JPS62188994A - Thermal shielding device for fast breeder 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 [Technical Field of the Invention] The present invention relates to a heat shielding device for a fast breeder reactor that uses liquid metal sodium or the like as a coolant.

[Technical background of the invention]

Generally, fast breeder reactors use liquid metal, such as liquid metal sodium, as a coolant. Since the liquid metal coolant has an extremely large heat transfer capacity, the temperature of the reactor vessel peripheral wall that is in contact with the coolant quickly follows the temperature change of the coolant.

However, the portion of the reactor vessel above the liquid level of the coolant does not follow the temperature change of the coolant very quickly. For this reason, when the temperature of the coolant changes rapidly, such as when a reactor starts or shuts down, there is a large gap between the part of the reactor vessel peripheral wall below the coolant liquid level and the part above the liquid level. A temperature difference occurs. Therefore, a large temperature gradient occurs on the reactor peripheral wall near the coolant liquid level, generating excessive thermal stress, which impairs the integrity of the reactor after it is shut down.

Therefore, in order to avoid such a situation, a cylindrical body with a diameter slightly smaller than that of the reactor vessel is placed inside the reactor vessel, and atoms are placed in the cylindrical space between this cylindrical body and the inner peripheral surface of the reactor vessel. It has been proposed to circulate a portion of the low-temperature cooling side discharged from a circulation pump inside the reactor vessel so that the high-temperature coolant flowing out from the top surface of the reactor core does not come into direct contact with the reactor vessel.

Furthermore, after the nuclear reactor is shut down, decay heat produces an output equal to the total output from the core, so the reactor vessel is provided with an auxiliary cooling system to remove this decay heat.

[Problems with background technology]

However, in the above heat shielding device, a part of the coolant discharged from the circulation pump is made to flow in the cylindrical space between the cylindrical body and the inner surface of the reactor vessel. In the event of an emergency such as a trip or explosion, there is a problem in that it is difficult to cool the peripheral wall of the reactor vessel through the flow of low-temperature coolant and, by extension, to ensure the integrity of the reactor vessel. Furthermore, since the cooler of the auxiliary cooling system was placed inside the reactor vessel, there was also the problem that the reactor vessel became large.

[Purpose of the invention]

The present invention was made based on these circumstances, and
The purpose of this is to maintain the flow of coolant between the reactor vessel circumferential wall and the cylindrical body even in the unlikely event that the circulation reactor is tripped, to cool the reactor vessel circumferential wall, and to reduce thermal stress in the reactor vessel. An object of the present invention is to provide a heat shielding device for a fast breeder reactor that can maintain the integrity of a reactor vessel by reducing the amount of damage caused by the reactor, and can also remove decay heat during reactor shutdown without increasing the size of the reactor vessel. be.

[Summary of the invention]

In order to achieve the above object, the heat shielding device of the present invention is provided inside the reactor vessel so as to form a low-temperature coolant ascending flow path between the inner peripheral surface of the reactor vessel and the upper end of the heat shielding device Located slightly below the coolant liquid level in the container,
An outer cylindrical body allows a portion of the low-temperature coolant discharged from the circulation pump in the reactor vessel to flow into the low-temperature coolant ascending passage from its lower end, and a low-temperature coolant downward flow is formed between the outer cylindrical body and the outer cylindrical body. The lower end of the low-temperature coolant descending flow path is located further inside the inner cylindrical body so as to form a passageway, and its upper end is located above the coolant liquid level in the reactor vessel. an inner cylindrical body communicating with the plenum; a cooling pipe disposed at the upper end of the low-temperature coolant descending flow path; and a cooling pipe disposed outside the reactor vessel to allow a cooling medium to flow through the cooling pipe. It is configured with a mechanism.

[Embodiments of the invention]

An embodiment of the present invention will be shown below. FIG. 1 shows a schematic configuration of a tank-type fast breeder reactor, and FIG. 2 shows the vicinity of a heat shield installation part of a reactor vessel.

Further, FIG. 3 shows a schematic configuration of the heat shield installation.

As shown in Figure 1, the concrete caisson 1 of the reactor
Two large and small rotary shield plugs 3 and 4 are rotatably mounted on the roof slab 2 that closes the roof slab.

The reactor vessel 5 and a safety vessel 6 disposed outside the reactor vessel 5 at a predetermined interval are directly suspended from the roof slab 2 and housed within the concrete caisson 1. A reactor core 7 and a coolant (for example, liquid metal such as metallic sodium) 8 are housed within the reactor vessel 5 . Additionally, an intermediate heat exchanger 9 is installed inside the reactor vessel 5.
and a circulation pump 10, which are supported by the roof slab 2.

The coolant 8 liquid level in the reactor vessel 5 and the roof slab 2
There is a cover gas space filled with inert gas.

The reactor core 7 is loaded with a large number of fuel assemblies. Is this the core? It is inserted into the lower lattice plate 12 from above and supported from below, and the lattice plate 12 is partially provided with communication holes 1.
It is placed on a floor plate 13 having a length of 3 m. The outlet 14 of the circulation pump 10 is connected to a diagonal grid I5 formed between the grid plate 12 and the floor plate 13 via a conduction pipe 16.

