JP2544487B2 - Channel Box Deformation Evaluation Method - Google Patents

Description

The present invention relates to a method for evaluating deformation of a channel box, and more particularly to a method for evaluating a channel box deformation during one combustion cycle period of a nuclear reactor.

[Conventional technology]

Generally, a fuel assembly for a boiling water light water reactor (BWR) has, for example, 62 fuel rods and 2 water rods arranged in a grid with 8 rows and 88 columns (referred to as 8 × 8), an upper tie plate and a lower tie plate and spacers. The structure is such that the fuel bundle configured to be held by is housed in a channel box made of Zircaloy 4 (zirconium alloy).

A large number of fuel assemblies configured as described above are arranged and housed in the reactor core as shown in FIG. The number of fuel assemblies in the core is about 400 to 764, depending on the required power of the reactor.

Four fuel assemblies in the core constitute one cell. A cross-shaped control rod is inserted into a cross-shaped gap formed between four fuel assemblies at the center of each cell. An identification number and core array position coordinates (I, J) are given to each fuel assembly in the core so that they can be identified.

Conventionally, the amount of deformation of the channel box during the loading period inside the reactor has been calculated using an empirical formula created based on the measured data of the actual reactor.

[Problems to be Solved by the Invention]

The present invention has been made by studying the deformation prediction of a channel box as shown below.

The deformation of the channel box of the fuel assembly during the combustion cycle of the reactor is shown in Fig. 23 (a).
And FIG. 23 (b).

FIG. 23 (a) and FIG. 23 (b) are explanatory views of the deformation state when the channel box is irradiated in the furnace.
FIG. 24 is a cross sectional view showing one cell showing four assembly channel boxes and a cross-shaped control rod.

When the fuel assembly is loaded in the core, a small amount of coolant flows not only in the main coolant passage formed in the channel box but also in the gears between the fuel assemblies.
Therefore, the pressure difference (ΔP) inside and outside the channel box
Occurs. This pressure difference ΔP and reactor water temperature (280-300
C.), the channel box undergoes creep deformation and swells in the horizontal direction as shown in FIG. 23 (a). In addition, since the creep rate of zircaloy under irradiation is faster than that under non-irradiation, the swollen amount of the channel box depends on the fast neutron flux (φ). The pressure difference ΔP, which is the main factor of swelling, becomes maximum at the lowermost end of the fuel assembly, and the fast neutron flux φ becomes maximum at the central portion in the core axis direction. Therefore, the expansion amount of the channel box has an axial distribution, and becomes the largest at a position about 1/3 from the lowermost end of the fuel assembly. Further, the swelling of the channel box varies depending on the loading position of the corresponding fuel assembly in the core, is large in the central portion of the core, and is small in the outermost peripheral portion of the core.

Further, the zircaloy used for the channel box has crystal grain orientations aligned in a fixed direction during manufacturing, and therefore, it deforms in a specific direction under the radiation irradiation environment even in the absence of external stress. This phenomenon is called irradiation growth, and is responsible for the widthwise bending of the entire channel box.

The irradiation growth amount of zircaloy largely depends on the difference in material properties and the irradiation condition of radiation, especially fast neutron flux. If there is a large difference in the fast neutron flux between the opposite sides of the channel box, there will be a difference in the amount of irradiation growth between the opposite sides. Since the upper and lower ends of the channel box are supported by the fuel assembly, the axial center of the channel box is displaced based on the difference in irradiation growth amount described above,
The entire channel box is bent in the axial direction as shown by the broken line in FIG. The bend of the channel box also differs depending on the loading position in the core. Since the fast neutron flux gradient is small in the central part of the core, the bending amount of the channel box is small, but at the outermost core part, a large fast neutron flux gradient is generated between the facing sides of the channel box, so the bending amount is large.

When the loading period of the inner core of CHANNEL BOX is increased, the above-mentioned blistering and bending also increase. For this reason, the gear gap between the channel box and the control rod is reduced, and the control rod may not be inserted.

The gearbox between the channel box and the control rod before use is about 3 mm on average. Further, the amount of deformation induced by these irradiations of radiation greatly varies depending on the core position.

