JPS5821235B2 - Genshiro - Google Patents

Description

[Detailed description of the invention] The present invention relates to a liquid sodium cooled fast reactor.

In more precise terms, the invention relates to a nuclear reactor with a special and novel configuration for cooling the main vessel wall of said nuclear reactor, in particular the upper part of said wall.

The so-called integral reactor concept is generally understood to apply to a type of nuclear reactor in which the primary coolant circuit is entirely located within the main vessel of the reactor.

In other words, the primary heat exchange as well as the pumps that circulate the primary fluid are all located within the main reactor vessel.

A fuller understanding of the problem solved by the present invention may be achieved by reference to the accompanying FIG.

In the figure, the main vessel of the liquid sodium-cooled monolithic nuclear reactor is shown in longitudinal section.

FIG. 1 shows a concrete vaulted ceiling 2 of a nuclear reactor enclosed by a vaulted roof 4, which includes plugs 6 and 8 such as
1. Suitable for carrying the rotating shield plug.

The vessel housing the reactor itself is constituted by the main vessel wall 10, which contains the entire amount of primary sodium.

The main vessel 10 is suspended directly from the vaulted roof 4, and the reactor core 12 is constituted by fuel assemblies inserted at the lower end of the reactor core support grid 14.

A support grid 14 rests on a diagrid 16, which is supported by the main container 10.

Within the main vessel are provided several primary pumps, such as pump 18, and a primary heat exchanger, such as heat exchanger 20.

The areas reserved for hot sodium 21 and relatively cold sodium 22 are separated by a cylindrical shell 34 and an annular oblique wall 24.

The interior of the cylindrical shell 34 constitutes a primary container containing hot sodium, while the relatively cold sodium is confined within the space 22, i.e. between the cylindrical shell 34, the main vessel 10 and the diacrylate 16. within the so-called inter-vessel zone.

Sodium flows upwardly through the fuel assemblies of the reactor core 12 and is discharged at an elevated temperature into the primary vessel, then into the heat exchanger 20 and from the heat exchanger at 26 into the intermediate vessel section 22. The sodium is therefore in a relatively cold state in the area.

This cooler sodium is pulled up by a pump 18 and passed through a conduit 28 to the core support grid 14 of the reactor.
The cycle continues from there at low pressure.

A layer of pressurized argon (blan) is used to protect the vaulted roof 4 of the reactor and the rotating shield system.
ket) 30 is provided at the top of the main container 10.

The main vessel 10, which supports the complete assembly of all equipment, is subjected to extremely large thermal gradients.

In detail, the main container 10 is connected to the vaulted roof 4
The temperature of the upper edge of the main container 10 suspended is the temperature of the roof 4, that is, a relatively low temperature.

This is because the roof 4 is isolated both by a layer of argon 30 and by a heat removal device provided below the roof 4.

On the other hand, the middle part between the upper and lower parts of the main vessel 10 contains high temperature sodium (approximately 560°C) flowing from the reactor core 12, while the bottom of the main vessel 10 It is in contact with relatively cool sodium (approximately 400° C.) leaving exchanger 20.

In order to minimize the above-mentioned temperature gradient that the main container 10 experiences, direct contact between the main container and the sodium is prevented, and the intermediate portion of the main container 10 is "cooled" by the relatively low temperature sodium. "It is known.

To achieve this purpose, a small portion of the relatively cold sodium leaving the heat exchanger 20 is transferred to the wall of the main vessel.
0 and a cylindrical shell 32 disposed concentrically with the cylindrical shell 34, and rises through the annular space 36 until reaching a layer 30 of argon. The flow is then diverted and flows downwardly into the annular space 38 defined between the two cylindrical shells 32 and 34 forming elements of the deflecting member and back into the intermediate container section 22. , to cool the hot sodium confined within the inner cylindrical shell 34.

It is clear that in the cooling system described above, only relatively cool sodium comes into contact with the cylindrical shell 34, so that this system solves the problem of minimizing the temperature gradients experienced by the main vessel 10.

