RU2795981C1 - Nuclear reactor core - Google Patents

Abstract

FIELD: nuclear power plants (NPP).

SUBSTANCE: nuclear reactor comprises a core with vertically installed fuel assemblies in it, fastened with spacer grids, and vertical channels made around the circumference of the core configured for coolant flow through them and connected to the core by horizontal channels adapted for its supply. Moreover, each spacer grid adjacent to the vertical channels corresponds to at least one horizontal channel, each of which is installed in close proximity to the spacer grid above or below it. Some of the vertical channels are equipped with filter gratings in the upper or lower part.

EFFECT: increased safety of operation of a nuclear reactor by providing effective cooling of its core in emergency conditions.

3 cl, 6 dwg

Description

Technical field

The invention relates to the field of ensuring the safe operation of nuclear power plants (NPP) in various modes, including emergency, and is aimed at preventing clogging of the reactor core with debris.

Prior Art

During the operation of a nuclear power plant in the core of a nuclear reactor, a coolant constantly circulates (in pressurized water reactors - water), which takes heat from the core and transfers it further to the turbine to generate electricity. In the event of an accident at a nuclear power plant, the circulation of the coolant ensures the removal of residual heat from the core, which is extremely important to prevent overheating of the core, which can lead to the most serious consequences. In an accident with loss of coolant, under the influence of the dynamic impact of a jet from a gap, thermal insulation coatings, wall coatings, and other building and metal structures are destroyed. As a result, debris is formed, which also includes debris that is constantly present in the containment rooms (latent debris).

This debris is delivered to the sump (sump tank) by the flow of coolant flowing out of the gap. From the sump tanks, the coolant is fed back to the core by pumps of the emergency core cooling systems (ECCS). Since the coolant is contaminated, filters are installed in front of the ECCS pumps, however, part of the debris penetrates through the filters and, therefore, can enter the reactor core. Fibrous debris is especially dangerous, which can linger in narrow places and block the coolant flow, leading to overheating of the walls of fuel elements (fuel elements) in places of such blocking. The most likely place for debris to get stuck and, accordingly, to block the coolant flow is the spacer grids of the fuel assemblies.

Various technical solutions have been proposed to solve this problem.

Known modular radial neutron reflector (US 8615065, publ. 28.04.2011), located in the core of a nuclear reactor and having a structure that corresponds to the internal structure of the core and in contact with it along its entire length, the reflector is fixedly connected to the inner surface of the core by a set fasteners.

The closest to the claimed invention in terms of the achieved technical result and functionality is a nuclear reactor with an active zone (Technical evaluation report of in-vessel debris effects, WCAP-17788-NP, Enclosure December 2019, Volume 1, Revision 1), in which fuel assemblies, fastened with spacer grids, and vertical channels made around the circumference of the core with the possibility of coolant flowing through them and horizontal channels connected to the core with the possibility of its supply to the core.

The disadvantage of these solutions is the possibility of accumulation of debris brought by the coolant flow near the spacer grids with subsequent blockage of the coolant flow by the debris, which can lead to core overheating and a severe accident.

Disclosure of invention

The objective of the claimed invention is to create a nuclear reactor with an increased safety core by providing its cooling in emergency conditions.

The technical result of the claimed invention is to increase the safety of operation of a nuclear reactor by providing cooling of its core in emergency conditions.

The technical result is achieved by the fact that in a known nuclear reactor containing a core bounded by the upper and lower plates, with fuel assemblies installed vertically in it, consisting of fuel elements fastened with spacer grids, vertical channels made around the circumference of the core with the possibility of flowing along coolant through the upper and lower plates and connected to the core by horizontal channels with the possibility of its supply to the core that each spacer grid adjacent to the vertical channels corresponds to at least one horizontal channel, each of which is installed in close proximity to the spacer grid above or below her.

It is preferable to provide one part of the vertical channels with filter gratings in the part passing through the upper plate, and the other part in the part passing through the lower plate, while the characteristic cell size of the living section of the filter gratings is equal to that of the spacer gratings.