Therefore, in order to increase the interior loading period of the channel box over the entire core area, predict the deformation amount of each channel at each core position, and make sure that the channel and control rod do not interfere with each other. It is necessary to confirm.

The above-mentioned empirical formula for predicting the deformation amount of the channel box is made based on the data obtained in the current burnup range. Therefore, if the loading period of the channel box in the core becomes long, the loading period to which the conventional empirical formula is applied greatly exceeds. Therefore, the predicted value of the channel box deformation amount obtained by simply extrapolating the conventional empirical formula becomes too rough. Therefore, it is necessary to secure a large design margin for the channel box and a safety margin for the usage method.

Conventional channel boxes are decomposed and disposed of at the reactor site after 3 to 4 combustion cycles have been used, but the manufacturing cost of the channel boxes is the second highest among fuel assembly components after the fuel rods. Moreover, its disposal is also quite expensive. Further, when the discarded channel boxes are accumulated, a larger storage space is needed to safely store the channel boxes.

Japanese Patent Application No. 56-59807 proposes a structure in which the service life of the channel box is extended by changing the wall thickness of the channel box.

However, such a change in wall thickness necessitates a change in the design of the channel box and presents problems of economy and usability.

An object of the present invention is to provide a channel box deformation evaluation method that facilitates resetting of a channel box loading pattern and can efficiently reduce the number of channel boxes whose predicted deformation amount is outside the allowable range.

[Means for solving the problem]

The features of the present invention that achieve the above object are the first step of retrieving the amount of deformation in the past combustion period of the channel box for evaluating the deformation from the storage device, and the core for the new combustion period of the corresponding channel box. The second step of setting a loading pattern in step 3), and the third step of predicting the deformation amount after the lapse of the new combustion period at the loading position corresponding to the loading pattern by the arithmetic processing means, for each of the corresponding channel boxes. Step, a fourth step of determining whether the predicted deformation amount of each channel box is within an allowable range by the arithmetic processing means, and a fifth step of displaying the determination result on the display means.
Step, and when there is the channel box in which the predicted deformation amount is outside the allowable range, the loading pattern for the new combustion period of the channel box is re-executed by the arithmetic processing means by using the selected arrangement rule. And a sixth step of setting, and then to perform the third, fourth and fifth steps again.

[Action]

The loading pattern for the new combustion period of the channel box is reset by the arithmetic processing means using the selected arrangement rule, so that the loading pattern of the channel box can be easily reset and the prediction after resetting can be performed. It is possible to efficiently reduce the number of channel boxes whose deformation amount is outside the allowable range. In addition, since the deformation amount of the channel box is predicted based on the loading pattern data of the channel box, specifically, the fuel assembly,
The deformation amount can be predicted for each individual channel in the core, and the interference between the control rod and the channel box can be evaluated for each cell. Preferably, since the deformation amount of the channel box is predicted using the core characteristic data, the shape data of the channel box, and the material characteristic data of the channel box, especially the core characteristic data, the accuracy of the obtained deformation amount becomes high. .

〔Example〕

An embodiment of the channel box deformation evaluation method and apparatus according to the embodiment will be described below with reference to FIGS. 1 and 2.

As shown in FIG. 2, the channel box deformation evaluation apparatus of this embodiment includes a display device 1, an arithmetic processing device 2, an input device 3, and storage devices 5 to 8. The arithmetic processing unit 2 includes an arithmetic unit 2a, a processing procedure storage unit 2b, an intermediate data storage unit 2c, an image data output unit 2d, and an input unit 2e. The data created by the arithmetic processing unit 2 is displayed on the display screen of the display unit 1 as images and characters.

The storage device 5 stores the core characteristic data, the storage device 6 stores the channel box deformation amount actual measurement data, the storage device 7 stores the material physical property and shape data, and the storage device 8 stores the set loading pattern.