In fact, the relatively cold sodium flowing upwardly within the annular space 36 and then redirecting downwardly and coming into contact with the hot sodium trapped therein via the cylindrical shell 34 is heated to a high temperature. Although it tends to be heated by heat conduction from the sodium, it is permanently circulated by the action of the primary pump 18 so as to maintain a relatively low temperature at all times.

However, the above-mentioned known cooling system has the following drawbacks.

In the structure of the cooling system described above, as shown in FIG. It can be seen to define a free liquid level (free Ievel) in contact with the layer 30 of argon.

The sodium contained in the main container 10 is circulated by the pump 18 through the heat exchanger 20 from the high temperature part to the low temperature part of the sodium chloride, so that the sodium at a high temperature and the sodium at a relatively low temperature form a free liquid. It is easy to understand that the surface area varies depending on the operating speed of the pump.

Therefore, relatively low temperature sodium flows upward in the annular space 36 and then downward in the annular space 38, and the upper edge of the cylindrical shell 32 is necessarily lower than the upper edge of the cylindrical shell 34. (See Figure 1) Considering that,
It is clear that:

■) The relatively low-temperature sodium free liquid level is a cylindrical shell 32
When above the upper edge, only the relatively cool portion of sodium immediately above this upper edge is in the annular space 36.
to the annular space 38, but the layer above said portion of relatively cold sodium is not circulated.

This immobile, stagnant layer of sodium allows heat to be transferred from the hot sodium 21 to the main vessel 10, but this has disadvantages that are outweighed by the desired benefits.

2) The free surface of relatively cold sodium has a cylindrical shell 32
When below the upper edge, this is only visible in the annular space 38, since the sodium flows upwardly within the annular space 36.

This causes an overflow phenomenon from the upper edge of the cylindrical shell 32 to the relatively cool free sodium liquid level in the annular space 38.

In other words, sodium falls from the upper edge of the cylindrical shell 32, resulting in the formation of an argon bubble which (
It is well known that there is a risk of introducing relatively cold sodium (as when water falls).

This means that if argon is present in sodium,
This is clearly undesirable since it reduces the specific heat of the sodium to a significant degree.

The aim of the invention is to remedy the deficiencies of the solutions of the prior art mentioned above and to minimize the temperature device to which the main container is exposed.

In order to achieve the above object, in the present invention, relatively low temperature sodium, which is circulated between hot sodium and the main vessel to cool the main vessel, is used to cool the siphon directed to the bottom of the reactor. Two annular spaces 58
and 60, relatively cool sodium flows upwardly in the outer annular space 58 and downwardly in the inner annular space 60. It is suggested that you do so.

By having the above characteristics, in the nuclear reactor of the present invention, the cylindrical shell 50 and the 5
It is clear that the flow of relatively cool sodium circulating between the two points does not stagnate, nor does it cause any overflow phenomenon.

According to the present invention, the present invention has a cylindrical main container provided with an end wall and a cylindrical shell disposed within the main container, and the cylindrical shell is arranged inside the cylindrical shell within the main container. a primary vessel constituting a primary vessel and an intermediate vessel area located below the primary vessel; and a fuel assembly disposed within said main vessel and located on a support structure. a primary heat exchanger and a pump disposed within the main vessel; the reactor core is powered by liquid sodium flowing upwardly through the fuel assembly of the reactor core; Liquid sodium cooled and having cooled the reactor core flows into the secondary vessel, is introduced from the secondary vessel into the secondary heat exchanger, and flows out of the secondary heat exchanger. The cold sodium chloride is discharged into the intermediate vessel area, and the cold sodium chloride is discharged into the intermediate vessel area.
IJum is removed from the intermediate vessel area for re-injection under pressure into the lower part of the fuel assembly of the reactor core by the pump, and at least one assembly of cylindrical shells is removed from the main vessel. and arranged to form a siphon having the same axis as the main vessel axis and located between the hot sodium and the wall of the main vessel at least in the upper part of the main vessel, the siphon including a bottom part of the reactor. There are two annular spaces facing the reactor, and the one closest to the wall of the main vessel receives a portion of the relatively cold sodium that is injected into the reactor core. A nuclear reactor is provided, the other annular space opening into said intermediate vessel area.

A clearer understanding of the invention can be obtained from the following description of several embodiments of the invention, which are illustrated without limitation with reference to the accompanying drawings, in particular figures 2 to 4. This can be given as an example.

