JPS6356957B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control rod holder for supporting the upper end of a control rod of a boiling water nuclear reactor on an upper grid plate.

In the core of a boiling water reactor, control rods having a cross-shaped cross section move up and down from the bottom of the core between a set of four fuel assemblies, guided by the sides of the fuel assemblies. When the control rods are fully inserted into the reactor core, their horizontal movement is restrained by the side surfaces of these fuel assemblies. Therefore, if it is necessary to fully insert the control rods into the reactor core, such as during fuel exchange, it is necessary to load at least two fuel assemblies diagonally across the control rods. There is. If fuel assemblies cannot be left diagonally, a pair of dummies called blade guides are inserted diagonally in place of the fuel assemblies to support the control rods.

Conventionally, two fuel assemblies or blade guides must be inserted diagonally to support the control rods, which limits the number and position of fuel assemblies that can be inserted and removed at once. is,
The procedure for inserting and removing them is also cumbersome. Additionally, when blade guides are used, it is time-consuming and time-consuming to insert a pair of long blade guides into the reactor water at the correct position, which increases the radiation exposure of workers. In addition to causing
It is also one of the reasons why the operating rate of nuclear reactors decreases.

This invention was made based on the above-mentioned circumstances, and its purpose is to correctly hold the upper end of the control rod to the upper grid plate with a single holder without using a pair of fuel assemblies or blade guides, and to facilitate fuel exchange. An object of the present invention is to provide a control rod holder that can sometimes refuel four fuel assemblies at once.

The present invention will be explained below based on an illustrated embodiment. In the figure, 1 is a cylindrical shroud housed in a reactor pressure vessel, and an upper grid plate 2 is attached to the upper part of this shroud 1, and a core support plate 3 is attached to the lower part. A control rod guide tube 5 is vertically provided between the core support plate 3 and the reactor pressure vessel bottom 4, and a control rod 6 is moved up and down between this guide tube 5 and the upper grid plate 2. It's becoming like that. This control rod 6 has a neutron absorbing material housed inside a blade 6a having a cross-shaped cross section.A lifting handle 7 is provided at the upper end of the blade 6a, and a flange-shaped speed control is provided at the lower end. A fitting 8 and a coupling socket 9 are provided. This coupling socket 9 is connected to a control rod drive mechanism 10 so that the control rod 6 can be driven up and down. Further, a fuel support fitting 11 is installed on the core support plate 3.
The fuel support fitting 11 has a cross-shaped control rod insertion slit 12 in the center thereof, and the control rod 6 is inserted through the slit 12 so as to be able to move up and down. Further, four fuel support holes 13 (only one is shown as a representative) are provided around the slit 12 to vertically support the lower end of the fuel assembly (not shown). It is designed so that a set of four fuel assemblies can be loaded by sandwiching them. That is, around the control rod 6, there are four fuel assembly insertion spaces 14 along the blades between the blades 6a...
is formed. Note that the side surface of the upper end of the fuel assembly is supported by the upper grid plate 2.

A control rod holder 15 according to the present invention can be detachably attached to the upper grid plate 2. 16 is the main body of the control rod holder. The holder main body 16 has a rectangular column shape similar to a shortened fuel assembly, and has a rounded and tapered lower nose portion 16a at the lower end, and a lifting handle 17 at the upper end. have. The fuel assembly insertion space 14 can be inserted into any one of the fuel assembly insertion spaces 14 from above the upper grid plate 2. Note that, as shown in FIG. 1, the total length of the holder main body 16 is determined by
The length is set to such an extent that the lower end nose portion 16a reaches the upper part of the control rod 6 when the rod b is locked to the upper lattice plate 2.