FIGS. 3 to 6 show the contents of each data stored in the corresponding storage device. The core characteristic data shown in FIG. 3 are core name, core type, core shape, and fast neutron flux. It includes a three-dimensional distribution. The channel box deformation amount actual measurement data shown in FIG.
It includes the burnup of each fuel assembly, the measured value of swelling amount, and the measured value of bending amount. The set loading pattern data shown in FIG.
It includes fuel assembly label maps, channel label labels, etc. for each cycle. The material physical properties and shape data shown in FIG. 6 include Young's modulus, Poisson's ratio, bending rigidity, etc. of the channel box material.

Based on these data, the processing procedure using the channel box deformation evaluation method and apparatus according to the present embodiment,
As shown in FIG. This processing procedure is stored in the processing procedure storage unit 2b. Further, FIG. 7 functionally represents the processing procedure. That is, in FIG. 7, the channel box deformation amount predicting means performs the processing of step 24. The interference determination means performs the processing of step 25. The loading pattern resetting means executes the processing of steps 27, 28 and 29. The display method selection means executes the processing of step 26. Furthermore, FIGS. 8 to 11 show the processing procedure shown in FIG.
The detailed processing procedure of each step is shown. Hereinafter, the channel box deformation evaluation according to the present embodiment will be sequentially described with reference to FIG. The calculation unit 2a calls the processing procedure shown in FIG. 1 and executes the processing based on this processing procedure.

Referring to FIG. 1, first in step 21, the third
The core data shown in the figure is input by the input device 1 and stored in the storage device 5. Similarly, the channel box deformation amount actual measurement data shown in FIG. 4 is stored in the storage device 6. In addition, the physical properties and shape data of the material shown in FIG.
And the setting mounting pattern shown in FIG. 6 is stored in the storage device 8. Display device 1 for these data
Can be displayed by the arithmetic processing unit 2 executing a predetermined process based on an output command input from the input device 1 by a keyboard. FIG. 12 is an example of an image in which the material physical property and shape data retrieved from the storage device 7 is displayed on the screen of the display device 1. FIG. 13 shows that in the channel box deformation amount actual measurement data retrieved from the storage device 6, the channel number is 413 and the core array position coordinates (4,1
The example of the image which displayed the measured value of the creep deformation amount and irradiation bending after the 3rd irradiation cycle with respect to the channel box in the position of 1) on the screen of the display device 1 is shown. The reading of the actual measurement data is performed in step 22.

Next, in step 23, the fuel cycle in which the radiation irradiation is performed on the channel box whose deformation amount is predicted and the mounting pattern in the core of the channel box are set. Here, the channel box that predicts the amount of deformation is
A channel box removed from a spent fuel assembly, which is attached to a new fuel assembly loaded in the core instead of the spent fuel assembly. In step 24, the predicted deformation amount of the channel box is calculated for each set one channel box by the calculation unit 2a for each axial position and radial position using the measured deformation amount data and the analysis model. The obtained calculation result is stored in the intermediate data storage unit 2c. The processing of step 24 will be described in detail with reference to FIG.

First, at step 24A, the fast neutron flux φ is calculated. That is, the fast neutron flux distribution in the core is read from the core characteristic data stored in the storage device 5. Further, the fuel assembly label map and the channel box label map are read from the set loading pattern stored in the storage device 8 to recognize which position in the core and which fuel assembly and channel box are loaded. The fast neutron flux φ is calculated based on the data read above.
The fast neutron flux φ is calculated using the result of the calculation by the three-dimensional nuclear characteristic calculation program. However, the fast neutron φ obtained based on the calculation results of the nuclear characteristic calculation program
Is given at the center point of each fuel assembly in the core, so by interpolating the fast neutron flux φ between adjacent fuel assemblies, the high speed on each side of the channel box attached to the fuel assembly Find the neutron flux φ. The fast neutron flux φ obtained based on the calculation result of the three-dimensional nuclear characteristic calculation program (three-dimensional nuclear characteristic calculation model) is three-dimensional data. This fast neutron flux φ is a kind of core characteristic data. The fast neutron irradiation dose FU is calculated by the following formula (step 24B).

FU = φ · t (1) where t is the irradiation time of radiation.

