JPH08313669A - Method and device for operating control rod - Google Patents

Abstract

PURPOSE: To perform start and stop in a short time at the time when start and stop operation of a reactor is manually performed by drawing out a control rod fast until a reactor core eigenvalue reaches a specified value and pulling out the control rod gradually thereafter. CONSTITUTION: Each control rod 3 of the reactor core 2 of a reactor pressure vessel 1 is driven by a control rod drive mechanism 5 and a motor 6. The detector 10 of a neutron flux monitor 4 for detecting neutron flux at the time of reactor start is disposed in the core 2. The monitor 4 converts the output signal of the detector 10, and a neutron flux level signal and a period signal are output to a control rod automatic controller 14. The value (core eigenvalue) of a ratio of the neutron flux at the time of the whole insertion of the control rod 3 to the other neutron flux at the time point of the insertion thereof is monitored. The control rod 3 is drawn out fast until the value of the ratio reaches a specified value, thereafter it is pulled out gradually, so that the state of a reactor is turned critical. Thereby accurate operation is made possible even by manual operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for starting and stopping a nuclear reactor, and more particularly to a boiling water reactor (BW).
The present invention relates to a control rod operating method and a control rod operating device suitable for starting and stopping R) in a short time.

[0002]

2. Description of the Related Art When starting a boiling water nuclear power plant, the control rods inserted in the core are gradually pulled out to increase the power output of the nuclear reactor. In this process, in order of decreasing reactor power, (1) critical proximity mode that makes a subcritical core critical (2) temperature rising boost mode (R) that raises reactor pressure and reactor water temperature to rated values 3) Reactor output control mode that bypasses the steam generated in the core without sending it to the generator (4) It is roughly divided into generator output mode that sends the generated steam to the generator and increases the output to the rated output. it can. The control rod operation in these processes is conventionally performed by an operator.

Of these modes, the first "critical proximity mode" is the mode in which the operator has a large amount of control rod operation and requires careful operation. In this critical proximity mode,
The operator must operate the control rods according to a given control rod operating procedure so as not to give a sudden reactivity to the reactor. Here, "control rod operating procedure" means
It shows which control rod is pulled out in what order and how much. In the conventional start-up operation, the operator
The approximate subcriticality (distance from the criticality) is grasped, and the timing for operating the control rod is judged based on the information and the reactor cycle (period) τ that represents the time change rate of the neutron flux. The reactor is controlled so that it does not become smaller.

In this conventional method, the operator does not operate the control rod slowly because there is no appropriate instruction for the critical position and the operating condition for keeping the period smaller than a certain value is not clear. . In consideration of the convenience of the operation of the operator, a predetermined control rod withdrawal amount is also set to a relatively small input reactivity. As a result, the time required to reach criticality by manual operation by the operator is generally twice as long as that in the optimal control.

In recent years, a method for automating the control rod operation as described above or outputting an appropriate instruction has been devised for the purpose of saving labor and shortening the starting time. As a publicly known example of the control rod operation automation technology, there is a technology described in JP-A-50-146796. This known example relates to a device for automatically operating a control rod to make a subcritical reactor critical, and determines the operation timing and the withdrawal amount of the control rod based on the reactor cycle.
That is, when the reactor cycle is a predetermined value (for example, 200 seconds) or more for determining the criticality of the reactor, a control rod drawing operation command is output, and the drawing amount at that time is set as a value proportional to the size of the reactor cycle. Looking for.

Similarly, as a conventional technique for making a subcritical nuclear reactor critical, there is one disclosed in JP-A-60-179689. In this conventional technique, the core reactivity is estimated using a one-point dynamic characteristic equation, and the drawing speed is set from the number of control rods to be operated and the control rod positions. Also, the Journal of the Atomic Energy Society of Japan Vol.
34 In p161, "Automated control rod operation at start-up of boiling water nuclear power plant", an appropriate drawing speed is calculated based on the estimated core reactivity, and continuous drawing start, continuous drawing stop and notch A method for determining the timing of starting pulling out is described.

Further, Japanese Patent Laid-Open No. 63-286793 discloses the total amount of control rods withdrawn, the amount of control rods with which the control rod was operated last time, and the reactor cycle when the reactor is brought from a subcritical state to a critical state. It is shown that a fuzzy control method is used to calculate the next pull-out amount of the control rod, and the control rod is operated according to this information.

These known prior arts utilize the capacity of a computer to judge the amount of control rod withdrawal according to the state of the reactor each time, enabling the shortest time control that can safely start the reactor. There is.

