EA042249B1 - NUCLEAR REACTOR WITH LIQUID METAL COOLANT - Google Patents

Description

Technical field

The invention relates to nuclear power, in particular to the safety of nuclear reactors (NR), primarily reactors with heavy liquid metal coolant (HLMT) based on lead or alloys based on lead and bismuth.

When choosing the thermal parameters of a nuclear reactor, in particular, the maximum coolant temperature, the limiting factors are, first of all, the corrosion resistance of materials and the strength characteristics associated with the loading features of the structure. In this case, the maximum coolant temperature in reactors with liquid metal cooling, as a rule, is reached at the exit from the core. Usually, the heating of the coolant in the core is uneven, which is due to the uneven flow of the coolant along the radius of the core and the unevenness of the energy release field over the volume of the core. Thus, the structural elements located in the area of the coolant outlet from the core are under the influence of the coolant with maximum temperatures and temperature inhomogeneities.

Special measures are being taken to equalize the heating of the coolant in the core, but the effectiveness of these measures is limited, and the non-uniformity of the coolant temperature at the exit from the core in HLMC reactors can reach several tens of degrees. Depending on the type of coolant in the NR secondary circuit, the coolant circulation scheme in the chamber above the core and on the way to the heat exchanger or steam generator, the coolant is mixed and the coolant temperature is gradually equalized. An increase in the reliability and safety of the reactor facility is facilitated by the use of special design solutions that limit the impact of unfavorable factors, such as high local temperatures in the chamber at the exit from the core or high temperature gradients in the structural elements that limit the specified chamber.

State of the art

From patent RU 2461085 known reactor with HLMT pool type. The disadvantage of the design of this type of reactor is the large volume of hot coolant, the temperature of which corresponds to the temperature of the exit from the core. As a result, part of the internal elements, the connecting elements between the drives of the control and protection system (CPS) and the reactivity control elements (rods or assemblies of CPS rods) are exposed to high temperatures and / or large temperature gradients.

From patent RU 2153708 known reactor with HLMT integral type. The main advantage of reactors of this type is the possibility of placing the core, a pump that circulates the coolant in the primary circuit of the nuclear reactor, and a heat exchanger (steam generator) to remove the heat generated in the core in one NR vessel.

Temperature gradients in the structural elements separating the hot coolant with the exit temperature from the core from the cold coolant after leaving the heat exchanger (steam generator) play a significant role in the development of the nuclear reactor design. Taking into account the fact that in modern designs of nuclear reactors with HLMC, the difference between the maximum temperature and the minimum temperature in the primary circuit is, as a rule, in the range of 100-150°C, in order to create favorable working conditions for internal structural elements separating hot and cold coolant flows requires the development of special design solutions.

An important feature of the known NR with HLMT is the need to control the oxygen concentration in a certain range. The presence of oxygen in the coolant is necessary for the formation of protective oxide coatings on the surface of steels, which prevents the release of metal impurities, primarily iron, into the coolant, due to corrosion and erosion processes mainly in the hot part of the primary circuit. When significant volumes of iron impurities enter the primary circuit, it is necessary to use special systems to capture them, which complicates the design of the nuclear reactor.

Thus, the maximum limitation of the area of surfaces in contact with the hot coolant will significantly reduce the thermal load on the internal elements of the nuclear reactor, and is a task that must be solved by using special design solutions.

RF patent RU 2521863 discloses a nuclear reactor with a liquid metal coolant, containing a housing, inside which a separating shell is installed, forming an annular space, and in which at least one steam generator and at least one pump are installed, each installed in its own shell. Inside the separating shell, in its upper part, there is a protective plug, and in the lower part there is an active zone, above which there is a hot collector that communicates with the steam generator along the height in the middle or upper part of the steam generator by means of an inlet pipe for separating the liquid metal coolant flow into ascending and descending streams washing respectively the upper and lower parts of the steam generator.

A nuclear reactor with liquid metal cooling according to RF patent RU 2408094 contains a hot collector above the active zone and a cold collector surrounding the hot collector, separated by a separating structure, where the primary fluid circulates to cool the active

- 1 042249 zones. The reactor also includes at least one integrated circulation and heat exchange assembly comprising a pump, at least one heat exchanger, and a conveyor structure through which the primary fluid passes from the pump to the heat exchanger, the latter being firmly connected to each other to form a single structure. The integrated assembly is located entirely in the cold manifold and has an inlet attached to the hot manifold and at least one outlet section in the cold manifold.

