RU2808006C1 - Pipe protection device - Google Patents

Abstract

FIELD: nuclear power plants.

SUBSTANCE: pipe protection device belongs to the emergency protection systems of nuclear power plants, in particular to the pipe protection devices for the passive filling of the melt trap shaft and can be used in severe accidents leading to the destruction of the reactor vessel. The pipe protection device contains a housing with a drain hole and vertical tubular filter elements mounted on its lower support panel in several rows, secured with their upper ends in the upper support panel. Above the filter elements there is an overflow chamber connected to them, below the filter elements there is a collection chamber, also connected to the filter elements and the outlet pipeline located below it. The cross-section of the hole in the top panel is made smaller than the total cross-section of the internal holes of the filter elements.

EFFECT: increasing the safety of using a pipe protection device by ensuring filtration of the coolant when a solution with a large amount of foreign impurities flows.

4 cl, 3 dwg

Description

Technical field

The technical solution relates to emergency protection systems for nuclear power plants, in particular, to devices for protecting pipes for passive filling of the melt trap shaft and can be used in severe accidents leading to the destruction of the reactor vessel.

Prior Art

One of the technical means of controlling a severe accident is a melt localization device (MLD), which provides reception, placement and cooling of the core melt. In this case, the cooling of the ULR is provided by the coolant passively entering the trap shaft during the process of coolant leakage from the primary circuit. This coolant (water) can carry solid foreign particles from the destruction of thermal and other reactor structures. The presence of such particles in the trap shaft and their deposition on the body of the melt trap reduces the efficiency of its cooling.

Pipe protection devices (PDDs) for passive filling of the ULR shaft must ensure a reduction in the concentration of foreign particles in the coolant supplied for cooling the ULR to acceptable values. UZTs must have high structural strength, since they are located in the zone of possible direct impact of large flying objects that form during an emergency. To protect the UZT, they are placed inside concrete structures, while leaving a minimal opening at the top for the coolant to enter.

The filter elements themselves are located vertically in the UZT housing and are filter pipes, the side surface of which has slots. The problem with using UT is the danger of a large number of foreign particles entering, which can lead to clogging of the filter elements and a sharp drop in the efficiency of the filter elements, which reduces the cooling efficiency of the melt trap body.

Various solutions are known that can be used as a device for protecting pipes for the passive filling of a trap shaft.

There is a known filter module for the pit protection device in the emergency cooling system of a water-cooled nuclear reactor (RF patent for invention No. 2686684, published on April 30, 2019), characterized by the fact that it has filter elements located inside, which are a set of filter pipes.

The closest to the claimed invention is a pipe protection device (RF patent for utility model No. 211181, published on May 24, 2022), containing a housing and vertical tubular filter elements installed on its support panel, equipped with intermediate solid support elements that fasten groups of filter elements and arranged in a checkerboard pattern.

Such pipe protection devices have increased efficiency, but are susceptible to clogging when large volumes of coolant with debris flow.

The objective of the present invention is to develop a pipe protection device that provides filtration of the coolant when a solution with a large amount of foreign impurities flows.

The technical result of the claimed invention is to increase the safety of using the pipe protection device by ensuring filtration of the coolant when a solution with a large amount of foreign impurities flows.

The technical result is achieved by the fact that in the known pipe protection device, containing a housing with a drain hole and vertical tubular filter elements installed on its lower support panel in several rows, fixed with their upper ends in the upper support panel, an overflow chamber connected to them is located above the filter elements , below the filter elements is a collection chamber, also connected to the filter elements and the outlet pipeline located below it, while the cross-section of the hole in the top panel is made smaller than the total cross-section of the internal holes of the filter elements.

It is preferable to ensure that the upper part of the housing is provided with a filter grid.

It is advisable to equip the pipe protection device with a pipeline installed on the top panel and configured to drain the air plug.

It is recommended to make a pipe protection device with a ratio of the cross-sections of the opening in the top panel and the total cross-section of the internal openings of the filter elements of at least five.

Brief description of drawing figures

In fig. Figure 1 shows the principle of operation of the pipe protection device at the initial stage of liquid entry.

In fig. Figure 2 shows the principle of operation of the pipe protection device at the intermediate stage of liquid entry.

In fig. Figure 3 shows the principle of operation of the pipe protection device at the final stage of liquid entry.

The pipe protection device consists of a housing 1, filter elements 2, a lower support panel 3, an upper panel 5 with a hole 6. Below the upper panel 5, with a gap, an intermediate panel 7 is installed, in which the filter elements 2 are fixed. These two panels form the upper overflow chamber 12, which is connected to the internal cavity of the filter elements 2 through holes 8.

