JPH0687079B2 - Reactor operation control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reactor operation control method applied to an operation involving a change in output, for example, in a pressurized water reactor.

[Prior Art] For example, in a pressurized water reactor, an operation involving a change in the output of the reactor corresponding to a change in load is divided into the following three basic modes, which are operated alone or in combination with each other. To be done.

(1) Operation mode based on a predetermined output change pattern (2) Operation mode in which output is changed randomly in response to external demand (3) External demand or load This is an operation mode that automatically changes the output according to changes.

Generally, the demand for the power variation range of a nuclear reactor is high in the order of (1), (2), (3), and the demand frequency for the power variation is in the order of (3), (2), (1). high.

Conventionally, for these operations, reactivity was adjusted by moving one type of control rod group with multiple groups and manually adjusting the boron concentration in the temporary coolant. When the rate of change is large, the range of output change is limited from the viewpoint of keeping the output distribution and distortion within the limit values, and the operation mode of (1) above is limited.

Therefore, in order to eliminate this point, a method of using two types of control rod groups having different degrees of influence on the output distribution has been proposed.

As a concrete example of this, as shown in Japanese Patent Publication No. 58-34795, the insertion degree of a control rod group (hereinafter referred to as a weak absorption control rod), which has a smaller effect on the power distribution, is a function of the turbine required output. The control rod group that is uniquely determined and has a greater effect on the power distribution (hereinafter referred to as the strong absorption control rod) moves according to the deviation from the reference value of the primary coolant average temperature, and the axial direction. This is a method of keeping the axial power distribution deviation within a predetermined range by changing the average temperature by adjusting boron, which is performed according to the power distribution deviation (hereinafter referred to as the F method).

In addition to the F method, as shown in Japanese Patent Application No. 61-206836, the output of the strong absorption control rod changes and the deviation of the average primary coolant temperature from the reference value occurs in accordance with the output change. Then, the strong absorption control rod is moved according to the axial power distribution deviation, and the strong absorption control rod is moved through the average temperature deviation thereby, so that the axial power distribution deviation deviation is kept within a predetermined range. The adjustment is a method (hereinafter, referred to as M method) used exclusively as an auxiliary for the weak absorption control rod.

The above-mentioned F method and M method have the following differences in performance. In general, the performances for the above operations (1) to (3) are evaluated mainly in the following points.

(4) Arbitraryness to load pattern, that is, followability to sudden load changes and unplanned random load changes (5) Water treatment amount It is necessary to treat the discharged water accompanying the boron concentration adjustment,
The amount of treated water in the plant increases as the boron concentration adjustment range increases. Further, even if the adjustment range is about the same, the water treatment amount increases as the boron concentration in the primary coolant decreases.
Therefore, in the case of the operating method having a high dependency on the boron concentration adjustment, the load following operation is limited at the end of the life of the core.

(6) Burden on equipment The number of operations of each control equipment increases due to various parameter fluctuations that accompany changes in output, but especially because the control rod drive mechanism is difficult to replace, the control rod movement amount should not be excessive. is necessary.

(7) Equipment cost This is the equipment cost required to perform load following operation.

[Problems to be Solved by the Invention] However, in the operation of a nuclear reactor including output changes as described in (1) to (3) above, control elements such as control rods and boron are generally accompanied by combustion of fuel. In addition to long-term core reactivity adjustment, it is necessary to compensate for the following two reaction changes.

(8) Change in reactivity caused by change in temperature of moderator and fuel due to change in output (hereinafter referred to as output loss).

(9) Changes in reactivity due to changes in the amount of xenon (hereinafter referred to as Xe) in the core caused by changes in power (hereinafter referred to as Xe
Called a defect).

In the method of F, since the weak absorption control rod is substantially inserted so as to compensate for the loss of the output, the full output can be rapidly returned at any time, and the random absorption like the above (2) is performed. Although it is adaptable to output change requirements, the above
Compensation for the Xe deficiency is substantially only by adjusting the boron concentration, so the amount of water treatment described in (5) above becomes large, which is not preferable. Further, when performing the operation of (3) above, there is a very frequent output change, but when the weak absorption control rod position is controlled as a unique function of output as in this method, the above (3) The output deficiency due to the operation of is compensated only by the weak absorption control rod, and the control rod movement amount becomes excessive due to the small reactivity value, and there is a problem as described in (6) above.

The method of M can solve the problems of the method of F described above, but the relationship in which the axial power distribution deviation is corrected by the strong absorption control rod through the change of the primary coolant average temperature due to the movement of the weak absorption control rod Moreover, in order to avoid mutual interference between the control rods of both groups, it is necessary to make the influence on the output distribution of the weak absorption control rods much smaller than that of the above method F, and the number of control rods required is inevitable. Increases, causing the problem (7) above.