Next, for the channel box actually loaded in the reactor and taken out after radiation irradiation and the deformation amount is measured, the measured value of the deformation amount is read from the memory device 6 (step 24c), and this measured value is initialized. The value. Also,
For the channel box for which there is no measured value of deformation,
The predicted value calculated is used. Further, material physical property and shape data are read from the storage device 7.

Further, the amount of swelling is calculated in step 24D and the amount of bending is calculated in step 24E, and then the total sum of these deformation amounts is obtained (step 24F). The total deformation of the channel box is
It is represented by the sum of the amount of swelling and the amount of bending. Step 24D, 24E
Details of 24F will be described later. These calculations are carried out for the channel boxes of all fuel assemblies loaded in the core (step 24G). When the determination at step 24G is "YES", it means that the deformation amount of each channel box at each fuel cell arrangement position (I, J) in the core has been obtained. This is possible because the loading pattern of the fuel assembly in the core is set in step 23). Further, the calculation is performed for all the loaded fuel assemblies during the set fuel cycle period, for example, each fuel cycle from the first fuel cycle to the fifth fuel cycle (step 24H).

The calculation contents of steps 24D, 24E and 24F will be described in detail below. First, the calculation of step 24D will be described.

The bulge amount at the axial position z is represented by the sum of the elastic deformation amount δ and the bulge increase amount Δδ during the period of the time width Δt, and is calculated by the following equations.

Δδ = RΔt (3) where P is the load caused by the differential pressure, L is the width of the channel box, and R is the bending radius of curvature (mm). (2)
The flexural rigidity D and the creep rate of the zirconium alloy in the equation (3) are obtained by the following equation.

Here, E is Young's modulus, ν is Poisson's ratio, d is thickness of Cyanne box, T is temperature of Cyanne box (K), φ is fast neutron flux (1 / mm ² · s) (En> 1Me)
V) and σ are tensile stresses.

Here, the fast neutron flux φ in equation (5) is
Use the result calculated in A.

Next, the calculation of the bending amount in step 24E will be described.

The bending of the channel box is caused by the irradiation growth of the zirconium alloy as described above. The bending moment that the channel box receives in the channel axis direction Z due to irradiation growth strain is defined as M _{X in} the x direction. Displacement X (z) due to bending in the x direction at the position in the axial direction z
Is given by the following equation according to the beam theory.

However, I _X is the second moment of area with respect to the x-axis.

The bending moment M _X and the irradiation growth strain ε (ΔH / H) are respectively calculated by the following equations.

Where ΔS _j is the area of the channel segmentation area, H is the channel box height, and A is a constant (= 1.435).
× 10 ¹³ ), t is the irradiation time (S), and (FU) _j is the fast neutron irradiation dose.

(7) fast neutron irradiation amount in the formula (FU) _j uses a fast neutron irradiation amount (FU) _j calculated in step 24B.

By solving the equation (5) using the equations (6) and (7), the bending displacement amount X (z) can be obtained.

The contents of step 24F will be described. The total deformation amount D (z) of the channel box, which is obtained by combining the bending amount and the swelling amount, is obtained by the following equation.

D (z) = δ _o + δ + Δδ + X (Z) (9) where δ _o is the initial deformation amount.

The fast neutron flux φ, the temperature T, and the weight P caused by the pressure difference ΔP in each region are obtained by nuclear calculation and thermal-hydraulic calculation, respectively, and are stored in the storage device 5 as core core characteristic data. The width L, height H, thickness d of the channel box, Young's modulus E of the zirconium alloy, and Poisson's ratio ν are stored in the storage device 7 as material characteristic data. Δ _o in the equation (8) is stored in the storage device 6 as the actual measurement data of the channel box initial deformation amount.

According to the processing of step 24, the deformation amount of the channel box is predicted by using the core characteristic data, the shape data of the channel box, and the material characteristic data of the channel box, especially the core characteristic data. The accuracy of the obtained deformation amount is significantly increased.

The calculation results of the swelling amount, bending amount, and deformation amount of the channel box obtained as described above are stored in the intermediate data storage unit 2c.
Is transferred to and stored there (step 24I).

