JPH0651080A - Fuel assembly fixing device - Google Patents

Abstract

PURPOSE:To enhance the adaptability to a nuclear reactor in which the upper opening of a riser pipe is throated, enhance the effectiveness in works of replacing fuel assembly, reduce the labor therein, and enhance the fixation strength in high temp. condition. CONSTITUTION:A fuel assembly fixing device concerned includes a dint-shaped detention part 20b formed in a fuel assembly insertion hole 20a, a detaining cylinder 14a located at the bottom of a fuel assembly 14, a restraining rod 23 to be supported movably by the detaining cylinder 14a, a thermally actuated element which is deformed into the stored shape and detains the rod 23 with the detention part 20b, and a resilient member which is installed on the thermally actuated element and moves the rod 23 inward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel assembly fixing device, and more particularly to a fuel assembly fixing device for narrowing a riser pipe for guiding rising primary cooling water from a core to a steam generator. The workability at the time of installation or replacement in the core part is improved.

[0002]

2. Description of the Related Art Conventionally, as a technical example related to the replacement of a fuel assembly, Japanese Patent Application Laid-Open No. 3-252599 (fuel assembly replacement device), Japanese Patent Application Laid-Open No. 3-252594 (fuel assembly replacement device), JP-A-3-252595 (fuel assembly exchange device) is proposed.

Further, in these publications, FIGS.
The technique shown in is described. In each drawing, reference numeral 1 is a reactor pressure vessel, 2 is a core, 3 is a steam generator, 4 is an upper lid, 5 is a control rod driving device, 6 is a primary cooling water pump, 7 is a control rod support structure, and 8 is Riser part, 9 partition wall, 10 telescope part, 11 fuel rod gripper, 12 carrier car, 13 traverse car, 14 fuel assembly, 15 riser pipe, 16 poison tank, 17 cooling water inlet , 18 is a hydraulically operated valve, 19 is a poison distributor, 20 is a core support plate,
P is a boric acid water (pool water in the furnace), a working space Y, and a fuel exchange device X.

In the nuclear reactor shown in FIG. 4, the structure located above the core 2 is removed to obtain the state shown in FIG.
By inserting the telescope unit 10 and the fuel rod gripper 11 into the riser unit 8, the fuel assembly 14 is pulled out and loaded.

Even in the reactor shown in FIG. 6, the telescope section 10 and the fuel rod gripper 11 are inserted into the riser pipe 15 with the primary cooling water pump 6 and the like located above the reactor core 2 removed. Further, by making full use of the exchange device described in each publication, the fuel assembly 14 can be pulled out and loaded.

On the other hand, during operation of the nuclear reactor, it is necessary to fix each fuel assembly 14. FIG. 4 example and FIG.
In the example, the fuel assembly fixing device 21 is arranged between the core 2 and the control rod support structure 7 to fix each fuel assembly 14. In the example of FIG. 6, since there are no control rods, it is planned to fix each fuel assembly 14 by disposing the fuel assembly fixing device 21 in the portion of the core support plate 20, for example.

[0007]

However, in both cases of FIG. 4 and FIG. 6, there remains a problem to be solved in terms of workability and labor for fixing and releasing each fuel assembly 14. There is. That is, in the example of FIG. 4 and the example of FIG. 5, when withdrawing the fuel assembly 14, it is necessary to remove the fuel assembly fixing device 21 to the outside of the nuclear reactor, and the labor becomes great. In the example of FIG. 6, if the fuel assembly fixing device 21 is larger than the upper opening of the riser pipe 15, simple withdrawal becomes impossible, and in the case of dividing and removing, labor of removal, removal, and reattachment work is performed. Grows larger.

The present invention has been made in view of the above circumstances, and it is necessary to improve the fixing strength in a high temperature state such as during the operation of a nuclear reactor, and to eliminate the disassembly and removal of the fuel assembly fixing device when replacing the fuel assembly. The purpose is to reduce the diameter of the riser pipe, increase the applicability to the reactor that increases the installation space of the steam generator, and reduce the labor required for fixing or releasing the fuel assembly. There is.