Therefore, it is an object of the present invention to provide a reactor operation control method capable of ensuring the load following ability required by a relatively small number of control rods and reducing the amount of water treatment.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a weak absorption control rod and a strong absorption control rod as control rods that are inserted into and removed from the core of a reactor vessel, and In operating a nuclear reactor having the average temperature deviation calculating device and the axial power distribution deviation calculating device, the average temperature deviation of the reactor coolant and the axial power distribution deviation (ΔI) are monitored to detect the strong absorption control rod. By pulling or inserting, the strong absorption control rod is driven when both the average temperature deviation of the reactor coolant and the axial power distribution deviation are small, and the weak absorption control rod is driven in other cases. Then, the reactivity of the reactor is adjusted to control the operation of the reactor.

[Operation] As described above, by selecting either the strong absorption control rod or the weak absorption control rod according to the deviation of the average temperature and moving the rod, the load following ability required by a relatively small number of control rods can be obtained. It can be secured and the amount of water treatment can be reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First, the concept of the operation control method of the present invention will be described with reference to FIG. The weak absorption control rod GR or the strong absorption control rod D is selected and driven according to the axial output distribution deviation ΔI represented by the following equation by the deviation signal from the reference value of the primary coolant average temperature. This selection is made when the deviation of the axial output distribution deviation ΔI from the control target value at that time is corrected simultaneously with the temperature deviation when the control rod movement is performed by the strong absorption control rod D. If the strong absorption control rod D is selected, and in other cases or if the deviation from the target value becomes larger due to the movement of the strong absorption control rod, the weak absorption control with less influence on the axial output distribution deviation ΔI. Do so that bar GR is selected.

ΔI = P _T −P _B P _T : Ratio of upper half power to rated core power (%) P _B : Ratio of lower half power to core rated power (%) Next, referring to FIG. The concept of drive control rod selection based on the axial output distribution deviation ΔI will be described. When the deviation from the reference value of the primary coolant average temperature, that is, the temperature deviation ΔT is negative, that is, when the demand is continued, when the strong absorption control rod D is pulled out, the axial output distribution deviation ΔI shifts to the positive side. As shown in FIG. 2A, when ΔI is on the negative side to some extent (for example, 2%) with respect to the control target [shaded portion in FIG. 2 (a)], the strong absorption control rod D is selected. Is
In other cases, the weak absorption control rod GR is selected. Similarly, when the temperature deviation ΔT is positive and the control rod is inserted, the opposite is true, and as shown in FIG. 2 (b), ΔI is a deviation on the positive side to some extent (for example, 2%) or more from the control target. If you have [the shaded area in Fig. 2 (b)], the strong absorption control rod D
Is selected and inserted, otherwise the weak absorption control rod GR is selected and inserted.

With such a method, the control rod is moved in the best way from the viewpoint of the output distribution at that time, ignoring the useless movement of the control rod, and controlling the mutual movement of the two types of control rods. Control can be performed by ignoring interference. Moreover, in the case of the selection index as shown in FIG. 2, the weak absorption control rod is used during the operation of (3) above.
In many cases, the GR is driven selectively, and as a result, the amount of movement of the weak absorption control rod GR increases, and when the problem of (6) above occurs, the control rod selection boundary with respect to the control target in FIG. This can be dealt with by changing the position of the line (solid line in the figure) and changing the set value, for example. That is, as shown in FIG. 2 (a), the boundary line is shifted to the ΔI positive side (right side of the figure), and to FIG. 2 (b) to the ΔI negative side (left side of the figure). The amount of weak absorption control rod movement decreases and the amount of strong absorption control rod movement increases.

In this case, the increase amount of the strong absorption control rod movement amount becomes smaller than the decrease amount of the weak absorption control rod movement amount due to the difference in the control rod value. FIG. 3 shows a case where the boundary line is shifted in order to reduce the movement amount of the weak absorption control rod in FIG.
FIG. 3 (a) shows the case where the temperature deviation is negative, that is, the drawing request, and FIG. 3 (b) shows the case where the temperature deviation is positive, that is, the insertion request.

Next, an example of the present invention will be described. Here, the object of control is for a 4-loop pressurized water reactor, and the weak absorption control rod has a neutron absorption capability in the vertical axis direction. The lower half is set small and the upper half is set large, and four are used as one group and used in a two-group configuration.

FIG. 4 shows an example of the weak absorption control rod moving range, in which the horizontal axis represents relative output and the vertical axis represents the weak absorption control rod insertion degree. Within the range surrounded by the drawing limit of the solid line and the insertion limit of the broken line in the figure, the weak absorption control rod, according to the primary coolant average temperature deviation, by the value of the axial power distribution deviation,
Driven when the weak absorption control rod is selected, by compensating not only the output loss but also a part or all of the Xe loss,
The amount of water treatment can be reduced. That is, the typical movement of the weak absorption control rod is as follows.

(A) When the output is decreased, the average temperature is sequentially inserted due to an increase in the deviation on the positive side → (b) After the output has been decreased, it is pulled out due to the temperature deviation on the negative side due to the accumulation of Xe → (c) When the extraction limit is pulled out Is stopped → (d) If the partial output state is long, insert due to the positive side temperature deviation due to the collapse of Xe → (e) When the output rises, pull out due to the negative side temperature deviation.

