JPS583118Y2 - Liquid absorbent safety device for nuclear reactors - Google Patents

Description

[Detailed description of the invention] The present invention provides a liquid absorbent material related to a safety device that reduces the reactivity of a nuclear reactor by rapidly introducing an absorbent liquid into a gap provided in the core of the reactor. The nuclear reactor shutdown device by introducing
than conventional devices such as control rods that can perform similar actions.
This has advantages in case of an explosion or serious accident.

Some known liquid absorbent shutdown systems operate by injecting the absorbent directly into the cooling liquid or moderator.

However, this makes it very difficult to extract the absorbent material, and the equipment for separating the absorbent material is very bulky and expensive.

In other systems, absorbent material is circulated in tubes that cross the reactor orthogonally; the absorbent material is maintained outside the reactor core by pressurization; The gas is stored in a drum that is exposed to gas pressure outside of the drum.

To release the absorbent material into the tubes passing through the reactor core, it is sufficient to rapidly increase the pressure of the gas in the drum and reduce the pressure maintaining the absorbent material outside the core.

These devices have the disadvantage of requiring external manipulation to operate.

On the other hand, the liquid-filled conduits are also quite long, which causes load losses and slows down the liquid flow.

In other words, this loss prevents a rapid response and requires considerable pressure.

Furthermore, this slowness has a detrimental effect at the ends of the flow path, which necessitates the use of damper devices to suppress the flow of the liquid.In order to eliminate these disadvantages, the present invention has been devised. This is an absorber safety device that starts automatically and uses only the amount of liquid corresponding to the liquid column at the height of the reactor core.

The low inertia of this liquid column allows the absorbent to move rapidly and be stopped without complex control equipment.

The apparatus shown in the accompanying drawings is one embodiment of the present invention, and the present invention is not limited thereto.

The safety device shown in the figure consists of a vertical cylindrical container 1 which is divided approximately in the middle by a dividing wall 2 into an upper compartment 3 and a lower compartment 4 .

The lower compartment 4 has a height slightly higher than the height of the reactor core in which it is located.

The upper compartment 3 is therefore located above the core of the nuclear reactor.

These two compartments communicate with each other by an annular pipe 5 which adjoins the internal partition of the vessel 1, and the iron pipe exits from the bottom of the lower compartment 4 and is connected to the partition 2 by means of a device with a siphon 6. It opens into the compartment 3 above.

The lower compartment 4 is provided with an axial vertical tube 7 whose upper end adjoins the partition wall 2'.

Further, its lower end communicates with the outside of the container 1 and is closed by a closing member 8.

This closure member 8 is a uranium cap soldered around the periphery with a soluble metal.

The vessel 1 has a small volume container 9 with a valve 10 and a closing orifice 11 in the upper part.

This container 9 communicates with the lower compartment 4 by a vertical pipe 12.

This vertical tube is located off-axis of the container 1 and traverses the upper compartment 3.

The vessel 1 is preferably arranged in a case (not shown) that houses the reactor core.

The function of the safety device of the present invention is as follows.

The vessel 1 is located outside the reactor and a liquid absorbing material, for example lithium, is poured into it through an opening 11 until the liquid reaches the lower side of the upper part of the vertical tube 7 in the lower compartment 4 .

Opening 11 is then sealed. The container 1 is pressurized via a valve 10 by injecting a gas, for example argon or helium, so that the liquid rises via the annular tube 5 into the upper compartment 3.

When all of the liquid is introduced into the upper compartment 3 and the pressure of the gas in the lower compartment 4 becomes clearly higher than the pressure in the reactor core, the gas inlet is blocked and the valve 10 is closed.
Then seal the mouth.

The gas in the upper compartment is therefore at a pressure P1 slightly lower than the pressure P2 present in the lower compartment, and the pressure difference P2-PI is equal to the pressure exerted in the column of liquid.

The vessel is then lowered into a case (not shown) within the core of the nuclear reactor containing fuel.

In practice, only the lower compartment is located within the core, while the upper compartment is above the core.

In the case of fast nuclear reactors, the vessel is immersed in a cooling liquid, for example liquid sodium.

When the uranium cap 8 receives a normal flux of neutrons, it remains at a temperature below the melting point of the solder metal, and the liquid absorber remains in the upper compartment 3 above the reactor core.

When the reactor becomes overreactive, the neutron flux increases significantly, warming the cap 8 and melting the solder metal.

The cap is therefore injected into the lower compartment 4 under gas pressure.

As a result, a sudden drop in air pressure occurs in the lower compartment, and the liquid absorbent falls into the compartment 4 due to the expansion of the gas contained in the upper compartment 3.

The liquid absorbent material lies horizontally below the upper end of the vertical tube 7 and remains within the lower compartment.

The safety device of the present invention acts like a fuse that virtually instantaneously reduces the operation of the nuclear reactor.

It is clear that in the event of an explosion which causes a mechanical deformation of the core, the liquid absorbent material will likewise descend into the lower compartment 4.

The start-up of the device does not require any external manipulation and does not require the use of external energy sources in the reactor.
Very accurate.

In the case of gas reactors, the uranium cap of the safety device may be replaced with a pressure-sensitive membrane member.

The container equipped with the membrane member is not subjected to pressure and the valve 1
It is lowered into the core without any sealing.

- When the gas reactor is pressurized, a pressure equal to the pressure present in the reactor is also created in the lower compartment 4 via the valve 10 and the liquid absorbent is sent to the upper compartment 3.

The membrane senses any pressure drop within the reactor and ruptures as soon as the pressure drop exceeds a pre-predicted value.

That is, gas escapes from the lower compartment 4 and liquid absorbent material enters the compartment.

Of course, the above-mentioned safety devices are considered to have the greatest advantage in the implementation of the invention, but it is not possible to deviate from the spirit of the invention by replacing the constituent elements with elements having the same or equivalent technical function. It is something that can be changed and transformed in many ways.

[Brief explanation of drawings]

The attached drawing is a sectional view showing one embodiment of the safety device of the present invention.
1 is a vertical cylindrical container, 2 is a partition, 3 is an upper compartment, 4 is a lower compartment, 5 is an annular tube, 7 is a vertical tube, 8 is a closing mechanism,
9 is a container, and 10 is a valve.

Claims (1)

[Claims for Utility Model Registration] In a liquid absorbent safety device for a nuclear reactor that includes a cylindrical container extending in a vertical direction, the cylindrical container 1 is located above the reactor core and is filled with a liquid absorbent material. an upper compartment 3 having a pressure P1, and a lower compartment 4 located within the core;
It is located above the upper compartment 3. a chamber 9 at a pressure P1 greater than said pressure P1; a tube 12 communicating said chamber 9 with the top part of said lower compartment 4; and a bottom part of said upper compartment 3 communicating with the bottom part of said lower compartment 4. a siphon 6 inserted between the bottom portion of the upper compartment 3 and the annular tube 5;
and a vertical pipe 7 extending vertically within the lower compartment 4 and communicating the top portion of the lower compartment 4 with the outside of the container 1, the vertical pipe 7 being connected to the container outlet portion thereof. A liquid absorbent safety device for a nuclear reactor, characterized in that the device is closed by a closing member 8 that opens when an abnormality occurs in the operating state of the nuclear reactor.