FIG. 2 shows a partial view in diametrical section of a reactor vessel equipped with a cooling system according to the invention.

The reactor structure is obviously a body of revolution that is formed as a whole about an axis that is not shown.

The shells described below are all cylindrical shells in the form of a body of revolution formed around the axis of the reactor vessel.

The figure shows the main vessel 10 suspended from the vaulted roof or shield plug system 4 of the reactor.

The main vessel is surrounded by a leakage jacket 40 which serves to collect the sodium without causing a significant drop in the sodium level in the event of an accidental leak.

The figure also shows a nuclear reactor core 12 surrounded by a cylindrical wall 42 and supported by a diagonal grid 16 secured to the main vessel by a beveled shell element 44.

The primary vessel is defined by a cylindrical shell 34 and by a frusto-conical shell element 24 which is connected to the reactor jacket 42 and thus contains the heated l-IJum.

It is clear that the shell 48 is traversed by the heat exchanger 20 and also by the pump 18.

The cooling system itself consists of a series of cylindrical shells parallel to each other and coaxial with the main reactor vessel.

First cylindrical shell 5 sequentially from the outside to the inside of the container.
0, a second cylindrical shell 52 and a third cylindrical shell 56 are arranged, and the first cylindrical shell 50 has its upper part joined to the arched ceiling roof 4 of the reactor.

The second cylindrical shell 52 is joined at its lower end to the container 10, and its upper end 54 is free.

The third cylindrical shell 56 includes the three cylindrical shells 50 and 52.
and 56 are joined at their upper ends to the first cylindrical shell 50 so as to constitute a siphon formed by annular passages 58 and 60 communicating with each other at their upper ends by a chamber 62.

The passage 58 opens directly towards the diagonal grid 16 and thus towards the reactor core support grid 14, whereas the passage 60 opens towards the intermediate vessel area 22.

Finally, the shell 34 defining the primary container has a cylindrical shell element 64
It has an extension in the form of.

The annular chamber 62 includes a number of branches 66 and 66' which are uniformly spaced along the length of the chamber.

Said branch pipe is a conduit 7 that crosses the vaulted ceiling roof of the reactor.
It opens into a central manifold 68 which is coupled to 0.

The design functions of these branches will be explained in more detail below.

Branch 66, manifold 68, and conduit 70 all contain pressurized argon and are fitted with devices for regulating the amount of argon introduced therein.

This argon circuit is independent of the circuit that supplies the top blanket of the reactor primary vessel.

The operation of this device is as follows.

At the moment of reactor startup, a low pressure of argon is developed in manifold 68 and conduit 70.

A constant value of negative pressure is therefore created in the chamber 62.

annular passages 58, 52 and 60 constitute a siphon;
This is triggered by the negative pressure or partial vacuum created in chamber 62.

The siphon is supplied with relatively cold sodium emerging from the support grid of the reactor core 12 and therefore under low pressure.

Once the siphon is started, conduit 70 and manifold 6
The amount of argon in chamber 62 is adjusted to establish a relatively cool sodium level in chamber 62 during normal operating regimes.

Annular space 72 defined by main container 10 and shell 50
The relatively cold sodium present within the siphon is isolated from the hot sodium contained within the primary vessel 21 by a double wall of relatively cold sodium circulating within the siphon (passages 58 and 60). is encouraged.

The relatively cool sodium that is continuously circulated within the siphon is not heated by the radiation of heat from the hot sodium contained in the primary vessel 21.

Likewise, the sodium stored in the annular space 72 in direct contact with the reactor main vessel 10 is not heated by the thermal radiation of the hot sodium chloride.

The increase in the level of relatively cold SoI in chamber 62 due to the increase in the level of hot sodium in the primary vessel is limited by the increase in the pressure of the argon contained within chamber 62.

This is because an increase in the level of sodium at relatively low temperatures reduces the amount available for a given amount of argon.

Similarly, a drop in the level of hot sodium in the primary vessel results in a drop in the level of relatively cold sodium in acid 62.

This level drop is limited by the reduction in argon pressure within chamber 62.

