JPS6140591A - Controller for recirculation flow rate 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 regeneration system that achieves good response characteristics and suppresses abnormal increases in reactor output by adjusting the control gain of a recirculation control system. The present invention relates to a circulation flow rate control device.

[Technical background of the invention and its problems] Power control of a boiling water reactor (hereinafter referred to as BWR) is normally performed not only by selective operations related to the movement (withdrawal or insertion) of control rods within the reactor core, but also by This is done by combining the flow rate of cooling water flowing through the core (hereinafter referred to as core flow rate).

By the way, the principle of BWR coolant flow rate control and output control based on V (2) utilizes the relationship between the change in the state of void generation in the reactor due to the increase in flow rate tX and the negative reactivity coefficient of the void. In other words, when increasing the reactor power, the light and coolant flow rates are increased, and the increase in reactivity associated with the transient decrease in the void volume within the reactor causes an increase in power. This continues until the reaction IIJ increase i- during operation and the new amount of void generation in the reactor are balanced, and a new power level is achieved.

The core flow rate is obtained forcibly by guiding a portion of the cooling water out of the reactor pressure vessel and supplying it into the reactor core using a recirculation pump. The core flow rate is regulated by a flow control system connected to the recirculation pump, but it does not settle at the same value as the recirculation flow rate. However, since there is a certain relationship between the two, the core flow rate can be indirectly adjusted by adjusting the recirculation flow rate. In addition, two adjustment methods are used to adjust this continuous circulation flow: adjusting the opening degree of the flow rate control valve on the discharge side of the recirculation pump, or controlling the rotation speed of the recirculation pump. 0 However, as is clear from the above, BWR
By controlling the core flow rate, the reactor output can be easily adjusted, but the rate of change in the core flow rate and reactor output depends on the control rod pattern.

Quite different. For example, the core flow rate is 100% of the rated value.
When , between a control rod pattern in which the reactor output is exceptionally 100% and a control rod pattern in which the reactor output is exceptionally 50%, the rate of change in the reactor power with respect to the reactor core flow rate is about half of the former in the latter. For this reason, the optimum gain of the recirculation control system is usually set with a control rod pattern of 100-inch output, but in this case, a quick response cannot be expected when the control rod pattern of 50-inch output is reached. Sweet s Ion
If burnup compensation is performed by selecting a control rod pattern that is even larger than % power, the rate of change in reactor power with respect to core flow rate will become even larger, and the effective gain of the recirculation control system will increase accordingly. If it is too high, there is a high possibility that unstable phenomena such as hunting will occur. On the other hand, when the reactor core flow rate is less than the rated flow rate, the reactor output reaches 100% rated, so
For some reason, the core flow rate increases further 1. It is assumed that the reactor output will increase excessively.

Conventionally, core monitoring systems have been installed to deal with problems such as those mentioned above. This core monitoring system.

Average power range monitor (APRM), thermal output monitor (T
PM) and a rod block monitor (RBM), each of which operates as follows based on signals from a neutron east instrumentation system that includes multiple local power range monitors (LPRMs); The average power of the core obtained by averaging all LPRM power is monitored, and when the average power of the core reaches a predetermined rod block setting value due to control rod withdrawal, control rod withdrawal is prevented, and the control rod The reactor is scrammed when the reactor output reaches a predetermined scram setting value due to withdrawal of the reactor, increase in core flow rate, etc. The TPM converts and monitors the APRM power through a time delay circuit to fuel surface-transfer heat power, and causes the reactor to scram when the fuel rod surface-transfer heat power reaches a predetermined scram set point. RB M is LPRM
changes in the readings of the control rods and prevents withdrawal when any LPRM reading reaches a predetermined rod block set point. An example of such a core monitoring system is disclosed in US Pat. No. 3,565,760 and Japanese Patent Publication No. 54-21518.

However, if the reactor core flow rate increases and the reactor power increases due to a negative Ff operation error or equipment malfunction, the reactor power will reach the APRM or TPM scram set value as described above, and the reactor will scram. It just keeps going up until it does. Therefore, there is a problem that the number of scrams increases unnecessarily, which impedes driving.

[Purpose of the invention] The present invention was created in view of the above circumstances.