Next, based on the channel box deformation amount calculation result of the intermediate data storage unit 2c, in the operation processing 2a, the interference determination between the channel box 9 and the control rod 12 is performed for the channel box containing the set aggregate (step 2
Five). Step 25 is shown in detail in FIG. The contents will be explained. From the intermediate data storage unit 2c, the deformation amount calculation result of the channel box of all the fuel assemblies loaded in the core during the set fuel cycle period, which is obtained in step 24, is read (step 25A). Next, the channel box to be subjected to the interference determination is selected in a predetermined order (step 25B). This order is stored in memory. For all fuel assemblies loaded in the core,
It is determined whether the control rod and the channel box interfere with each other (step 25C).

The interference determination is carried out for each four blades of the cross-shaped control rod in one cell composed of the four aggregate channel boxes shown in FIG. FIG. 24 is a cross-sectional view showing the arrangement of the channel box for housing the fuel assembly and the cross-shaped control rod. 9 is a channel box, 12 is a control rod, 13 is a control rod roller, A, B, C and D is a fuel assembly. The four fuel assemblies in the cell are A, B, C and D,
Assuming that the side of each channel is 1,2,3,4 counterclockwise from the top in Fig. 24, the collision judgment is A3 and B1.
Surfaces B4 and C2, C1 and D3, and D2 and A4. In addition, the interference determination is performed for each area divided in the channel box axis direction.

For example, in the case of FIG. 25 (a), it is determined that the channel box 9 and the control rod 12 do not interfere with each other, and in the case of FIG. 25 (b), the channel box 9 and the control rod 12 interfere with each other. In FIG. 25 (b), both sides of one blade of the control rod 9 are in contact with the adjacent channel boxes. The selection of the channel box for judging the interference (step 25B) and the judgment of the interference (step 25C) are all performed by the calculation unit.
Automatically in 2a.

These interference determinations are performed for all fuel assemblies loaded in the core (step 25D), and for all designated fuel cycles (step 25C).
The obtained interference determination result is transferred to and stored in the intermediate data storage unit 2c (step 25E).

Next, the interference determination result and the calculation result are displayed by a table or graphic output (step 26). The detailed processing procedure of step 26 is shown in FIG. First, the intermediate storage data
The interference judgment result and deformation amount calculation result are read from 2c (step 26A). After that, the operator designates the display area from the input device 1 in order to display the result of a certain portion in the core. The computing unit 2a inputs the designated display area, and based on this display area, the steps 26C, 26D and 26E are input.
It is determined which of the following processes is to be performed (step 26B). There are the following three areas in the core that can be designated.

1. Display of calculation results and judgment results of channel boxes of all cores (step 26C).

2. Designated partial core area (1/2 core or 1/4 core)
Display the judgment result of the channel box (step 26
D).

3. Display of judgment result of arbitrary channel box integrated (step 26E).

Further, after the display area is determined, it is determined that the operator selects the corresponding display method based on the display method specification information specified by the input device 1 (step 26F). The display method can be selected from a table display and a graphic display. Creation of the display data by the table is performed in step 26G, and creation of the display data by the graphic is performed in step 26H. The calculation unit 2a creates display data by the process of step 26G or 26H based on the information specified by the operator, and outputs the display data to the display device 1. The display data is displayed on the display device 1.

An example in which the display data created in step 26G is displayed on the display device 1 is shown in FIG. FIG. 14 is a display example of the channel number 413, the core position coordinate (11, 9), and the axial deformation amount after the third fuel cycle irradiation. The display data shown in FIG. 14 is a table summarizing the deformation conditions and the interference determination results of the set arbitrary channel boxes. FIG. 15 shows an example in which the same information is displayed on the screen of the display device 1 as display data created in step 26H. In the example shown in FIG. 15, the set deformation state of an arbitrary channel box is displayed as a figure that imitates the channel box together with the amount of bending and the amount of swelling.

