JPH04259897A - Planning of fuel shuffling - Google Patents

Abstract

PURPOSE:To increase freedom regarding schedule of maintenance works of reactor core related equipment and also to shorten working period of periodical inspection. CONSTITUTION:A cell is constituted of four fuels 1 surrounding a control rod 2. Cells in maintenance work space of reactor core related equipment, is divided into two groups, group A and group B. The group B is constituted of cells that contain only the maintenance work space in which a double blades guide can be remained in the cell, during the maintenance works. The group A is constituted of cells that contain maintenance work space other than said above. In the group B cells, for the cell from which the control rod 2 has to be withdrawn, the control rod 2 is made to be supported by the double blades guide, even if the double blades guide is put on and all the four fuels 1 are taken out.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel transfer planning method for adjusting work interference with maintenance work inside the reactor in a work plan for fuel transfer work in a nuclear reactor.

0002

2. Description of the Related Art At nuclear power plants, periodic inspections are carried out every approximately one year of operation, and fuel is replaced and major equipment is inspected and maintained. Among these, work related to the reactor core is important, including fuel movement work that replaces and rearranges part of the fuel that is the source of output as it burns, and measuring instruments to monitor and control combustion. Core-related equipment maintenance work, which involves inspecting and replacing control rods, is essential. These tasks occupy a large portion of the periodic inspection work that takes three months or more, and form a so-called critical path that affects previous and subsequent work processes. In addition, from the viewpoint of efficient operation and safety of the reactor, the content of these fuel transfer work and core-related equipment maintenance work is determined based on a long-term plan, taking into consideration the entire operating period of the reactor. Ru.

Regarding the fuel arrangement in the reactor core, fuel design and fuel arrangement design are based on nuclear, thermo-hydraulic, and economic considerations of the reactor. A new fuel arrangement is determined at each periodic inspection. Regarding core-related equipment maintenance work, we consider the deterioration of equipment due to radiation and thermal effects within the reactor, and also take into account inspection plans and maintenance plans for nuclear equipment and parts, as well as the history of the frequency and trends of these deteriorations. A maintenance work plan will be established. What is actually done during periodic inspections is removing fuel,
These include fuel movement work, such as changing locations or adding new fuel, and equipment maintenance work, which involves inspecting and replacing each piece of equipment.

[0004] For maintenance work on core-related equipment, neutron measurement LPRM (Local Power Range)
Monitor) replacement, control rod replacement, CRD (Control Rod Drive) of the control rod drive mechanism
There are inspections, etc.

As for the working space, it is necessary to take out the fuel 1 indicated by diagonal lines in FIGS. 4 to 6, and the control rod 2 from which the surrounding fuel 1 is taken out needs to be pulled out in advance. Furthermore, in the control rod exchange shown in FIG. 4 and the CRD inspection shown in FIG. 6, it is necessary to remove the coupling between the target control rod 2 and the CRD.

[0006] When inspecting the CRD, it is possible to remove the guides from the lower part of the core and perform inspection work, so it is possible to leave the guides other than the fuel 1 in the work space, but when replacing the control rods 2 shown in FIG. When replacing the LPRM 3 shown in FIG. 5, it is necessary to suspend the replacement equipment from the upper part of the core, so it is necessary to take out both the guide and the fuel 1 from the work space.

The guide used to support the control rod 2 includes:
There are double-blade guides that sandwich the control rod 2 and single-blade guides that replace the fuel 1. The double-blade guide takes out the fuel 1 around the control rod 2 and removes it from the control rod, as shown in Figures 7 to 12. 2, and domestic BWR nuclear power plants usually have several of them available.

Next, how to use the double blade guide will be explained. When using, first, as shown in Fig. 7, of the four fuels 1 around the control rod 2 that make up the cell, two diagonal fuels 1 are removed, and then the double blade is removed as shown in Fig. 8. Attach the guide 4 and take out the remaining two diagonal fuels 1. Thereafter, the control rod 2 is pulled out as shown in FIG. 9, and the control rod 2 is inserted as shown in FIG. 10, and two diagonal fuels 1 are attached as shown in FIG. Then, as shown in FIG. 12, the double blade guide 4 is removed.

