JPH10293189A - Reactor wall cooling protection structure of fast reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a thermosiphon from occurring by providing a partitioning wall whose lower edge is dipped to an area below a cooling material free surface between an outer liner and an inner liner of the upper part of an inner annulus part and preventing a heated rising flow from flowing into a submergence weir part. SOLUTION: A cylindrical outer liner 42 and inner liner 43 are arranged concentrically. An outer annulus part 48 is formed between a reactor container 10 and the outer liner 42 and an inner annulus part 49 is formed between the outer liner 42 and the inner liner 43, thus enabling the upper edge part of the outer liner to submerge below a free liquid surface. A low-temperature cooling material flows in from a flow hole 44 and rises, flows down the inner annulus part 49, passes the flow hole 46, and flows into an upper plenum 24. The flow that rises after being heated on the outer surface of the inner liner 43 cannot reach the free liquid surface between a partitioning wall 50 and the reactor container 10 and circulates so that it descends while being accompanied by the descending flow of the submergence weir (outer liner 42) part. Neither thermo fin nor temperature stratification occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace wall cooling protection structure for cooling a furnace wall of a fast reactor to maintain structural integrity, and more particularly, circulates a low-temperature coolant along the furnace wall. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a submerged weir type fast reactor furnace wall cooling protection structure.

[0002]

2. Description of the Related Art In a fast reactor, a reactor wall cooling protection structure is installed in order to maintain the structural integrity of a reactor vessel without causing a significant reduction in plant efficiency. This furnace wall cooling protection structure includes an overflow weir system as shown in FIG. 3 and a dive weir system as shown in FIG. In the fast reactor, a core 12 is located inside a furnace vessel 10, an upper opening of the furnace vessel 10 is closed with a shielding plug 14, a core upper mechanism 16 is attached to the shielding plug 14, and a cold leg pipe 18 is connected to a high pressure plenum 20. And the hot leg piping 22 is led out from the upper plenum 24. Coolant sodium enters the high pressure plenum 20 from the cold leg piping 18, reaches the core 12 through the low pressure plenum 21, is heated in the core 12, exits to the upper plenum 24, passes through the hot leg piping 22, and enters the furnace vessel. An external intermediate heat exchanger (not shown) is reached. A part of the coolant passing through the low-pressure plenum 21 flows out to the intermediate plenum 23.

[0003] The upper plenum temperature of a fast reactor is 500 ° C or higher, and when this free liquid level comes into direct contact with the furnace vessel wall, the liquid level fluctuation causes temperature fluctuation on the furnace vessel wall, and the furnace vessel due to high cycle thermal fatigue. There is concern about the impact on structural integrity. Therefore, a furnace wall cooling protection structure is provided. This furnace wall cooling protection structure basically forms a cooling flow path for low-temperature coolant sodium on the inner surface of the furnace vessel in the upper plenum, and functions to keep the free liquid surface temperature in contact with the furnace vessel low. .

The overflow weir-type furnace wall cooling protection structure 30 shown in FIG. 3 is provided with a double annulus structure comprising an outer liner 32 and an inner liner 33 arranged at intervals near the side wall surface of the furnace vessel 10. The low-temperature coolant flowing from the intermediate plenum 23 through the lower flow hole 34 rises in the outer annulus 38 (between the outer liner 32 and the furnace vessel 10), overflows from the upper end of the outer liner 32, and flows inward. The configuration is such that the annulus portion 39 flows down. However, this type of overflow weir system involves liner vibration, gas entrapment during overflow,
There are inherent problems such as fluctuation of the liquid level.

In order to solve these problems, there has been proposed a configuration in which a swirling flow component is given to a coolant rising along a furnace vessel wall to generate a swirling flow (Japanese Patent Laid-Open No. 7-1040).
No. 91). Alternatively, a configuration has been proposed in which a channel is provided at the top of the liner, and a connecting flow path for allowing the coolant to flow down from the bottom of the channel is provided (Japanese Patent Laid-Open No. 8-1366).
No. 87).