[0009]

In order to solve the above problems, a recessed engagement portion formed on the inner wall of a fuel assembly insertion hole of a core support plate and a fuel assembly mounted on the core support plate. An engaging cylinder part that is integrally arranged at the lower end of the body and is inserted into the fuel assembly insertion hole, and a plurality of restraint rods that are supported on the outer periphery of the engaging cylinder part so as to be movable in the radial direction thereof. A thermal actuation body disposed between the cylindrical portion and the restraining rod and transformed into a memory shape near the operating temperature of the reactor cooling water to engage the restraining rod with the locking portion; The fuel assembly fixing device is configured to include an elastic member that moves the restraining rod inward.

[0010]

The heat actuating body is deformed, the restraining rod is retracted inward, and the engaging cylinder portion of the fuel assembly is inserted into the fuel assembly insertion hole of the core support plate. When the thermal working body is heated to near the operating temperature of the reactor cooling water, the thermal working body transforms into a memory shape and moves the restraining rod outward, and the restraining rod engages with the locking portion. The fuel assembly is fixed to the core support plate. When the ambient temperature of the thermal actuator falls, the thermal actuator deforms inward by the elastic force of the elastic member, and the fuel assembly can be pulled upward.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the fuel assembly fixing device according to the present invention will be described below with reference to FIGS.
In FIGS. 1 to 3, reference numeral 14a denotes an engaging cylinder portion, 20
Reference numeral a is a fuel assembly insertion hole, 20b is a locking portion, 22 is a housing, 22a is a mounting seat, 23 is a restraining rod, 24 is a thermal actuator, and 25 is an elastic member. 1 to 3
Shows an embodiment when applied to the nuclear reactor shown in FIG. 6, and in FIG. 1, when the fuel assembly is inserted in the right half,
The left half shows the state of the restraint rod 23 during operation of the reactor.

The engagement cylinder portion 14a is integrally arranged at the lower end portion of the fuel assembly 14 and is formed in a cylindrical shape having a reduced diameter.

The core support plate 20 has a fuel assembly 14
A fuel assembly insertion hole 20a for inserting the engagement cylinder portion 14a at the lower end of the fuel assembly insertion hole 20a is opened, and a recessed locking portion 20b such as an annular groove is provided on the inner wall of the fuel assembly insertion hole 20a. To be done.

The housing 22 is integrally arranged at a plurality of places (for example, divided into four places) on the outer peripheral surface of the engaging cylinder portion 14a by the mounting seats 22a with the circular hole portion thereof directed outward in the radial direction. It

The restraining rod 23 is arranged inside the housing 22 with a part thereof protruding outward, and the restraining rod 23 is attached to the mounting seat 2
The thermal actuating body 24 and the elastic member 25 in a combined state are arranged between the 2a and the restraining rod 23 in an interposing state.

As shown in FIGS. 2 and 3, the thermal actuator 24 is, for example, in the form of a coil as a whole, and a shape memory alloy that transforms into a memorized shape at high temperature to increase the coil length,
For example, a Ti-Pd alloy is applied, and the transformation temperature of its high temperature phase is near the operating temperature of the reactor cooling water, or below the temperature based on heat transfer from the fuel assembly 14 and the core support plate 20 during operation of the reactor, etc. Is set to.

The elastic member 25 is provided along with the thermal actuator 24 and has a coil shape in FIGS. 2 and 3, and both ends thereof are connected to the mounting seat 22a and the restraining rod 23. And is restrained by elastic force 23
I am trying to move inward. That is, it is set such that the contraction force of the elastic member 25 is larger than the deformation resistance force of the thermal actuator 24 at a low temperature such as a room temperature state, and at a high temperature such as a reactor operating state. , Thermal actuator 2
The transformation force to the memorized shape in the high temperature state of 4 is set to be larger than the contraction force of the elastic member 25.

The operation for fixing and withdrawing the fuel assembly 14 by the fuel assembly fixing device thus constructed will be described below.

At the time of low temperature, the contracting force of the elastic member 25 acts largely, and the restraining rod 23 is in a recessed state as shown in the right half of FIG. 1 and FIG. Therefore,
The engaging cylinder portion 14a of the fuel assembly 14 is inserted into the fuel assembly insertion hole 20a of the core support plate 20 so as to be supported by the core support plate 20, and the fuel assembly 14 is removed from the core support plate 20.
It becomes possible to carry out the work of pulling out upward.

