JPS60158389A - Cooling device for furnace wall of reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a tank-type nuclear reactor bulkhead structure, and in particular to a reactor wall of a nuclear reactor suitable for reducing thermal stress during thermal transients in the wall of a reactor vessel. Regarding a cooling device.

[Background of the invention]

To explain the reactor wall cooling structure of a conventional nuclear reactor,
First, as an example of a conventional tank-type nuclear reactor structure, the reactor structure of a tank-type fast breeder reactor will be explained with reference to FIG.

The reactor main body includes a circulation pump 5 for forced circulation of coolant and coolant within a large vessel composed of a reactor vessel 1 and a roof slab 4. It houses the reactor core 2 and an intermediate heat exchanger 8 for exchanging heat between the coolant and the secondary coolant.

The flow of coolant within the reactor body is described below.

The low-temperature coolant in the cold pool 3 is sucked into a circulation pump 5 suspended from the roof slab 4, pressurized, and led into a high-pressure plenum 6.

Thereafter, it passes through the reactor core 2, reaches a high temperature, and reaches the hot pool 7. Furthermore, 2 is introduced into the intermediate heat exchanger 8 from an opening 9 in the hot pool of the intermediate heat exchanger 8 suspended from the roof slab 4, and circulates through a steam generator (not shown).
By exchanging heat with the secondary coolant through the heat transfer tubes, the temperature becomes low and returns to the cold pool 3. The above is an explanation of the flow of the coolant within the reactor main body.

On the other hand, the temperature of the upper part of the reactor vessel 1 in contact with the hot pool 7 will be approximately equal to the temperature of the coolant in the hot pool 7 unless special consideration is taken.

The temperature is often about 500° C. from the viewpoint of steam temperature for driving the turbine.

Further, the support structure of the reactor vessel 1 is made of concrete with a roof slab 4 interposed therebetween. The permissible temperature of this concrete is as low as about 70°C. Also,
The roof slab 4 includes a control rod drive device, a fuel handling device,
Since major equipment such as the rotating plug, intermediate heat exchanger 8, and ring pump 5 are installed, the temperature of the roof slab 4 is approximately 60°C from the viewpoint of inspection, maintenance, and repair of these equipment.
It is necessary to keep the temperature low.

Hot pool 7 at approx. 500℃, roof slab 4 at approx. 60℃
C., there is a large temperature difference of approximately 440.degree. C. between the hot plenum 7 and the roof slab 4, making this a very difficult point in terms of structural strength.

The above is a general explanation of the conventional tank-type nuclear reactor structure, and is the background why the reactor wall cooling structure described below is required.

A conventional furnace wall cooling method is shown in FIG. A heat insulating structure 10 using a gas layer or a laminated plate and a cooling path 11 are provided between the reactor vessel 1 and the hot pool 7. The cooling path 1 is dealt with by guiding the low temperature coolant in the high pressure plenum 6 through the cooling pipe 12 as shown by arrow A.

This coolant is the coolant in the cold pool 3 pressurized by the circulation pump 5, and the coolant that has not passed through the reactor core is bypassed, so its temperature is approximately the cold pool temperature (usually around 350°C). )be equivalent to. The coolant that has cooled the furnace wall returns to the cold pool 3 as shown by arrow B.

The temperature distribution in the height direction of the reactor vessel 1 in such a steady state will be explained. The right side of FIG. 2 shows the temperature distribution in the height direction. The top of the reactor vessel 1 is
The cooling end structure provided on the roof slab 4 and the laminated plate 14 installed at the bottom of the roof slab 4 reduce the temperature to approximately room temperature.

On the other hand, the parts of the reactor vessel 1 that are above the coolant liquid level and in contact with the atmosphere inside the vessel are affected by the radiation from the high-temperature hot pool 7 and the temperature rise due to gamma heat generation of the structural materials. Therefore, the temperature of the coolant in the cold pool 3 is maintained higher than that of the coolant.

Also, the coolant flowing through the cooling path 11 is in the high pressure plenum 6.
It is pushed up through the inner cooling path 1] at a temperature equal to that of the cold pool 12, reversed at the upper end of the flow path forming shroud I3, and descended through the outer cooling path in contact with the reactor vessel 1. Due to the effect of the heat insulating layer 10, the coolant flowing through the cooling path 11 is not affected much by the high temperature of the hot pool 7, so the temperature hardly rises. Therefore, the portion of the cooling path 11 in the reactor vessel 1 that is in contact with the coolant is maintained at the temperature of the cold pool 3.

As a result, the temperature distribution in the height direction of the reactor vessel 1 has a convex shape near the liquid level, as shown on the right side of FIG. However, since the temperature difference in such a steady state is not so large, the thermal stress generated is small.

However, when a nuclear reactor is shut down, large thermal stress occurs. In the case of shutdown, the temperature of the coolant in the hot pool 7 and cold pool 3 drops rapidly. Coolant generally has good thermal conductivity, so cooled coolant rapidly removes heat from the reactor vessel it is in contact with. The temperature followability of this portion of the reactor vessel 1 with respect to the temperature drop of the coolant is extremely good.

On the other hand, the parts of the reactor vessel 1 that are in contact with the atmosphere are kept at a high temperature by radiation from the hot pool 7 and gamma heat generated by the structural materials, but when the reactor is shut down, they are not in direct contact with the coolant. As a result, temperature tracking is poor, and the reactor remains at a high temperature immediately after the reactor is shut down.

Therefore, as shown in Figure 3, the temperature distribution in the height direction of the reactor vessel 1 during shutdown is such that the temperature drop in the part in contact with the coolant is faster than the temperature drop in the high temperature part near the liquid level. Therefore, it has a very large convex shape and generates large thermal stress.