Further, FIG. 16 is an example of a display showing the amount of deformation of the channel box at each position in the 1/4 region of the core A after the fuel cycle of FIG. In the display example shown in FIG. 16, the deformation state of the channel in the set partial core (1/4 core), the core internal load position, and the number of irradiated fuel cycles are summarized in the table. An example in which the same information is displayed as graphic display data is shown in FIG. In the display example shown in Fig. 17, the deformation state of the channel box in the set partial core (1/4 core) is color-coded according to the degree of maximum deformation amount, and is a figure simulating a partial core. .

Further, FIG. 18 shows an example in which the determination result is displayed as display data by a table. This example is for the channel box of the whole A core after the 6th fuel cycle,
The figure shows five positions where interference occurs. In the display example of FIG. 18, the deformation state, the core internal load position, and the number of irradiation fuel cycles are summarized in the table for the channel boxes that have caused interference with the control rods among the channel boxes in the entire core. FIG. 19 shows an example in which the same information is displayed as graphic display data. In the display example of FIG. 19, among the channel boxes in the entire core, the channel boxes that have caused interference with the control rods are indicated by crosses on the figure simulating the entire core.

In the entire processing procedure, as shown in FIG. 1, if there is no interference with the adjacent channel control rods during the set core region and fuel cycle period, the processing is ended. On the other hand, when the interference occurs, with respect to the channel where the interference occurs, it is predicted that the control rod and the channel will not interfere with the furnace interior load position,
Reset the shuffling pattern and loading direction (step 28 in Fig. 1).

Details of step 28 are shown in FIG. First, step 25
The interference determination result at is read from the intermediate data storage section 2c (step 28A). Next, the loading pattern for moving the channel box of the interfering fuel assembly is reset (step 28B). There are several methods for this resetting, and the operator selects from the display screen. For example, the information as shown in FIG. 21 (the display device is heated by the action of the calculation unit 2a) is displayed on the screen of the display device 1. The operator selects a necessary rule from the rules displayed on the screen. The selected rule is input from the input device 3 to the calculation unit 2a.

 The following examples can be considered as rules.

(1) Move the fuel assembly irradiated in the same fuel cycle to a position where it can be replaced.

(2) In the cell, the two side surfaces of the channel box facing the control rod are not changed.

(3) The fuel cycle (the (n-1) th fuel cycle) before the fuel cycle (the nth fuel cycle) in which the interference has occurred
In the n-th fuel cycle, the side surface where the bending amount of the channel is convex up to is moved to the inner core position and the inner cell position facing the outer core direction.

(4) The direction of the curve of the channel box generated during the irradiation period of the nth fuel cycle at the moved position moves to the position in the cell away from the control rod.

Next, in the arithmetic processing unit 2a, a channel box that satisfies the rule selected by the operator is automatically selected from all the channel boxes (step 28).
C). At this time, since there are multiple exchangeable channel boxes that satisfy the selected rule,
Select the channel box of the body. In this selection, there are cases where the arithmetic processing unit 2a automatically determines, and cases where the guidance is displayed on the screen of the display device 1 and the operator selects.

In the case where the arithmetic processing unit 2a automatically determines, among the channel boxes satisfying the specified rule, the (n-
1) The channel box with the smallest amount of deformation up to the fuel cycle is selected.

When the operator makes a selection, a guidance is displayed on the display unit to indicate the position in the core where the channel box satisfying the specified rule is loaded, and the operator determines based on the guidance.

As a guidance method, based on the set rules, target core positions that meet each rule and core positions that satisfy all the rules are displayed. Figure 20 shows a display example of the guidance. FIG. 20 is a display example showing interference occurrence and changeable position of the channel box after the third fuel cycle in the 1/4 core region of the A core. In this example, based on these guidances,
The operator selects a channel box to replace the interfering channel box for the optimum loading pattern. The channel box selected in this manner is input from the input device 3 into the calculation unit 2a. After that, the interference channel and the channel selected in step 28C are exchanged (step 28D). The interfered channel boxes are loaded at the selected channel boxes, and the selected channel boxes are loaded at the interfered channel boxes.

