JPS6122798B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in refueling devices for nuclear reactors.

In a nuclear reactor, the decay heat is large, so in order to prevent the fuel assembly from being exposed to the gas atmosphere, it is necessary to pull it out from the core while immersed in a coolant to replace the fuel. As shown in FIG. 1 showing the fuel exchange state and FIG. 2 showing the operating state, a reactor core b has a plurality of fuel assemblies a arranged in a row.
, a reactor vessel c surrounding the reactor core b, a reactor internal structure d, a shutoff plug e sealing the upper part of the vessel c, a coolant inlet nozzle f, a coolant outlet nozzle g, and a control rod. It is composed of a drive mechanism j and an in-core upper mechanism k, and if an attempt is made to pull out the fuel assembly a from the core b while immersed in the coolant h so as not to expose it to the gas atmosphere, the coolant h will be removed. The depth must be at least twice the length of fuel assembly a. Therefore, the reactor vessel c and control rod drive mechanism j
The control rods became longer in the vertical direction, making it difficult to insert the control rods. Furthermore, as described above, the reactor vessel c and the control rod drive mechanism j are elongated, which increases the cost and causes an increase in the coolant inventory.

The present invention addresses the above-mentioned problems, and includes: a reactor vessel surrounding a reactor core in which a plurality of fuel assemblies are arranged; a fuel storage pot provided adjacent to the core within the reactor vessel; a rotary shielding plug rotatably provided at an eccentric position of the shielding plug sealing the upper part of the reactor, and the reactor core and the fuel storage pot are immersed in a coolant flowing in and out of the reactor vessel. , the rotary shielding plug is a multiple rotary shielding plug, a fuel assembly receiving cylinder is provided through the innermost rotary shielding plug of the multiple rotary shielding plug, and the lower end of the fuel assembly receiving cylinder is connected to the nuclear reactor. opening into the coolant in the container, and making the fuel assembly receiving cylinder movable between a position directly above the reactor core and a position directly above the fuel storage pot;
A fuel exchange machine for exchanging fuel assemblies by lifting or lowering them into the fuel assembly receiving cylinder is installed in the upper part of the fuel assembly receiving cylinder, and the inside of the fuel assembly receiving cylinder is depressurized to replace the fuel assembly in the reactor vessel. This relates to a fuel exchange device for a nuclear reactor, characterized in that a pressure regulator for sucking coolant into the fuel assembly receiving cylinder is installed in the upper part of the fuel assembly receiving cylinder. An object of the present invention is to provide an improved fuel exchange device for a nuclear reactor that can perform fuel exchange even if the vertical dimension of the reactor vessel is shortened, and can make the reactor vessel more compact.

The present invention is constructed as described above, and the multi-rotation shielding plug is rotated to move the fuel assembly receiving cylinder above the fuel assembly to be replaced, and then the pressure regulator is actuated to The pressure inside the reactor vessel is reduced and the coolant in the reactor vessel is sucked into the fuel assembly receiving cylinder, and then the fuel exchange machine is operated to lift the fuel assembly into the fuel assembly receiving cylinder. Then, the multi-rotating shielding plug is rotated to move the fuel assembly receiver into a position directly above the fuel storage pot, while the refueling machine is activated to place the fuel assembly into the fuel storage pot and then into the fuel storage pot. The fuel assembly is carried out of the reactor vessel in each fuel storage pot. Also, carry out the process in reverse order to the above.

As described above, when replacing a fuel assembly, the present invention operates a pressure regulator to reduce the pressure inside the fuel assembly receiving cylinder and suck the coolant in the reactor vessel into the fuel assembly receiving cylinder. Fill the fuel assembly receiving cylinder with coolant and lift the fuel assembly into it, or
Since the fuel assembly is suspended from within the receiving cylinder and the fuel is replaced, even if the distance between the core and the shielding plug is short, the fuel assembly can be replaced while immersed in the coolant. In other words, even if the vertical dimensions of the reactor vessel are shortened, fuel exchange can be performed and the reactor vessel can be made more compact.

