JPH0799399B2 - Decay heat removal device for nuclear reactor - Google Patents

Description

The present invention relates to a reactor vessel sodium cooling device such as a decay heat removal device used in a nuclear reactor, particularly a liquid metal cooling type fast breeder reactor.

“Prior Art” Various devices for removing decay heat of a nuclear reactor have been proposed.

In general, there are those that directly remove the decay heat from the primary cooling system of the nuclear reactor, those that remove the heat from the secondary cooling system, and the like.

FIG. 6 is a schematic diagram showing a collapse removal device that directly removes heat from the primary cooling system of a nuclear reactor. In the figure, heat generated by normal operation of the nuclear reactor 1 is taken out by a steam generator via liquid sodium (not shown) and is used as electric energy by rotating a turbine. On the other hand, the decay heat when the normal operation of the nuclear reactor 1 is stopped is the heat that is placed in the air cooler 4 by the liquid sodium in the pipe section 3 through the heat exchanger 2 that is placed in the primary cooling system. It is discharged by the exchanger 5. Here, the liquid sodium in the pipe portion 3 is forcibly circulated and controlled by the electromagnetic pump 6, and the air cooler 4 is connected to the blower 7.

Further, an outlet damper 8 and an inlet damper 9 are provided above and below the heat exchanger 5 in the air cooler 4 and are closed during steady operation of the nuclear reactor 1. The electromagnetic pump 6 is also stopped. In the decay heat removal apparatus having such a configuration, when cooling the decay heat generated when the reactor is stopped, the blower 7 is first activated, and then the outlet damper 8 and the inlet damper 9 are opened to remove air from the air cooler 4. The heat exchanger 5 is cooled by forced circulation inside. Further, by driving the electromagnetic pump 6, the liquid sodium in the pipe portion 3 is circulated and the heat exchanger 2 releases the heat absorbed from the inside of the furnace. On the other hand, reactor 1
During normal operation, the damper is closed so that the heat in the furnace is not radiated from the cooling device, and the heat generated in the furnace is effectively used.

"Problems to be Solved by the Invention" By the way, in the conventional decay heat removal device described above,
There was a drawback that the failure rate of dynamic equipment such as entrance / exit dampers, blowers, and electromagnetic pumps was large both during startup and during operation. This leads to a decrease in the reliability of the decay heat removal device, and eventually the reactor.

The object of the present invention was made in view of the above-mentioned drawbacks,
To provide a natural circulation type collapse removal device capable of reliably removing heat only in an abnormal state without removing heat in a normal state by utilizing only a natural heat release phenomenon without using a dynamic device. It is in.

"Means for Solving Problems" In the present invention, (a) the first heat exchange section, (b) the second heat exchange section, and (c) the heat received by the first heat exchange section, The working substance to be conveyed to the second heat exchange unit, (d) the cooling substance that promotes the release of heat in the second heat exchange unit, and (e) the working substance are arranged in the pipe through which the cover gas is filled. The chamber formed by the above, the separator that closes the piping flow path to a position that is higher than the liquid level of the working substance at the normal time but lower than the liquid level at which the working substance rises at a predetermined temperature, and below the separator. A decay heat removing apparatus is provided with a switch mechanism that is provided and that is configured by a valve member that opens and closes a pipe flow path.

[Operation] As described above, since the decay heat removal apparatus for a nuclear reactor according to the present invention is configured without using any dynamic equipment, it is possible to significantly reduce the failure occurrence rate and improve the reliability of the apparatus. Become.

