JPS6195291A - Load follow-up operation design device for boiling water type nuclear power plant - 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 load following operation planning device for a boiling water nuclear power plant.

[Technical Background PI of the Invention] In recent years, the proportion of nuclear power plants in the power system has increased, and nuclear power plants are no longer limited to base load operation.
It is necessary to perform load following operation. Core heat output control methods for boiling water reactors include a recirculation flow ffi control method that changes the density of the core, which is a neutron moderator, by changing its flow rate, thereby changing the core thermal output; There is a control rod operation method in which the core thermal output is changed by inserting and removing control rods, which are neutron absorbers, from the reactor core.

On the other hand, as a result of nuclear fission in the reactor core, iodine-135 and its daughter nucleus, xenone-135, are produced, but this xenone-135 is a neutron-absorbing substance, and when the core thermal output is changed, the xenone concentration changes temporally and spatially. It fluctuates. Therefore, when transitioning from high-output operation in the daytime to low-output operation at night in load following operation, or vice versa, the fluctuations in the xenone concentration distribution and, therefore, the accompanying fluctuations in the output distribution must be taken into consideration. The core flow rate must be adjusted and the control rods operated 41.

Figure 3 shows core thermal output, core flow rate, iodine concentration, and Zenon i7g when load following operation is performed with only core flow rate adjustment.
! Each shows a change in degree. In the Zunawara diagram, time is plotted on the horizontal axis, and core thermal output, core flow rate, xenone concentration, and iodine concentration are plotted on the vertical axis, and the curve a
represents the core thermal output, the curve C represents the core flow rate, the curve C represents the xenone concentration, and the curve d represents the temporal fluctuation of the iodine concentration.

As is clear from this figure, when the core flow h% is lowered, the core thermal output is lowered, and when the core flow rate is increased, the core thermal output reaches an upper limit. 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 ω 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 allowed only within the power distribution (hereinafter referred to as the PC envelope) obtained when the nuclear fuel is run-in in advance.

Therefore, when performing load following operation in a boiling water reactor, the above-mentioned core flow rate and core thermal power distribution must be
It is necessary to do so while adhering to certain restrictions.

By the way, when reducing the output during load following operation,
It is possible that the core flow rate falls below the lower limit of the core flow rate shown in FIG. In addition, when reducing the core flow rate in proportion to the decrease in Zenone concentration in order to maintain the output at a high level,
It is possible that the core flow rate may be below the minimum allowable core flow rate for high power. Furthermore, the power distribution changes during the flow rate drop during the above-mentioned power output, and there is a risk that the power will deviate from the PC envelope. There is a high possibility of envelope deviation. However, it is more difficult to expand the PC envelope in the lower part of the core through 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, control, and rod operation is required.

By the way, when operating control rods in order to limit the core flow rate and keep it within a certain value, it is necessary to select the control rods to be operated with sufficient consideration of the effect on the local flow rate. .

In addition, if the output exceeds the I) C envelope, insert a control rod near such a part and
It would be possible to relatively reduce the power output near the 11121I core, but the control rods cannot be easily manipulated because the power distribution in the core changes greatly by manipulating the control rods.

[Problems with inheritance technology] In general, operating control rods involves local fluctuations in the power distribution, so when planning m1ll m m operation, it is necessary to calculate the core state using a detailed three-dimensional reactor and core performance calculation program. There is. In load following operation planning that includes control rod operations, it is necessary to calculate how local output fluctuations caused by control rod operations change over time. Therefore,
It is necessary to calculate the core state not only at the time of control rod operation, but also at least during the period when local power fluctuations due to control rod operation remain, using a detailed three-dimensional core investigation program.

However, in general, in load following operation, output changes and shifts are repeatedly performed by control rod operations, so the number of plans for a three-dimensional core investigation program becomes enormous. For example, if you run a 3D core performance calculation program that takes 21 minutes per calculation using an online calculator that calculates 24 times per hour per day, and do this for one week, 5.6 hours will be spent on online calculations. becomes. In order to obtain the optimal operation plan, it is necessary to repeatedly perform such calculations, and there is a problem in that it is extremely time consuming and impractical to perform such calculations using a total of n1rA on-line meters.