The result thereby obtained is a self-regulation of the level of sodium in the chamber.

FIG. 3 shows a first alternative embodiment used to cool the main vessel according to the invention.

For the components already shown in FIG.
In the figure, the same reference numerals as those used in FIG. 2 are used.

The shell 50' which performs the same function as the cylindrical number 50 in FIG.
In this embodiment, said shells 50' and 56 and the semicircles are not joined to the roof 4 of the vaulted ceiling of the reactor, but instead to the shell 56 by a semicircle 74. The cross section formed integrally by the body 74 is an inverted U.
The letter-shaped member will be referred to as the first shell.

A second cylindrical number 54 is arranged between the two arms of the first shell having an inverted U shape so as to form two annular spaces inside the first shell.

In this embodiment, shells 50' and 56 are no longer secured to the reactor shield plug system.

To fix said shell, for example fins 76 and 7
8, and these fins are welded to the main vessel 10.

The drawings do not show an auxiliary tube that opens into the top of the siphon through the semicircular ring 74 and initiates flow into the siphon by creating a partial vacuum.

As mentioned above, the embodiment shown in FIG. 3 is different from the embodiment shown in FIG. 2 in its structure, but the relatively low temperature sodium existing inside the annular space 72 is The relatively low temperature sodium circulating in the siphon is separated from the high temperature sodium contained in the primary vessel 21 by a double wall of the relatively low temperature sodium circulating in the siphon, and the annular space It is exactly the same as in the embodiment shown in FIG. 2 that the sodium stored in 72 is not heated together by the heat radiated by the hot sodium.

The embodiment shown in FIG. 3 is simpler in construction than the embodiment shown in FIG. 2, but allows for varying the amount of gas in the upper chamber (i.e. chamber 62 shown in FIG. 2). I don't do it.

In fact, by ensuring that a relatively small flow cross section is formed between the upper end of the shell 54 and the semicircular ring 74 made of sheet metal, the amount of gas in the upper chamber is kept substantially constant. maintain.

Therefore, if the height of the sodium above the upper end of the shell 54, that is, the height of the cross section of the above-mentioned flow, becomes too large, there is a risk that a layer will be formed above where the sodium does not flow. Since the height of the cross section is small and as uniform as possible and does not change (the shape of a semicircular ring), the above-mentioned formation of a layer in which the sodium does not flow is prevented from forming above.

In another embodiment shown in FIG. 4, the members corresponding to the shell 50 shown in FIG. 2 and the shell 50' shown in FIG. 3 are omitted,
The role played by the shell is replaced by the wall of the main container 10 itself.

In other words, in the embodiment shown in FIG. 4, where the passage 72 shown in FIGS. 2 and 3 is not formed, the third cylindrical number 56 is joined at its upper end to the wall of the main container 10. and its lower part freely enters the intermediate container area 22.

A second cylindrical number 54 is arranged between the wall of the main container 10 and a third cylindrical number 56, thereby forming two annular spaces 58' and 60', which Space constitutes a siphon.

A chamber 62' is thus formed in the upper part of the siphon.

The relatively cool sodium coming from the support grid 14 and from the reactor 12 passes upwardly into the chamber 6 through an annular passage 58'.
2' and returns downwardly to the intermediate container area 22 through the annular passage 60'.

The amount of argon placed in the annular chamber 62' is regulated at the outlet.

As in the first embodiment, the compression and expansion of the amount of argon enclosed within the chamber 62' occurs as a function of changes in reactor power, i.e. as a function of changes in the level of hot sodium in the primary vessel of the reactor. As a result, the relatively low temperature in chamber 62' allows for almost complete control of the level of IJ.

It will be clear that the above-described apparatus may be modified in shape or form without departing from the scope or spirit of the invention.