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

FIG. 1 is a configuration diagram showing a decay heat removal apparatus of one embodiment of the present invention. In the figure, the decay heat removal device is a reactor
The first heat exchange section located in the hot pool near 10
11, cooling means 12 open to the atmosphere, cooling means 12
A second heat exchanging portion 13 disposed therein, and a working substance 14 that conveys the heat received by the first heat exchanging portion to the second heat exchanging portion, such as liquid sodium, and the working substance 14 has a predetermined temperature. The switch mechanism 15 and the like permitting the movement between the first heat exchanging section 11 and the second heat exchanging section 13 only when it reaches

FIG. 2 is a configuration diagram showing an internal configuration of the switch mechanism 15. In the figure, a switch mechanism 15 includes a valve member 18 provided immediately below a pipe 16 for flowing liquid sodium and a separator 17 for closing a flow passage in the pipe, and a chamber 19 filled with a cover gas such as argon or nitrogen. During normal operation of the reactor, as shown in FIG. 2 (A), the liquid level of liquid sodium, which is the coolant, is at X, and the flow path is closed. Therefore, during normal operation, the heat generated in the furnace is effectively used to drive a turbine or the like (not shown).

Next, when the temperature inside the furnace rises abnormally, the liquid sodium, which is the working substance in the first heat exchange section 11 immersed in the hot pool, rises in temperature and expands. The expanded working substance of the volume raises the liquid level in the switch mechanism 15 communicating with the pipe to Y. At this time, as shown in FIG. 2 (B), at the liquid level Y, the liquid level of the liquid sodium exceeds the upper end of the separator 17, so that the secondary system pipes on the left and right of the separator 17 communicate with each other to form a flow path. . Therefore, liquid sodium, which is a working substance, circulates through the first heat exchange section 11, the switch mechanism 15, the second heat exchange section 13, and the cooling means 12, and the inside of the furnace is cooled. As described above, in the switch mechanism 15 of the present embodiment, the flow path of the working substance can be opened and closed without using a dynamic member.

Also, in the decay heat removal mode immediately after stopping the normal reactor operation, if the temperature of the hot pool rises, the level of liquid sodium rises as in the case of the decay heat removal mode during an abnormality. The mechanism 15 forms an open loop. On the other hand, when the temperature of the hot pool is decreased, the valve member 18 is opened to form an open loop of the working substance to remove the decay heat. Even if the opening operation of the valve member 18, which is a dynamic device, is not performed due to a failure, it is possible to remove heat by the same mechanism as in the abnormal state described above. Therefore, safety as a cooling device can be ensured.

FIG. 3 is an explanatory view showing the principle of liquid level rise for turning on / off the switch mechanism 15 of this embodiment. T ₁ when the temperature of the working substance in the first heat exchange section 11 of the decay heat removal apparatus immersed in the hot pool of the nuclear reactor 10 (see FIG. 1) is normal
Assuming that the temperature rises to T ₂ at the time of abnormality, the increase amount Δh _H of the liquid level of the switch mechanism unit 15 is given by the following equation (1).

That is, Δh _H is the amount of thermal expansion due to temperature rise,
It is determined by the length of the pipe section (first heat exchange section) immersed in the hot pool, the total cross-sectional area, and the cross-sectional area of the switch mechanism section. Further, in the decay heat removal mode during normal operation, the temperature of the working substance in the hot pool is lower than that during rated operation. Now, the temperature during normal operation is T ₁ ,
Assuming that the temperature at the time of decrease is T ₂ , the amount of decrease in liquid level height Δh _L is
It is given by the following equation (2).

In this way, the switch mechanism in the three cases of the rated heat operation, the abnormal operation, and the normal decay heat removal mode of the reactor
The internal liquid level of 15 can be arbitrarily set by the combination of the above parameters. Here, S ₁ , S ₂ , and S ₃ are cross-sectional areas of each pipe, Δh _N is the difference between the liquid surface during the rated operation and the top of the separator, Δh _H is the liquid level increase amount during an abnormality, and Δh _L is Liquid level drop in normal decay heat removal mode, T ₁ and ρ ₁ are hot pool temperature and density during rated operation, T ₂ and ρ ₂ are hot pool in abnormal or normal decay heat removal mode Temperature and density.

Further, the chamber 19 (see FIG. 2) in which the cover gas is sealed is installed in order to prevent the pressure increase due to the liquid level increase inside the switch mechanism 15. In order to prevent the working substance 14 from solidifying in the cooling means 12 during normal operation, the working substance used may be NaK, for example.