At startup, the coolant transfers heat quickly, but the reactor vessel 1 above the coolant liquid level has poor temperature tracking, and the parts in contact with the coolant quickly become hot. On the other hand, the area above the coolant liquid level remains at a low temperature, and the temperature distribution becomes concave, opposite to when it is stopped.

The thermal stress generated near the liquid surface of the reactor vessel 1 when the reactor is started and stopped has a large absolute value and has opposite signs because the humidity distribution is reversed. The range of stress is therefore very large.

In addition, the operating states of starting and stopping a nuclear reactor are always required due to periodic inspections and the like. Therefore, the large thermal stress generated during shutdown impairs the structural reliability of the reactor vessel.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reactor wall cooling device for a tank-type nuclear reactor that reduces thermal stress generated near the liquid level of a reactor vessel due to supercooling during a nuclear reactor shutdown.

[Summary of the invention]

The present invention is a tank-type nuclear reactor in which the reactor core and cooling system equipment are housed in the same container, and which has a heat insulation and reactor wall cooling structure between the high-temperature coolant and the reactor wall. It is possible to stop the circulation of the coolant for cooling the reactor wall or adjust the flow rate of the coolant in order to reduce the thermal stress generated near the liquid surface of the reactor vessel due to supercooling during thermal transients such as This is a reactor wall cooling device for a nuclear reactor, characterized in that it is equipped with a device.

[Embodiment of the Invention] An embodiment of the present invention will be described with reference to FIG. In the large vessel constituted by the reactor vessel 1 and the roof slab 4, a heat insulating structure 10 is provided between the hot pool 7 and the reactor vessel 1. A cooling path lla and a cooling path llb are provided, and both cooling paths communicate with the cold pool 3 through piping. A furnace wall cooling pump 15 is installed so as to penetrate through the roof slab 4 and the laminated plate 14 so as to reach the coolant liquid level in the cooling bath Ila.

A plurality of such furnace wall cooling pumps 15 are installed in the circumferential direction on the roof slab 4.

The furnace wall cooling pump 15 is controlled by a control system 19 that is separate from the circulation pump 5.

The dynamic part 20 in the casing of the furnace wall cooling pump 15 can be easily pulled out during maintenance.

The operation of this embodiment will be explained.

The coolant led from the cold pool 3 to the coolant path lla is sucked in from the pump inlet 16 and is discharged from the pump outlet 17 to the cooling path llb on the reactor vessel side, and the discharged coolant is passed through the pipes. through cold pool 3
By returning to and circulating, the reactor vessel 1 is cooled.

When the reactor is shut down, the control system 19 stops the reactor wall cooling pump 15. Unlike the conventional example, cooling paths Ila, b
The coolant inside will no longer flow, so there will be no heat exchange,
The temperature drop of the coolant can be made very gradual, and the thermal stress generated near the coolant liquid level in the reactor vessel 1 is significantly reduced.

FIG. 5 shows the temperature distribution in the height direction of the reactor vessel 1. The solid line is the temperature distribution during steady operation, and the broken line is the temperature distribution when stopped. Since the temperature drop in the reactor vessel 1 in contact with the coolant has become more gradual, the temperature difference occurring near the liquid level has become smaller.

A modification of the present invention will be described.

FIG. 6 shows another embodiment of the invention.

After the cooling pipe 12 that guides the coolant from the high-pressure plenum 6 to the cooling path Ila is routed to above the coolant liquid level, the inflow control valve 18 is installed. The reason why the flow control valve 18 is located at the top is to facilitate maintenance since it is a dynamic device.

The coolant in the cooling path 11b is led to the cold pool 3.

When the nuclear reactor is shut down, by closing the flow control valve 18, all flow paths leading from the high pressure plenum 6 to the cooling path 11 are closed, and the flow of the coolant in the cooling path 11 is stopped. Therefore, thermal stress near the liquid surface of the 1M child furnace vessel 1 can be reduced.

〔Effect of the invention〕

According to one embodiment of the present invention, the following effects can be achieved.

(1) It is possible to reduce the thermal stress generated near the liquid surface of the reactor vessel when the JJI subreactor is shut down.

(2) The flow rate of the coolant for cooling the furnace wall can be adjusted in a system separate from the 41iii ring pump.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional tank-type nuclear reactor, Figure 2 is a diagram of a conventional reactor wall cooling structure, Figure 3 is a temperature distribution diagram in the height direction of a conventional reactor vessel, and Figure 4 is a diagram of the present invention. FIG. 5 is a temperature distribution diagram in the height direction of the reactor vessel according to the present invention.
FIG. 6 is a cross-sectional view of an example of a barrel according to the present invention. 1... Reactor vessel, 2... Nuclear reactor, 5... Circulation pump. 6...High pressure plenum, 7...Hot boule, 8...
・Intermediate heat exchanger,】3...Flow path forming shroud, 15
... Furnace wall cooling pump, 16... Pump suction 0.1
7... Pump discharge port, 18... Flow rate adjustment valve, 1
9...Control rate 1 and 2, Te height 5 and 6

Claims (1)

[Claims] 1. In a nuclear reactor with a reactor wall cooling structure, it is possible to stop the circulation of the coolant for cooling the reactor wall or adjust the flow rate of the coolant that circulates along the reactor vessel wall during thermal transients such as reactor shutdown. 1. A reactor wall cooling device for a nuclear reactor, characterized in that it is equipped with a device capable of cooling the wall of a nuclear reactor.