Next, the fuel exchange system for a nuclear reactor according to the present invention will be described with reference to an embodiment shown in FIG. is a reactor internal structure that supports the reactor core 1 in the container 3 and supplies the coolant 5 to the reactor core 1, 6 is a shielding plug fixed to the upper part of the container 3, and 7 is rotatable on the shielding plug 6. 8 is a rotary shielding plug rotatably mounted on the rotary shielding plug 7, 9 is a rotary shielding plug rotatably mounted on the rotary shielding plug 8, 10 is a rotary shielding plug 9 is a fuel assembly receiving cylinder whose lower end is opened into the coolant 5 by penetrating the eccentric position of the cylinder, and includes a rotation center 7a of the plug 7, a rotation center 8a of the plug 8, and a rotation center 9 of the plug 9.
When a suitable one of the plugs 7 to 9 is rotated, the receiving tube 10 moves above the desired one among the fuel assemblies 2 arranged in the reactor core 1, or into the reactor vessel 3. It is designed to move above the fuel storage pot 11 installed inside. Further, 12 is a fuel exchanger attached to the upper part of the receiving tube 10, 13 is a pressure regulator communicating with the receiving tube 10, 14 is a fuel inlet/output device attached to the rotary shielding plug 7, and 15 is a coolant inlet nozzle. , 16 is a coolant outlet nozzle.

Next, the fuel exchange operation of the nuclear reactor will be explained. First, the receiving tube 10 is inserted through the rotating shielding plug 9 to open the lower end of the receiving tube 10 into the coolant 5 in the reactor vessel 3, and then the rotating shielding plugs 7 to 9 are rotated appropriately to open the receiving tube 10. Move above the fuel assembly 2 to be replaced, then operate the pressure regulator 13 to reduce the pressure inside the receiving cylinder 10, suck the coolant 5 in the reactor vessel 3 into the receiving cylinder 10, and then The fuel exchanger 12 is operated to pull up the fuel assembly 2, the rotary shielding plugs 7 to 9 are rotated appropriately to move the receiving tube 10 above the fuel storage pot 11, and the fuel exchanger 12 is operated to lift the fuel assembly 2. The body 2 is placed into the fuel storage pot 11. Thereafter, the fuel assembly 2 is transported out of each fuel storage pot 11 using the fuel loading/unloading machine 14.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of the drawing]

FIG. 1 is a vertical side view showing the fuel exchange state of a conventional nuclear reactor, FIG. 2 is a vertical side view showing the operating state of the same reactor, and FIG. 3 is a part of the nuclear reactor fuel exchange system according to the present invention. FIG. 2 is a longitudinal side view showing an example. DESCRIPTION OF SYMBOLS 1...Reactor core, 2...Fuel assembly, 3...Reactor vessel, 5...Coolant, 6-9...Eccentric rotation shielding plug, 10...Fuel assembly receiving tube, 12...Fuel exchange machine, 13...Pressure regulator.

Claims (1)

[Claims] 1. The reactor vessel surrounding the reactor core where multiple fuel assemblies are lined up, the fuel storage pot located adjacent to the reactor core within the reactor vessel, and the eccentric position of the shielding plug that seals the top of the reactor vessel. A nuclear reactor having a rotatably provided rotary shielding plug, wherein the reactor core and the fuel storage pot are immersed in a coolant flowing into and out of the reactor vessel, the rotary shielding plug being a multiple rotary shielding plug, A fuel assembly receiving cylinder is installed through the innermost rotating shielding plug among the multiple rotating shielding plugs, and the lower end of the fuel assembly receiving cylinder is opened into the coolant in the reactor vessel. The fuel assembly receiving cylinder is movable between a position directly above the reactor core and a position directly above the fuel storage pot, and a fuel exchange machine for exchanging fuel assemblies by lifting or lowering them into the fuel assembly receiving cylinder is provided. A pressure regulator is installed in the upper part of the fuel assembly receiving cylinder and reduces the pressure inside the fuel assembly receiving cylinder and sucks the coolant in the reactor vessel into the fuel assembly receiving cylinder. A nuclear reactor fuel exchange device characterized by being installed at the top of a cylinder.