JPH04132994A - Fast breeder reactor - Google Patents

Abstract

PURPOSE:To enable refueling without a rotary plug by making a control rod drive mechanism and a guide tube of the control rod drive mechanism, to be of retractable structure and also by making a supporting table of the control rod drive mechanism guide tube, to be able to be housed in the vicinity underneath a roof slab, freely to its telescopic movement. CONSTITUTION:Inside a nuclear reactor vessel 11, a reactor core 12, a reactor core supporting structure 13, a supporting table 21 of the control rod drive mechanism guide tube, a supporting mechanism 22 which supports and moves vertically the supporting plate 21, and the like, are housed in. To a roof slab 19 constituting a lid of the vessel 11, a control rod drive mechanism 15 is attached freely detachably and re-attachably. For refueling, the mechanism 15 is detached, the supporting plate 21 is housed in the vicinity of an underside surface of the roof slab 19 by the mechanism 22 and an arm typed refueling machine is set up at the center of the roof slab 19. By this whole constitution, new and spent fuels can be exchanged without using a rotary plug, and the similar works can be done as well.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) The present invention relates to a fast breeder reactor that uses liquid metal as a coolant. This invention relates to a fast breeder reactor that can be constructed from a small reactor vessel.

(Prior Art) As shown in FIG. 3, a conventional fast breeder reactor includes a reactor core 12, a core support structure 13, a core upper mechanism 14, a control rod drive mechanism 15, and a fuel exchanger 16 in a reactor vessel 11. , an intermediate heat exchanger 17, and a primary main circulation pump 18, and the upper end of the reactor vessel 11 is closed by a lid consisting of a roof slab 19 and a rotating plug 20.

The rotating plug 20 is rotatably mounted on the roof slab 19, and the control rod drive mechanism 15 is accommodated, supported, and positioned by the core upper mechanism 14 attached to the rotating plug 20.

In a fast breeder reactor with such a configuration, the amount of heat generated in the core 12 is controlled by a gripper of a control rod drive mechanism 15 that moves the control rods gripped by the handling head at the upper end up and down.

On the other hand, when exchanging fuel in a fast breeder reactor, after inserting all the control rods into the reactor core, the control rods gripped by the grippers of the control rod drive mechanism 15 are separated, and the grippers of the control rod drive mechanism 15 are moved slightly upward. The reactor core 12 and the upper core mechanism 14 are moved to
Untie the sides. After the rotary plug 20 equipped with the core upper mechanism 14 is made rotatable in this manner, the rotation of the fuel exchanger 16 and the rotary plug 20 causes the fuel assemblies in the reactor core that require replacement to be removed. Grasp the handling head part with the gripper of the fuel exchanger, lift the fuel assembly upward, and after completely removing the bow from the reactor core, use the rotation of the rotary plug and the rotation function of the fuel exchanger to move it to a predetermined position inside the reactor. After moving the fuel assembly horizontally to the relay position in the reactor and lowering the fuel assembly downward at that location,
Separate the fuel assembly that was being held.

Next, grab the new fuel assembly at the same relay position in the reactor,
A new fuel assembly is loaded into the reactor core by performing exactly the opposite operation to the above.

By repeating the above operations, fuel exchange of the fast breeder reactor can be performed, but the main point is that the control rod drive mechanism 1
Separate the control rods held by 5 and move the upper core mechanism 14 that accommodates, supports, and positions the control rod drive mechanism 15 using the rotary plug 20 to secure the space above the core necessary for fuel exchange. It's about doing.

The types of rotary plugs 20 for fuel exchange include single rotation plugs, double rotation plugs, and triple rotation plugs, and the fuel exchange machines 16 include arm-type fuel exchange machines, direct-acting fuel exchange machines, It is also possible to use an arm type and a direct-acting fuel exchanger together, or to use two direct-acting fuel exchangers.

However, in a fuel exchange system using a combination of a rotary plug and a fuel exchanger as described above, considering the arrangement in the upper part of the furnace, that is, the arrangement of the loose flag 19 and the rotary plug 20, the rotary plug 20 is not connected to the rotating mechanism device or the rotating part. Seal devices, shielding structures, cables for power and measurement control, etc. are required, and the radial dimension also occupies a large space, which is one of the critical factors in determining the diameter of the reactor vessel 11. .

(Problem to be Solved by the Invention) As explained above, the rotary plug 20 and the fuel exchanger 16
In conventional fast breeder reactors that employ a fuel exchange system consisting of Ta.

The present invention has been made in view of the above points, and aims to provide a fast breeder reactor that can be configured with a reactor vessel having a small diameter by adopting a system that allows fuel exchange without a rotating plug. This is the purpose.

[Structure of the Invention] (Means for Solving the Problems) The fast breeder reactor of the present invention comprises a reactor vessel, a reactor core and a core support structure housed therein, and a lid of the reactor vessel. In a fast breeder reactor equipped with a roof slab, the roof slab is not provided with a rotating plug,
The control rod drive mechanism and the control rod drive mechanism guide tube are selectively installed as a structure that allows the bow to be pulled out, and the support plate supporting the control rod drive mechanism guide tube is attached to the roof via a telescopic support mechanism. It is characterized by being able to be stored near the bottom surface of the slab.

