JPS6231920Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to the core structure of a nuclear reactor, and in particular, by dividing the core in the radial direction with a lattice plate that supports the fuel assemblies and securing the flow rate of coolant flowing through the fuel assemblies, This relates to a nuclear reactor core structure that eliminates the need for channel boxes surrounding fuel rods.

A conventional reactor internal structure is shown in FIG. A conventional reactor internal structure includes an upper grid plate 2 for supporting a fuel assembly 1, a lower grid plate 3 for supporting a fuel assembly 1, and control rods 4 and LPRMs 5 for controlling and monitoring nuclear reactions in the reactor core.

Further, in the fuel assembly 1, the fuel rods 6 are surrounded by a channel box 7 in order to ensure a flow rate of coolant flowing through the fuel assembly and to give strength to the fuel rods 6.

However, since Channel Box 7 was made of expensive Zircaloy and was disposable, it had the following three drawbacks.

(a) Problem of secondary waste Because Channel Box 7 was activated by neutron absorption, radioactive secondary waste was generated every time the fuel was replaced. Currently, fuel and Channel Box 7 are considered secondary waste with high radioactivity.
Since the fuel is reused after being reprocessed, the disposal of the channel box 7 is the biggest problem.

(b) Problem of high cost Since the channel box 7 is made of expensive Zircaloy, the cost of the fuel assembly 1 is high.

(c) Work process during gamma scanning During regular inspections, gamma scanning is performed to confirm the integrity of the fuel rod 6. During this process, the channel stator is removed and the channel box 7 is inserted into the fuel rod. Separated from 6, the fuel rod γ
I'm scanning. This caused a lot of time and trouble for the workers.

The purpose of this proposal is to provide a nuclear reactor core structure that is economical, suppresses the generation of secondary waste, provides effective cooling during emergencies, and has improved earthquake resistance.

The feature of the present invention is that it includes a lattice plate that surrounds the fuel assembly along its entire length in the axial direction, and the lattice plate is
It has a coolant passage therein connected to the emergency core cooling system, and a side wall provided with a plurality of openings through which the coolant in the coolant passage is injected into the fuel assembly. This prevents the lateral flow of coolant that occurs within the core during normal operation, ensures a sufficient flow rate of coolant per fuel assembly, and eliminates the need for channel boxes.

This has the effect of easing the economic burden of manufacturing the channel box, suppressing the generation of secondary waste, effectively cooling the core in an emergency, and improving earthquake resistance.

An embodiment of the present invention will be described with reference to the drawings.

This proposal consists of a core support structure 8 as shown in Figure 2.
It is located within the reactor core. This core support structure 8 includes a lattice plate 9 that divides the core in the radial direction.
The lattice plate 9 is composed of double plates having smooth planes along the axial direction.

Furthermore, the control rods 4 move up and down between the double-structured lattice plates 9 to control the nuclear reaction.

In addition, in the center of the area divided by the grid plate 9,
An LPRM guide pipe 10 is provided, and an LPRM 5 is installed in the guide pipe 10 to monitor nuclear reactions in the reactor core.

In addition, in the area partitioned by the grid plate 9, the LPRM
The guide tube 10 is fixed, and a partition plate 11 is installed to ensure a coolant flow rate per fuel assembly.

In the present invention, every fourth fuel assembly 1 from which the channel box 7 has been removed is inserted into each area divided by the grid plate 9.

This makes it possible to secure the coolant flowing through the fuel assembly 1 and maintain a good core power distribution.

Furthermore, in the conventional example, in order to efficiently control nuclear fission in the reactor core and monitor it accurately, control rods 4 and LPRM
5 was placed outside the channel box 7 in an area free of steam bubbles.

Also in the present application, control by the control rods 4 is performed inside a double-structured lattice plate 9 that does not contain air bubbles,
Since the monitoring by LPRM is carried out in the guide tube 10, the same effect as before can be achieved.

As shown above, since the core support structure 8 has the sufficient function of the channel box 7, the channel box 7 can be eliminated from the fuel assembly 1.

By this, the following four effects can be obtained.

(a) Reduction of secondary waste With the abolition of Channel Box 7, secondary waste that is activated by neutron absorption will no longer be generated.

Further, the site bunker used to store the channel box 7 for a long period of time becomes unnecessary.

(b) Cost reduction Instead of disposable channel boxes 7,
By installing the provided core support structure 8, the manufacturing cost of the fuel assembly can be significantly reduced, and the manufacturing process can also be shortened.

This makes it possible to provide an economical nuclear power generation facility.

(c) Shortening the work process during gamma scanning During periodic inspections, gamma scanning is performed to confirm the integrity of the fuel rods 6, but the process of separating the channel box 7 is no longer necessary, and the process can be shortened. It can be significantly shortened. Furthermore, the radiation exposure of workers during work can also be reduced.

(d) Improving seismic resistance By forming the core support structure 8 into an integral structure, the seismic resistance of the core can be improved.

In particular, as shown in FIG. 2, by installing reinforcing materials 12 on the double-structured lattice plates 9, earthquake resistance can be further improved, and the intervals between the hollow lattice plates 9 can be made uniform. It is possible to ensure scram during an earthquake.

FIG. 3 shows another embodiment of the present invention, in which the same parts as in FIG. 2 are designated by the same reference numerals.

In this embodiment, the control rod 4 and
This is an example of exchanging the position of LRPM5. In this embodiment, the control rod 4 is inserted into the center of the area surrounded by the grid plate 9, and the control rod 4 and the fuel rod 6
The periphery of the control rod 4 is protected by a fixed control rod guide plate 13 to avoid contact with the control rod 4. In addition, the grid plate 9
LPRM5 is installed at the intersection of the reactor cores to monitor nuclear fission in the reactor core.

Figure 4 shows a structure in which the double-structured lattice plate 9 of the core support structure is made hollow, and the emergency core cooling system (ECCS) 14 can flow into this hollow part in the event of an accident to cool the core. .

In this embodiment, holes are provided at each location of the grid plate 9, and ECCS water is sprayed directly onto the fuel rods 4 from the holes, thereby achieving the effect of effectively cooling the reactor core. In this case, close the top of the double grid plate to prevent ECCS14 water from leaking.

FIG. 5 shows another embodiment in which the core shape is changed from a square shape to a hexagon shape.

This makes it possible to improve earthquake resistance and the neutron economy of the core.

According to the present invention, by providing the core support structure with the function of a channel box, an economical and highly reliable nuclear reactor can be provided.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the prior art, Fig. 2 is an embodiment of the present invention, Fig. 3 is a diagram showing an application example of the present invention, and Fig. 4 is a diagram showing an example of application of the present invention.
The figure shows an example of an ECCS function, and FIG. 5 shows a hexagonal core support structure. 1...Fuel assembly, 2...Upper grid plate, 3...
Lower grid plate, 4...Control rod, 5...LPRM, 6...
...Fuel rods, 7...Channel boxes.

Claims (1)

[Scope of utility model registration request] The reactor core includes a plurality of fuel assemblies loaded into the reactor core, and a lattice plate surrounding the fuel assemblies over the entire length in the axial direction, and the lattice plate includes a cooling system connected to an emergency core cooling system. In addition to having a material passage,
A nuclear reactor core structure comprising a side wall provided with a plurality of openings through which the coolant in the coolant passage is injected into the fuel assembly.