[0009] For the above-described work, it is necessary to determine work procedures and processes such as detailed order and schedule based on the implementation status of each periodic inspection so that the work can be carried out smoothly and safely. When moving fuel, it is necessary to take into consideration work space and safety for maintenance work that will be carried out during the process, and when moving fuel, there are also nuclear restrictions and mechanical restrictions such as installation location and securing support. Therefore, special attention is paid to planning the fuel transfer procedure for efficient operation.

A conventional fuel movement planning method is shown in FIG.
As shown in Figure 14, there is a method of planning to remove all the necessary fuel in advance in order to secure the work space related to the maintenance work in order to carry out the maintenance work inside the reactor all at once, and as shown in Figure 14. A known method is to repeat the procedure of removing fuel from a work space for each maintenance work, proceeding with that work, and filling the work space with fuel in the next target location.

[0011]

[Problems to be Solved by the Invention] The conventional fuel movement planning method shown in FIG. It is difficult to shorten the work period because the maintenance work is completely separated and the work cannot be carried out alternately during the day and night. Furthermore, if there is a delay in maintenance work, there is also the problem that subsequent fuel transfer work cannot proceed.

On the other hand, in the conventional fuel movement planning method shown in FIG. 14, by adjusting the amount of fuel movement and maintenance work that are performed all at once, it is possible to carry out the work alternately day and night, which shortens the work period. However, there is a problem in that the degree of freedom regarding the maintenance work process is reduced, and if the maintenance work schedule changes, the fuel transfer work is also affected.

The present invention has been made in consideration of these points, and it is an object of the present invention to provide a fuel transfer planning method that provides a greater degree of freedom regarding maintenance work and can shorten the work.

[0014]

[Means for Solving the Problems] As a means for achieving the above object, the present invention provides a method for controlling each cell composed of four fuel bodies around a control rod in a maintenance work space for core-related equipment during a maintenance work period. The cells are divided into a first group consisting of cells that include only a work space in which a guide can be left, and a second group consisting of cells that include other work spaces, and a control rod is extracted from the cells of the first group. A feature of the present invention is that the control rod of a cell that has to be moved is supported by a double blade guide.

[0015]

[Operation] In the fuel movement planning method according to the present invention, each cell in the maintenance work space is divided into a first group consisting of cells that include only work spaces where guides can be left in the cells during the maintenance work period, and a first group consisting of cells that include only work spaces where guides can be left in the cells during the maintenance work period, and The cells are divided into a second group consisting of cells including spaces, and among the cells of the first group, for cells whose control rods must be pulled out, the control rods of the cells are supported by double blade guides. . Therefore, even when all the fuel in the cell is to be removed, there is no need to pull out the control rods in advance, and the work can be carried out by pulling out the control rods before the work. Therefore, the degree of freedom regarding the maintenance work process increases, and it becomes possible to perform maintenance work in parallel and to perform maintenance work and fuel transfer work in parallel, making it possible to shorten the work period.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the fuel movement planning method according to the present invention will be explained below with reference to the drawings. The present invention uses a larger number of double blade guides than conventional fuel transfer operations. Normally, the number of cells (consisting of four fuel bodies surrounding the control rods) from which control rods are emptied for maintenance work is 1/3 to 1/2 of the total number of control rods. Among these, some control rods are inspected at intervals of about five years as part of planned CRD inspections, and approximately one-fifth of the cells of the total number of control rods must be emptied. The total number of control rods is 185 for the 1100 MWe class BWR and 89 for the 520 MWe class BWR. Since having a large number of double-blade guides requires storage space, in the present invention, the number of cells that are emptied to leave double-blade guides is suitable as the total number of double-blade guides. Double blade guide, 10
Prepare about 1/3 of the total number of control rods from the body.

Next, regarding the combination of maintenance work spaces (fuel removal points) for core-related equipment as shown in FIGS. 4 to 6, we will discuss the locations from which the control rods are pulled out, that is, the two adjacent fuel units around the control rods. The areas where it is necessary to extract the above are
Decide to keep it as low as possible.

[0018] The cells containing the removed fuel are classified into cells that include only a work space where a guide can be left in the cell, such as for CRD inspection during maintenance work, and cells that include other work spaces. Among the cells in which guides can be left, cells from which all fuel must be taken out and control rods must be pulled out are grouped as group A, and cells that can support the control rods are grouped as group A'. Further, among the cells in which guides cannot be left, cells from which all fuel must be taken out and control rods must be pulled out are grouped as group B, and cells capable of supporting control rods are grouped as group B'. FIG. 1 shows an example of the relationship between group A and group B, in which reference numeral 1 represents fuel and reference numeral 2 represents control rods.