The above operation is repeated for all the channel boxes where interference has occurred (step 28E). When the moving destinations of all the interfering channel boxes are obtained, the reset result is transferred to the intermediate data storage unit 2c and stored there (step 28F). The loading pattern obtained by the resetting is displayed on the screen and at the same time, the intermediate data storage unit 2c.
Stored in. FIG. 22 shows a display example of the loading pattern. The display example in FIG. 22 is the one in which the channel box after the third fuel cycle of the A core is reset according to the rule. When the processing of step 28 is completed, steps 24, 25 and 28 are repeated based on the set use method of the channel box again to maximize the number of channel boxes which do not interfere with the control rod throughout the set irradiation period.

If it is determined that interference with the control rods will occur during the irradiation period regardless of which core interior load position the used channel box is set to, a display indicating that the channel cannot be used is displayed on the display screen, and the corresponding channel is displayed. Detailed information such as the box shuffling pattern, loading direction, and driving history is displayed on the screen.

In each of the embodiments, in the step of resetting the loading pattern based on the interference determination result of the channel box and the control rod, the guidance of the loading pattern that does not cause the interference is provided based on the limiting condition and the rule provided in advance. Although the operator determines the optimum loading pattern by displaying it on the screen of the display device 1 and looking at the guidance, the resetting loading pattern is stored in the storage device 8 in the loading pattern resetting process. Alternatively, this may be automatically determined.

As another embodiment of the present invention, a processing procedure as shown in FIG. 26 can be considered. That is, the processing of steps 23, 24, 25 and 26 is repeated for all the channel boxes loaded in the core and each set fuel cycle.
If necessary, steps 28 and 29 are processed.

According to the embodiment shown in FIGS. 1 and 2, it is possible to accurately predict the deformation amount of the channel box that is reused after being taken out as a spent fuel assembly. Based on the prediction result, the interference between the channel box and the control rod can be accurately determined. If interference is predicted to occur, the loading position in the core of the relevant channel box (preferably including the loading pattern and loading direction of the channel box) can be reset and evaluated. Therefore, while ensuring safety, it is possible to maximize the number of channel boxes that can be used even when the core interior loading period is extended. As a result, the fuel cycle cost can be reduced, and at the same time, the amount of discarded channel box can be reduced and the storage space can be prevented from increasing.

In short, it is possible to easily determine the presence or absence of interference between the channel box and the control rod during the furnace interior loading period, and set the usage method of the channel box that maximizes the number of channel boxes that do not interfere with the control rod. Therefore, the channel box can be used efficiently.

〔The invention's effect〕

According to the present invention, it is possible to easily reset the loading pattern of the channel box and efficiently reduce the number of channel boxes in which the predicted deformation amount after resetting falls outside the allowable range. That is, the number of channel boxes to be reused can be increased.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a processing procedure of a channel box deformation evaluation method which is a preferred embodiment of the present invention, and FIG.
FIG. 4 is a block diagram of a channel box deformation evaluation device that executes the processing procedure of FIG. 1, FIG. 3 is an explanatory diagram of an example of data stored in the storage device 5 of FIG. 2, and FIG. 4 is FIG. 5 is an explanatory view of an example of data stored in the storage device 6 of FIG. 5, FIG. 5 is an explanatory view of an example of data stored in the storage device 8 of FIG. 2, and FIG. 6 is a storage device 7 of FIG. 7 is an explanatory view of an example of data stored in FIG. 7, FIG. 7 is an explanatory view functionally expressing the flow chart of FIG. 1, and FIG. 8 is an explanatory view showing a detailed processing procedure of the step 24 of FIG. , Fig. 9 shows the first
FIG. 10 is an explanatory diagram showing the detailed processing procedure of step 25 in the figure, and FIG. 10 is an explanatory diagram showing the detailed processing procedure of step 26 in FIG.
FIG. 11 is an explanatory view showing a detailed processing procedure of the step 28 in FIG. 1, FIG. 12 is an explanatory view showing a display example of material physical properties and shape data of the channel box, and FIG. 13 is actually measured data of the channel box deformation amount. Explanatory diagram showing a display example of No. 14
Figure is an explanatory view showing a display example of data related to the deformation of the channel box, Figure 15 is an explanatory view showing another display example of data related to the deformation of Figure 14, and Figure 16 is each channel in the 1/4 core part. Fig. 17 is an explanatory view showing a display example of data regarding deformation, Fig. 17 is an explanatory view showing another display example of data regarding deformation of Fig. 16, and Fig. 18 is a display example showing an interference occurrence position of the channel box of the entire core. Illustration of the 19th
Figure is an illustration of another display example related to the information in Figure 18, Figure 20 is an illustration of a display example of guidance for re-setting the mounting pattern,
FIG. 21 is an explanatory view of a display example of a rule used when the mounting pattern is reset, FIG. 22 is an explanatory view of another display example regarding the information of FIG. 21, and FIG. 23 (a) is a modified channel box. Fig. 23 (b) is a side view of the deformed channel box, Fig. 24 is a sectional view showing the relationship between the channel box in the cell of the core and the control rod, 25 (a) and 25
FIG. 18B is an explanatory view showing an example of interference between the deformed channel box and the control rod, and FIG. 26 is a flow chart of another embodiment of the present invention. 1 ... Display device, 2 ... Arithmetic processing device, 2a ... Arithmetic unit,
2b ... Processing procedure storage section, 2c ... Intermediate data storage section, 2d ...
… Image data output part, 2e …… input part, 3 …… input device,
5,6,7,8 ... Storage device, 9 ... Channel box, 10
…… Deformed channel box, 11 …… Display screen, 12
…… Control rod, 13 …… Control rod roller.

