JPS60256091A - Cooling structure of nuclear reactor vessel - 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 cooling structure for cooling the inner wall surface of a reactor vessel of a tank-type fast breeder reactor.

[Background of the invention]

FIG. 1 shows an example of a tank-type fast breeder reactor. In FIG. 1, the reactor vessel 10 includes a support skirt 1
Roof slab 16 fixed on foundation 14 via 2
It is suspended. Inside the reactor vessel 10, an upper part is a real plenum 18 and a lower part is a cold plenum 20, and the hot plenum 18 and the cold plenum 20 are separated by a heat insulating plate 22 and a core support structure 24. The core support structure 24 supports the core 2 in the central part.
The outer peripheral edge of the reactor vessel 1a is supported by the reactor vessel 1a. A plurality of intermediate heat exchangers 28 and a main circulation pump 30 are arranged around the core 26 so as to penetrate through the heat insulating plate 22 and the core support structure 24 . A discharge pipe 32 of the main circulation pump 30 opens into a high-pressure blenum 34 provided at the lower part of the reactor core 26.

In such a tank-type fast breeder reactor, the coolant in the cold plenum 20 is sucked into the main circulation pump 30,
It is pumped into a high pressure plenum 34 through a discharge pipe 32.

Coolant entering high pressure blenum 34 is heated in core 26 before exiting into hot plenum 18 . The coolant in the hot plenum 18 is then transferred to the intermediate heat exchanger 2.
After flowing into the cold plenum 8 and exchanging heat with the secondary coolant, it is returned to the cold plenum 20 from the lower part of the intermediate heat exchanger 28.

Incidentally, the reactor vessel 10 of the evening breeder reactor functions as a joint member that supports the reactor vessel 26, structures within the reactor vessel IO, and the entire weight of the sodium that is dissolved in the coolant. Therefore, it is necessary to keep the reactor vessel wall at a temperature as low as possible even during normal operation of the reactor when the inside is at a high temperature. Therefore, as shown in FIG. 2, a vertical partition wall 36 is provided inside the reactor main vessel around the hot plenum 18 to block the heat from the high-temperature sodium in the hot plenum 18 and to protect the reactor vessel from the heat.
A furnace vessel wall cooling structure 38 is provided adjacent to the inner wall of the furnace. This reactor vessel wall cooling structure 38 includes a coolant flow path 40 provided along the inner wall surface of the reactor vessel 10, and a coolant flow path 40 provided along the inner wall surface of the reactor vessel 10.
It consists of a distribution pipe 42 that guides the coolant (sodium) in the high ratio plenum 34 to the cold plenum 34 and a return pipe 44 that returns the coolant in the coolant flow path 40 to the cold plenum 20. The coolant flow path 40 includes a flow baffle 46 as shown in FIG.
As a result, an upward path 48 and a downward path 50 are formed. Note that the reference numeral 52 shown in FIGS. 2 and 3 indicates a horizontal partition wall provided above the core support structure 24.

Figure 4 shows hot plenum 18 and cold plenum 20.
This figure shows an example of a tank-type fast breeder reactor in which a jacket 52 and a partition wall 54 are used to separate the coolant flow path 4.
This figure shows an example in which the ascending passage 48 of No. 0 is closer to the reactor vessel 10 than the descending passage 50.

In the conventional reactor vessel wall cooling structure 38 configured as described above, the coolant in the high-pressure plenum 34 is guided to the ascending passage 48 through the distribution pipe 42, ascends through the ascending passage 48, and then passes through the descending passage. 50, cools the side wall of the reactor vessel 10, and flows into the upper part of the p-cold plenum 20 through the return pipe 44. Therefore, at the upper end of the cold plenum 20, there is a so-called temperature stratification interface 5 with a temperature difference, as shown in FIG.
The high-temperature coolant remains on top of the coolant 6 to form a stagnation layer 58, resulting in temperature stratification. That is, cold plenum 2
In the region from the center to the bottom of the hot plenum 18, the coolant in the hot plenum 18 flows from the intermediate heat exchanger 28 and undergoes turbulent mixing. In contrast, cold plenum 20
The flow of the coolant is small in the upper part of the partition wall, that is, the lower surface of the partition wall, and the coolant tends to stagnate and form a stagnant layer 58.

Moreover, since heat is input from the hot plenum 18 side through the horizontal partition wall 52 and the core support structure 24, this retention layer 58 easily becomes hotter than the lower part of the cold plenum 20.