Here, we will consider LPRM replacement and control rod replacement as work for which the cells including the maintenance work space will be in groups A and A', and CRD inspection and external appearance of the fuel assembly as work that will be in groups B and B'. Consider taking out the inspection target. The work of groups A and A' and the work of groups B and B'
For cells that commonly include work in groups A and A,
’.

The cells that need to be emptied and their control rods pulled out are groups A and B. In LPRM replacement, control rod replacement, and CRD inspection, the LPRM to be inspected or the four pieces of fuel around the control rod are removed. In LPRM replacement and control rod replacement, as shown in Figures 4 and 5, The fuel for the three bodies adjacent to one was also taken out, and space was secured to insert a camera to check the work. Note that additional fuel may be extracted in consideration of ease of operation. Regarding the fuel extraction area to be added, since there is some discretion in the direction in which it should be secured, the direction is selected to increase the overlap with other work areas and minimize the fuel extraction area. In particular, avoid losing support for the control rod and causing the control rod to be pulled out outside the work area as much as possible.

[0021] Regarding the maintenance space determined in this way, groups A and B of cells at the control rod extraction point are determined, and the number of double blade guides used is determined by dividing the number of cells in group B and the total number of double blade guides into two. Make it smaller.

First, for the cells of group A, as shown in FIGS. 7 and 8, one of the diagonal two-body fuel removals is performed, followed by double blade guide installation. If the number of cells in group A is smaller than the number of double blade guides used, double blade guides are similarly installed for the cells in group B by the number of remaining double blade guides. Next, as shown in FIG. 8, the remaining two fuel bodies from the cell with the double blade guide installed are taken out. As for the cells in Group A, the guides will interfere with maintenance work, so after the control rods are pulled out, the double-blade guides are moved to the other cells in Groups A and B that are not empty. For this, for the destination cell,
Perform fuel removal in either diagonal direction before moving. In this way, the double-blade guides that could not be moved to the group B cells are finally taken out of the furnace. The fuel to be taken out as a maintenance work space for the cells of groups A' and B' does not require a double blade guide, so it is taken out after the fuel is taken out of the cells of groups A and B or between these fuel transfers.

As a result, as shown in FIG. 2, all the fuel in the maintenance work space is removed, and the same number of control rods 2 as double-blade guides 4 remain in the group B cells. In the case of Fig. 2, control rod 2 is attached to all cells of group B.
Indicates when .

[0024] Finally, double blade 4 is attached to the cell.
The direction in which to install the cell should be selected so that the next targeted fuel to be installed in this cell can be brought directly from the fuel pool rather than from the core. This is because there is no need to consider control rod support during fuel movement. If fuel is to be transferred from the reactor, it is desirable that the cell can support the control rod as it is during the fuel transfer, but if this is not possible, it is possible to fill the empty space in the source cell with another fuel transfer first. Fuel transfer can be achieved.

Next, maintenance work is performed, and in the maintenance work process, LPRM replacement is first performed. There are no guides or control rods left in the work space for LPRM replacement, so
A refueling machine can be used to remove the LPRM from the top of the core and replace it. Control rod exchanges can be performed in parallel, but since the refueling machines are used in different ways, they should be performed together as much as possible. Once the LPRM exchange is complete, control rod exchange will be performed. Replacing the reactor core from the top using a refueling machine is similar to replacing the LPRM, and there are no operational problems. If it is possible to select the execution order of LPRM replacement or control rod replacement, the target fuels to be installed in any two diagonal directions of cells in the work area are selected from those that can be brought directly from the fuel pool if possible. Next, the execution priority of the work is as follows.
Select those work areas that have overlapping work spaces for CRD inspection. This is to ensure that when the work progresses in parallel with the CRD inspection work, the maintenance work at that location can be completed quickly. However, these priorities are not absolute and can be selected as appropriate depending on the progress of the work.

[0026] Next, CRD inspection is performed, and priority is given to those belonging to group A. For those belonging to Group B, it is necessary to withdraw the control rod before starting work, but since a double blade guide is installed, this can be carried out as long as safety is confirmed during operation. When inspecting the CRD, the coupling of the control rod that has been pulled out is removed, and the CRD section is taken out from the bottom of the core and inspected. Since the LPRM exchange and control rod exchange that are carried out in the upper part of the reactor core can be carried out independently, maintenance work can be carried out in parallel. In addition, fuel for visual inspection is taken out to the fuel pool, and inspection can proceed independently from core work.