The disadvantage of these well-known NRs is a significant temperature difference in the pipe through which the hot coolant flow enters the steam generator or pump for subsequent cooling, which affects the service life and reliability of this structural element.

The closest analogue of the claimed invention is NR according to RF patent RU 2331939. This patent discloses the design of a nuclear reactor with the predominant use of a liquid metal coolant as a primary coolant. The thermal protection of the reactor pressure vessel contains a core basket, annular steel shells installed and fixed in the basket, and a separating shell fixed to the bottom of the vessel. The composition of the thermal screen includes blocks with boron carbide; they are located behind the separating shell and form a multilayer annular screen in plan over the entire height of the core. The gaps between the specified blocks of one layer are overlapped by the blocks of the next layer.

The disadvantage of the closest analogue is the rigid fastening of the shells in the reactor vessel, which, when the shells come into contact with the hot coolant flow leaving the core, will create a significant thermal load in the junctions of the elements and can lead to coolant leaks. The rigid fastening of the shells in contact with the hot coolant flow also complicates routine maintenance and repair work.

Disclosure of the essence of the invention

The technical problems solved in the claimed invention are the reduction of the volume and surface area of the internal structural elements of the reactor in contact with the hot coolant flow, the provision of thermal insulation of the hot chamber and a favorable temperature regime for the internal structural elements, in which temperature drops are limited to values at which thermal stresses do not exceed the yield point, as well as ensuring ease of assembly and control of coolant leaks in detachable connections.

The technical result of the claimed invention is to reduce the thermal load on the elements of the hot chamber, primarily the body of the hot chamber and the hot coolant outlet pipes, including smoothing and reducing the temperature gradient that occurs in these elements, and as a result, increasing their service life, as well as the entire nuclear reactor .

The set technical problems are solved, and the claimed technical result is achieved by the fact that the integral-type nuclear reactor with a liquid metal coolant contains a reactor vessel with a lower chamber, an active zone, a hot chamber, an upper chamber and heat exchangers, and the hot chamber is located above the active zone and contains a hot chamber vessel , essentially cylindrical in shape with nozzles for removing the hot coolant coming from the core to the heat exchangers. The body of the hot chamber contains an inner shell of the hot chamber and at least one additional shell of the hot chamber, installed with a gap outside and concentric to the inner shell of the hot chamber, in contact with the cold coolant from the outside and forming at least one channel communicating with the cold coolant. In this case, each branch pipe contains an inner shell of the pipe and at least one additional shell of the pipe, installed with a gap outside and concentric to the inner shell of the pipe, in contact with the cold coolant from the outside and forming at least one channel communicating with the cold coolant. The cold heat carrier enters at least one channel of the hot chamber and at least one channel of the branch pipe from the outlet of the heat exchangers.

The described design of the NR hot zone makes it possible to evenly distribute the temperature over the body of the hot chamber and the branch pipe, as well as to reduce the thermal load on the indicated elements of the NR design, which has a positive effect on their reliability and service life.

There are also private versions of the invention, in which the tasks are also solved and the claimed technical result is achieved.

So, to additionally ensure uniform temperature distribution over the body of the hot chamber and the branch pipe, through holes are made in at least one additional shell of the hot chamber and/or in at least one additional shell of the nozzle. These through holes provide an additional flow of the coolant in cases where the length of the channels closing on the chambers with cold coolant is significant and prevents the coolant from flowing into them. The coolant flow is necessary, among other things, to maintain the required concentration of oxygen dissolved in the coolant in the channels. The shape of the holes can be arbitrary and is determined only by the functional purpose of these holes. The requirements for the level of oxygen concentration are determined by known ratios.

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The intensity of the coolant flow passing through the gaps between the shells is regulated, among other things, by the width of the gaps between the shells and the holes in the additional shells. The specified intensity is selected in such a way as to ensure a uniform distribution of the temperature difference between the inner shell and the corresponding additional shells, preferably in a linear fashion.

To ensure the convenience and reliability of assembly, compensation for temperature movements of the elements, mating the plug, the inner shell of the hot chamber and the inner shell of the branch pipe, as well as to prevent the ingress of hot coolant into the cavities between the additional shells and / or inner shells and the corresponding additional shells, in the design of the hot chamber piston ring seals may be provided. In particular, it is preferable if at least one first sealing piston ring is placed between the inner shell of the hot chamber and the plug, at least one second sealing piston ring is placed between the inner shell of the hot chamber and the additional shell of the hot chamber adjacent to it, and between the inner At least one third sealing piston ring is placed by the pipe shell and the additional pipe shell adjacent to it.