[0009]

The above-mentioned conventional technique is
The control rod manipulated variable is calculated by solving the dynamic equation and by using the estimated core reactivity and fuzzy theory. Therefore, it is difficult for the operator to use the technique to independently determine the control rod operation. On the other hand, the reactor needs to be able to be started by not only automatic operation but also manual operation. Although manual operation is possible if the guide is output to the operator using the above-mentioned conventional technique, it is difficult for the operator to independently determine whether the guide provided by the computer is appropriate. For operators, the experience of manual operation, which is carried out based on their own judgment, is important for understanding the characteristics of the reactor and developing the potential to respond to unexpected situations.

An object of the present invention is to allow an operator to manually start and stop a reactor so that the operator can operate the reactor at his or her discretion.
Another object of the present invention is to provide a simple control rod operating method and device that can be started and stopped in a short time.

[0011]

[Means for Solving the Problems] The above-mentioned object is to control the neutron flux φA when the control rod is fully inserted and the neutron flux φ when the control rod is inserted (φ / φA) in operating the control rod at reactor startup. Of the control rod is rapidly extracted until the value of the ratio reaches a predetermined value, and thereafter, the control rod is gradually pulled out to bring the reactor into a critical state.

The above-mentioned object is also to rapidly pull out the control rod by presetting the control rod temporary stop position so that the reactor period signal does not become smaller than the set value during the control rod withdrawal operation in the operation of the control rod of the reactor. The high-speed drive mode, the block drive mode in which the control rod temporary stop position is set in advance to drive the control rod in a predetermined block amount unit so that the loading reactivity during control rod operation is almost equal, and the control rod minimum operation A step drive mode in which the control rod temporary stop position is set in advance to a unit amount (hereinafter referred to as a step) and the control rod is operated step by step is prepared, and the current subcriticality of the reactor is set. It is achieved by operating the control rod in each of the drive modes based on the above.

[0013]

It is understood that in order to bring the reactor into a critical state quickly, the control rod can be pulled out at a high speed up to near the critical level and gradually pulled out after reaching the critical level. But,
It is necessary to accurately determine to which position the control rod should be pulled out at high speed. In the present invention, this judgment is based on the core eigenvalue (or neutron flux φA when the control rod is fully inserted).
To the neutron flux φ at the time of inserting the control rod (φ /
(φA) value) enables accurate judgment.

Further, in the present invention, the control rod drive mode is divided into three modes, that is, the high speed mode, the block mode, and the step mode, and the control operation is performed while switching between the modes based on the reactor conditions. Precise operation is possible.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, prior to the description of a specific embodiment, the principle of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram showing a control rod operating method in a critical proximity mode in which a subcritical core is made critical. The horizontal axis is the time after the start of pulling out the control rod. The vertical axis represents the core eigenvalue keff, where the eigenvalue "1" indicates criticality, less than "1" is subcritical, and more than "1" indicates supercritical state. The critical proximity mode realizes the operations from full insertion of the control rod (point A) to criticality determination (point D).

In the present invention, three drive modes are used to operate the control rod. This drive mode is divided into points A to B, points B to C, and points C to D in FIG.

First, the point B at which the core eigenvalue becomes approximately 0.99 is determined by the ratio (φ / φA) of the neutron flux φA when the control rod is fully inserted and the neutron flux φ at that time. When the neutron flux detector is installed in the core, its characteristics change over time due to the influence of radiation, but by taking the ratio, the influence of the characteristic change can be removed and the core eigenvalue can be estimated with high accuracy. Up to point B, the subcriticality is relatively large, and there is little concern that it will exceed the criticality.
If the period is not small, the control rod can be pulled out at a relatively high driving speed. This mode is a high-speed drive mode.
Called Do. The period signal is built into the safety system of the nuclear reactor, and when it becomes shorter than the set value, the control rod is prohibited from being pulled out or scrammed. The period τ becomes small between the points A and B when the control rod passes near the neutron detector and the neutron flux φ locally increases. Therefore, in the high-speed drive mode, the control rod operation is temporarily stopped at a position where the period τ is expected to become short, and the control rod is pulled out at a relatively high drive speed otherwise.

Period τ, neutron flux φ and core reactivity ρ
The relationship (ρ <0 in subcritical) can be expressed by the following mathematical expression 1.

[0019]

## EQU00001 ## 1 / .tau. = D (ln.phi.) / Dt = 1 / .phi..d.phi. / Dt.apprxeq.-1 / .rho..d.rho. / Dt At the temporary stop position, for example, at least 10 seconds are stopped. As a result, the input reactivity dρ / dt per unit time
It can be seen that the value becomes smaller and the period τ can be increased by the equation 1. The position to stop temporarily is decided in advance.