Moreover, the coolant flowing into the upper part of the cold glenum 20 through the return pipe 44 cools the reactor vessel 10 and becomes high temperature, resulting in a temperature difference between the coolant and the low temperature coolant in the cold plenum 20. Due to the buoyancy effect caused by this, it tends to stay in the retention layer 58, making it even more likely to cause temperature stratification. As a result, the reactor vessel 10 and the core support structure 24 near the temperature stratification interface 56 are
There is a large temperature difference of about 10 to 50 C, which corresponds to the difference between the temperature of the return coolant that cooled the reactor vessel wall and the coolant temperature in the cold plenum, and a temperature cycle that fluctuates at a high frequency of several Hz locally. The drawback was that very severe thermal fatigue occurred in the additive structure material.

[Purpose of the invention]

The present invention has been made in order to eliminate the drawbacks of the prior art, and provides a reactor vessel that can eliminate thermal shock to reactor internals and reactor vessel walls due to high temperature coolant retention at the upper end of a cold plenum. The purpose is to provide a cooling structure.

[Summary of the invention]

In the present invention, the ash pipe that returns the coolant that has cooled the reactor vessel wall to the cold plenum is arranged at the outlet of the intermediate heat exchanger or the suction of the main 1 mJJ pump, and the coolant that has cooled the reactor vessel wall is returned to the cold plenum. By mixing the coolant discharged from the intermediate heat exchanger with the coolant in the cold plenum that is sucked into the main circulation pump, there is no area where high-temperature coolant accumulates at the upper end of the cold plenum. So,
It is constructed to prevent thermal shock between the reactor internals and the wall of the reactor vessel.

[Embodiments of the invention]

K to ensure the integrity of the structure above the lower plenum.
This requires a mechanism that prevents temperature acidification in the cold plenum and at the same time quickly mixes and diffuses the coolant that has cooled the reactor vessel wall with the coolant in the cold plenum. In order to realize such a mechanism, it is necessary to consider the following three matters.

(1) Forming a velocity field with a large Reynolds number in the region where the coolant that has cooled the reactor vessel wall mixes with the coolant in the cold plenum.

(2) Reduce the temperature difference between the coolant that cooled the reactor vessel wall and the coolant in the cold plenum.

(3) Creating a flow field that increases the turbulent mixing distance in which the coolant that has cooled the reactor vessel wall and the coolant in the cold plenum mix.

Therefore, in the present invention, in contrast to (1) above, the coolant that has cooled the reactor vessel wall is guided to the intermediate heat exchanger outlet or the main circulation pump suction, where sodium in the cold plenum is flowing at high speed. The coolant and the low-temperature coolant are quickly mixed to prevent temperature stratification due to density differences due to temperature differences. Also (:2
), the coolant that has cooled the walls of the reactor vessel is routed through the cold plenum before being transported to the outlet of the intermediate heat exchanger or the suction of the main circulation pump. The temperature difference between the wall and the coolant temperature is reduced. Furthermore, for K (3), the coolant that has cooled the furnace vessel wall is dispersed and discharged to the intermediate heat exchanger outlet or main circulation bong suction to increase mixing efficiency. As a result, it is possible to prevent thermal separation between the coolant that cooled the reactor vessel wall and the coolant in the cold plenum, thereby preventing the occurrence of temperature stratification and thermal loading of the structure in the upper part of the cold plenum. Conditions can be relaxed.

Preferred embodiments of the cooling structure for a reactor vessel according to the present invention will be described in detail below with reference to the accompanying drawings. Note that the same reference numerals are given to the parts corresponding to those explained in the above embodiment, and the explanation thereof will be omitted.

FIG. 5 is an explanatory diagram of an embodiment of a cooling structure for a reactor vessel according to the present invention. In FIG. 5, the distribution pipe 42, which has one end open in the high-pressure plenum 34, extends toward the inner peripheral edge of the reactor vessel along the lower surface of the bulkhead structure 58. A distribution ring header 60 is connected thereto. Meg header 6 for this distribution
0 is connected to a circumferential distribution pipe 62 whose tip end opens to the ascending path 48 of the coolant flow path. And ascending road 4
An overflow hole 64 is formed near the top i of the flow baffle 46 that separates the descending path 50 from the flow baffle 8.
Coolant in the ascending passage 48 is allowed to flow into the descending passage 50. A return pipe 44 is provided at the lower end of the descending path 50.
One end is connected to the reed, and the lower end of the return pipe 44 is connected to the outlet nozzle portion 66 of the intermediate heat exchanger 28. This outlet nozzle portion 66 is formed at the lower end of an intermediate heat exchanger stained pipe 68 provided around the intermediate heat exchanger 28.

