JPH0463360B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for dispersing thermal stress acting on the side wall of a high-temperature liquid container such as a fast breeder reactor, and more specifically to a method for dispersing thermal stress acting on the side wall of a high-temperature liquid container such as a fast breeder reactor. The present invention relates to a method for distributing the position of thermal stress generated on the side wall near the liquid surface of a high-temperature liquid container.

(Prior Art) In fast breeder reactors, liquid sodium is used as a coolant and circulated through the cooling system. However, the liquid sodium level in the reactor vessel fluctuates depending on the operating status of the liquid sodium circulation pump installed in the cooling system, so overflow is required to maintain the liquid level at a constant level. A system is installed.

An overview of this overflow system will be explained with reference to FIGS. 4 and 5.

Liquid sodium in an overflow tank 1 is pumped up into a reactor vessel 4 via a pumping pipe 3 by an electromagnetic pump 2. Then, the level of liquid sodium in the reactor vessel 4 rises and reaches the overflow roller 5. The overflowing liquid sodium then returns to the overflow tank 1 via the overflow pipe 6 and the return pipe 7. The upper side of the liquid sodium in the reactor vessel 4 is filled with a cover gas G such as argon to prevent oxidation of the liquid sodium.

In FIG. 4, 10 is an inlet pipe for liquid sodium in the primary cooling system, 11 is an outlet pipe, and 12 is a reactor core.

(Problems to be Solved by the Invention) However, the temperature of liquid sodium is high, and the temperature of the cover gas is low compared to the temperature of liquid sodium. Therefore, a sharp temperature gradient is generated on the side wall 9 of the reactor vessel 4 near the interface 8 between the high temperature liquid sodium and the lower temperature cover gas G due to the difference in thermal expansion. Thermal stress occurs. This thermal stress adversely affects the durability of the reactor vessel 4 and the like. In particular, if the nuclear reactor is started and stopped rapidly, an even steeper temperature gradient will occur and even greater thermal stress will be generated in the side wall 9 of the reactor vessel 4.

In order to suppress the occurrence of such thermal stress, nuclear reactors have traditionally been started and stopped over time.
By lengthening the start and stop times, the temperature gradient that occurs between the liquid sodium and the cover gas G becomes as gentle as possible. However, if the startup and shutdown are slowed down, a problem arises in that the operating rate of the reactor decreases.

Therefore, the purpose of the present invention is to improve the above-mentioned drawbacks,
A thermal stress acting side wall in a high temperature liquid container that changes the position of the thermal stress that occurs by making the liquid level changeable, thereby improving the durability of the high temperature liquid container and improving the operating rate of nuclear reactors, etc. Provides a method for distributing locations.

(Means for Solving the Problems) A feature of the present invention is that the liquid level of a high-temperature liquid container such as a fast breeder reactor can be changed, and the liquid level is operated at each liquid level for a predetermined time, and then the liquid level is changed to another liquid level. Furthermore, the system is operated for a predetermined period of time, thereby changing the location of the thermal stress generated on the side wall near the liquid surface.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the invention.

Inside the reactor vessel 4, a reactor core 12 is arranged and liquid sodium is accommodated as a coolant. In this embodiment, the reactor vessel 4 is a high temperature liquid container, and the liquid sodium is the high temperature liquid.

The upper part of the reactor vessel 4 is closed by a plug 13 . The reactor vessel 4 is connected to an inlet pipe 10 and an outlet pipe 11 for liquid sodium in the primary cooling system. Moreover, a cover gas G such as argon is filled above the liquid level of the liquid sodium to prevent oxidation of the liquid sodium.

In addition to the cooling system, the reactor vessel 4 is provided with an overflow system, and regardless of the operating state of the liquid sodium circulation pump (not shown) in the cooling system, the liquid level of the liquid sodium in the reactor vessel 4 remains constant. is maintained at a certain level.

An overview of this overflow system will be explained with reference to FIG.

Liquid sodium in an overflow tank 1 is pumped up into a reactor vessel 4 via a pumping pipe 3 by an electromagnetic pump 2. Liquid sodium returns to the overflow tank 1 via an overflow pipe 6 and a return pipe 7.

As shown in FIG. 2, the overflow pipe 6 stands up inside the reactor vessel 4, and a funnel 14 is provided at the upper end of the overflow pipe 6. An overflow port 5 is opened. Note that the same effect can be achieved even if the overflow port is a vertically long slit, and the overflow port of the present invention also includes a vertically long slit.

In this embodiment, since the overflow ports are provided in the vertical direction, the total opening area of the overflow ports 5 during which liquid is being discharged varies depending on the liquid level. Therefore, the overflow flow rate differs depending on the liquid level, and by utilizing this fact, the liquid level of the liquid sodium is changed by changing the pumping amount of the electromagnetic pump 2.