Claims (6)

(57) [Claims] 1. A method for evaluating deformation of a channel box of a fuel assembly loaded in a core, the first step of retrieving an amount of deformation of a channel box for evaluating deformation in a past combustion period from a storage device. A second step of setting a loading pattern in the core for a new combustion period of the channel box, and for each of the corresponding channel boxes after the new combustion period has elapsed at a loading position corresponding to the loading pattern. A third step of predicting the deformation amount by the arithmetic processing means, a fourth step of judging by the arithmetic processing means whether the predicted deformation amount of each channel box is within an allowable range, and the result of this judgment is displayed. A fifth step of displaying on the means, and the channel in which the predicted deformation amount is outside the allowable range. A sixth step of resetting the loading pattern for the new combustion period of the channel box by the arithmetic processing means using the selected arrangement rule when the box is present, and then the third and fourth steps. And a method for evaluating deformation of a channel box, which comprises performing the fifth step again. 2. The deformation of the channel box according to claim 1, wherein the third, fourth, fifth and sixth steps are repeated until the number of the channel boxes in which the predicted deformation amount falls within the allowable range becomes maximum. Evaluation methods. 3. The method of displaying the loading pattern of the reset channel box on the display means.
Alternatively, the channel box deformation evaluation method according to claim 2. 4. The deformation evaluation method for a channel box according to claim 1, wherein the deformation amount includes a deformation amount due to creep deformation and bending of the channel box. 5. The predicted deformation amount is based on core characteristic data, material characteristic data and shape data of the channel box, loading pattern data, and burnup data of a fuel assembly to which the channel box is attached. The method for evaluating deformation of a channel box according to claim 1, wherein 6. A method for evaluating channel box deformation of a fuel assembly loaded in a core, comprising: a first step of retrieving a deformation amount in a past combustion period of a channel box for evaluating deformation from a storage device; A second step of setting a loading pattern in the core for a new combustion period of the channel box, and the deformation after the new combustion period elapses at a loading position corresponding to the loading pattern for each corresponding channel box. A third step of predicting the amount by the arithmetic processing means, a fourth step of judging by the arithmetic processing means whether or not the predicted deformation amount of each channel box is outside the allowable range, and a display result of this judgment means The fifth step of displaying on the channel, and the channel in which the predicted deformation amount is outside the allowable range. And a sixth step of resetting the loading pattern for the new combustion period of the channel box by the arithmetic processing means using the selected placement rule when the switch exists. And execute the fifth step again. A method for evaluating deformation of a channel box, which is characterized in that