FIG. 4 is a block diagram showing another embodiment of the switch mechanism 15 in the present invention. In the figure, the switch mechanism 15 '
Is a valve member 20, a bifurcated pipe 21, and a bifurcated pipe 21 that are openably and closably provided in a pipe 16 through which liquid sodium as an operating substance flows.
And a chamber 19 'filled with a cover gas.

In the case of the above configuration, the bifurcated tube 21 serves as the separator in the first embodiment. That is, when the cover gas is pushed up and the liquid level rises to reach the Y position at the time of abnormality, the switch mechanism 15 'forms an open loop and the cooling action is performed. Further, during the rated operation with the liquid level at the X position, the flow path is closed and the cooling operation is not performed. Then, in the normal decay heat removal mode, when the liquid level is at the Z position, the valve member 20 is opened, the flow path is opened, and the cooling operation is performed. Even with such a configuration, it is possible to open and close the flow path without using a dynamic device.

FIG. 5 is a block diagram of a switch mechanism showing another embodiment of the present invention. In the figure, the switch mechanism 15 ″ is a pipe
A valve member (20) provided inside the box (16) to open and close, a box body (22) communicating the left and right sides of the valve member (20), and a partition plate (23) erected inside the box body.
Etc. And at the upper end of the box 22,
Governor gas is enclosed. Even if the switch mechanism 15 ″ configured as described above is used, the flow path can be opened and closed without using a dynamic device.

Therefore, the decay heat removal device can be reliably turned on and off without failure. As described above, according to the decay heat removing apparatus of the present invention, the reactor does not operate during the rated motion of the reactor, but can operate only during an abnormality or when decay heat is generated.

The decay heat removal apparatus of the present invention is not limited to the above-described embodiment, and various design changes can be made based on the technical idea of the present invention.

[Advantages of the Invention] As described above, according to the present invention, the static switch mechanism is activated when the operating substance reaches a predetermined temperature. By changing the liquid level, decay heat can be removed by natural circulation without using a dynamic mechanism. Since a completely passive natural circulation type cooling device is configured in this way, there are few failures even during abnormal times, and the reliability indispensable to a nuclear reactor can be significantly improved.

Further, in the present invention, since the valve member is used for the switch mechanism, even when the temperature of the hot pool drops in the decay heat removal mode under normal conditions, the decay heat can be removed by opening the valve. You can also do it.

[Brief description of drawings]

1 to 5 are diagrams for explaining an embodiment of the present invention. FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIGS. 2 (A) (B) (C) are FIG. 3 is a configuration diagram showing an internal configuration of the switch mechanism, FIG. 3 is an explanatory view of the principle of the switch mechanism of the present invention,
FIG. 4 is a block diagram of another embodiment showing the switch mechanism, and FIG.
FIG. 6 is a configuration diagram showing another embodiment showing the switch mechanism of the present invention, and FIG. 6 is a schematic diagram showing a decay heat removal device for directly removing heat from the primary cooling system of a nuclear reactor. 11 …… First heat exchange section, 12 …… Cooling means, 13 …… Second heat exchange section, 14 …… Working substance, 15,15 ′, 15 ″ …… Switch mechanism, 16 …… Piping, 17 ...... Separator, 18,20 …… Valve member, 19,19 ′ …… Chamber, 21 …… Bifurcated tube, 22 …… Box, 23 …… Partition plate.

Claims (1)

[Claims] 1. A first heat exchange section, a second heat exchange section, an operating substance that conveys the heat received by the first heat exchange section to the second heat exchange section, and the second heat exchange section. A cooling substance that promotes the release of heat in the heat exchange section, a chamber that is arranged in a pipe through which the working substance flows, and is formed by filling a cover gas, and the working substance is higher than the normal liquid level, A switch mechanism including a separator that closes the pipe flow passage to a position lower than the liquid level at which the working substance rises at a predetermined temperature, and a valve member that is arranged below the separator and that opens and closes the pipe flow passage. An apparatus for removing decay heat, which comprises: