector, 9...Switching contact. 10... Second computing unit, 11... Flow rate controller, 12
...Third arithmetic unit, 13...Contact, 14...First-order delay circuit, 15...Contact. No. Agent Patent Attorney Crest 1) Makoto) Figure 1 Figure 2 Figure 3 t1 Figure 4 Figure 5 Figure 6

Claims (2)

[Claims] (1) A water level controller that calculates a command flow rate signal for the reactor feed water pump according to the deviation water level signal between the reference water level signal and the actual water level signal of the reactor, and a signal of the command flow rate signal and the actual flow rate signal of the reactor feed water pump. and a flow rate controller that controls the flow rate of the reactor feed water pump according to the deviation flow rate signal, and a flow controller output signal that is used as a feedback signal to this flow rate controller when the reactor feed water pump flow rate is low. If the flow rate is not low, a switching circuit selects the reactor feed water pump flow rate signal, and a correction signal is calculated based on the reactor feed water pump flow rate signal and the flow rate controller output signal, and when the switching circuit is activated, the correction signal is set to the flow rate signal. A nuclear reactor water supply control device characterized by comprising a correction circuit added to a controller. (2) A nuclear reactor feed water control system according to claim 1, wherein the correction circuit is a first-order lag circuit.