From point B to point C, the control rod is pulled out in the block drive mode. The block drive mode is a drive mode in which the control rod is pulled out by the amount of one block set so that the input reactivities are substantially equal. Since the reactivity of the control rod varies greatly depending on the fuel characteristics and the position of the control rod, one block may be configured by one step, which is the physical minimum operation unit of the control rod, or one block by 20 steps. Sometimes. The extraction amount corresponding to one block is calculated beforehand and given as data. The reactivity per block is preferably about 0.05% Δk. Even after pulling out one block, the control rod is always stopped for a certain period (for example, 10 seconds) or more. Assuming that the reactivity per block is 0.05% .DELTA.k, the eigenvalue at the time of shifting to the block drive mode is about 0.99, and when 20 blocks are pulled out, the critical value is reached. One of the advantages of having a block drive mode is that the operator can easily estimate the expected position to reach criticality.

From the point C immediately before the critical point to the point D where the critical point is determined, a minute adjustment of the reactivity is required, so that the control rod has a minimum operation unit amount (1 notch for the hydraulic drive type control rod, electric drive type control). Drive only one step). In a boiling water reactor, the input reactivity per minimum manipulated variable is generally 0.0.
It is designed to be 5% Δk or less. This drive mode is defined as a step drive mode.

The control rod withdrawal position at which the eigenvalue becomes approximately 0.99 varies depending on the temperature of the reactor water and the progress of fuel combustion, and therefore cannot be determined in advance. A major feature of the present invention is that the point at which the eigenvalue becomes approximately 0.99 is accurately determined, and the high speed drive mode in which the control rod stop position is set so that the period signal does not become shorter than the set value up to that point. The control rod is operated by the mode, and thereafter, the control rod is operated by the block drive mode in which the control rod stop position is set so that the reactivities per block become substantially equal. According to this method, unlike the conventional manual operation, the extraction amount is changed according to the state of the core, so that the startup time can be shortened. Further, since the control rod operation amount of each drive mode is presented to the operator in advance, the operation of the operator is easy.

As described above, in the critical proximity mode in which a subcritical reactor is made critical, when the core eigenvalue is small (subcriticality is large), the control rod is pulled out by the high speed drive mode, When the criticality is reached, the control rod is pulled out at a substantially constant period using the block drive mode and the step drive mode. The switching of each drive mode can be determined by the neutron flux or the period, which can be easily determined by the operator. The control rod operation procedure for high-speed drive mode and block drive mode is predetermined, and the mode switching is easy, so it is easy for the operator to manually operate and the control is close to the minimum time control. Stick operation can be realized.

Specific examples of the present invention will be described below.
FIG. 1 is a configuration diagram of a control rod operating device according to an embodiment of the present invention. A plurality of control rods 3 for controlling the output of the nuclear reactor are arranged in the core 2 in the reactor pressure vessel 1. Each control rod 3 has a control rod drive mechanism 5 and a motor for moving the control rod 3.
Driven by the motor 6. A control rod position detector 8 is installed on each control rod 3. The core 2 has a neutron flux monitor (SRNM) that detects the neutron flux at the time of reactor startup.
4 detectors 10 are arranged. Neutron flux monitor 4
Converts the output signal of the neutron flux detector 10 to convert the neutron flux level signal and the period signal into the control rod automatic control device 14
Output to.

The control rod operating device of this embodiment includes a control rod automatic control device 14 for calculating the operation timing and operating method of the control rod, and a control rod drive control device 2 for managing the operation of the control rod.
1 and a control rod operation instructing device 13 in charge of an interface for presenting information from the control rod automatic control device 14 to the operator and transmitting the operator's instructions to the control rod drive control device 21.

The operation of the control rod operating device in this embodiment will be described below by taking the critical proximity mode as an example. When the operator selects the critical proximity mode from the input device 12 of the control rod operation instructing device 13, the control rod automatic control device 14 determines the control rod based on the neutron flux level and the period signal from the neutron flux monitor 4. Determines whether the operation (pull-out or insertion) is permitted or not, and further determines an appropriate drive mode signal from the high-speed drive mode, block drive mode, and step drive mode, and controls it. It is transmitted to the stick operation instruction device 13.

The control rod operation instructing device 13, based on the above-mentioned signals and the control rod operation procedure data 9 inputted in advance, arranges the control rods to be operated by the operator in the core,
The present control rod pulling-out position, the target control rod pulling-out position, the drive mode suitable for the operation, and information on whether or not the control rod can be operated are displayed on the display device 11.
If the operator wishes to change the displayed drive mode, he or she changes it using the input device 12, and then presses the pull-out or insert-in control rod operation button if there is a display indicating that the control rod can be operated.