On the other hand, it is necessary to control the level of liquid sodium to be constant. Therefore, in this embodiment, the liquid level detection signal detected by the liquid level detector 15 is inputted to the controller 16, and processed by the controller 16, and the liquid level of the liquid sodium is maintained constant according to the command from the controller 16. The pumping amount of the electromagnetic pump 2 is automatically adjusted so that the amount of pumping is automatically adjusted.

The present embodiment configured as described above operates as follows.

As shown in FIG. 2, it is assumed that the liquid sodium level is now at the highest level L1. At this liquid level L1, liquid sodium flows into the overflow pipe 6 from the overflow port 5 at the upper end as well as from all the overflow ports 5 at the rising portion.

After operating at this liquid level L1 for several years, the pumping amount of the electromagnetic pump 2 is reduced to lower the liquid level to L2. At this liquid level L2, liquid sodium flows into the overflow pipe 6 from the overflow port 5 below the liquid level L2.

Next, when the liquid level is set to L3, the pumping amount of the electromagnetic pump 2 is reduced in the same manner as above. Then, at each liquid level, the liquid level detection signal detected by the liquid level detector 15 is input to the controller 16,
The pumping amount of the electromagnetic pump 2 is automatically adjusted according to a command signal from the controller 16 so as to maintain the level of liquid sodium at a constant level.

By changing the liquid level of liquid sodium in the reactor vessel 4 in this manner, the locations where thermal stress occurs in the reactor vessel 4 can be dispersed, and the durability of the reactor vessel 4 can be improved. Furthermore, since the locations where thermal stress occurs can be dispersed, the rate of rise and fall of the temperature of the reactor can be increased, and the operating rate of the reactor can be improved.

In addition, in order to be able to change the liquid level over a wide range, it is necessary to provide the overflow port 5 widely in the vertical direction. However, if the overflow port 5 is installed too widely in the vertical direction, the overflow flow rate will become too large when the liquid level is set at the highest position, and the amount pumped by the electromagnetic pump 2 will increase. This means that electromagnetic pump 2
This means increasing the size of the product, which increases manufacturing and operating costs. Therefore, in such a case, a flow control valve 18 is installed in the overflow pipe 7.
It is effective to provide a flow rate control valve 18 to reduce the flow rate. However, the present invention does not require the installation of this flow rate control valve 18, and the flow rate control valve 18 is installed as necessary.

Note that the present invention is not limited to the embodiments described above.

For example, the overflow pipe may have a structure in which funnels 14 are provided at each predetermined liquid level, as shown in FIG.

Furthermore, the high temperature liquid container is not limited to a nuclear reactor container.

Furthermore, the high temperature liquid is not limited to liquid sodium.

(Effects of the Invention) In the present invention, since the liquid level of the high-temperature liquid in the high-temperature liquid container can be changed arbitrarily, the position of thermal stress generated on the side wall by the high-temperature liquid can be dispersed, and the durability of the high-temperature liquid container can be improved. It is possible to improve the operation rate and improve the operating rate.

[Brief explanation of the drawing]

FIG. 1 is a system diagram illustrating one embodiment of the present invention. FIG. 2 is a partially enlarged view of FIG. 1.
FIG. 3 is a diagram showing the main parts of another embodiment of the overflow port. FIG. 4 is a system diagram of the prior art. FIG. 5 is a partially enlarged view of FIG. 4. 1... Overflow tank, 2... Electromagnetic pump, 3... Pumping piping, 4... Reactor vessel, 5...
Overflow port, 6...Overflow pipe, 7
... Return piping, 8 ... Boundary line, 9 ... Side wall, 10
...Inlet piping, 11...Outlet piping, 12...Reactor core, 13...Plug, 14...Funnel, 15...Liquid detector, 16...Controller, 17...Flow control valve.

Claims (1)

[Claims] 1. Pump up liquid into a high-temperature liquid container using a pump, make the high-temperature liquid pumped into the high-temperature liquid container overflow from an overflow port, and send the high-temperature liquid overflowing from the overflow port from a return path. In an overflow system for a high-temperature liquid container that maintains a constant liquid level by balancing the amount pumped by the pump and the overflow flow rate overflowing from the overflow port, By overflowing, the liquid level changes when the pumping amount of the pump is changed, the liquid level is detected by the liquid level detecting means, and the detected signal is sent to the controller. The amount of pumping of the pump is controlled so that the liquid level reaches a predetermined level. A method for distributing thermal stress acting positions in a high-temperature liquid container, the method comprising dispersing the positions of thermal stress acting on a side wall.