Piston rings are preferably made from a high strength and corrosion resistant material, such as gray cast iron with lamellar graphite alloyed with chromium and silicon.

In the vertical direction, above the active zone, the hot chamber is limited by a plug. The preferred shape of the plug is a cone-shaped trapezoid, which makes it possible to smooth the direction of the hot coolant flow leaving the core and rotate the flow by approximately 90° to facilitate its passage from the hot chamber to the hot coolant outlet pipe, which has a positive effect on the distribution of the heat load attributable to on the hot cell components. In particular, the plug may consist of at least two disk elements, spaced one above the other and made of steel.

Further, possible embodiments of the invention are disclosed in more detail with reference to the figures.

Brief description of the drawings

In FIG. 1 is a 3-D view of an integral type reactor according to the invention.

In FIG. 2 shows fragment A of a 3-D view of the reactor.

In FIG. 3 shows a section 1-1 of an integral type reactor according to the invention.

In FIG. 4 shows a section 2-2 of an integral type reactor according to the invention.

In FIG. Figure 5 shows the area of the hot coolant flow outlet branch pipe in section.

No fig. 6 shows a variant of the implementation of the removal of the hot coolant only upwards.

The positions in the figures show:

- reactor vessel;

- down Cam;

- active zone;

- hot chamber;

- upper chamber;

- heat exchanger (steam generator);

- pump;

- coolant supply channel;

- pipe branch;

- body of the hot chamber;

- cork;

- inner shell of the hot chamber;

- additional shell of the hot chamber;

- cooling channel of the hot chamber;

- inner shell of the branch pipe;

- additional shell of the branch pipe;

- cooling channel of the branch pipe;

- heat exchanger outlet;

- the first sealing piston ring;

- the third sealing piston ring;

- a disk element of a stopper.

In general, a nuclear reactor, simplified in FIG. 3, includes a reactor vessel 1, in which the lower chamber 2, the core 3, the hot chamber 4, the upper chamber 5 and the heat exchangers (steam generators) 6 are located. , therefore, only the features of the execution of individual components of the NR related to the present invention will be described below.

The arrows in the figures show the directions of the coolant flows.

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The cold coolant is fed through the pump 7 into the lower chamber 2, from where it enters the core 3 through the coolant supply channels 8. In the core 3, the coolant is heated and enters the hot chamber 4, located above the core 3, with the temperature of the exit from the core . Next, the hot coolant is sent to the hot coolant outlet pipes 9, which provide the hot coolant flow to the heat exchangers (steam generators) 6.

The hot chamber 4 (Fig. 2) contains a body 10 of the hot chamber, essentially cylindrical in shape with branch pipes 9 for the removal of the hot coolant coming from the core to the heat exchangers 6, and a plug 11.

According to the invention, the hot cell body 10 comprises an inner hot cell shell 12 and at least one additional hot cell shell 13. The additional hot cell shells 13 are spaced outside and concentric to the inner hot cell shell 12, thus forming at least one hot cell cooling channel 14 .

According to the invention, each nozzle 9 also contains an inner shell 15 of the nozzle and at least one additional shell 16 of the nozzle, installed with a gap outside and concentric with the inner shell 15 of the nozzle and forming at least one cooling channel 17 of the nozzle.

The cooling channels 14 of the hot chamber and the cooling channels 17 of the branch pipe communicate with the outlets 18 (Fig. 3) of the heat exchangers to direct the flow of the cooled coolant into these cooling channels 14, 17.

In FIG. 3 shows that after the hot coolant enters the heat exchanger 6, the flow is divided into two parts: The first part of the hot coolant flow, moving upward, is cooled by the coolant of the second circuit and enters the upper chamber 5. The second part of the hot coolant flow, moving downward, is also cooled by the coolant of the second circuit and enters the outlet 18 of the heat exchanger, where it turns around and moves upward along the cooling channels 14, 17.

Such a movement of the coolant, including its passage through the cooling channels 14, 17, contributes to equalizing the temperature along the cross section of the body 10 of the hot chamber and the branch pipe, reducing the thermal load on them and the resulting thermal stresses, which affects the reliability of operation and the service life of these structural elements of the nuclear reactor.

The size of the gaps between the inner shells 12, 15 and the corresponding additional shells 13, 16, as well as between the corresponding additional shells 13, 16, is selected in such a way that as a result of thermal expansions and movements of the structural elements of the nuclear reactor, there is no direct contact between these shells, i.e. . so that in any case a guaranteed gap remains between the said shells for the circulation of the coolant in the cooling channels 14, 17.

