JPH0456958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a load following operation planning device for a nuclear power plant that plans load following operation of a boiling water nuclear power plant.

[Technical Background of the Invention] Recently, the proportion of nuclear power generation in the electric power system has increased, and it has become necessary to perform load following operation without keeping nuclear power plants in base load operation. Core thermal output control methods for boiling water reactors include a recirculation flow rate control method that changes the core thermal output by changing the core flow rate of the neutron moderator, which changes its density, and this changes the core thermal output. There is a control rod operation method that changes the core thermal output by inserting and removing control rods from the reactor core.

Meanwhile, as a result of nuclear fission in the reactor core, iodine-135
and its daughter nucleus Zenon 135 is produced,
This Zenon-135 is a neutron absorbing substance, and when the core thermal output is changed, the Zenone concentration fluctuates temporally and spatially. Therefore, when transitioning from high-output operation during the daytime to low-output operation at night during load following operation, or vice versa, it is important to fully consider the fluctuations in the xenone concentration distribution and, therefore, the associated fluctuations in the output distribution. The reactor core flow must be adjusted and the control rods operated.

FIG. 3 shows changes in core thermal output, core flow rate, iodine concentration, and xenone concentration when load following operation is performed only by adjusting core flow rate. In other words, in the figure, the horizontal axis represents time, and the vertical axis represents core thermal output, core flow rate, xenone concentration, and iodine concentration, where curve a represents core thermal output, curve b represents core flow rate, and curve c represents core thermal output. The xenone concentration and the curve d represent the temporal fluctuations of the iodine concentration.

As is clear from this figure, decreasing the core flow rate lowers the core thermal output, and increasing the core flow rate increases the core thermal output. Furthermore, in order to maintain a constant output, the core flow rate must also be increased or decreased in response to the increase or decrease in the xenone concentration. In addition, the core thermal power distribution also changes temporally and spatially as the Zenone concentration distribution changes and the core flow rate changes.

In addition, in boiling water reactors, the relationship between core thermal output and core flow rate is regulated in order to maintain the integrity of the nuclear fuel and various equipment, and the reactor must be operated within these limits. FIG. 4 shows such a limited range, with the horizontal axis representing the core flow rate and the vertical axis representing the core thermal output, with the shaded area being the reactor operating range. Furthermore, in order to maintain the integrity of the nuclear fuel, changes in the power distribution are only allowed within the power distribution (hereinafter referred to as the PC envelope) that was established when the nuclear fuel was run-in in advance.

Therefore, when load following operation is performed in a boiling water reactor, it is necessary to maintain the two restrictions on the core flow rate and core thermal power distribution described above.

By the way, when reducing the output in the load following operation, the core flow rate may fall below the lower limit of the core flow rate shown in FIG. 4. Furthermore, when the core flow rate is reduced in proportion to the decrease in the xenone concentration in order to maintain the power at a high power level, the core flow rate may fall below the minimum allowable core flow rate for the high power level. Furthermore, there is a possibility that the output distribution changes during the above-mentioned flow rate drop at high output, resulting in a region where the output deviates from the PC envelope. In particular, the power fluctuations in the lower part of the core are large, so there is a high possibility of deviation of the PC envelope in the lower part of the core. However, it is more difficult to expand the PC envelope in the lower part of the core during the break-in operation than in the upper and middle parts of the core.

Therefore, in order to change the core thermal output within the above-mentioned two limits, a combination of core flow rate adjustment and control rod manipulation is required.

By the way, when operating control rods in order to keep the core flow rate within a limit value, it is necessary to select the control rods to be operated while fully considering the influence on the local power distribution.

In addition, if the output deviates from the PC envelope, it is possible to insert a control rod near such a part to relatively reduce the output near the control rod, but by operating the control rod, The control rods cannot be easily manipulated because the power distribution of the reactor core changes significantly.

[Problems with the background technology] As described above, boiling water nuclear power plants generally have various constraints, so in order to implement load following operation, detailed calculations including so-called Zenon transition calculations are required using an offline large-scale computer. After performing detailed confirmation calculations on the target load-following operation pattern using a core performance calculation program, it was necessary to implement load-following operation. In some cases, it may be necessary to expand the PC envelope to implement the target load-following operation pattern, but in this case, the control rod pattern should be adjusted and a break-in operation performed prior to load-following operation. There is a need to.