The return piping 44 is fixed to a piping support 70 provided on the outer surface of the intermediate heat exchanger stand vibro 8 as shown in FIG. This serves as a pipe discharge nozzle 72. As shown in FIG. 7, the piping support stand 70 has a fixed part 74 and a tightening part 76, and the fixing part 74 and the tightening part 76 are connected to each other.
6 and the return pipe 44, and tighten the return pipe 44 with bolts or the like, so that it can be attached to the intermediate heat exchanger stand vibro 8.

In the embodiment configured as described above, the high pressure blenum 3
The coolant in the multi-distribution ring header 60 is guided through the distribution pipe 42 to the multi-distribution ring header 60 . The coolant that has entered the distribution ring header 60 is further distributed in the circumferential direction of the reactor vessel 10 through the circumferential distribution pipe 62 and enters the ascending passage 48 . The coolant in the ascending passage 48 ascends through the ascending passage 48, reaches the descending passage 50 from the over hole 64, and is routed through the cold plenum 20 by the return piping 44 for intermediate heat exchange. into the outlet nozzle section 66 of the vessel.

For tank-type fast breeder reactors, the hot blenheim temperature is approximately 5
ooc and the cold plenum temperature is approximately 3650. And the coolant flow rate is 1 to cool the reactor vessel wall.
-, and the temperature of the return coolant that cooled the wall of the reactor vessel at this time was approximately 3800° C., and the temperature difference with the coolant in the cold plenum 20 was 5 to 15 C. Therefore, if the coolant that has cooled the wall of the furnace vessel with this temperature difference is discharged to the outlet nozzle section 66, there is a possibility that thermal striping due to the temperature difference will occur at the outlet nozzle section. However, in this embodiment, the coolant that has cooled the reactor vessel wall is routed through the cold plenum 20 through the return pipe 44, and the temperature difference between the coolant that has cooled the reactor vessel wall and the coolant in the cold plenum is reduced. /''1, it is possible to prevent thermal striping from occurring at the outlet nozzle portion 660. Moreover, as shown in FIG. 6, the coolant that has cooled the wall of the reactor vessel is distributed and discharged to the outlet nozzle 66 through a plurality of return pipes 44, and the coolant is mixed at the outlet nozzle 66. This makes it easy to plan. Moreover, the outlet nozzle portion 66 of the intermediate heat exchanger 28 is a place where the flow of the coolant is large, and the coolant of class 24* having a different temperature can be mixed and diffused smoothly.

That is, the shape of the cold plenum is as shown in FIGS. 8 and 9. A three-dimensional analysis of the flow state of the coolant during constant operation in this cold V-num is shown in FIGS. 10 and 11. Figure 0 is a sectional view showing the flow situation along a-am in Figure 8.
FIG. 11 is a sectional view showing the flow situation along line cc in FIG. 8. As is clear from these FIGS. 10 and 11, the flow field of the coolant in the cold plenum 20 with strong flow inertia is
This is the bell mouth at the entrance. In addition, when observing the flow of coolant during steady operation of a nuclear reactor, the areas with strong flow inertia other than those mentioned above include the area below the intermediate heat exchanger outlet up to the reactor vessel, and the area from below the intermediate heat exchanger outlet to the bong. There is a central region of the cold plenum leading up to the entrance of the robel mouse. However, in these places,
When the flow rate decreases, such as when the reactor tree knobs,
Turbulent mixing of the coolant in the cold plenum results in a relatively low flow velocity. Therefore, in all operating conditions of the nuclear reactor, the locations in the cold plenum where the flow velocity of the coolant is always the highest are the above-mentioned intermediate heat exchanger nozzle section and pump inlet bellmouth section. Therefore, when evaluating whether temperature stratification occurs at the intermediate heat exchanger outlet nozzle section and the pump inlet bell mouth section using the Richard Nonn number R+, it is found that during steady operation of the reactor, R
+ = 5.0X10-' to 6.0X10-'', which is an order of magnitude smaller than R+ = 10-', where temperature stratification is likely to occur. The coolant that has cooled the wall is guided to a location where the flow velocity is high, such as the intermediate heat exchanger outlet nozzle section or the pump inlet bell mouth section, and is discharged under a flow condition that increases the turbulent mixing distance, resulting in temperature stratification. It mixes and diffuses smoothly with the coolant in the cold plenum without causing any oxidation.Therefore, the stagnation layer where high-temperature coolant stagnates in the upper part of the cold plenum, which conventionally occurs, can be eliminated, and the It is possible to eliminate the applied local heat shock.