The purpose is to provide a reactor recirculation flow control device that has good response characteristics and suppresses abnormal increases in reactor output by adjusting the control gain of the recirculation control system depending on the difference in control rod patterns. .

[Summary of the Invention] In order to achieve the above object, the present invention provides a detector for detecting reactor power and reactor core flow rate respectively.

An output/flow rate circuit that normalizes and outputs the reactor output and the core flow rate, a gain conversion circuit that determines the normalized reactor output and output output from the output/flow rate circuit, and this gain conversion circuit. The present invention relates to a nuclear reactor recirculation flow rate control device that includes a flow rate controller that controls a recirculation flow t based on a normalized gain output from a nuclear reactor recirculation flow rate control device. The operating point discrimination circuit has a flow rate control curve, an output limit set value line, an output stability limit line, and an overpower limit line stored in the operating point discrimination circuit, and the flow rate controller is configured by a multiplier circuit and a flow rate control circuit. It is configured.

[Embodiments of the invention] An embodiment of the present invention will be described with reference to rotation.

Diagram N1 shows a system diagram of a recirculation flow rate measurement system of a boiling water nuclear reactor plant according to an embodiment of the present invention. In the figure, a reactor core 2 is housed in a reactor pressure vessel 1, and a plurality of control rods (not shown) are selectively moved inside the reactor core 2 by a control rod drive device 11 (not shown) 42. It is configured to be inserted and removed. In addition, the reactor pressure vessel 1 contains a coolant (cooling water) that cools the reactor core 2, and the cooling water is transferred to the reactor pressure vessel by a recirculation pump 3 that receives a portion of the coolant.
It is guided into the reactor core 2 through a jet pump (not shown) provided therein. Within the core 2, cooling water rises within the fuel assembly. The heat generated in the fuel assembly is transferred to the cooling water, which is heated and turned into steam. This steam is led from the reactor pressure vessel 1 to the turbine 9 connected to the generator IO, and after doing work in the turbine 9, is discharged to the boiling water type 8.

It is condensed in the water capper 8. This condensed water is fed to the reactor pressure vessel 1 as feed water as follows.

A control valve 4 is provided on the discharge side of the recirculation pump 3, and by changing the opening degree of the control valve 4 using the flow rate control system 1.1, the recirculation flow rate is adjusted and the core flow rate is controlled.

In addition, 11 again! The core flow may be adjusted by controlling the rotation speed of the I-ring pump 3.

Next, we will discuss the details of the flow rate control system 11.

6 Ka, I,. □. 8, □15. Yo. - As a function of the deviation between the output signal from the Q main controller 12, which is given to the main controller 12 as a traveling speed deviation signal from the Papin controller @ 6, and the measurement signal from the neutron flux instrumentation system 16, the neutron The controller 13 outputs a flow rate request signal. In addition, in order to make the deviation between the flow rate control @14 Fi neutron side controller 13 output signal and the measurement signal of recirculation flow rate measurement system 7 to be zero, and to give good response characteristics to the TFC recirculation control system. The output signal from the control gain conversion determining device 18 described in FIG.

Based on this signal, the opening degree of the flow rate control valve 4 is adjusted to control the cooling water flow rate to meet the demand. Recirculation pump rotation speed control is also controlled by a similar signal system. Note that this is a 7-piece turbine bypass valve.

An example of an operation pattern of a boiling water reactor in which the core flow rate is adjusted by the flow rate control system 11 is shown in FIG.

In Figure 2, the horizontal axis represents the core flow rate.

The vertical axis shows the reactor power, and when the core flow rate is rated at 100 cm, the reactor power is 25 t, 50%, 751100 t, 1
2596 flow rate control curves are A, B, and C, respectively.

Shown as D and B. Note that, as described above, although the core flow rate and the recirculation flow rate are not the same value, they have a certain relationship and can be substituted for each other.

In addition, the APRM monitors the increase in average power due to the increase in core pressure due to control rod withdrawal, increase in core flow, load shedding, etc., and this average power is determined by the scram installation value line G in Figure 2 (: Once reached, it sends a signal to the control rod drives, causing the reactor to scram.

