JPS5840115B2 - air cooling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in air cooling devices, and particularly to an air cooling device suitable for cooling liquid metal in an auxiliary core cooling system of a nuclear reactor.

In fast breeder reactors, liquid metal (mainly liquid metal) is used as a coolant.
IJum is used.

In this case, the cooling system is comprised of a primary cooling system that guides heat from the core to a main intermediate heat exchanger, and a secondary cooling system that leads heat from this heat exchanger to a steam generator.

To this secondary cooling system, an air cooling device is usually branched and connected as an auxiliary core cooling system in order to remove the core decay heat generated during fuel exchange, maintenance, or power loss.

Figure 1 shows the secondary cooling system of a conventional fast breeder reactor using an air cooling system. vessel 200
On the secondary side, between the hot leg piping 21 and the cold leg piping 22, there is an SG isolation valve 23, a superheater 24, an evaporator 25, an SG
An isolation valve 26 and a main circulation pump 27 are connected in sequence, and each of them is filled with liquid sodium to form a secondary cooling system.

The air cooling device has a piping 3 for introducing liquid sodium connected to the upstream side of the SG isolation valve 23, and a piping 4 connected to the downstream side of the SG isolation valve 26 via a flow rate control valve 28. Forms the core cooling system.

Note that the auxiliary core cooling system is not separated from the secondary cooling system side and operated independently as an air cooler device during reactor operation.

In other words, the auxiliary core cooling system is used in an emergency during reactor operation, such as when power is lost or when the superheater 24 or evaporator 2
5. In the event of an accident, etc., the SG isolation valves 23 and 25 are closed, the flow rate control valve 28 is fully opened, and the blower 6 is closed.
Since the reactor core will be cooled by starting the reactor, there is no need to disconnect it from the secondary cooling system in preparation for such an emergency operation.

Also, during maintenance, for example when inspecting the main circulation pump 27, the secondary cooling system drains sodium and is shut down. Such maintenance is not performed on all systems at the same time, and at least one or more secondary cooling systems continue core cooling operation.

The operation of the auxiliary core cooling system in this case is the same as the above-mentioned emergency operation, and there is no separate operation from the secondary cooling system.

As illustrated in FIG.
is arranged in a coil shape, and piping 3 and 4 for introducing and discharging liquid sodium are connected to both ends thereof, and a two-person damper 7 is connected between the artificial duct 5 and the blower 6, and an outlet duct 9 and a rain cover are connected. 10 and an outlet damper 11 connected therebetween.

8 indicates a suction vane. The air cooling system configured in this manner enables immediate response in the event of an emergency operation of the auxiliary core cooling system, and also allows for immediate response even when the auxiliary core cooling system is not in operation, in order to alleviate the thermal stress conditions at that time. A small amount of liquid (IJ) is always flowed into the heat transfer tube 2, and the tube is kept in a so-called standby operation state.

In this case, the blower 6 is stopped and the damper 7.1
1 is closed, but since these dampers cannot completely shut off the air flow path, if the outside temperature drops abnormally, the liquid sodium in the heat transfer tube 2 may freeze if the flow rate is low. There is that.

However, freezing of this liquid must be avoided at all costs.

On the other hand, flowing a large amount of liquid IJum into the air cooling system during standby operation wastes the reactor output during operation, which should have been channeled to the steam heater and used effectively. This is not desirable in terms of energy conservation.

FIG. 3 shows an installation example of an auxiliary core cooling system different from that in FIG. 1.

While FIG. 1 shows an example in which the system is branched from the secondary cooling system, FIG. 3 shows an example in which the core is directly cooled.

That is, there is an auxiliary intermediate heat exchanger 32 inside the reactor vessel 31, a pipe 3 connected to this intermediate heat exchanger 32 and having a stop valve 29 in the middle, and a second pipe 3 connected to this pipe 3 and having a stop valve 29 in the middle.
This is an auxiliary core cooling system consisting of an air cooler device having exactly the same configuration as shown in the figure, and a pipe 4 that communicates between the air cooler device and the reactor vessel 31 and has a flow control valve 30 in the middle.

The functions and features in this case are completely the same as those in Figures 1 and 2, except that they are provided completely independently of the secondary cooling system, so explanations will be omitted, but in this case, However, coolant is constantly flowing into the auxiliary core cooling system, and countermeasures against freezing of the coolant are an important issue.

The present invention has been made to eliminate the above-mentioned disadvantages of conventional devices.

That is, the present invention provides an air bypass path between the artificial duct of the artificial main body of the cooler main body and the outlet duct, and circulates the air inside the cooler main body with a fan inserted in this bypass path. The purpose of the present invention is to provide an air cooling system that prevents liquid sodium from freezing and also prevents waste of nuclear reactor power.

The present invention will be described in detail below with reference to the embodiments shown in FIGS. 4 and 5.

In FIG. 4, the same members as those shown in FIG. 2 are given the same symbols as in the same figure.

A blower 6 is attached to the inlet duct 5 connected to the cooler body 1 via an artificial damper 7, and a rain cover 10 is attached to the outlet duct 9 via an outlet damper 11.

Bypass piping 16.17 and an axial fan 18 are installed between branch pipes 12 and 13 branching from the inlet duct 5 and outlet duct 9 via stop valves 14.15, forming an air bypass path. There is.

Although not shown in the drawings, each of the above-mentioned structures is coated with a heat insulating layer to provide thermal insulation.

One or more heat transfer tubes 2 (only one tube is shown in the drawing) arranged in a coil shape inside the cooler body 1 have liquid at both ends. Piping 4 is connected.