[Object of the invention] The present invention has been made in response to such conventional circumstances,
Load following for boiling water nuclear power plants that can significantly reduce the total number of q times of three-dimensional core performance calculation program, which takes a total of 9 hours, compared to conventional methods when planning load following operations including control rod operations. It is intended to provide driving 41 strokes 5iiiia.

[Summary of the Invention 1 In other words, the present invention provides a plant/suspension 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, and a target load pattern and control system. An operator input device that inputs a sequence specifying the order of rod operation from an operator, and an operator input device that inputs the plant quantity, target load pattern, and sequence and creates a load following operation pattern based on these input data. A control rod pattern estimating device for high output that calculates a υ111a rod pattern in a high output period of This is a load following operation planning device for a boiling water nuclear power plant, characterized in that it is equipped with a bar pattern estimating device.

[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 system for a boiling water nuclear power plant according to the present invention. The plant that inputs the quantity has an input device v
12, an operator interaction device 5 equipped with an operator input device 3 and a display device 4, a high power control rod pattern estimation device 6, a low power control rod pattern estimation device 7, and a control rod pattern adjustment device 1'' device 8. The main part consists of

That is, the plant quantity 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.

The operator input device 3 receives input from the operator of a target load pattern (temporal change in generator output) or a sequence specifying the order of control rod operations.

The high output control rod pattern designation device 6 is a plant quantity manual v
The equipment 2 manually inputs the plant field, and the operator-powered equipment 3 manually inputs the load patterns of 11 stations, sequences specifying the order of control rod operations, etc., and controls Gj during the high output period of the load pattern based on these values. Find the bar pattern.

Figure 2 shows the flow of processing in the high output control rod pattern 111 setting device d6, and in this high output control rod pattern 111 setting device 66, J3 is in negative fishing follow-up operation, and during the Takayama/J operation period. The characteristic that the amount of variation in core characteristics depends only on the load pattern and not on the control rod pattern at that time is utilized.

In other words, this high output control rod pattern (1 [standard M6
First, an initial control rod pattern equilibrium Zenon sieve is performed using the current control rod pattern input manually from the plant quantity input device u2 as an initial pattern, and an equilibrium Zenon is assumed.
Ru. From this state, changes in the core state after target load-following operation is performed without any intermediate it or II lit rod operations are predicted using a one-dimensional core model. and,
Based on the results, the amount of excess from the operational limit value of the reactor operable range and the PC envelope is determined.

During the high-output operation period, if the operation m1ll limit is not exceeded, the current control rod pattern is adopted as the control rod pattern for high-output operation, and the control rod pattern estimation system for low-output M7 described below is used. An action is taken.

On the other hand, if the operating limit value is exceeded, this deviation m
A control rod pattern that has more margin than the initial control rod pattern by that amount is searched for.

That is, another i, II m rod pattern included in the control rod sequence input from the operating noble saw device 3 is estimated, and the balanced Zenon sieve is performed in the same way as the previous time, and this and the previous initial 1-1w dedication are estimated. The results of the equilibrium Zenon meter etc. in the pattern are compared, and it is determined whether there is enough margin to compensate for the above-mentioned deviation. If this condition is not met, the control rod pattern is further changed and this control rod pattern is evaluated.

The above-described operations are repeated until a control rod pattern with enough margin to compensate for the deviation is found.

In this high-power control rod pattern estimating device 6, only the calculation of the equilibrium Zeno state of different control rod patterns is performed using a three-dimensional core performance calculation program, and load following operation is performed from the equilibrium Zeno state of the initial control rod pattern. Calculations of temporal fluctuations are performed using a one-dimensional reactor core model.

Note that since there is no local variation in the change in the three-dimensional output distribution at this time, it can be estimated using the following equation from only the change in the one-dimensional output distribution in the axial direction.