For example, when the average output reaches about 120% of the exceptional output,
Make it scrum. The H line is an overpower limit line,
The limit line is set at 102-105%1 rated power or less to prevent the reactor output from becoming abnormally high. F
This line is a stability limit line, which is related to the generally known BWR core/channel stability, and the limiting conditions are high mountain force/low core flow rate.

FIG. 3 shows a block diagram of the control gain conversion determining device 18 and flow controller 14 of the reactor recirculation flow rate control system shown in FIG. As shown in the figure, the power control gain conversion grading device 18 calculates the reactor power P and the core flow -1i-F.
An output/flow rate circuit 19 that determines the operating state from the relationship, an operating point discrimination circuit 20 that inputs the output from this output/flow rate circuit 1819, and a gain conversion circuit 21 that inputs the output of this operating point discrimination circuit 20. It is composed of fl. Further, the flow rate controller 14 is shv'ed from a multiplication circuit 22 that calculates the multiplication of the output of the gain conversion circuit 21 and the flow rate deviation signal 24, and a flow rate control circuit 23 that inputs the output of this multiplication circuit 22.

By the way, the reactor power P and the core flow iF are input to the power/flow command FO 19 and normalized relative to the respective rated reactor power and rated core flow 'm, and are expressed, for example, as a percentage.

On the other hand, in the operating point discrimination circuit 20, first, A-
The H line is expressed as Y=aX+b (here, Y: M child reactor output, X: core flow rate, a, b: coefficients). Next, the output/flow rate circuit 19
The reactor core flow rate f outputted from
-YH is determined and compared with the reactor output p input from the output/flow rate circuit 19.

Approximate one point to the C line 17 and output.

Note that such a logic circuit can be easily integrated into a microprocessor.

Next, the operation of this embodiment will be explained.

When the reactor power P and the core flow 1F are input to the power/flow 1 circuit 19, the output/flow circuit 19 calculates the relative values of the rated reactor power and the rated core flow. is output. This output is the next operating point discrimination IC!
4B Input to 20. On the other hand, this operating point discrimination circuit 2
0, the WR flow rate control curve A-B is as shown in Fig. 2.
is memorized, and the reactor power P and core flow i! The operating point of the flow rate control curve, that is, the flow rate control characteristic diagram, closest to the tF data is determined and output. Based on this output, the normalized gain at each operating point is determined by the gain conversion circuit 21.
An example □ is shown in Figure 4. The normalized gain in this figure is the normalized gain to which the X% output flow rate control curve is normalized based on the control gain on the 100% output flow rate control curve. Multiplier circuit 2 of flow rate controller 14
In 2, the flow rate deviation signal is multiplied by the normalized gain and this value is input to the flow rate control circuit%, so this method has the same effect as actually changing the gain of the control circuit. . It goes without saying that the gain conversion means can also directly change the gain of the flow rate control circuit 23.

Next, when the operating point enters the operating control 4i IJ region (indicated by diagonal lines) where S''1 is reached between the H line and the F line in FIG. The output from the gain conversion circuit 21 shown in FIG. 3 has a function of avoiding the operation restriction area.

[Effects of the Invention] As explained above, the reactor recirculation flow rate control device of the present invention has good stability and response characteristics over a wide range of operation, and prevents overpowering due to hunting, etc. As a result, the nuclear reactor can be operated safely and efficiently, which is an excellent effect.

[Brief explanation of drawings]

Claims (3)

[Claims] (1) A detector that detects the reactor power and the core flow rate, a power/flow circuit that normalizes and outputs the reactor power and the core flow rate, and a normalized output that is output from the power/flow circuit. An operating point discrimination circuit that determines the operating state based on reactor output and core flow rate, a gain conversion circuit that determines a normalized gain based on the output of the operating point discrimination circuit, and a normalized gain that is output from the gain conversion circuit. A nuclear reactor recirculation flow rate control device comprising: a flow rate controller that controls a recirculation flow rate based on . (2) The reactor recirculation flow rate control device according to claim 1, wherein the operating point determination circuit stores a flow rate control curve, an output scram set value line, an output stability limit line, and an overpower limit line. (3) The reactor recirculation flow rate control device according to claim 1, wherein the flow rate controller is comprised of a multiplication circuit and a flow rate control circuit.