The control rod operation command from the operator is transmitted to the control rod drive control device 21 through the control rod operation instructing device 13 together with the drive mode signal. Control rod drive controller 21
Is based on the control rod operation procedure data 9 that has been input in advance,
A control rod to be operated is selected from a hundred or more control rods, and a pull-out command or an insertion command and a control-rod reaching target position are instructed to the motor drive control device 7 of the selected control rod. The motor drive control device 7 compares the instruction value of the control rod position detector 8 with the control rod reaching target position, and controls the rotation speed of the motor 6 so that the control rod 3 stops at the target position. When the target position is reached, a signal indicating that the target position is reached is transmitted to the control rod drive control device 21.

The control rod drive control device 21, which has received the target position arrival signals from the motor drive control devices 7 of all the selected control rods, reaches the target position to the control rod automatic control device 14 and the control rod operation instruction device 13. Send a signal. Upon receipt of this signal, the control rod automatic control device 14 again determines the driving mode for the next operation, and displays it to the operator together with a signal for permitting / denying the control rod operation. With the above configuration, it is possible to realize the control rod operation adopting the starting method using the above-mentioned three drive modes.

FIG. 3 shows the automatic control rod controller 14 described above.
FIG. 6 is a diagram showing a driving mode and a control rod operation permission / non-permission determination algorithm performed by FIG. The calculation algorithm is composed of a portion (FIG. 3) that determines whether the control rod operation is permitted or not and a portion (FIG. 4) that determines the drive mode.

In FIG. 3, when the operator selects the critical proximity mode, it is judged whether or not the initial setting process is completed, and if not already executed, the initial setting process is executed. In this initial setting process, the following three settings are made. The first is to set the initial value for predicting the number of drawing steps Δm to the critical level by the inverse multiplication method, the second is to set the control rod operation mode to the high speed drive mode, and the third is , To set the control rod withdrawal permission signal to ON.

Next, it is judged whether or not the control rod is withdrawn. If the control rod is currently in operation and the period is small (50 seconds or less in this example), the control rod withdrawal is not permitted, and otherwise the control rod withdrawal is permitted. If the control rod is currently stopped, the control rod stop time exceeds the set value (10 seconds in this example), and the period is sufficiently large (200 seconds in this example), control rod withdrawal is permitted, and In all other cases, pulling out the control rod is not permitted.

Next, the control rod operation mode in the critical proximity mode.
The determination algorithm of the code will be described with reference to FIG. When the current drive mode is the high-speed drive mode, the transition to the block drive mode is judged by the neutron flux. The principle will be briefly described below. External neutron source intensity is S, core eigenvalue kef
f is the neutron flux level φ of the subcritical reactor

[0034]

It can be approximated by φ = S / (1-keff).

Let neutron flux be φA when all the control rods are inserted.
In a BWR plant, the eigenvalue at this time is generally 0.88.
Since it is ~ 0.92, from equation 2, the neutron flux φB when the eigenvalue is 0.99 is

[0036]

## EQU00003 ## .phi.B / .phi.A = 8-12.

Therefore, the transition from the high speed drive mode to the block drive mode can be determined by the neutron flux level φ,
In the present embodiment, Q = 8 and the neutron flux level φ is

[0038]

## EQU4 ## When φ ≧ Q × φA, the transition condition from the high speed drive mode to the block drive mode is set. When shifting to the block drive mode, a control rod pull-out disapproval signal is issued at the same time.

When the current drive mode is the block drive mode, in the present embodiment, the shift to the step drive mode is determined by using the inverse multiplication method. According to the inverse multiplication method, the expected number of extraction steps Δm from the current position to the critical point is
The total number of extraction steps up to the present is m1, the total number of extraction steps up to the last control rod operation is m0, the current neutron flux level is φ1, and the neutron flux level during the previous control rod operation is φ0.
Then, the next number 5

[0040]

[Expression 5] Δm = (m1-m0) / (φ1 / φ0-1)

From Equation 5, M = 12 steps in this embodiment.

[0042]

## EQU6 ## When .DELTA.m.ltoreq.M, the transition condition from the block drive mode to the step drive mode is set.

The eigenvalue when shifting to the step drive mode is about 0.995 to 0.999. The advantage of shifting to the step drive mode with the expected number of drawing steps up to the critical value instead of the eigenvalue is that the number of control rod operations in the step drive mode is almost constant.

After shifting to the step drive mode, after the control rod is stopped, the period measures a duration of 200 seconds or less, and if the time exceeds 120 seconds, it is judged that the criticality has been reached, and the display device The operator is notified by 11 and the processing of the critical proximity mode is completed.

