JPH0584477B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method and apparatus for periodic inspection of a nuclear reactor, and in particular, to a nuclear reactor fuel suitable for shortening the periodic inspection (hereinafter referred to as periodic inspection) process of a nuclear reactor. This article relates to movement and control rod drive mechanism (hereinafter referred to as CRD) replacement methods and equipment.

[Background of the invention]

The periodic inspection process of a boiling water nuclear power plant (hereinafter referred to as a BWR plant) includes critical work that determines the overall period of periodic inspection, and non-critical work that proceeds behind the critical work. Currently, various efforts are being made to shorten this critical work.

During regular inspections of BWR plants, the most important critical inspection work includes fuel transfer work and CRD replacement work.

The fuel transfer work mainly involves replacing new fuel and shuffling on the reactor building operation floor, and the standard process for a 1100MWe class BWR plant takes approximately 16 days.

In addition, the main purpose of CRD replacement work is to replace the carbon seal inside the CRD according to its lifespan, and the CRD is removed inside the reactor pedestal and the CRD
After inspection and seal replacement, reinstall and complete the work. Under the standard process for a 1,100 MWe class BWR plant, it takes approximately 18 days to replace approximately 37 CRDs.

Currently, these two critical operations cannot be carried out in parallel due to core constraints, even though they are carried out in two separate areas: inside the reactor pedestal and on the reactor building operation floor. It is being implemented in

To replace the CRD, the CRD and control rod (hereinafter referred to as CR) must be replaced.
) must be separated, and the entire CR must be removed. However, as a general rule, it is not allowed to pull out two or more CRs from a handle loaded with fuel assemblies during periodic inspections due to administrative safety regulations. Therefore, when replacing a CRD, when one CRD is removed, that CRD is restored and reinstalled, and all CRs are inserted before the next CRD is inspected.

In the end, fuel transfer work and CRD replacement work, which are critical tasks in the BWR plant periodic inspection process, require
The standard process for a 1,100 MWe class takes an enormous amount of time, approximately 34 days.

In order to carry out the fuel transfer operation smoothly, inventions and improvements have been made, such as blade guides for preventing the fuel assembly from falling over. For example, those related to this type of blade guide include:
No. 198798 etc.

However, the main purpose of this method is to prevent the fuel assembly from falling over, and it has not yet reached the point of significantly shortening critical work.

[Purpose of the invention]

An object of the present invention is to provide a reactor fuel transfer and CRD replacement method that can shorten the periodic inspection process while ensuring safety in a nuclear reactor, particularly in a BWR plant, and an apparatus used therefor.

[Summary of the invention]

According to the present invention, a device called a CR blade guide is provided that is inserted from the top of the reactor instead of the CR that is pulled out for CRD replacement.

The feature of the present invention is that by inserting this CR blade guide, it is possible to eliminate the restriction on the reactor core that it is not allowed to pull out more than one CR from the handle loaded with fuel assemblies, and to perform periodic inspections. The reason is that it is now possible to carry out critical work such as fuel transfer work and CRD replacement work at the same time.

Also, if you insert this CR blade guide,
There is no longer a need for blade guides to prevent the fuel assembly from tipping over during fuel transfer work.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3.

FIG. 1 is a structural diagram of a CR blade guide 1, which is an instrument used to carry out the method of the present invention.
This CR blade guide 1 consists of a neutron absorption control plate 2, a handle 3 for inserting the blade guide, and a hook 4 for attaching the blade guide. FIG. 2 is a conceptual diagram of the operation of inserting the CR blade guide 1 of the present invention from the upper part of the reactor using the main grapple 6 of the fuel exchanger 5. In the same figure, 7
8 is a fuel assembly, 8 is a CRD, 9 is a CR pulled out by CRD 8, 10 is a reactor pressure vessel, 11 is an upper lattice plate, and 12 is a lower lattice plate.

FIG. 3 shows an example of the arrangement of four fuel assemblies 7 loaded in the upper grid plate 11. A channel box 14 and a spacer 15 are attached to each of the channel boxes 13 of the fuel assemblies 7 in order to prevent the four fuel assemblies 7 from coming into contact with each other.

The blade guide 1 of the present invention has a simple cross shape.
Instead of a CR blade guide, four neutron absorption control rods 2 are combined in a cross shape, and a space is provided at the intersection of these rods, so that when inserted from the top of the reactor,
The structure is such that the channel fastener 14 and the spacer 15 can be easily escaped. In addition, each fuel assembly 7
The lower part of the blade guide is tapered in order to smoothly insert this blade guide from the upper part of the reactor into the small gap between the two.

After the blade guide is inserted, the blade guide mounting hook 4 is seated on the upper lattice plate 11 to complete the blade guide mounting.

Now, with reference to FIG. 2, details of the CR blade guide mounting method of the present invention will be explained.