The flow rate of the coolant supplied to the cooling channels 14, 17 is calculated in such a way that the heat transfer along the cooling channels 14, 17 is significantly less than the heat transfer between the inner shells 12, 15 and the corresponding additional shells 13, 16, as well as between the respective additional shells 13, 16.

In addition, according to the present invention, through holes can be made in at least one additional shell 13 of the hot chamber and/or in at least one additional shell 16 of the nozzle (Fig. 5b, 5c). These through holes provide hot coolant flow, as shown by arrows in the figures. The shape of the holes can be arbitrary and is determined only by the functional purpose of these holes. The intensity of the coolant flow passing through the cooling channels 14, 17 is regulated, among other things, by the indicated through holes in the additional shells. This intensity is selected in such a way as to ensure a uniform distribution of the temperature difference between the inner shell 12, 15 and the corresponding additional shells 13, 16, preferably in a linear fashion.

To avoid the occurrence of large stresses when moving the structural elements of the nuclear reactor as a result of thermal expansion, the inner shells 12, 15 do not have a strong connection with the corresponding mating components of the nuclear reactor. In this case, movable seals must be provided, the preferred option of which are seals of the piston ring type.

So, between the inner shell 12 of the hot chamber and the plug 11 can be placed at least one first sealing piston ring 19; between the inner shell 13 of the hot chamber and the adjacent additional shell of the hot chamber can be placed at least one second sealing piston ring (not shown in the figures); between the inner shell 16 of the nozzle and the additional shell of the nozzle adjacent to it, at least one third sealing piston ring 20 can be placed.

The most preferred material for said piston rings is a high-strength and corrosion-resistant material, in particular chromium-silicon alloyed gray cast iron with lamellar graphite.

The plug 11 limits the hot chamber 4 in the vertical direction, above the core.

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The preferred shape of the plug 11 is a cone-shaped trapezoid, which makes it possible to smooth the direction of the hot coolant flow leaving the core 3 and rotate the flow by approximately 90° to facilitate its passage from the hot chamber 4 to the hot coolant outlet pipe 9, which has a positive effect on the distribution heat load on the components of the hot chamber 4. In particular, the plug 11 may consist of at least two disk elements 21, installed with a gap one above the other and made of steel.

Thus, the present invention makes it possible to reduce the volume and surface area of internal structural elements of a nuclear reactor in contact with the hot coolant flow, provide thermal insulation of the hot chamber and favorable temperature conditions for these elements, ensure ease of assembly and control of coolant leaks in detachable joints. As a result, temperature differences in these elements are limited to values at which thermal stresses do not exceed the yield strength, the thermal load on them decreases, primarily on the body of the hot chamber and hot coolant outlet pipes, and their service life increases.

Claims (6)

CLAIM 1. A nuclear reactor of an integral type with a liquid metal coolant, containing a reactor vessel with a lower chamber, an active zone, a hot chamber, an upper chamber and heat exchangers, the hot chamber being located above the active zone and containing a body of a hot chamber, essentially cylindrical in shape with hot outlet pipes coolant coming from the core to the heat exchangers and a plug, and said pipes are washed from the outside with cold coolant from the exit of the heat exchangers, characterized in that the hot chamber body contains an inner shell of the hot chamber and at least one additional shell of the hot chamber, installed with a gap on the outside and concentric to the inner shell of the hot chamber and forming at least one channel of the hot chamber, each nozzle contains an inner shell of the nozzle and at least one additional shell of the nozzle installed with a gap outside and concentric to the inner shell of the nozzle and forming at least at least one branch pipe channel, and at least one hot chamber channel and at least one branch pipe channel communicate with the outlet of the heat exchangers to direct the flow of cold heat carrier into these channels. 2. Nuclear reactor according to claim 1, in which at least one additional shell of the hot chamber and/or at least one additional shell of the branch pipe has through holes. 3. The nuclear reactor according to claim 1, in which at least one first sealing piston ring is placed between the inner shell of the hot chamber and the plug, at least one second sealing piston ring is placed between the inner shell of the hot chamber and the additional shell of the hot chamber adjacent to it. , and between the inner shell of the branch pipe and the additional shell of the branch pipe adjacent to it, at least one third sealing piston ring is placed. 4. Nuclear reactor according to claim 3, wherein said sealing piston rings and/or plug are made of high strength and corrosion resistant material. 5. Nuclear reactor according to claim 4, wherein said material is gray cast iron with lamellar graphite alloyed with chromium and silicon. 6. A nuclear reactor according to any one of the preceding claims, wherein the plug contains at least two disk elements.