FIG. 5 is a diagram showing the contents of the control rod operating procedure data 9 shown in the embodiment of FIG. In this example,
It is assumed that a group is formed by a plurality of control rods, and control rods belonging to the same group perform a control rod gang operation in which they are simultaneously operated. Gr. Represents a control rod group, and pulling out the control rod is Gr.1 → Gr.2 → Gr.3.
→ Gr. We will proceed in the order of 4. Control rod position 200
(Step) represents the control rod full withdrawal position.

In the control rod operating procedure data of the high speed drive mode, the control rod stop position is set around the 80 step position where the neutron flux detector is installed and the period is likely to be small. For example, the control rods of Gr.1 are 36, 72,
Pause at the positions of 80, 84, 88 and 200 steps respectively. The temporary stop position is determined in advance by evaluating it with a three-dimensional core characteristic analysis code. High-speed drive mode is 3
The number of control rod stops is the smallest among the two drive modes.

On the other hand, in the block drive mode, the control rod stop position is set so that the control rod charging reactivity is substantially equal. In this example, the charging reactivity per block is approximately 0.05%. Δk. The temporary stop position is determined and evaluated in advance by a three-dimensional core characteristic analysis code, as in the high-speed drive mode. In the step drive mode, the operation is temporarily stopped at each step, which is the minimum operation amount.

The control rod operating procedure data 9 inputs new data each time one fuel cycle is completed and a new fuel is replaced with an old fuel. As an input method, in the present embodiment, the control rod operation instruction device 13 and the control rod drive control device 21 are both input, but the control rod operation instruction device 13 is input and the control rod drive control device 21 is input. The control rod operating procedure data 9 may be transferred to the. At this time, it is possible to prevent a mistake such that the control rod operation procedure data input to the control rod operation instructing device 13 is different from the control rod operation procedure data input to the control rod drive control device 21.

In this embodiment, the data of the step driving mode is prepared in advance, but the stop position of the step driving mode is

[0050]

## EQU7 ## It can also be calculated from the current control rod stop position + control rod minimum operation amount.

In this case, since it is not necessary to input the stop position of the step drive mode, the control rod operation instructing device 13
The capacity of the storage device built in the control rod drive control device 21 can be reduced. Further, for example, when it is known in advance that the control rods of Gr.1 and Gr.2 are driven only in the high-speed drive mode, the block drive mode and the step of Gr.1 and Gr.2 are set. The drive mode data can be omitted. Also in this case, the capacity of the storage device can be reduced.

According to the above-described embodiment, the operation amount is switched from the high speed drive mode to the block drive mode according to the state of the nuclear reactor, so that there is an effect that the startup time is shortened. At that time, there are only 3 patterns (the step drive mode can be easily obtained from the equation 7 so that it is practically 2 patterns) that the operating procedure of the control rod is presented to the operator in advance, and the drive mode is only available. Since the switching of the mode is also based on a simple algorithm, it is easy for the operator to operate. At the time of shifting to the block driving mode, it can be expected that the criticality will occur at about 20 blocks ahead, and at the time of further shifting to the step driving mode, it will become critical at about 12 steps ahead. Since it is understood, there is an effect that the operator can easily operate the control rod.

A feature of the above-described embodiment is that the manual operation method is simple and clear, and can be directly used for automatic operation. FIG. 6 is a diagram showing the configuration and operation of a device for automatically operating the control rod by the control rod operating device. The device configuration is the same as that of FIG. 1 showing the manual operation method by the operator, and only the function of the control rod operation instructing device 13 is different.

In FIG. 6, when the operator selects the automatic control function from the input device 12 of the control rod operation instruction device 13, the control rod operation instruction device 13 causes the control rod automatic control device 1 to operate.
The drive mode signal and the control rod operation permission signal received from No. 4 are directly transmitted to the control rod drive control device 21 as a drive mode signal and a control rod operation command, respectively. As a result, the control rod operation is automatically performed according to the algorithm of the control rod automatic control device 14. The operation procedure is the same as in manual operation. The points different from the manual operation are that the period from the time when the operator sees the control rod operation permission signal until the control rod operation button is pressed can be shortened, and the control can be performed faster than the manual control. When the operator wants to return to the manual operation, the manual operation can be performed by selecting the manual operation function from the input device 12.

FIG. 7 is a diagram showing the results of evaluation of the critical proximity mode startup time during automatic operation using the control rod automatic operating device shown in FIG. The condition for switching from the high-speed drive mode to the block drive mode is φ ≧ 8 in Equation 4.
× φA, the condition for switching from the block drive mode to the step drive mode is to use Δm ≦ 12 steps of Equation 6,
The control rod operating procedure data shown in FIG. 5 is used. The horizontal axis of FIG. 7 represents the time after the start of the control rod withdrawal, and the vertical axis represents the total amount of control rod withdrawal (steps) and the reciprocal of the period (1 / second).