On the other hand, a submerged-furnace type furnace wall cooling protection structure 40 shown in FIG. 4 is provided with an outer liner 42 and an inner liner 43 near the side wall surface of the furnace vessel 10 at a distance from each other. The structure (the outer annulus portion 48 and the inner annulus portion 49) has a structure in which the low-temperature coolant flowing from the intermediate plenum 23 through the lower flow hole 44 rises between the outer liner 42 and the furnace vessel 10, and the outer liner 42 Inner liner 43 and outer liner 42 through the upper end of
And flows out through a flow hole 46 formed in the lower part of the inner liner 43. Furnace container 10
A common free liquid level is provided between the inner liner 43 and the inner liner 43, and the upper end of the outer liner 42 is submerged below the free liquid level. The submerged weir system has an advantage that problems such as liner vibration, liquid level fluctuation, gas entrainment, and the like that occur in the overflow weir system are essentially unlikely to occur.

[0007]

However, in the submerged weir system, the flow becomes unstable under low flow rate conditions. Investigation by multi-dimensional heat and fluid analysis suggested that thermal stratification and thermosiphon might occur, and a large temperature difference was applied to structural materials such as furnace vessels, which could impair the structural integrity.

[0008] Upon receiving the heating from the high-temperature coolant in the upper plenum via the inner liner, the coolant in the inner annulus rises by buoyancy, and a high-temperature portion is formed on the free liquid surface of the dive weir. And since the low-temperature coolant that turns from the outer annulus to the inner annulus flows under the high-temperature fluid in contact with the free liquid level, near the free liquid level above the dive weir, the low-temperature coolant flows between the upper high-temperature fluid and the low-temperature fluid flowing through the lower part. A temperature stratification having a large temperature gradient is formed. The rise in temperature of the liquid surface and the temperature gradient affect the soundness of the furnace vessel wall structure.

On the other hand, in the lower part of the dive weir, the temperature of the inner annulus 49 is higher than that of the coolant that turns from the outer annulus 48 to the inner annulus 49 and flows down. , A thermosiphon-like flow field is formed. This flow field is unstable because the upper fluid is heavy and the lower fluid is light. For example, the cooling conditions are such that 2% of the total rated flow of coolant flows at 395 ° C. from the bottom of the outer annulus and reaches 550 ° C.
In the multi-dimensional heat-hydraulic analysis, which is assumed to be discharged to the upper plenum at ℃, the heavy low-temperature fluid is predicted to flow down from two limited locations in the circumferential direction as a waterfall.
A result has been obtained in which a temperature difference exceeding 50 ° C. occurs in the circumferential direction. Such circumferential temperature differences can affect the structural integrity of the inner and outer liners.

[0010] These problems can be prevented by increasing the flow rate of the coolant because the instability of the flow is eliminated, but this leads to a decrease in plant efficiency. Therefore, it is difficult to achieve the original purpose of protecting the furnace wall with the conventional structure.

[0011] It is an object of the present invention to provide a new flow stabilization method capable of preventing temperature stratification and the generation of a thermosiphon without impairing cooling efficiency, plant efficiency and safety in a submerged weir-type furnace wall cooling protection structure. It is to propose.

[0012]

SUMMARY OF THE INVENTION The present invention provides a furnace vessel wall and an outer liner which are concentrically spaced apart from each other inside a furnace vessel wall of a fast reactor. The outer annulus portion is formed between the outer liner and the inner liner, and the inner annulus portion is formed between the outer liner and the inner liner, so that the upper end of the outer liner is submerged below the free liquid level. A dive weir system that flows in from the lower flow hole and rises, turns the upper end of the outer liner, flows down the inner annulus, and flows into the furnace vessel body through the flow hole formed at the lower part of the inner liner. Furnace wall cooling protection structure. Here, the feature of the present invention is that a ring-shaped partition wall whose lower end is immersed below the coolant free liquid level is provided between the outer liner and the inner liner above the inner annulus.