Stoppers 18a and 18b are attached to the upper part of the holder main body 16. These stoppers 18a and 18b each have a downward hook shape,
By hooking the holder main body 16 onto the upper surface of the upper grid plate 2, as shown in FIG.
It is designed so that it can be locked in the corner of the Further, a pair of blade holding members 19a, 19b are attached below the stoppers 18a, 18b.
The blade holding parts 19a and 19b are respectively attached to the adjacent left and right side surfaces of the holder main body 16 like the stoppers 18a and 18b, and have blade insertion grooves 20a and 20b along the vertical direction, respectively. It is a letter-shaped member. The side edges of the blade 6a are inserted into these blade insertion grooves 20a, 20b to hold the upper part of the blade 6a.

Blade holder 15 configured as above
The handle 17 is suspended by remote control from the upper part of the core, for example, a fuel exchange platform, and inserted into the upper grid plate 2 from above. Then, the blade 6a is fitted into the blade insertion grooves 20a, 20b, and the stoppers 18a, 18b are locked to the upper lattice plate 2. By doing this, the upper end of the control rod 6 is fixed to the upper lattice plate 2, so that the control rod 6 will not fall even if all the fuel assemblies around the control rod 6 are extracted.

Therefore, the fuel assemblies can be inserted and pulled out freely without inserting a pair of fuel assemblies or blade guides diagonally as in the conventional case. Moreover, the blade holding member 1 can be easily inserted by simply inserting it from above the upper lattice plate 2.
9a, 19b can be fitted into the blade 6a, and the stoppers 18a, 18b can be engaged with the upper lattice plate 2, so the work is extremely simple and the blade 6a can be held securely.

In short, the stopper only needs to have the function of fixing the holder main body to the upper lattice plate, so the specific aspects such as the shape and mounting position of the stopper are not limited to those of the embodiments. For example, the pair of stoppers may be attached to the back side of the holder main body, contrary to the embodiment. Furthermore, although the blade holding portion is fitted to the side edge of the blade in the above embodiment, it may be configured to be fitted to the upper edge of the blade from above, for example.

As explained above, the present invention allows the fuel assembly to be inserted from above into any one of the four fuel assembly insertion spaces formed between the control rod, which has a cross-shaped cross section, and the upper grid. a square prism-shaped holder body, a lifting handle provided at the upper end of the holder body, and a handle attached to the upper part of the holder body that fits into the upper lattice plate to lift the holder body to the upper lattice plate. A pair of stoppers that lock onto the corners of the plate; and an L-shaped blade holding member that is attached to adjacent left and right side surfaces of the holder body and holds the blade of the control rod between the left and right side surfaces. As a result, the control rod can be held vertically without inserting two fuel assemblies or blade guides diagonally as in the past, and four fuel assemblies can be refueled at once. Can be done. In addition, the control rod holder of the present invention has two parts like the conventional blade guide.
Only one guide is needed instead of a set of guides, and the length can be made much shorter than a blade guide, so even when transferred in reactor water, it is less likely to cause lateral vibration like a blade guide, making it easier to work underwater. is extremely good. Therefore, it can be quickly inserted into a desired position, reducing the amount of radiation exposure to workers. Furthermore, by streamlining work, the operating rate of the reactor can be improved, which has great effects.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a vertical cross-sectional view of a part of a boiling water reactor with a control rod holder inserted, and FIG. 2 is a part of the reactor. FIG. 2... Upper grid plate, 6... Control rod, 6a... Blade, 14... Fuel assembly insertion space, 15... Control rod holder, 16... Holder body, 17... Handle, 1
8a, 18b...stopper, 19a, 19b...blade holding member, 20a, 20b...blade insertion groove.

Claims (1)

[Claims] 1. A square column-shaped holder body that is inserted from above into any one of the four fuel assembly insertion spaces formed between the control rod, which has a cross-shaped cross section, and the upper grid. and a lifting handle provided at the upper end of the holder body, which is attached to the upper part of the holder body and fits into the upper lattice plate to lock the holder body to the corner of the upper lattice plate. A control characterized by comprising: a pair of stoppers; and an L-shaped blade holding member that is attached to adjacent left and right side surfaces of the holder body and holds the blade of the control rod between the left and right side surfaces. rod holder.