Therefore, conventionally, in order to perform load following operation, a large amount of calculation time and break-in operation time are consumed, and the amount of work involved is enormous.

Furthermore, in order to change the target load following operation pattern that has become executable after these operations and implement another load following operation pattern, it is necessary to perform the aforementioned operations again.

It is extremely difficult to change a load following operation pattern once created in this way, and as a result, conventional nuclear power plants have extremely limited operational flexibility.

[Object of the Invention] The present invention has been made in response to the above-mentioned conventional circumstances, and is a method for high-output operation during daytime using a predetermined control rod operation method within the allowable operating range of a boiling water nuclear power plant. The present invention aims to provide a load-following operation planning device for a nuclear power plant that can quickly create an operable load-following operation pattern while ensuring the output level and operation period.

[Summary of the Invention] That is, the present invention provides a plant data input device that inputs plant quantities such as core flow rate, core pressure, and neutron flux from various measuring instruments installed in a nuclear reactor;
A control rod operation procedure storage device that stores control rod operation procedures input in advance, and a low output operation at night based on the high output level during the day and the required value of the operation period by inputting the plant amount and control rod operation procedure. A low output operation possible range prediction device that calculates the output level, inputs the low output level instructed by the operator, gives an operation period in which this low output level operation is possible, and inputs the low output operation period specified by the operator. This is a load following operation planning device for a nuclear power plant, characterized by comprising a load pattern creation device that provides a minimum output level that can be operated over the low output operation period.

[Embodiment of the Invention] The details of the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 shows an embodiment of the load following operation planning device for a nuclear power plant according to the present invention. 2. The main part consists of an operator console 5 equipped with a display device 3 and an input device 4, a control rod operation procedure storage device 6, a low power operation possible range prediction device 7, a load pattern creation device 8, and an operation characteristic evaluation device 9. has been done.

That is, the plant data input device 2 inputs plant quantities such as core flow rate, core pressure, neutron flux, etc. from various measuring instruments installed in the nuclear reactor 1.

A display device 3 disposed within the operator console 5 outputs various information created within the load following operation planning device and transmits this information to the operator.
Further, the input device 4 inputs various requests from the operator.

The control rod operating procedure storage device 6 stores control rod operating procedures input in advance from the input device 4 of the operator console 5.

The low power operation possible region prediction device 7 inputs the daytime high power level and the required value of the operation period from the input device 4, and also inputs the plant amount from the plant data input device 2 and control rod operation from the control rod operation procedure storage device 6. Enter the procedure and determine the output level that allows low-output operation at night based on this information.

That is, this low power operation possible region prediction device 7
Now, predictions of changes in core state quantities such as reactor power, core flow rate, and power distribution are carried out using a one-dimensional core model that includes Zenon dynamic characteristic calculations, as described in, for example, JP-A-54-39795. be done.

On the other hand, since control rod operations are determined in advance, changes in power distribution due to control rod operations can be calculated by storing the results calculated in advance using the three-dimensional core model described in, for example, JP-A-56-168595. , for changes in the actual core state, the power distribution can be determined by the following correction calculations.

P _ijk = P° _ijk × (P1 _k )/(P1° _k ) where P _ijk : Three-dimensional power distribution corresponding to the actual core state P° _ijk : Pre-calculated three-dimensional power distribution P1 _k : Actual One-dimensional power distribution corresponding to the core state (predicted by a one-dimensional core model) P1° _k : One-dimensional power distribution obtained by averaging P° _ijk in the radial direction Furthermore, the low-power operation possible region prediction device 7 From the power distribution obtained in this way, the linear power density and critical power ratio, which are constraints on the fuel, are calculated to determine the lowest possible output level within the operating range and while satisfying the fuel constraints. demand.

The low power operable region prediction device 7 performs such calculations at each time point, but as described above, a one-dimensional model is sufficient for core performance calculations, so calculations can be performed in a very short time.

The thus predicted low power operation possible region is displayed on the display device 3 in the operator console 5 in the form of a graph as shown in FIG. 2, for example.

That is, in FIG. 2, P _H indicates the required high output level, and T _H indicates the required high output operation period. Further, curve a indicates a low output operation limit line, and load following operation at output levels such as curves b and c shown by broken lines above this line is permitted.

The load pattern creation device 8 inputs the low output level instructed by the operator from the input device 4, calculates the possible operating period, and outputs it to the display device 3. Conversely, the operating period specified by the operator is input from the input device 4, and the lowest possible output level within this operating period is calculated and output to the display device 3.