First, the blade guide 1 is attached to the main grapple 6 of the fuel exchanger 5. This main grapple 6 is normally used for removing and installing the fuel assembly 7 and the simulated fuel assembly blade guide during fuel transfer.

Next, in order to replace CRD8, the operation to pull out CR9 is started. After confirming that all the parts have been pulled out, the fuel exchanger 5 is moved onto the handle to be replaced with the CRD, with the blade guide 1 attached to the main grapple 6 of the fuel exchanger 5, the main grapple 6 is lowered, and the blade guide is inserted. Seating of the blade guide is completed by attaching the blade guide attaching hook 4 to the upper lattice plate 11.

After confirming that the blade guide 1 is inserted and seated using a load meter (not shown), preparations for inserting the next blade guide are started again, and the blade guide is inserted into the bundle at the next CRD inspection point, completing the series of operations. In a 1100MWe class BWR plant, it is necessary to insert approximately 37 blade guides.
It is thought that it will take about 4 days.

The CR blade guide of the present invention is different from the conventional blade guide for simple fall prevention, and because it combines the neutron absorption control rod 2, the CR8 that has been pulled out is in the same state as when it was fully inserted.
The fuel assembly 7 can be maintained. Therefore, once all blade guides have been inserted and confirmed, the CRD
This means that the replacement work and the fuel transfer work can be carried out simultaneously.

Using the CR blade guide of the present invention, approximately
Even if it takes about four days to insert 37 blade guides, the subsequent CRD replacement work and fuel transfer work can be done simultaneously, which has the effect of significantly shortening the regular inspection period.

Figure 4 shows the conventional standard process when CRD replacement work and fuel transfer work are carried out in series, and the present invention.
The improvement process is shown when a CR blade guide is inserted and CRD replacement work and fuel transfer work are performed in parallel. As is clear from this figure, compared to the conventional standard process, this method has the effect of shortening the periodic inspection process by approximately 12 days.

By the way, if the CR blade guide of the present invention is inserted, the blade guide for preventing the fuel assembly from tipping over, which was conventionally necessary during fuel transfer work, will of course become unnecessary.

〔Effect of the invention〕

According to the present invention, instead of the CR that is pulled out for CRD replacement, a CR blade guide that is inserted from the top of the reactor is provided, and when this is inserted, the CR
Since the fuel assembly can be kept in the same state as when it was fully inserted, it is possible to pull out two or more CRs at the same time. Therefore, fuel transfer work and CRD replacement work, which are critical work for periodic inspection, can be carried out simultaneously, and the periodic inspection process can be significantly shortened.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the structure of the CR blade guide of the present invention, Figure 2 is a conceptual diagram of the work of inserting the CR blade guide shown in Figure 1 from the top of the reactor, and Figure 3 is an example of the arrangement of fuel assemblies. The diagram shown in FIG. 4 is a comparison diagram of the present invention and the conventional periodic inspection process. 1... CR (control rod) blade guide, 2... Neutron absorption control board, 3... Handle for inserting the blade guide, 4... Hook for attaching the blade guide, 5...
Fuel exchanger, 6... Main grapple, 7
...Fuel assembly, 8...CRD (control rod drive mechanism),
9...CR (control rod), 10...Reactor pressure vessel,
11... Upper lattice plate, 12... Lower lattice plate, 13
...Channel Boxes, 14...Channel Fur Asuna, 15...Spacers.

Claims (1)

[Scope of Claims] 1. In a periodic inspection method for a nuclear reactor that includes reactor fuel transfer work and control rod drive mechanism replacement work, control rod blades are used instead of control rods that are pulled out for control rod drive mechanism replacement. A periodic inspection method for a nuclear reactor, characterized by inserting a guide to create the same condition as fully inserting the control rods, and simultaneously performing at least fuel transfer work and control rod drive mechanism replacement work. 2. In claim 1, by the main grapple of the fuel exchanger used for fuel transfer work,
A periodic inspection method for a nuclear reactor characterized by inserting a control rod blade guide from the top of the reactor. 3.In equipment used for periodic inspections of nuclear reactors, including moving fuel assemblies loaded in channel boxes and replacing control rod drive mechanisms while maintaining a specified relationship to prevent mutual contact, each channel box must be It consists of a control rod blade guide containing multiple neutron absorption control rods that is inserted between fuel assemblies within the fuel assembly, and is inserted in place of the control rod that is pulled out to replace the control rod drive mechanism, and is in the same state as when the control rods are fully inserted. 1. A periodic inspection tool for a nuclear reactor, characterized in that the periodic inspection equipment for a nuclear reactor is characterized in that it creates a fuel transfer operation and a control rod drive mechanism replacement operation at the same time. 4. The periodic inspection instrument for a nuclear reactor according to claim 3, wherein the tip of each neutron absorption control rod of the control rod blade guide is formed into a tapered shape.