It is advisable to arrange the horizontal channels connecting the active zone with the vertical channels equipped with a filter grate in the part passing through the upper plate, above the spacer gratings, and the horizontal channels connecting the active zone with the vertical channels equipped with a filter grate in the part passing through the bottom plate - below the spacer bars.

Brief description of the figures of the drawings

In FIG. 1 shows the core of a nuclear reactor according to the claimed invention.

In FIG. 2 shows the operation of the core of a nuclear reactor when a number of spacer grids are blocked by debris.

In FIG. 3 shows the operation of the core of a nuclear reactor when a number of spacer grids are blocked by debris in the reverse direction of the coolant flow.

In FIG. 4 shows the active zone of a nuclear reactor with filter grids in the inlet and outlet openings of the vertical channels.

In FIG. 5 shows the operation of the core of a nuclear reactor with filter grids in the inlet and outlet openings of the vertical channels when a number of spacer grids are blocked by debris.

In FIG. 6 shows the operation of the core of a nuclear reactor with filter grids in the inlet and outlet openings of the vertical channels when several rows of spacer grids are blocked by debris.

Embodiments of the invention

The nuclear reactor preferably contains a core 1, in which fuel assemblies 2 are vertically installed, fastened at different levels by spacer grids 3. The core 1 is limited by the top plate 4 and the bottom plate 5, respectively, from above and below. Both plates 4 and 5 are adapted, among other things, for the installation and fixation of fuel assemblies 2, as well as vertical channels 7, formed in the preferred embodiment in the baffle body 6. In the upper 4 and lower 5 plates, respectively, upper 9 and lower 8 holes are made, providing coolant supply to the vertical channels 7 and its removal from them. In the wall separating the vertical channels 7 from the active zone 1, in the immediate vicinity of the spacer grids 3, channels 10 are made, which ensure the supply of coolant from the vertical channels 7 to the active zone 1, or in some embodiments of the invention, vice versa: from the active zone 1 to the vertical channels 7. In the inlet 8 or outlet 9 openings of some vertical channels 7, filter gratings 11 are installed with a characteristic cell size of the free section the same as that of the spacer gratings 3 of the active zone 1.

The operation of a nuclear reactor with an active zone 1 in emergency modes can occur in different ways, depending on the version. In the first variant shown in FIG. 1, part of the horizontal channels 7 is made in the immediate vicinity of the spacer gratings 3 adjacent to the vertical channel 7, somewhat above them, and part is somewhat below. In the case of complete blockage by debris of any of the spacer grids 3, or even a whole series of spacer grids 3, as shown in FIG. 2, the coolant will flow through the core, cooling it, to the blocked spacer grid 3, after which it will leave through the horizontal channels 10 to the vertical channel 7 to the upper chamber of the reactor, where it will mix with the main flow leaving the core. This will provide cooling of the core and thereby prevent the unfavorable development of the emergency mode.

Connecting the active zone under the gratings and above the gratings to various horizontal channels 10 of the baffle 6 allows you to streamline the supply and removal of the coolant depending on the place of the break. If the break occurs along the side of the hot leg of the reactor plant, then the total movement of the coolant occurs from the ECCS to the cold leg, through the core 1 and baffle 6 from the bottom up, and in the case of blockage by debris, the operation of the core proceeds as described above. If the rupture occurs on the side of the cold leg, then the direction of flow through the core changes, since the coolant flows into the rupture. The general movement of the coolant in this case occurs from the ECCS into the hot leg through the core 1 and baffle 6 from top to bottom, and in the case of blockage by debris, the coolant flows through the core 1 to the blocking point and leaves through the baffle 6 into the horizontal channels 10 located above the spacer grids 3, and through the channels 10 located below the spacer grids 3, the coolant in the core is replenished (Fig. 3).