The inside of the reactor vessel 5 is divided into a high temperature plenum 18 and a low temperature plenum 19 by partition walls 17m and 17b. The primary coolant outlet 21 and the inlet 22 of the circulation line pump 10 are made two.

A heat shielding device 23 as described below is installed inside the peripheral wall of the reactor vessel 5. In other words, as shown in FIG. 2, there is a space inside the peripheral wall of the reactor vessel 5 from a position slightly below the coolant liquid level to near the vertical lower end of the peripheral wall of the reactor vessel 5. An outer cylindrical body 24 with a diameter of 1 is installed, and a cylindrical low-temperature coolant upward passage 25 communicating with the space below the floor plate 13 is formed between the outer cylindrical body 24 and the peripheral wall of the reactor vessel 5. There is.

Further inside the outer cylindrical body 24, an inner cylindrical body 26 is installed. This inner cylindrical body 26 has an upper end located slightly higher than the coolant liquid level, and a lower end located near the upper end of the temporary coolant outlet 21 of the heat exchanger 9, so that it is connected to the outer cylindrical body 24. A low-temperature coolant downward flow path 27 is formed between them. The lower end of the outer cylindrical body 24 is joined and supported by the floor plate 13, and the inner cylindrical body 26 is supported near its lower part by the partition wall 17m. At the upper end of the low-temperature coolant downward flow path 25, spiral cooling pipes 28t and 28b are arranged along the inner circumferential surface of the outer cylindrical body 24 and the outer circumferential surface of the inner cylindrical body 26, respectively. Both of these cooling pipes 28a.

28b have their lower ends communicated with each other, and each upper end is connected to a cooling mechanism 29 provided outside the reactor vessel 5.

A cooling medium (for example, air) supplied from this cooling mechanism 29 is configured to flow through both cooling pipes 2B&, 28b.

FIG. 3 shows a schematic configuration of the cooling mechanism 29, in which a pump 30 causes the cooling medium to flow through the supply pipe 32 via the air cooler 31, and the cooling medium is passed through the supply pipe 32 via the air cooler 31. is guided into the cooling pipe 28 of. After this cooling medium cools the coolant near the inner peripheral surface of the outer cylindrical body 24, it flows into the inner cooling pipe 28b and flows into the inner cylindrical body 26.
to cool the coolant near the outer peripheral surface of the After that, return pipe 3
3, the air flows into the air cooler 31 for heat removal and temperature adjustment, and then passes through the supply pipe 32 again to the cooling pipe 28.
guided by a. In addition, in FIG. 3, the reference numeral 34 is a proar that supplies cooling air to the air cooler 31, which is connected to the peripheral wall of the reactor vessel 5, the peripheral walls of the outer and inner cylindrical bodies 24, 26,
and each temperature of the coolant in their vicinity, and
It is equipped with a calculation function that adjusts the coolant temperature in order to reduce the temperature difference between them and the thermal stress on the peripheral wall.

In addition, a switching valve 35 is provided in the piping of the cooling mechanism 29.
．． 36, 37, 38, 39, 40, 41 and a filter 42 are inserted. In addition, the code|symbol 43 is a cooling medium supply system.

Next, the action will be explained.

The circulation cycle of the coolant 8 within the reactor vessel 5 is as follows. As shown in FIG. 1, when passing through the reactor core 7 from the bottom to the top, it is heated by nuclear reaction heat. The thus heated coolant 8& flows from the high temperature plenum 18 into the intermediate heat exchanger 9 through its primary coolant inlet 20, where it exchanges heat with the secondary coolant and is cooled. The coolant 8b flows out from the primary coolant outlet 21 into the low temperature plenum 19. Furthermore, this low-temperature coolant 8b is sucked into the circulation pump 10 from its port 22, and is discharged into the diagonal grid 15 below the core 7 through the outlet 14, and this circulation is repeated thereafter.

The action of the heat shielding device 23 is as follows.

A part of the coolant 8 discharged into the diagonal grid 15 from the outlet of the circulation pump 10 flows into the lower part of the floor plate 13 through a communication hole 13a provided in a part of the floor plate 13. The low-temperature coolant 8b below the floor plate 13 flows from below into the low-temperature coolant ascending channel 25 between the peripheral wall of the reactor vessel 5 and the outer cylindrical body 24 as shown by the arrow in FIG. Rotate the upper end of the cylindrical body 24 and connect the cooling pipes 28*, 28b.
The low-temperature coolant descends in the downflow path 27 while contacting the coolant.

The low temperature coolant 8b passed through the lower end of the inner cylindrical body 26.
is combined with the low temperature coolant 8b flowing out from the primary coolant outlet 21 of the intermediate heat exchanger 9, and its population 22 is transferred to the circulation pump f1o.
It's more absorbing. The low temperature coolant 8b circulating through the above route removes heat from the inner circumferential surface of the reactor vessel 5 when rising through the low temperature coolant ascending channel 25. Therefore, the reactor vessel 5 is not affected by the heat of the high-temperature coolant 8a, and its integrity is maintained.