At a high temperature, the transformation force of the thermal actuator 24 into a memorized shape has a large effect, so that the restraint rod 23 moves outward as shown in the left half of FIG. 1 and FIG. Become. When the thermal working body 24 is heated to the vicinity of the operating temperature of the reactor cooling water by the operation of the nuclear reactor or the like, the restraining rod 23 causes the restraint rod 23 to be inserted into the fuel assembly insertion hole 20a based on the transformation of the thermal working body 24 into the memory shape. The engaging portion 20b of the fuel assembly 14 is restrained from moving upward of the thermal actuator 24, and the fuel assembly 14 is prevented from moving upward.
Is in a restrained state in which it is fixed to the core support plate 20.

[Other Embodiments] In the present invention, the following technique can be adopted instead of each embodiment. It should be applied to light water cooled reactors where the upper opening of the riser pipe 15 is narrowed other than the example shown in FIG. The present invention should be applied to a reactor in which the upper opening of the riser portion 8 is equal to or larger than the outer diameter of the core 2 or a control rod drive device installed below the core.

[0022]

In the fuel assembly fixing device according to the present invention, the recessed engagement portion formed in the fuel assembly insertion hole of the core support plate and the lower end portion of the fuel assembly are arranged. The engaging cylinder part, the restraining rod movably supported on the outer circumference of the engaging cylinder part, and the thermal actuation that transforms into the memory shape near the operating temperature of the reactor cooling water and engages the restraining rod with the locking part. Since the structure including the body and the elastic member that is provided adjacent to the thermal actuator and moves the restraining rod inward is adopted, the following effects are achieved. (1) Since the restraint rod is moved and inserted into the locking portion, it is possible to improve the fixing strength in a high temperature state such as during operation of the nuclear reactor. (2) Since the thermal actuation body is assembled to the lower end portion of the fuel assembly, it is possible to remarkably improve workability by eliminating disassembly and removal of the fuel assembly fixing device having the conventional structure when exchanging the fuel assembly. . (3) Since the heat actuating part forms a fixed state at high temperature,
The labor required when fixing or releasing the fuel assembly can be reduced. (4) Since the fuel assembly is attached and detached by moving the fuel assembly in the vertical direction, it is possible to smoothly perform the work of exchanging the fuel assembly in the upper core space even in a reactor in which the riser tube is narrowed. it can. (5) With the above, the diameter of the riser pipe can be reduced to increase the installation space for the steam generator.

[Brief description of drawings]

FIG. 1 is a front cross-sectional view showing a state of a restraining rod in an embodiment of a fuel assembly fixing device according to the present invention when a fuel assembly is inserted in a right half and a reactor is operated in a left half. .

2 is a front sectional view showing a state of a restraining rod at a low temperature in FIG.

FIG. 3 is a front sectional view showing a state of a restraining rod at a high temperature in FIG.

FIG. 4 is a front sectional view showing a conventional example of a light water reactor.

5 is a front sectional view showing a state in which a working space is formed above the core in the example of FIG.

FIG. 6 is a front cross-sectional view showing a conventional example of a light water nuclear reactor with a riser tube being narrowed.

[Explanation of symbols]

 1 Reactor Pressure Vessel 2 Core 3 Steam Generator 8 Riser Section 9 Partition Wall 10 Telescope Section 11 Fuel Rod Gripper 12 Transport Cart 13 Traverse Cart 14 Fuel Assembly 14a Engaging Tube 15 Riser Pipe 16 Poison Tank 17 Cooling Water Inlet 18 Water Pressure Actuated Valve 19 Poison Distributor 20 Core Support Plate 20a Fuel Assembly Insertion Hole 20b Locking Part 21 Fuel Assembly Fixing Device 22 Housing 22a Mounting Seat 23 Restraint Rod 24 Thermal Activator 25 Repulsive Member P Boric Acid (inside the Reactor) Pool water) X Refueling device Y Working space

Claims (1)

[Claims] 1. A fuel assembly which is integrally arranged at a lower end portion of a fuel assembly mounted on the core support plate and a recessed engagement portion formed on the inner wall of the fuel assembly insertion hole of the core support plate. Engagement tubular portion inserted into the body insertion hole, a plurality of restraint rods supported on the outer periphery of the engagement tubular portion so as to be movable in the radial direction, and an intervening state between the engagement tubular portion and the restraint rod. And a thermal actuation body that transforms into a memory shape near the operating temperature of the reactor cooling water and engages the restraining rod with the locking portion, and an elastic member that is attached to the thermal actuating body and moves the restraining rod inward. And a fuel assembly fixing device.