The operating characteristics evaluation device 9 inputs the load pattern determined by the operator from the input device 4, evaluates the core characteristics when this load pattern is implemented, and outputs the results to the display device 3.

That is, this operating characteristic evaluation device 9 calculates the core state quantity by using substantially the same means as the low power operation possible region prediction device 7 described above. Then, the linear power density and critical power ratio, which are the constraint conditions for the fuel, are calculated from this core state quantity, and the margin for each limit value is evaluated, and the results are output to the display device 3. do.

The load following operation planning device for a nuclear power plant configured as described above is used as described below.

That is, first, a high output level and its operating period are input into the input device 4 by an operator, giving priority to ensuring high output operation during the day in order to maintain a high availability rate of the nuclear power plant.

The high output level and its operating period input into the input device 4 in this way are output to the low-output operation possible range prediction device 7, and in this low-output operation possible range prediction device 7, the high output level and its operating period are calculated. The low power operation possible range prediction device 7 predicts a low power level that can be operated within the range that can be secured and without changing the control rod operation procedure stored in the control rod operation procedure storage device 6.

In this way, the low power operation possible region prediction device 7
The predicted low power operation possible region is displayed on the display device 3 of the operator console 5 in the form of a graph as shown in FIG. 2, which has already been described.

In this way, the operator determines the optimal load following operation pattern within the operable area displayed on the display device 3, but in order to make this determination, the operator must, for example, The output level shown by curve b is input to the input device 4.

The output level input to the input device 4 is output to the load pattern creation device 8, the load pattern creation device 8 determines a period during which operation is possible at this output level, and this operation period is output to the display device 3. The low output period is displayed on the screen in the form shown in FIG.

If the operator who sees this display determines that this period is not appropriate due to reasons such as being too short, the operator re-enters another low output level and the load pattern creation device 8 calculates it. A redo will take place.

Moreover, the operator can obtain the lowest output level at which operation is possible using the load pattern creation device 8 by inputting the low output operation period into the input device 4 instead of the output level.

In this way, the load following operation planning device for a nuclear power plant of this embodiment can determine the load following operation pattern through interaction with the operator.

Once the low power level and its operation period are determined by such a procedure, the core characteristics when the operation is carried out are evaluated by the operation characteristics evaluation device 9,
The evaluation contents of this driving characteristic evaluation device 9 are displayed on the display device 3.
The information is output to the operator and communicated to the operator.

[Effects of the Invention] As described above, according to the load following operation planning device for a nuclear power plant of the present invention, the high output level and its operation period required to avoid unnecessarily lowering the operating rate of the nuclear power plant can be adjusted. Once this is ensured, the load following operation pattern can be easily changed without violating various constraints on the core.

In addition, since the operable area is displayed on the display, operators can easily formulate a load following operation plan, and this can also be used in the event that it is necessary to urgently change the load following operation pattern. Can be dealt with quickly.

As a result, the flexibility of nuclear power plants can be significantly increased compared to the past.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the load following operation planning device for a nuclear power plant of the present invention, Fig. 2 is a graph showing a low output operation possible region displayed on a display device, and Fig. 3 is a load following operation planning device for a nuclear power plant according to the present invention. A graph showing changes in core thermal output, xenone concentration, and iodine concentration during operation, and FIG. 4 is a graph showing the limit range for reactor operation. 1... Nuclear reactor, 2... Plant data input device, 3... Display device, 4... Input device, 5... Operator console, 6... Control rod operation procedure storage device, 7... Low power operation possible area Prediction device, 8...
...Load pattern creation device, 9...Driving characteristic evaluation device.

Claims (1)

[Claims] 1. A plant data input device that inputs plant quantities such as core flow rate, core pressure, and neutron flux from various measuring instruments installed in the reactor, and a control rod operation procedure memory that stores control rod operation procedures input in advance. a device, a low power operation possible range prediction device that inputs the plant amount and control rod operation procedure and calculates an output level that allows low power operation at night based on the daytime high power level and the required value of the operation period, and an operator. A load pattern that inputs the low output level instructed by the operator and gives an operation period in which this low output level operation is possible, and also inputs the low output operation period instructed by the operator and gives the lowest output level that can be operated over the low output operation period. 1. A load following operation planning device for a nuclear power plant, comprising: a creation device.