JPS6333677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an emergency reactor shutdown device for a nuclear reactor.

Conventionally, in a nuclear reactor, the temperature of the coolant is raised by the thermal energy generated by the fuel assemblies arranged in an orderly manner in the reactor core, and the coolant with the increased temperature generates steam via a heat exchanger, which is then used to generate electricity using a turbine. By rotating the machine, nuclear fission energy is converted into electrical energy. The coolant flow rate is adjusted by the output of the fuel assembly, and the temperature of the fuel assembly is controlled to the set value.
If the piping through which the coolant flows breaks or the pump that circulates the coolant stops abnormally, it will not be possible to obtain a sufficient flow of coolant, and the temperature of the fuel assembly will rise rapidly. There is a risk that the fuel cladding that houses the fuel pellets and prevents the release of radioactive fission products to the outside world will be damaged.

For this reason, nuclear reactors are generally equipped with an emergency reactor shutdown device, which is configured to immediately insert a neutron absorbing material into the reactor core to stop the nuclear fission reaction when an abnormality in the reactor is detected. However, in conventional emergency reactor shutdown systems, the operation of which is controlled by complex judgment circuits and operator judgment, so by providing an independent emergency shutdown system, it is possible to It is desired to further improve the safety of In particular, in conventional fast breeder reactors, the only emergency reactor shutdown device is to insert an emergency reactor shutdown rod into the reactor core, and if this function is lost, the reaction of the reactor is immediately stopped. Therefore, it is desired to improve safety by using an independent emergency reactor shutdown system based on another principle.

The present invention was made for the purpose of solving the above-mentioned problems, and it detects abnormalities in the reactor without using external power or judgment circuits, automatically operates on a principle different from conventional ones, and immediately restarts the reactor. The purpose is to provide an emergency shutdown system for a nuclear reactor that has inherent safety and is capable of shutting down a nuclear reactor.

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

FIG. 1 is a longitudinal cross-sectional view of the core of an embodiment of the emergency reactor shutdown system of the present invention.

In the figure, coolant is supplied from the lower part of the reactor, rises through the reactor core 1, is heated, and flows to the upper part of the reactor.

The emergency reactor shutdown device 2 of the present invention includes a cylindrical guide pipe 3 vertically arranged to pass through the reactor core 1;
It consists of an expansion tube 4 loosely inserted into the guide tube 3 and a neutron absorption device 6 connected to the expansion tube 4 by a connecting member 5 at a constant interval.

The guide tube 3 has a structure in which a heat insulating material 7 is covered with a highly corrosion-resistant metal 8 such as stainless steel, in order to prevent the coolant inside the guide tube 3 from being cooled by the coolant near the core inlet. A coolant outlet 10 and a coolant inlet 9 are provided at the upper end and at a position facing the upper part of the core, respectively.
is formed. The expansion tube 4 is formed of a metal bellows that can be easily contracted and expanded, and an inert gas 11 is sealed inside.

The neutron absorbing device 6 has a structure in which a neutron absorbing substance 12 such as B ₄ C is coated inside with a metal 13 having high corrosion resistance such as stainless steel. When the neutron absorption device 6 is located outside the core 1,
When the center of the expansion tube 4 is located near the coolant inlet 9, and on the other hand, when the neutron absorber 6 is located within the reactor core 1, the upper part of the expansion tube 4 is located near the coolant outlet 10.
The distance between the expansion tube 4 and the neutron absorption device 6 is maintained so that the expansion tube 4 and the neutron absorption device 6 are located near the neutron absorption device 6.

Next, the operation of the device of the present invention will be explained. During normal operation, a portion of the coolant heated in the core 1 flows into the guide tube 3 from the coolant inlet 9 as shown by the arrow, so that the The temperature of the active gas 11 is equal to the coolant outlet temperature of the core 1, and that temperature and
Due to external pressure Boilouchard's law PV=
The expansion tube 4 has a volume determined by nRT.
Due to its volume, it receives a buoyant force from the coolant determined by Archimedes' principle. At this time, the neutron absorbing device 6 connected by the connecting member 5 is stationary in a balanced state at a distance from the core at the bottom of the guide tube 3 due to its weight. Therefore, if the coolant flow rate decreases due to failure of the primary coolant piping, circulation pump, or incorrect operation of the control rods, or if the core output increases, the temperature of the coolant flowing from the coolant inlet 9 will decrease. increases, and the temperature of the inert gas 11 sealed in the expansion tube 4 also increases.
As a result, the volume of the inert gas 11 expands according to Boilouchard's law. Due to this volumetric expansion, the expansion tube 4 is subjected to a larger buoyant force than during normal operation, and the balance with the weight of the neutron absorption device is broken and it begins to rise, and the neutron absorption device 6 connected to it also moves upward. Move to.

FIG. 2 is a longitudinal sectional view showing the emergency reactor shutdown device 2 for a nuclear reactor according to the present invention in an activated state. In FIG. 2, the same parts as in FIG. 1 are designated by the same reference numerals. Due to the rise in coolant temperature, the expansion tube 4 that has floated to the surface is restrained by the upper cover at the upper end of the guide tube 3 and is restricted from rising any further. Therefore, the neutron absorption device 6 is inserted into the core 1. The neutron absorber 12 significantly reduces the reactivity of the reactor core,
The reactor is stopped by bringing the reactor core 1 into a subcritical state. When the heat generation of the reactor core 1 stops, the coolant temperature decreases, but since there is a locking mechanism (not shown) inside the upper end of the guide tube 3 that locks the raised expansion tube 4, the neutron absorption device 6 also moves naturally from the core. It won't go down.

Note that, if necessary, a locking mechanism may be separately provided for locking the inflation tube 4 raised inside the upper end of the guide tube 3.

As explained above, the nuclear reactor emergency shutdown system of the present invention uses
Because it uses natural phenomena, it is possible to detect abnormalities in the reactor core and immediately shut down the reactor without using any external power or judgment circuits, significantly increasing the inherent safety of the reactor. Moreover, since it does not require any complicated structure as seen in conventional nuclear reactor emergency shutdown systems, it has a simple structure and is highly reliable with few failures.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the emergency reactor shutdown device according to the present invention, and FIG. 2 is a diagram showing the state in which the emergency reactor shutdown device is activated. 1...Reactor core, 2 ...Emergency reactor shutdown device, 3
... Guide tube, 4 ... Expansion tube, 5 ... Connection member,
6... Neutron absorption device, 9... Coolant inlet, 1
0... Coolant outlet, 11... Inert gas, 12
...Neutron absorbing material.

Claims (1)

[Claims] 1. A guide tube that penetrates the reactor core, a coolant outlet provided at the upper end of this guide tube, a coolant inlet provided in a position opposite to the upper part of the core of this guide tube, and a It consists of a metal bellows that can be freely contracted and expanded so that it can be moved up and down, and is connected to an expansion tube with an inert gas sealed inside and a connecting member at a constant interval to the lower part of the expansion tube. In the emergency reactor shutdown device, the emergency reactor shutdown device is composed of a neutron absorber and a locking mechanism that locks the expansion tube raised inside the upper end of the guide tube, when the neutron absorber is located outside the core, the expansion The expansion tube is arranged such that the central part of the tube is located near the cooling member inlet, and on the other hand, when the neutron absorber is located in the reactor core, the upper part of the expansion tube is located near the coolant outlet. An emergency reactor shutdown device characterized by maintaining a distance between a tube and a neutron absorption device.