P+ , J , h ([)=P+ , J ,
k(0)X(Plh(t))/(Pli
(0)) Here, F'+, J Ik (11: Three-dimensional output distribution after time P+, J, h (o): Three-dimensional output distribution at the initial time point (equilibrium Zeno time point) Plh (t): Axial one-dimensional power distribution after time Plm(0): Axial one-dimensional power distribution at the initial time The low-output control rod pattern estimator N7 receives the high-output control rod pattern from the high-output control rod pattern estimator 6. The !l1IIIl bar pattern determined by the estimation device 6 is input, and the adl 10 bar pattern in the low output period of the load pattern is determined.

In other words, in this low power control rod pattern estimating device 27, restrictions on the power distribution such as the PC envelope do not pose a problem at low power, and there is only a possibility that the reactor deviates from the operable range. Using the one-dimensional reactor core model or point model described above, a control rod pattern that will bring the core flow rate within the operable range by 1° is estimated.

The control rod pattern adjustment device 8 adjusts the control rod pattern for high output (
"Station device 6 and low power control rod pattern estimation KiM7
R11l during the high output period obtained by
The optimum control rod pattern is determined by roughly adjusting the entire III rod pattern and the E control rod pattern during the low power period.

However, the control rod patterns determined by the high-power control rod pattern estimation device N6 and the low-power control rod pattern estimation device 7 are obtained without taking into account temporal fluctuations. The pattern adjustment device 68 uses these control rod patterns to calculate temporal fluctuations, and adjusts the control rod pattern by 1 degree if the control rod pattern deviates from the operating limit 11I'j.

Note that due to the characteristics of the load following operation described above, adjustment by the control rod pattern adjustment f1 device 8 is not required in most cases, and there are very few cases in which adjustment is required.

In addition, since final confirmation measurements are performed in this control rod pattern adjustment device 8, measurements are performed using the three-dimensional core control program during periods when there are local output fluctuations due to control rod operations, and other In this case, the core state is calculated by one-dimensional calculation.

[Effect of the invention 1] As described above, according to the load following operation planning device for a boiling water nuclear power plant of the present invention, the final confirmation period can be determined by performing calculations many times using a three-dimensional core performance calculation program. Is it done but the best l1ilJ w stick pa? In the process of determining the 3-dimensional core performance calculation program, calculations are performed only once for each control rod pattern, and as a result, the time required for operation planning can be significantly reduced compared to the conventional method. - Therefore, it becomes possible to create an operation plan using online 81 control, and the flexibility and responsiveness of nuclear power plant operation can be greatly improved compared to the past.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the load following operation planning system d for a boiling water nuclear power plant according to the present invention, and FIG. 2 is a block diagram of the high output control rod pattern estimating system shown in FIG. −
The chart, Figure 3 is a graph showing changes in the required heat output, Zenon 11 degrees and iodine concentration for load following operation, and Figure 4 shows the range in which the reactor can be operated. 1・・・・・・・・・・・・Reactor 2・・・・・・・・・・・・Plant quantity increase device n3・
・・・・・・・・・・Driving day human power system 4・・・・・・
... Display device 5 ... Operator interaction device 6 ...
...... Control rod pattern estimating device 7 for high power ...... It, II il for low power
L-rod pattern estimation device 8... Control rod pattern adjustment device 9
......3D Core Performance Calculation Program Patent Attorney Sasa Suyama - Figure 1 Figure 3 Gin Eyebrow Figure 4

Claims (1)

[Claims] (1) Core flow rate from various measuring instruments installed inside the reactor,
A plant quantity input device for inputting plant quantities such as core pressure and neutron flux, an operator input device for inputting sequences for specifying target load patterns and control rod operation orders from operators, A control rod pattern estimating device for high output that inputs a load pattern and a sequence and calculates a control rod pattern in a high output period of a load following operation pattern based on these input data; A load following operation planning device for a boiling water nuclear power plant, comprising: a low output control rod pattern estimating device that determines a control rod pattern during a low output period of a following operation pattern.