The present invention relates in practice to devices interposed between the walls of the main vessel and the primary vessel containing hot sulfur, which devices consist primarily of an annular siphon surrounding all parts of the main vessel; The main vessel is placed above the intermediate vessel area and is in contact with the hot sodium in the absence of the siphon.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a nuclear reactor according to the prior art. FIG. 2 shows a first embodiment in which the siphon includes a chamber containing pressurized gas at its top and a device for initiating flow within the siphon. FIG. 3 shows a first alternative embodiment in which the siphon does not include a gas chamber. FIG. 4 shows a second alternative embodiment in which the siphon is used directly on the main vessel wall. In the drawing, code 2 is the "ceiling inside the reactor," 4 is the "roof," and 6 is the "roof."
, 8 is the "plug," 10 is the "main vessel," and 12 is the "core."
, 14 is "supporting grid", 16 is "diagrid"
, 18 is "pump", 20 is "heat exchanger", 21 is "high temperature sodium", 22 is "relatively low temperature sodium", 24 is "annular inclined wall", 28 is "conduit", 30 indicates a "blanket" and 34 indicates a "cylindrical number".

Claims (1)

[Scope of Claims] 1. A cylindrical main container provided with an end wall, and a cylindrical membrane disposed within the main container, the cylindrical membrane disposed within the main container. a primary container constituting the inside of the membrane;
a nuclear reactor core delimiting an intermediate vessel area located below the primary vessel, and consisting of fuel assemblies disposed inside said main vessel and positioned on a support structure; a primary heat exchanger and a pump disposed within the main vessel, the reactor core being cooled by liquid sodium flowing upwardly through the fuel assembly of the reactor core; The liquid IJ flows into the secondary vessel, is introduced from the secondary vessel into the secondary heat exchanger, and the relatively low temperature liquid flows out of the secondary heat exchanger. Sodium is discharged into the intermediate vessel area, and the relatively cool sodium is discharged into the intermediate vessel area for re-injection under pressure into the lower part of the fuel assembly of the reactor core by the pump. removed from the container area and having at least one assembly of cylindrical membranes having the same axis as the axis of the main container and in at least an upper portion of the main container the hot sodium and the walls of the main container are arranged to form a siphon located between the reactor and the siphon, said siphon having two annular spaces directed towards the bottom of the reactor, and of these annular spaces closest to the wall of the main vessel. A nuclear reactor in which the annular space is supplied with a portion of the relatively cold sodium that is injected into the bottom of the reactor core, while the other annular space opens into said intermediate vessel area. 2. In the nuclear reactor described in claim 1,
The siphon has a third cylindrical membrane 56 which is joined at its upper end to the wall of the main container 10 and whose lower part extends freely into the intermediate container area; The cylindrical membrane 56 is disposed between the two
a second cylindrical membrane 54 forming two annular spaces 58', 60'; The second cylindrical membrane 54 is free to leave a passage therebetween, and the lower edge of the second cylindrical membrane 54 is joined to the reactor core supporting structure. 3. The nuclear reactor according to claim 1 (wherein the siphon is rigidly fixed to the roof 4 of the vaulted ceiling of the reactor with its upper edge and its lower edge free) a first cylindrical membrane 50 with a top edge extending towards said first cylindrical membrane 50 and joined to said first cylindrical membrane and a free bottom edge extending into said intermediate container area. a third cylindrical membrane 56 disposed between said first and third cylindrical membranes and having said two annular spaces 58 therebetween;
and a second cylindrical shell 52 forming an angle of 60 degrees, and the upper edge of the second cylindrical shell 52 is free to leave a passage between the two annular spaces 5B and 60. The lower edge of the second cylindrical shell 52 is joined to the reactor core supporting structure. 4 In the nuclear reactor described in claim 3,
The third cylindrical shell 56 has a tube 66 disposed in an overhanging portion of the shell having openings at uniformly spaced locations around the periphery of the shell, the tube being pressurized. The nuclear reactor is connected to a manifold 68 for introducing the gases that are present in the reactor. 5. In the nuclear reactor described in claim 1,
The siphon has a first shell 50', 56. 74 and a second cylindrical shell 54, said first shell being in the form of a body of revolution formed about the axis of said main container, said first shell passing through a diametric half-plane. The cross sections of the shells 50', 56, and 74 have an inverted U-shape with an open bottom end, and the second cylindrical shell 54 has two annular spaces inside the first shell. The upper end edge of the second cylindrical shell 54 is disposed between the two arms of the first shell having an inverted U shape to form a passageway between the two annular spaces. The lower edge of the second cylindrical shell 54 is joined to the core supporting structure.