The bottom of the housing 1 and the lower support panel 3, in which the filter elements 2 are fixed, form a collection chamber 13, which is connected to the internal cavity of the filter elements 2 through holes 4. In addition, the collection chamber 13 is connected to the pipe 9, through which the purified coolant enters the ULR mine.

To protect the device from flying objects resulting from the rupture of primary circuit pipelines and from trapping foreign objects of significant size, a fence 10 is provided, consisting of racks and a roof.

The air cushion formed inside the device is removed through pipeline 11 installed on the top panel 5.

The total cross-section of all internal holes of the filter elements 4 is no less than five times larger than the cross-section of hole 6 in the preferred embodiment.

The pipe protection device works as follows.

A severe accident, the initial event of which is the rupture of the primary circuit pipeline and the failure of the pumps of the emergency cooling system of the reactor installation, is characterized by the release of the primary coolant, and the flow rate into the leak may exceed 20 m ³ /s. The volume of coolant entering the containment shell is limited by the volume of coolant in the reactor installation (about 380 m ³ ).

This coolant (water) can carry solid foreign particles from the destruction of thermal insulation, nearby pipes or other reactor structures. The presence of such particles in the trap shaft and their deposition on the trap body reduces the efficiency of its cooling.

The time required for intensive coolant flow and complete drying of the reactor installation is tens of seconds. During this time, there is intense movement of the coolant in the premises of the containment shell, which ensures the transportation of foreign particles present in the coolant over a considerable distance, including their entry into the UZT. During this period of operation of the UZT, the coolant must be cleaned by filtration, while foreign impurities accumulate on the filter surfaces.

After the reactor installation is drained, the outflow from the primary circuit stops. The speed of movement of the coolant in the containment drops to almost zero and the impurities contained in it are deposited under the influence of gravity on the floor of the containment. The entry of foreign impurities into the UZT is significantly reduced, and the coolant can be supplied to the ULR shaft via other routes, bypassing the filter surfaces.

The trap shaft must be filled by the time the reactor melt enters the melt trap. The time required to melt the internal elements and the reactor vessel, according to calculations, is at least one hour.

The proposed design of the UZT makes it possible to solve the problem of limiting the entry of debris into the melt trap shaft.

At the initial stage of operation of the UZT (Fig. 1), the coolant with foreign impurities in a limited design volume enters the UZT through hole 6 in the top panel 5 and flows down to the bottom panel 3. Next, the coolant is cleaned on the filter elements 2 and enters the cavity 13 and pipe 9 The filtering surfaces of elements 2 become clogged with foreign impurities.

The operation of the UZT at the intermediate stage is shown in Fig. 2.

At this stage, a layer of foreign impurities 14 is formed on the filter surfaces 2. The coolant level in the UZT increases. Due to the increase in the coolant level inside the UZT, the outlet flow remains constant.

The air present inside the housing, and introduced with a stream of coolant, is removed from the housing through pipeline 11.

The nature of the operation of the UZT does not change until all filter surfaces become clogged with a sufficient layer of accumulated foreign impurities and the coolant level rises to the level of the intermediate panel 7.

The operation of the UT at the final stage is shown in Fig. 3.

By this time, the reactor installation is drained, the coolant movement drops, and foreign impurities settle on the floor of the containment shell. The filtering surfaces of the UZT are clogged with foreign impurities and the coolant level rises to the intermediate panel 7 and, accordingly, to the upper open ends of the filter elements 8, clean coolant flows into the filter elements 2 and then enters the collection chamber 10 and pipe 11.

Thus, the proposed design of the UZT ensures a reduction in the amount of foreign impurities entering the melt trap shaft and an increase in the efficiency of its cooling.

Industrial applicability

The pipe protection device can be used in emergency protection systems of nuclear power plants, in particular, in pipe protection devices for the passive filling of a melt trap shaft, as well as in other areas of technology that use filter elements.

Claims (4)

1. A pipe protection device containing a housing with a drain hole and vertical tubular filter elements installed on its lower support panel in several rows, fixed with their upper ends in the upper support panel, characterized in that above the filter elements there is an overflow chamber connected to them below filter elements - a collection chamber, also connected to the filter elements and the outlet pipeline located below it, while the cross-section of the hole in the top panel is made smaller than the total cross-section of the internal holes of the filter elements. 2. A pipe protection device, characterized in that the upper part of the housing is equipped with a filter grid. 3. Pipe protection device, characterized in that it is additionally equipped with a pipeline installed on the top panel and configured to drain the air plug. 4. A pipe protection device, characterized in that the ratio of the cross-sections of the opening in the top panel and the total cross-section of the internal openings of the filter elements is at least five.