(Function) When the above configuration is adopted, the control rod drive mechanism mounted on the roof slab allows the control rods to be inserted into and withdrawn from the reactor core during reactor power operation. Furthermore, the control rod drive mechanism guide tube support plate is effective in maintaining the functional integrity of the control rod drive mechanism during earthquakes and the like.

In addition, when replacing fuel, the entire control rod drive mechanism is removed and the telescoping support mechanism is retracted to accommodate the control rod drive mechanism guide tube support plate near the bottom of the roof slab, freeing up the necessary space above the core for fuel exchange. secure.

In this state, an arm-type refueling machine is installed directly above the center of the reactor core, that is, at the center of the roof slab, to perform fuel exchange.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

Note that in FIGS. 1 and 2, the same parts as in FIG. 3 are given the same reference numerals, and explanations of the same parts will be omitted.

FIG. 1 shows an embodiment of the present invention. FIG. 1(a) shows the state during reactor power operation, and FIG. 1(b) shows the state during fuel exchange.

As is clear from FIGS. 1(a) and (b), in the fast breeder reactor of the present invention, the conventional rotating plug 20 (FIG. 3) is not used, and the upper end of the reactor vessel 11 is covered with a roof. Covered by slab 19.

In FIG. 1(a), there is a reactor core 12 inside the reactor vessel 11.
, a core support structure 13, an intermediate heat exchanger 17, a primary main circulation pump 18, a control rod drive mechanism guide tube support plate 21, and a support mechanism 22 that supports the guide tube support plate 21 and moves it up and down. ing.

The roof slab 19 that constitutes the lid of the reactor vessel 11 includes:
A control rod drive mechanism 15 is detachably attached.

The support mechanism 22 includes, for example, a plurality of telescope-type support vibes.

On the other hand, at the time of fuel exchange, as shown in FIG. An arm type fuel exchanger 16 is installed in the center of the slab 19.

In the fast breeder reactor of the present invention described above, the control rods and the control rod drive mechanism can adjust the core output during reactor power operation and maintain the functional integrity of the control rods during earthquakes, etc., without using a rotating plug. In addition to meeting the requirements, it is also possible to exchange old and new fuel without any problems during fuel exchange.

As a result, restrictions on the upper reactor arrangement, which is one of the critical factors in determining the diameter of the reactor vessel, can be resolved, and a fast breeder reactor equipped with a reactor vessel having a reduced diameter can be provided.

Also, by eliminating the rotating plug, it is possible to eliminate the rotating mechanisms, rotating journals, shields, and cables that are required when using a rotating plug, which has a great effect on simplifying the furnace top arrangement. .

In addition, in the present invention, as shown in FIG. 2, the central part of the roof slab 19 on which the control rod drive mechanism 15 and the fuel exchanger 16 (FIG. 1(b)) are installed is a separate structure. , the furnace upper plug 23 may have no rotation function. In that case, the control rod drive mechanism guide tube support plate 2
1 and its support mechanism 22 can be easily removed from the roof slab, making it easy to take measures against any unexpected failures.

Furthermore, in the embodiment shown in FIGS. 1(a) and (b),
Although only one arm-type fuel exchanger 16 is mounted on the roof slab 19, in the case of a large reactor with a large diameter core, multiple arm-type fuel exchangers may be installed on the outer periphery of the control rod drive mechanism 15. It is also possible to set 16.

[Effects of the Invention] As described above, according to the present invention, the control rod drive mechanism mounted on the roof slab allows the control rods to be inserted into and withdrawn from the reactor core without any trouble, without using a rotating plug. It is possible to construct a fast breeder reactor using a reactor vessel with a small diameter.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are longitudinal cross-sectional views of an embodiment of the fast breeder reactor according to the present invention, in which FIG. 1(a) shows the state during reactor power operation, and FIG. ) indicates the condition at the time of fuel exchange. FIG. 2 is a vertical sectional view showing another embodiment of the present invention, and FIG.
The figure shows a longitudinal cross-sectional view of a conventional fast breeder reactor. 11... Reactor vessel 12... Core 13... Core support structure 14... Core upper mechanism 15... Control rod drive mechanism 16... Fuel exchanger 17... Intermediate heat exchanger 18... Primary main circulation pump 19... Roof slab 20... Rotating plug 21...Support plate 22...Support mechanism 23...Furnace upper plug

Claims (1)

[Claims] In a fast breeder reactor comprising a reactor vessel, a reactor core and a core support structure housed therein, and a roof slab forming a lid of the reactor vessel, the roof slab may be provided with a rotating plug. The control rod drive mechanism and the control rod drive mechanism guide tube are selectively installed as a removable structure, and the support plate supporting the control rod drive mechanism guide tube is attached to the roof slab through a telescoping support mechanism. A fast breeder reactor characterized in that it can be stored near the bottom surface of the reactor.