In the high speed drive mode, it takes 44 minutes in about 7 minutes.
Pull out the control rod up to 8 steps (48 steps of Gr.3). During this time, the control rod has stopped 15 times. G
When r.3 is extracted by 48 steps, the neutron flux level φ satisfies φ ≧ 8 × φA of the equation 4 and shifts to the block drive mode.

In the block driving mode, 16 blocks are pulled out, and Δm≤6 in the equation 6 at the 72 step position of Gr.3.
The condition of 12 steps is satisfied, and the mode is changed to the step drive mode.

In the step drive mode, 10 steps are extracted, and the criticality is reached at the 82 step position. This position is the position 19 blocks after the shift to the block drive mode, and almost coincides with the prediction that the criticality will be reached 20 blocks after the shift to the block drive mode.

The period after the block drive mode is 10
It shows a constant value from 0 to 200 seconds, indicating that the control is almost optimal. The time required to reach the transition criticality is about 17 minutes, which is a sufficiently short time to reach the criticality.

Here, the reason why the optimum control is achieved when the reactivity per block of the block drive mode is kept constant at about 0.05% Δk will be described. Critical proximity mode
In the mode, if the period is maintained at the minimum allowable value, the shortest time is controlled. Now, the neutron flux is φ, the period (reactor cycle) is τ, and the core reactivity is ρ (ρ is subcritical.
0), where S is the external neutron source intensity and L is the neutron lifetime

[0061]

[Formula 8] −ρ = LS / φ = c · φA / φ where φA is the neutron flux level when the control rod is fully inserted, and c is a constant, and the eigenvalue when the control rod is fully inserted is about 0.9. Therefore, c takes a value of 0.1 to 0.15.

From the above-mentioned equations 1 and 8, the following relationship can be derived.

[0063]

[Equation 9] 1 / τ = 1 / c · φ / φA · dρ / dt The neutron flux level φ / φA in the block drive mode is 8 to
20 and using 0.1 for the value of c, and substituting 200 seconds as the appropriate period τ in the critical proximity mode into the equation 9, the required input reactivity dρ / dt per unit time is the following value. To get

[0064]

## EQU10 ## dρ / dt = 0.0025 to 0.00625
(% Δk / sec) (φ / φA = 20) (φ / φA = 8) After one block operation, suspend the control rod for at least 10 seconds, and pull out the control rod when the period becomes 200 seconds or more. According to the analysis result, the control rod withdrawal interval when permitting is 10 seconds when φ / φA = 8 and about 20 seconds when φ / φA = 20. When the input reactivity Δρ per block where the time-averaged input reactivity is several tens is calculated from that, Δρ = 0.05 regardless of the neutron flux level φ.
% Δk. This reduces the reactivity per block to 0.
This is the reason why the constant value of 05% Δk should be used. When the control rod suspension time or the period value for allowing the control rod to be withdrawn greatly changes from the above conditions, the appropriate reactivity value per block changes.

In the embodiment shown in FIG. 1, permission to operate the control rod
Although the control rod automatic control device 14 calculates the disapproval and the driving mode and displays it to the operator, the burden on the operator is reduced. However, even in a general BWR plant without this function, the operation method according to the present invention can be applied. It is possible to apply. In this case, the operator is given the control rod operating procedure data as shown in FIG. 5 and the Q value (for example, 8) of the judgment condition for shifting from the high speed drive mode to the block drive mode. To be

Before the control rod operation is started, the operator records the neutron flux level φA at the time of fully inserting the control rods, and the neutron flux level from the high speed drive mode to the block drive mode Calculate the value of φ that satisfies. The operator operates the control rod according to the data in the high-speed drive mode until Expression 4 is satisfied. It stops for 10 seconds or more at the temporary stop position, but this time is inevitably elapsed while the operator inputs the next control rod stop position to the control device. Since the degree of reactivity per block is known, it is possible to predict the control rod withdrawal position that becomes critical to the operator at the time of shifting to the block drive mode. In the block drive mode, the operator pulls out one block of the control rod after confirming that the period has reached 200 seconds or more. Since the period does not become large when the criticality is approached, for example, if the period signal τ is 30 seconds or more and less than 200 seconds after one block is extracted, the block extraction is changed to the step extraction.

At the time of shifting to the block drive mode, the operator can predict how many more blocks to pull out to become critical, that is, the control rod position at the critical point. Being able to predict the control rod position at the critical point greatly reduces the burden on the operator.