In addition, in an emergency such as when the circulation pump 10 trips, the low-temperature coolant ascending channel 25 and the low-temperature coolant descending channel 2
The flow of low-temperature coolant 8b in 7 has stopped,
Although it becomes difficult to cool the peripheral wall of the reactor vessel 5, in such a case, as shown in FIG. 3, the switching valves 36.3B and 40.41 of the cooling mechanism 29 are closed, and
The other switching valves 35, 37, and 39 are opened to supply cooling medium to the pipe 35, the outer cooling pipe 28a1, the inner cooling pipe 28
It is circulated through the path of the b1 return pipe 33. As a result, the coolant in the upper part of the low-temperature coolant downflow path 27 is cooled, so the density of the coolant in this area is not thick, and the coolant with increased density flows inside the low-temperature coolant downflow path 27. descend.

Therefore, the coolant in the low-temperature coolant ascending flow path 25 passes through the upper end of the outer cylindrical body 24 and continuously flows into the low-temperature coolant descending flow channel 27. 25
And the flow of the coolant in the low temperature coolant downflow path 27 is maintained. In this way, the reactor vessel 6 is cooled even when the circulation pump 1° is tripped, and the integrity of the reactor vessel 5 is ensured.

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

For example, the circulation path of the coolant during nuclear reactor shutdown may be different.

Further, the cooling pipes 28m and 28b do not necessarily have to be spirally shaped. In short, it is sufficient that it is disposed at the upper end of the low-temperature coolant descending flow path 27, and may have a meandering shape, for example. Further, the cooling pipe does not necessarily have to have a double pipe structure consisting of an outer cooling pipe and an inner cooling pipe.

Furthermore, the configuration of the cooling mechanism 29 can also be varied.

〔Effect of the invention〕

As detailed above, according to the heat shielding device for a fast breeder reactor according to the present invention, low-temperature cooling is discharged from the circulation pump into the low-temperature coolant ascending channel and the low-temperature coolant descending channel during reactor operation. When the circulation pump is activated, the coolant is passed through the cooling pipe installed at the upper end of the low-temperature coolant downflow passage to cool the coolant in that part. By lowering the cooled coolant by increasing its density, the coolant in the low-temperature coolant ascending flow path and the low-temperature coolant downflow flow path is made to flow, thereby transferring high-temperature coolant to the reactor vessel. It is possible to alleviate the thermal effects caused by

In addition, when the reactor is shut down, a cooling medium is circulated through the cooling pipes to remove the decay heat generated in the reactor core.
In addition, the soundness of the reactor vessel can be ensured by removing heat from the peripheral wall of the reactor vessel. Furthermore, unlike conventional methods, there is no need to provide an auxiliary cooling system inside the reactor vessel.
There is no need for the reactor vessel to become large.

2 is a vertical cross-sectional view of a tank-type fast breeder reactor, FIG. 2 is a vertical cross-sectional view showing an enlarged view of the vicinity of the thermal TFJ device, and FIG. 3 is a schematic configuration diagram of a thermal shielding device.

5... Reactor vessel, 7... Reactor core, 8... Coolant,
10... Circulation pump, 18... Heat source plenum, 19
...Low temperature plenum, 23...Heat shielding device, 24...
・Outer cylindrical body, 25...Low temperature coolant ascending channel, 26・
...Inner cylindrical body, 27...Low temperature coolant descending flow path, 28
a.

28b... Cooling pipe, 29... Cooling mechanism.

Applicant agent Patent attorney Suzue Takeshi Sangyo 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) It is installed inside the reactor vessel so as to form a low-temperature coolant ascending flow path between the inner peripheral surface of the reactor vessel and its upper end is located slightly below the coolant liquid level within the reactor vessel. At the same time, a part of the low-temperature coolant discharged from the circulation pump in the reactor vessel flows into the low-temperature coolant ascending flow path from its lower end. The lower end of the low-temperature coolant downward flow path is located further inside the inner cylindrical body so as to form a low-temperature coolant downward flow path, and its upper end is located above the coolant liquid level in the reactor vessel. an inner cylindrical body communicating with the low-temperature plenum inside the reactor vessel, a cooling pipe disposed at the upper end of the low-temperature coolant downflow passage, and a cooling pipe disposed outside the reactor vessel for supplying a cooling medium into the cooling pipe. A heat shielding device for a fast breeder reactor, characterized in that it is equipped with a cooling mechanism for causing circulation. (2) The heat shielding device for a fast breeder reactor according to claim 1, wherein the cooling pipe is formed in a spiral shape. (3) The cooling pipe is characterized by comprising an outer cooling pipe disposed along the inner circumferential surface of the outer cylindrical body and an inner cooling pipe disposed along the outer circumferential surface of the inner cylindrical body. A heat shielding device for a fast breeder reactor according to claim 1 or 2.