Generally, the insertion limit shown in FIG. 4 may be set as necessary from the viewpoint of the safety of the core such as securing a stop margin, and the pulling-out limit is set from the partial output state required for the plant in operation. Determined by rapid output recovery capability. That is, if the pulling-out restriction line in FIG. 4 is set to the lower part of the drawing, the rapid output recovery capability is improved, and if it is set to the upper part, the required amount for the boron concentration, that is, the water treatment amount is reduced.

FIG. 5 shows a simulation calculation result for the operation (1) using the weak absorption control rod moving range shown in FIG. In the figure, G1 and G2 are the first and second groups of weak absorption control rods, respectively.
The second group G2 is allowed up to full withdrawal at 50% output, and D is a strong absorption control rod. As is clear from this figure, the output decreased from the full output to 50% output in 1 hour, and after the 50% output was maintained for 8 hours, the full output was restored in 1 hour. Then, the weak absorption control rod moves as described above, and the fluctuation of ΔI is controlled within a slight range.

FIG. 6 shows calculation results for the case where the weak absorption control rod insertion degree is used as a function of the output in order to clarify the effect on the boron concentration change. It can be seen that the range of change in boron concentration, that is, the amount of water treated is greatly reduced by the operation control method according to the present invention shown in FIG.

FIG. 7 shows the basic configuration of the control system according to the present invention.
A control rod drive request signal, a control rod drive system by a signal ΔI for selection, a boron concentration change request by a ΔI deviation, and a boron concentration control system by a boron concentration change request when the control rod position reaches its limit. Controlled by.

According to the embodiment of the present invention described above, the weak absorption control rod
Set the range where the GR can move freely even under constant output,
By moving the primary coolant average temperature in this range according to the temperature deviation ΔT from the reference value, the weak absorption control rod GR
Can compensate not only the output loss but also at least part of the Xe loss. In addition, strong absorption control rod D and weak absorption control rod GR
Is selected according to the deviation of the average temperature and moved, and the control of the axial power distribution is made good as an index for the selection, and only one control rod movement amount does not increase. Since the axial power distribution deviation signal is used for the, it is possible to secure the load following ability required by a relatively small number of control rods and reduce the amount of water treatment.

[Effects of the Invention] According to the present invention described above, it is possible to provide a reactor operation control method capable of ensuring the load following ability required by a relatively small number of control rods and reducing the amount of water treatment.

[Brief description of drawings]

1 is a diagram for explaining the concept of a nuclear reactor operation control method of the present invention, FIG. 2 is a diagram for explaining the concept of control rod selection based on the axial power distribution deviation ΔI in FIG. 1, FIG. 3 is a diagram for explaining a method for reducing the amount of weak absorption control rod movement in FIG. 2, FIG. 4 is a diagram showing an example of setting the weak absorption control rod movement range according to the present invention, and FIG. 5 is the present invention. FIG. 6 is a diagram showing parameter changes during load value following operation when the operation control method according to FIG. 6 is used, FIG. 6 is a diagram showing parameter changes during load following operation according to the conventional operation method, and FIG. 7 is a control system according to the present invention. It is a figure which shows the basic composition of. GR: Weak absorption control rod, D: Strong absorption control rod, ΔI: Axial output distribution deviation, ΔI: Primary coolant average temperature deviation.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 999999999 Japan Atomic Power Company 1-6-1, Otemachi, Chiyoda-ku, Tokyo (71) Applicant 999999999 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. No. (72) Inventor Akio Tamura 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Hiroyuki Dan, 2-1-2 Watanabe-dori, Chuo-ku, Fukuoka-shi, Fukuoka Kyushu Electric Power Co., Inc. In-house (72) Inventor Yoshinobu Takahashi 1-6-1, Otemachi, Chiyoda-ku, Tokyo Nihon Nuclear Power Co., Inc. (72) In-house Takashi Kanagawa 2-4-1, Shiba-koen, Minato-ku, Tokyo Mitsubishi Hara Within Riki Kogyo Co., Ltd. (72) Inventor ▲ Yoshi ▼ Ryoji Ki, 2-4-1, Shiba Park, Minato-ku, Tokyo Inside Mitsubishi Harako Riki Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A weak absorption control rod and a strong absorption control rod are provided as control rods that are inserted into and removed from a core of a reactor vessel, and a reactor coolant average temperature deviation calculation device and an axial power distribution deviation calculation device are provided. When operating the reactor, the average temperature deviation of the reactor coolant and the axial power distribution deviation (ΔI) are monitored, and the average temperature deviation of the reactor coolant is extracted by pulling out or inserting the strong absorption control rod. And the axial power distribution deviation are both small, the strong absorption control rod is driven, and in other cases, the weak absorption control rod is driven to adjust the reactivity in the core. Reactor operation control method.