The control rod operating method described above is mainly aimed at accelerating the manual operation in the critical proximity mode. However, there are three types of high speed drive mode, block drive mode and step drive mode. The control rod operating method using the drive mode is
It can also be used in the temperature rising and boosting mode, the reactor output control mode, and the generator output control mode. The device configuration in this case may be the same as that in FIG.

FIG. 8 is a diagram showing an embodiment of a control algorithm for the temperature rising / boosting mode incorporated in the automatic control rod controller 14. In the temperature rising boost mode, the control rod is operated so that the reactor water temperature change rate matches the target value, but in this embodiment, the target neutron flux is calculated from the target reactor water temperature change rate,
The neutron flux is controlled to match the target neutron flux.

First, the reactor water temperature change rate deviation signal 33 is obtained from the difference between the target reactor water temperature change rate 31 and the actually measured reactor water temperature change rate 32, and PI control of the proportional constant Kp and the integral time constant T is performed. An upper and lower limit limiter processing 36 is applied to the applied signal 35 to obtain a target neutron flux 37. Next, the neutron flux deviation signal 39 (Δφ) is obtained from the difference between the target neutron flux 37 and the actually measured neutron flux 38.

When the neutron flux deviation signal Δφ is larger than a preset positive number a and more than 10 seconds have passed after the control rod was stopped, a control rod extraction permission signal is generated. Further, when the neutron flux deviation signal Δφ is smaller than a preset negative number b and more than 10 seconds have elapsed after the control rod was stopped, a control rod insertion permission signal is generated.

The neutron flux deviation signal Δφ is also used for determining the driving mode. When the absolute value of the neutron flux deviation signal Δφ is larger than a preset positive number c, that is, c <│Δφ│, the high speed drive mode is selected. Neutron flux deviation signal Δ
For a positive number d whose absolute value of φ is smaller than c, | Δφ | <
When the relation of d <c is satisfied, the step drive mode is selected. If d <| Δφ | <c, block drive mode
Do The constants a, b, c and d depend on the response characteristics of the control system and the reactor, but the optimum values can be set in advance by simulation. Using this device, it is possible to instruct the operator whether the control rod operation is permitted or not and the driving mode in the temperature raising mode as in the critical proximity mode.

Basically, the reactor output control mode and the generator output control mode are based on the deviation signal between the target heat output and the actual heat output, as in the temperature raising / boosting mode. Moreover, the control rod operation timing and drive mode can be determined. That is,
Optimize the control rod operation amount by selecting step drive mode when the deviation signal is small, block drive mode when the deviation signal is slightly large, and high speed drive mode when the deviation signal is considerably large. And the start-up time can be shortened. The deviation signal can be easily recognized by the operator, and the driving mode can be switched based on the deviation signal to easily realize a short-time start-up operation close to automatic control even by manual operation.

[0074]

According to the present invention, the control rod operation in the reactor operation manually performed by the operator can be realized in a short time similar to the automatic control.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a control rod operating device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a control rod operating method in a critical proximity mode in the control rod operating device shown in FIG.

FIG. 3 is a flowchart showing an example of a processing algorithm of a critical proximity mode of the control rod automatic control system.

FIG. 4 is a flowchart showing an example of a processing algorithm of a critical proximity mode of the control rod automatic control system.

FIG. 5 is a diagram showing an example of a control rod stop position of each drive mode according to the present invention.

FIG. 6 is a configuration diagram of a control rod operating device according to a second embodiment of the present invention.

FIG. 7 shows a critical proximity mode according to a simulation of the present invention.
It is a figure which shows the analysis result of DO starting time.

FIG. 8 is a diagram showing an example of a processing algorithm of a temperature raising / boosting mode of the control rod automatic control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Reactor core, 3 ... Control rod, 4 ... Neutron flux monitor, 5 ... Control rod drive mechanism, 6 ... Motor, 7 ... Motor drive control device, 8 ... Control rod position detection Reactor, 9 ... Control rod operating procedure data, 10 ... Reactor neutron flux detector, 11 ... Display device, 12 ... Input device, 13 ... Control rod operating instruction device,
14 ... Control rod automatic control device, 21 ... Control rod drive control device, 31 ... Target reactor water temperature change rate, 32 ... Reactor water temperature change rate, 33 ... Reactor water temperature change rate deviation, 34 ... PI controller, 3
6 ... Upper / lower limit limiter, 37 ... Target neutron flux, 38 ... Neutron flux, 39 ... Target neutron flux deviation.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuichi Higashikawa 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Yukihisa Fukazawa 3-chome, Saiwaicho, Hitachi, Ibaraki No. 1 Hitachi Ltd. Hitachi factory