'The air cooling system of the present invention thus constructed is connected to the reactor secondary cooling system, as illustrated in FIG. 5, to form an auxiliary core cooling system.

That is, in the figure, the secondary side of the main intermediate heat exchanger 20 that exchanges heat with the primary cooling system (not shown) has an SG isolation valve 23 between the hot leg piping 21 and the cold leg piping 22.
, superheater 24, evaporator 25, SG isolation valve 26, and main circulation pump 27 are connected in sequence, and liquid is supplied to each of them) IJ
A secondary cooling system is formed by filling the tank with aluminum.

The device of the present invention is equipped with the liquid (liquid) pipe 3 for introducing IJum.
is connected to the upstream side of the SG isolation valve 23, and the pipe 4 is connected to the downstream side of the SG isolation valve 26 via the flow rate control valve 28, thereby forming an auxiliary core cooling system.

In the cooling system configured as described above, when operating the auxiliary core cooling system at its rated capacity during fuel exchange, maintenance, or power loss, the SG isolation valve 23,
26 and open the flow rate control valve 28 to allow IJum to flow into the heat transfer tube 2 of the secondary cooling system.

In this case, the stop valve 14.15 is closed, the damper 7.11 is opened to a predetermined opening degree, and the blower 6 is made to work overtime so that its suction vane 8 sucks in the outside air and sends it into the cooler body 1. The liquid flowing through the reactor cools the IJ and removes the core decay heat.

On the other hand, during normal operation of the reactor, liquid sodium discharged from the main intercooler 20 passes through the hot leg piping 21 and exchanges heat with water on the turbine generator side in a steam generator consisting of a superheater 24 and an evaporator 25. After turning this into superheated steam,
It is introduced into the main intermediate heat exchanger 20 again from the main circulation pump 27 .

In that case, since the flow rate control valve 28 is opened to an appropriate degree, a part of the liquid sodium in the hot leg piping 21 enters the heat transfer tube 2 of the cooler main body through the piping 3, and the air inside the cooler main body is absorbed. After being heated, it returns to the main intermediate heat exchanger 20 via the pipe 4, the flow control valve 28, and the cold pipe 22.

At this time, in the air cooling system, the stop valves 14 and 15 are opened, and the axial fan 18 is rotated to move the air warmed by the liquid sodium flowing through the heat transfer tube between the outlet damper 11 and the artificial damper 7. Because of forced circulation, the heat exchanger tubes 2 will not freeze no matter how low the outside temperature may be.

Here, Figure 6 qualitatively shows the temperature distribution of IJum inside the heat transfer tube and the temperature distribution of the air flowing inside the cooler body. The temperature inside the pipe drops below the freezing temperature in a certain part, and at first it freezes locally.

When this freezing starts, the flow of sodium stops and eventually it spreads over the entire area of the heat exchanger tube).
However, in the present invention, the air inside the cooler body is forcedly circulated,
Since the air heated by the IJum is sent into the inlet side of the cooler main body, the above-mentioned freezing is prevented.

However, if the air temperature inside the cooler body rises excessively, the sodium temperature at the outlet of the heat transfer tube will rise, and the temperature difference at the confluence with the cold leg pipe will become large, causing thermal problems. Adjust the temperature at the heat exchanger tube outlet by stopping the axial fan or opening and closing the stop valve as appropriate.

As described above, according to the device of the present invention, during standby operation of the auxiliary core cooling system, the reactor output during rated operation can be used without wasting it, and it can also be turned on when the outside air temperature drops.
Freezing of IJum can be completely prevented.

Furthermore, since forced circulation is performed by an axial fan, there is no deviation in the air flow within the air cooler body, and local temperature drops in the heat exchanger tubes can be resolved.

FIG. 7 is a system diagram showing an example in which an air cooler device according to the present invention is provided in an auxiliary core cooling system directly connected to a nuclear reactor.
Effects can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a conventional auxiliary core cooling system, Fig. 2 is a schematic diagram showing a conventional air cooling system, Fig. 3 is a system diagram showing another example of a conventional cooling system, and Fig. 4 5 is a schematic diagram showing an embodiment of the air cooling device of the present invention, FIG. 5 is a system diagram of a reactor secondary cooling system showing an example of use of the device of the present invention, and FIG. 6 is an air button in the air cooling device) A graph qualitatively showing the temperature distribution of IJum, and FIG. 7 is a system diagram showing another example of the present invention. 1... Cooler body, 2... Heat exchanger tube, 3
, 4...Piping, 5...Inlet duct, 6
...Blower, 7...Inlet damper, 9
...Exit duct, 11...Outlet damper, 12.13...Branch pipe, 14.15...
...stop valve, 16,17...bypass piping, 1
8... Axial fan, 20... Main intermediate heat exchanger, 21... Hot leg piping, 22...
... Cold leg piping, 24 ... Superheater, 2
6...Evaporator, 27...Main circulation pump, 28...Flow rate control valve.

Claims (1)

[Claims] 1. A cooler main body is installed between the air blow source and the exhaust port, and the inlet and outlet of the cooler main body can be opened and closed by a damper, and a heat transfer tube is installed inside the cooler main body. In this air cooling system, a part of the coolant flowing through the auxiliary core cooling system of the nuclear reactor is guided into the heat transfer tube; a bypass path is provided at the inlet and outlet of the cooler body to bypass the interior of the body. An air cooling device characterized in that the air cooling device is provided with a fan built into the air bypass path. 2. The air cooling device according to claim 1, wherein a stop valve is inserted in the air bypass path. 3. The air cooling device according to claim 1, wherein the Noan is an axial fan.