Furthermore, when the CRD inspection of the group B cells is completed, the CRD and control rod are reconnected, and since the guide has been installed, the control rod is reinserted as it is. When a fuel transfer operation is carried out to load two diagonal units of fuel to this cell, the double blade guide can be moved. If the CRD inspection of Group B cells progresses,
Such fuel transfer operations can be performed in parallel. The double blade guide is sequentially moved from the group B cell where fuel installation has been completed on the two diagonal cells to the group A cell where maintenance work has been completed, and the control rods are inserted and fuel is transferred on the diagonal two cells in the same way. I do. At this time, the installation direction of the double blade guide is also such that the target fuel to be installed diagonally is
If possible, choose from fuel that can be brought directly from the fuel pool. In this way, after all the core-related equipment has been repaired and the two diagonal fuel installations have been completed in cells of groups A and B, all but a few double-blade guides are taken out of the reactor.

[0028] Thereafter, the fuel movement work is continued in order to achieve the target fuel arrangement. This is done by searching for fuel at the target location where the fuel is being taken out, giving priority to fuel that will not lose support for the control rods, and moving sequentially, thereby ensuring that the fuel is moved without waste. In places where fuel movement is not possible due to constraints or work circumstances, guides may be used to assist, or fuel may be temporarily taken out into a fuel pool. Finally, once the core is in its target location, the fuel transfer operation is complete. Plan the fuel transfer work as described above.

[0029] Therefore, the degree of freedom regarding the maintenance work process is increased, and the maintenance work can be performed in parallel with each other, and the maintenance work and the fuel movement work can be performed in parallel, and the fuel movement plan can shorten the period of periodic inspection work. can be realized.

FIG. 3 shows a work process diagram of the fuel transfer plan according to the present invention. As is clear from FIG. 3, the work time can be shortened by carrying out fuel transfer and maintenance work in parallel, and maintenance There is still a lot of freedom in choosing the order of work. Therefore, it is possible to flexibly respond to problems or delays during work.

[0031]

[Effects of the Invention] As explained above, according to the present invention,
It is now possible to carry out fuel transfer work and maintenance work in parallel, shortening the work period and improving the efficiency of periodic reactor inspection work. In addition, the degree of freedom in selecting maintenance work processes has increased, making it possible to change the order according to the situation, and making it possible to plan so that even if a particular work is delayed, the schedule of the entire process does not need to be changed significantly. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of cell grouping in the fuel movement planning method according to the present invention.

FIG. 2 is an explanatory diagram showing a state in which all the fuel in the work space has been removed.

FIG. 3 is a work flow chart showing a fuel movement planning method according to the present invention.

FIG. 4 is an explanatory diagram showing fuel taken out during control rod replacement.

FIG. 5 is an explanatory diagram showing fuel taken out during LPRM replacement.

FIG. 6 is an explanatory diagram showing fuel taken out during CRD inspection.

FIG. 7 is an explanatory diagram showing a state in which two diagonal fuels are taken out from inside the cell.

FIG. 8 is an explanatory diagram showing a state in which a double blade guide is attached.

FIG. 9 is an explanatory diagram showing a state in which a control rod supported by a double blade guide is pulled out.

FIG. 10 is an explanatory diagram showing a state in which a control rod is inserted along a double blade guide.

FIG. 11 is an explanatory diagram showing a state in which two diagonal fuel rods are attached.

FIG. 12 is an explanatory diagram showing a state in which the double blade guide is removed.

FIG. 13 is a work process diagram showing an example of a conventional fuel movement planning method.

FIG. 14 is a work flow chart showing another example of a conventional fuel movement planning method.

[Explanation of symbols]

1 Fuel 2 Control rod 4 Double blade guide A, B Group

Claims (1)

[Claims] Claim 1: Each cell consisting of four fuel bodies around a control rod in a maintenance work space for core-related equipment is divided into a first cell consisting of only a work space where a guide can be left in the cell during the maintenance work period. and a second group consisting of cells that include other work spaces, and among the cells of the first group, the control rods of the cells whose control rods must be pulled out are double-bladed. A fuel movement planning method characterized by supporting by a guide.