Claims (16)

[Claims] 1. A method of operating a control rod at reactor startup, wherein the core eigenvalue is monitored when the control rod is inserted, the control rod is pulled out at high speed until the core eigenvalue reaches a predetermined value, and thereafter the control rod is gradually removed. A method for operating a control rod, comprising pulling out to a critical state of the reactor. 2. A method of operating a control rod at reactor startup, wherein the value of the ratio (φ / φA) of the neutron flux φA when the control rods are fully inserted to the neutron flux φ when the control rods are inserted, A control rod operating method characterized in that the control rod is pulled out at high speed until the ratio reaches a predetermined value, and thereafter the control rod is gradually pulled out to bring the reactor into a critical state. 3. The control rod operating method according to claim 1, wherein a change in the core eigenvalue or the ratio value due to the insertion of the control rod is displayed on a monitoring screen. 4. The control rod operating method according to any one of claims 1 to 3, wherein the predetermined value is 0.99. 5. The control rod according to any one of claims 1 to 4, wherein the control rod is temporarily stopped at a predetermined stop position until the reactor period signal does not become smaller than a set value until the predetermined value is reached. A control rod operating method characterized in that the control rod is pulled out at high speed while stopped. 6. A method for operating a control rod of a nuclear reactor, wherein a control rod temporary stop position is set in advance so that a control rod temporary stop position is set so as not to be smaller than a set value during a control rod withdrawing operation. Mode, a block drive mode in which the control rod temporary stop position is preset and the control rod is driven in a predetermined block amount unit so that the reactivity during control rod operation is almost equal, and the control rod minimum operation unit amount (Hereinafter, referred to as step.) A step drive mode in which the control rod temporary stop position is set in advance and the control rod is operated step by step is prepared, and based on the current subcriticality of the reactor. A control rod operating method comprising operating a control rod in each of the drive modes. 7. The method according to claim 6, wherein the switching from the high speed drive mode to the block drive mode and the switch from the block drive mode to the step drive mode are performed when the core eigenvalues have reached respective predetermined values. Control rod operating method characterized by. 8. The method according to claim 6, wherein the deviation between the target neutron flux and the actual neutron flux or the deviation between the target heat output and the actual heat output is used as a determination condition while switching between the drive modes. A control rod operating method characterized by operating a control rod. 9. A control rod operating device at the time of starting a reactor, and a monitoring means for monitoring the core eigenvalue when the control rod is inserted,
A control rod operating device comprising: a control means for rapidly pulling out the control rod until the core eigenvalue reaches a predetermined value, and thereafter gradually pulling out the control rod to bring the reactor into a critical state. 10. A control rod operating device at reactor startup, for monitoring a value of a ratio (φ / φA) of a neutron flux φA when the control rods are fully inserted to a neutron flux φ when the control rods are inserted. And a control means for pulling out the control rod at high speed until the value of the ratio reaches a predetermined value and thereafter gradually pulling out the control rod to bring the reactor into a critical state. . 11. The method according to claim 9 or 10,
A control rod operating device comprising display means for displaying a change in the core eigenvalue or the ratio value due to insertion of the control rod on a monitoring screen. 12. The control rod operating device according to claim 9, wherein the predetermined value is 0.99. 13. A stop position determined in advance so that the reactor period signal does not become smaller than a set value until the predetermined value is reached, according to any one of claims 9 to 12. The control rod operating device is characterized in that the control rod is pulled out at high speed while the control rod is temporarily stopped. 14. A high speed drive for pulling out a control rod at a high speed by presetting a control rod temporary stop position so that a reactor period signal does not become smaller than a set value during a control rod pulling operation in a reactor control rod operating device. Mode, a block drive mode in which the control rod temporary stop position is preset and the control rod is driven in a predetermined block amount unit so that the reactivity during control rod operation is almost equal, and the control rod minimum operation unit amount (Hereinafter, referred to as step.) It has three control rod drive modes, namely, a step drive mode in which the control rod temporary stop position is set in advance and the control rod is operated step by step. A control rod operating device comprising control rod control means for operating the control rod in each of the drive modes based on the degree of criticality. 15. The control rod control means according to claim 14, wherein the switching from the high speed drive mode to the block drive mode and the switch from the block drive mode to the step drive mode are performed by presetting the core eigenvalues. A control rod operating device characterized in that it is carried out when a value is reached. 16. The control rod control means according to claim 14, wherein a deviation between a target neutron flux and an actual neutron flux, or a deviation between a target heat output and an actual heat output is used as a determination condition. A control rod operating device for operating a control rod while switching between the drive modes.