The provision of the partition wall increases the downward flow velocity from the upper part of the outer liner to the inner annulus. Further, the flow that is heated and rises on the outer surface of the inner liner cannot reach the free liquid level of the dive dam, that is, the free liquid level between the furnace vessel wall and the partition wall. As a result, thermosiphon and temperature stratification do not occur, and flow instability can be prevented. The configuration in which the partition wall is provided is excellent in that the structure is simple, and according to the analysis, a remarkable flow stabilizing effect is obtained as compared with a simple swiveling method.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The partition wall is fixed to the outer liner by, for example, a large number of inclined blade-like fixing members arranged substantially evenly over the entire circumference. With such a structure, a swirling component can be imparted to the downward flow from the upper part of the outer liner to the inner annulus, which promotes fluid mixing in the circumferential direction and reduces the temperature difference in the circumferential direction, thereby stabilizing the flow. be able to.

Further, in the furnace wall cooling protection structure provided with the partition wall, a swirl imparting structure for imparting a swirl component to the inflowing low-temperature coolant can be further provided below the outer annulus portion. This makes it possible to impart a swirl component to the flow rising in the outer annulus, promote fluid mixing in the circumferential direction, and reduce the circumferential temperature difference, thereby stabilizing the flow. As a turning application structure,
There are a structure in which a number of inclined blades are juxtaposed, a structure in which an inclined inlet pipe is arranged in a flow hole for a low-temperature coolant, and a structure in which an inclined inlet nozzle is installed in a flow hole for a low-temperature coolant.

[0016]

FIG. 1 is an explanatory view of a main part showing an embodiment of a furnace wall cooling protection structure of a fast reactor according to the present invention. The entire configuration of the fast reactor may be the same as that of the prior art shown in FIG. 4, and a description thereof will be omitted.

As shown in FIG. 1, a cylindrical outer liner 42 and an inner liner 43 are arranged concentrically inside the furnace vessel 10 of the fast reactor, so that the furnace vessel 10 and the outer liner 42 Between the outer liner 42 and the inner liner 43.
9 are formed so that the upper end of the outer liner is submerged below the free liquid level. The low-temperature coolant flows in from the flow hole 44 below the outer annulus portion 48 and rises, as shown by a white arrow, turns around the upper end of the outer liner, flows down the inner annulus portion 49, and flows down the lower portion of the inner liner. Flows into the upper plenum 24 in the furnace vessel main body through a flow hole 46 formed in the furnace vessel. In this way, the furnace vessel wall comes into contact with the low-temperature coolant, so that it is cooled and protected.

Here, in the present invention, the inner annulus portion 49
A ring-shaped partition wall 50 whose lower end is immersed below the free coolant level is provided between the upper outer liner 42 and the inner liner 43, which is characterized in this point.
That is, a common free liquid level is formed between the partition wall 50 and the furnace vessel 10, and the outer liner 42 is completely submerged below the free liquid level, in other words, the upper end of the outer liner 42 is free liquid. It will be located below the surface. For this reason, the outer liner 42 is called a descent weir.

The following is a description of an example of specific numerical values. For example, for a furnace vessel having a radius of about 5 m, the height of the furnace wall cooling protection structure is about 6.5 m, and is provided upward from a position corresponding to substantially the upper end of the core. That is, the applicable range of the furnace wall cooling protection structure is the range of the inner surface of the furnace vessel in the upper plenum. The furnace vessel and each liner are made of steel, and the partition wall is also the same. The width (radial dimension) of the outer annulus part 48 is about 70 mm, the width of the inner annulus part 49 is about 120 mm, and the dive amount (distance between the free liquid surface and the upper end of the outer liner) of the outer liner 42 is about 100 mm.
The distance between the inner surface of the outer liner and the partition wall is about 50 mm.

When the ring-shaped partition wall 50 is provided at the free liquid level in the center of the inner annulus as described above, the flow rate of the coolant flowing down by turning the upper end of the dive weir (outer liner 42) is increased. Become. The flow (indicated by the black arrow) heated by the outer surface of the inner liner 43 and rising can reach the free liquid surface of the submerging weir portion, that is, the free liquid surface between the partition wall 50 and the furnace vessel 10. It circulates so as to descend along with the descending flow of the dive weir. Therefore, thermosiphon and temperature stratification do not occur, and flow instability can be prevented.