The baffle 6 in a specific design is an annular cylinder consisting of rings fastened together with pins and fixed in plan relative to each other with pins. The dimensions of such a partition can be: height - 4.070 m (along the rings); outer diameter - 3.485 m; weight - 35.8 tons. The inner contour of the baffle 6 is made in accordance with the outer contour of the section of the active zone 1 with a small structural gap (4 mm) between the edges of the baffle 6 and spacer grids 3 of the peripheral fuel assemblies. The total height of the rings of the baffle 6 covers the entire height of the active zone 1, which provides effective protection of the body from the flow of fast neutrons. The baffle rings 6 have through cylindrical longitudinal channels: 48 channels with a diameter of 50 mm, 72 channels with a diameter of 70 mm, 12 channels with a diameter of 40 mm and six channels with pipes with a diameter of 130/125 mm. On the end surface of the upper ring, six stops of the device are installed, which, in the event of a shaft break, impossibility of lateral displacement of the broken part of the shaft together with the core 1, to ensure the possibility of falling of the controls of the reactor control and protection system upon an emergency protection signal.

In the preferred embodiment, in the inlet 8 or outlet 9 openings of some vertical channels 7, filter gratings 11 are installed with a characteristic cell size of the open section the same as that of the spacer gratings 3 of the active zone 1 (Fig. 4).

In this case, the blocking of the spacer grids 3 and the blocking of such vertical channels 7 will occur to the same extent. As the spacer grid 3 becomes crowded with debris and its hydraulic resistance increases, the coolant flow rate through it will decrease. In this case, the hydraulic resistance of the exit from the vertical channel 7 will be squeezed in the same way and, accordingly, the hydraulic resistance will increase, in the outlet 9 of which a filter grate 11 is installed. 7 into the core 1 as the blocking of the spacer grid 3 increases, as shown in FIG. 5 will increase. Similarly, as shown in FIG. 5, will also occur with the flow of coolant from under the blocked spacer grate 3 of the grate into another vertical channel, the outlet 9 of which is free, and a filter grate 11 can be installed in the inlet 8. This solution will ensure the most efficient cooling of the core 1 even when blocking a number of spacer grids 3, as shown in FIG. 5, or when blocking several rows of spacer grids 3, as shown in FIG. 6. In this case, the cooling will be most effective if the horizontal channels 10 connecting the active zone with the vertical channels 7 with the filter grate 11 in the part passing through the top plate 4 are located above the spacer grids 3, and the horizontal channels 10 connecting the active a zone with vertical channels 7 with a filter grid 11 in the part passing through the bottom plate 5 - below the spacer grids 3, as shown in FIG. 6. Cooling of the active zone 1 also seems to be the most effective with the vertical channels 7 alternately arranged with the upper and lower arrangement of the filter elements 11.

Industrial Applicability

A nuclear reactor with an active zone equipped with horizontal channels in the immediate vicinity of the spacer grids has increased safety in emergency conditions and can be used in nuclear power plants of various types with a liquid coolant.

Claims (3)

1. A nuclear reactor containing an active zone bounded by the upper and lower plates, with vertically installed fuel assemblies in it, consisting of fuel elements fastened with spacer grids, vertical channels made around the circumference of the active zone with the possibility of coolant flowing through them through the upper and lower plates and connected to the active zone by horizontal channels with the possibility of its supply to the active zone, characterized in that each spacer grid adjacent to the vertical channels corresponds to at least one horizontal channel, each of which is installed in close proximity to the spacer grid above or below it . 2. The nuclear reactor according to claim 1, characterized in that one part of the vertical channels is equipped with filter grates in the part passing through the upper plate, and the other part in the part passing through the lower plate, while the characteristic cell size of the living section of the filter grates is equal to to that of spacer grids. 3. The nuclear reactor according to claim 2, characterized in that the horizontal channels connecting the active zone with the vertical channels equipped with a filter grate in the part passing through the upper plate are located above the spacer grids, and the horizontal channels connecting the active zone with the vertical channels, having a filter grate in the part passing through the bottom plate - below the spacer gratings.

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