12 to 14 show other embodiments of the return pipe discharge nozzle formed at the tip of the return pipe 44.

The embodiment shown in FIG.
The coolant that cooled the wall of the furnace vessel can be discharged from the discharge hole 80. In the embodiment shown in FIG. 13, the return pipe discharge nozzle 72 is connected to the intermediate heat exchanger stand vibe 68.
The temperature of the coolant that cools the wall of the furnace vessel is brought close to the temperature of the coolant at the outlet of the intermediate heat exchanger 28 by spirally swirling the coolant inside the furnace. In FIG. 14, a jet nozzle cover 82 is provided on the outside of the intermediate heat exchanger stand vibro 8. Then, the coolant that has cooled the wall of the furnace vessel is guided to the annulus formed between the intermediate heat exchanger stand vibro 8 and the jet nozzle cover 82 via the spacer 84, and is introduced to the outlet nozzle of the intermediate heat exchanger 28. It is designed to eject from 66.

FIG. 15 shows another embodiment of the reactor vessel cooling structure according to the present invention. In FIG. 15, the lower end of the return pipe 44 is led to the lower part of a pump inlet bell mouth 86, which is the suction port of the main circulation pump 3°. In addition,
Reference numeral 88 shown in FIG. 15 is a gas insulation layer formed inside the coolant flow path 38.

In this embodiment, the coolant that has cooled the wall of the reactor vessel is discharged to the lower part of the pump mouth 86 via the return pipe 44. Therefore, the coolant discharged from the return pipe 44 is mixed and diffused in the main circulation pump 30 with the coolant in the cold plenum 20 that is sucked into the pump inlet bell mouth 86 . Therefore, the same effects as those of the above-mentioned embodiments can be obtained in this embodiment as well.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent local thermal shock from being applied to the reactor internals and the walls of the reactor vessel in the upper part of the cold plenum, and it is possible to improve the health of the reactor internals.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a tank-type fast breeder reactor, Figure 2 is an explanatory diagram of a conventional reactor vessel cooling structure, and Figures 3 and 4 are return pipes in a conventional reactor vessel cooling structure. 5 is an explanatory diagram of an embodiment of the reactor vessel cooling structure according to the present invention, FIG. 6 is a detailed diagram of the tip of the return piping of the embodiment, and FIG. 7 is the A detailed view of the pipe support stand for attaching the return pipe of the embodiment to the intermediate heat exchanger standpipe, Figures 8 and 9 are explanatory diagrams showing the shape of the cold plenum, and Figure 10 is the a in Figure 8. - An explanatory diagram showing the flow state of the coolant in the cold plenum along line a,
FIG. 11 is an explanatory diagram showing the flow state of the coolant in the cold plenum along line c-c in FIG. 8, and FIGS. 12, 13, and 14 are other examples of the tip of the return pipe An explanatory diagram showing an example, FIG. 15 is an explanatory diagram of another embodiment of the cooling structure for a reactor vessel according to the present invention. 10...Reactor vessel, 18...Hot Blenheim, 2
0...cold plenum, 24...core support structure,
26... Core, 28... Intermediate heat exchanger, 30...
Main circulation pump, 34... High pressure plenum, 38... Coolant channel, 42... Distribution pipe, 44... Return pipe, 6
6... Outlet nozzle section, 86... Pump inlet bell mouth. Agent Patent Attorney Tatsuyuki Unuma '81 Figure 26 20 34- FuIZ Diagram 66 No. 130 No. 141 No. 15 (

Claims (1)

[Claims] 1. A coolant flow path formed along the inner wall surface of the reactor vessel, a distribution pipe that guides the coolant in the high-pressure plenum to this coolant flow path, and returning the coolant in the coolant flow path to the cold plenum. In the cooling structure of the reactor vessel consisting of the return piping,
A cooling structure for a nuclear reactor vessel, characterized in that the outlet end of the return pipe is disposed at an outlet of an intermediate heat exchanger or a suction of a main circulation pump.