The mounting structure of the partition wall is optional,
For example, it is fixed to an inner liner or an outer liner. When the partition wall is fixed from the outside liner or the furnace vessel wall side, it is possible to impart a swirling component to the flow by using an angled blade-like fixing member. An example is shown in FIG. This is an example in which the partition wall 50 is fixed to the outer liner 42 by a large number of inclined blade-shaped fixing members 52 which are arranged substantially evenly over the entire circumference. The number of inclined blade-shaped fixing members 52 to be installed is about 36 to 120,
Each is set at an angle of about 30 to 60 ° with respect to the vertical direction. In addition, the length of the inclined blade-shaped fixing member 52 is set to such an extent that adjacent inclined blade-shaped fixing members have an area where the fixing members overlap in the axial direction. As a result, a swirling component is imparted to the flow that descends by turning over the dive weir (outer liner 42) and promotes fluid mixing in the circumferential direction. Can be achieved.

A mechanism for imparting a swirl component to the flowing low-temperature coolant may be additionally provided below the outer annulus portion. For example, there are a structure in which a number of inclined blades are juxtaposed slightly above the flow hole, a structure in which an inclined inlet pipe is connected to the flow hole, and a structure in which an inclined inlet nozzle is installed in the flow hole.

[0023]

According to the present invention, as described above, a ring-shaped partition wall having a lower end immersed below the free coolant level is provided between the outer liner and the inner liner above the inner annulus. The flow velocity of the descending flow of the dive weir increases, and the ascending flow heated on the outer surface of the inner liner is prevented from flowing into the dive weir, thereby preventing temperature stratification and the generation of thermosiphon, and fluid stability. Is achieved. Therefore, even under low flow rate conditions, the flow state is stable, and the cooling efficiency, plant efficiency, and safety are not impaired.

In particular, when various types of swirl imparting structures are provided, the mixing of fluid in the circumferential direction is promoted and the temperature difference in the circumferential direction is reduced, so that the flow of the coolant can be further stabilized.

[Brief description of the drawings]

FIG. 1 is a main part explanatory view showing one embodiment of a furnace wall cooling protection structure according to the present invention.

FIG. 2 is an explanatory view showing an example of a structure for attaching the partition wall to an outer liner.

FIG. 3 is an explanatory view showing an example of a fast reactor having a conventional overflow weir type furnace wall cooling protection structure.

FIG. 4 is an explanatory view showing an example of a conventional fast reactor having a submerged weir type furnace wall cooling protection structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Furnace container 12 Core 18 Cold leg piping 20 High pressure plenum 22 Hot leg piping 24 Upper plenum 42 Outer liner 43 Inner liner 44, 46 Flow hole 48 Outer annulus part 49 Inner annulus part 50 Partition wall

Claims (2)

[Claims] A cylindrical outer liner and an inner liner are concentrically spaced apart from each other inside a furnace vessel wall of a fast reactor, thereby forming an outer annulus between the furnace vessel wall and the outer liner. An inner annulus is formed between the outer liner and the inner liner so that the upper end of the outer liner is submerged below the free liquid level, and the low-temperature coolant flows from a flow hole below the outer annulus. In the submerged weir-type furnace wall cooling protection structure, which rises, turns the upper end of the outer liner, flows down the inner annulus, and flows into the furnace vessel body through the flow hole formed in the lower part of the inner liner, A furnace wall cooling protection structure for a fast reactor, wherein a ring-shaped partition wall whose lower end is immersed below the free coolant level is provided between an outer liner and an inner liner at an upper portion of an annulus portion. 2. A cooling wall protection structure for a fast reactor according to claim 1, wherein the partition wall is fixed to the outer liner by a plurality of inclined blade-like fixing members arranged substantially evenly over the entire circumference.