RU2093909C1 - Nuclear power plant - Google Patents

Abstract

FIELD: nuclear power engineering; power plants with light-water tank reactors. SUBSTANCE: power plant has containment 1, reactor room 2 with crane 3, concrete shell 4, equipment room 5, reactor cavity 7, handling cavity 9, integral light-water tank reactor with cover 11, horizontal pumps 13 mounted in separate rooms 20 which are below cooling pond 5, inspection cavities, as well as tubings of primary and secondary heat exchangers below room holding connections 14, 15 and tubings 17. EFFECT: improved design. 3 cl, 2 dwg

Description

 The invention relates to the field of nuclear engineering, in particular to nuclear power plants (NPPs) with a light-body reactor.

 The safety of nuclear power plants is ensured, inter alia, by the design of the primary circuit and special safety systems designed to prevent accidents and limit their consequences.

 There are three types of structural design of the primary circuit, three types of layout of equipment and pipelines of the primary circuit: loop, block, integral.

 The loop arrangement is used in existing nuclear power plants with light-water reactor vessels. The main feature of this arrangement is the presence of large-diameter circulation pipelines between the main equipment of the primary circuit (reactor, heat exchangers of the first or second circuit, pumps).

 The maximum possible accident of a nuclear power plant with a loop layout is a rupture of a large diameter circulation pipeline with a full cross section with two-sided flow of the primary coolant.

 The block layout has not found application in existing nuclear power plants with light-water reactor vessels. It is used in low-power transport nuclear power plants. The main feature of this arrangement is the absence of large-diameter circulation pipelines. Small-sized cases of equipment of the primary circuit (reactor, heat exchangers of the first or second circuit, pumps) are interconnected by short nozzles cut from the base metal.

 The integrated layout allows you to combine in one housing the core, drives CPS, heat exchangers of the first or second circuit, pumps, volume compensator. The integrated arrangement renders unnecessary the circulation pipes of the primary circuit of large diameter. The integrated arrangement improves safety by limiting the possible size of the leakage hole in the primary circuit system in the event of a maximum accident. The size of the hole cannot exceed the cross section of a pipe with a diameter of 50.70 mm, which is about 200 times smaller than that of existing nuclear power plants with light-water reactor bodies. The integrated arrangement allows to reduce the level of dose loads for personnel, as well as the level of risk associated with embrittlement of the reactor vessel under the influence of neutron radiation.

 These features of the integrated layout simplify decommissioning operations after the end of their service life.

 Special safety systems control accidents by performing the following functions: installing a reactor, removing residual heat and limiting the spread of radioactive products. Distinguish between protective, localizing, controlling and providing security systems. The normal state of the security system is the standby mode of the accident, and the main requirement for them is guaranteed operation and ensuring the design characteristics during operation. In this regard, to increase their reliability, it is advisable to use passive devices and natural processes in them. The passive principle of operation of a system and device is one in which the performance of a given function does not require the operation of other systems and devices. Passive systems operate under the influence of influences directly arising from any initial event. As a rule, such systems are characterized by higher reliability compared to active ones, and therefore the principle of a single failure is usually applied only to active systems and devices. Passive safety devices include, for example, nuclear power plant containment shells related to localizing safety systems.

In the General case, the functioning of the protective shell is ensured by the action of various subsystems [1] while their main tasks are
withstand the increased pressure that occurs inside the protective shell when the primary coolant is lost;
in cooperation with cooling systems, to prevent an increase in pressure inside the shell over design limits with its subsequent decrease;
limit the release of radionuclides into the environment;
protect the installation from external influences;
prevent the occurrence of explosive concentrations of hydrogen.

Most of the current operating nuclear power plants with light-water reactor vessels are equipped with protective shells that meet the specified requirements. As a rule, they are made of prestressed reinforced concrete, have the shape of a cylinder with an elliptical (spherical) cover. The internal dimensions of these protective shells make it possible to place a reactor hall with a crane inside them, a concrete array with a fuel storage pool, rooms, reactor shafts, revision and transportation, a reactor, primary circuit equipment and pipelines, equipment and pipelines of other special safety systems [2]
There are other designs of containment shells that are used on existing foreign nuclear power plants with single-loop reactor boiling reactors (see, for example, [3]). The containment consists of two parts. One is placed inside the concrete mass of prestressed concrete; it houses the reactor, pumps and some special safety systems. The other consists of rooms inside the concrete mass, pipelines and cylinders located in the building, and is designed to reduce pressure in the event of an accident with the outflow of the primary coolant. The fuel storage pool, premises, revision and transportation shafts, the reactor hall with a crane are located outside the containment in a building made of ordinary reinforced concrete. The building and reinforced concrete slabs covering the reactor shaft and the exposure pool are designed to protect the nuclear power plant from external influences.

 For the newly developed nuclear power plant with an integrated SiR light-water reactor with an integrated vessel to improve economic performance, the possibility of using the protective shell design indicated above was considered.

 However, the condition for the use of the specified design of the protective shell for a nuclear power plant with a light-water reactor is to solve the problem of an accident with core melting.

 This new task of containment was added after the Chernobyl accident.

 In addition, the specified design of the containment does not solve the important problem of an accident during fuel overload in the reactor shaft or in the holding pool.

 An example that allows solving the problem of an accident with core melting can be developed by a nuclear power plant with a light-water reactor AR-600 (see, for example, [4]). The protective shell of the AR-600 is double. The outer shell of prestressed concrete protects against external influences. The inner metal shell withstands the increased pressure that occurs inside the shell when the primary coolant is lost and the core melts, limits the release of radionuclides to the environment, and gives off residual heat to the air naturally circulating between the shells. The reactor and the active zone are located in the lower part of the shell and, in the event of this accident, are filled with water stored inside the shell.

 The task of improving the safety of nuclear power plants with light-water reactor bodies is being solved simultaneously with the task of increasing the efficiency of plants. The task of increasing efficiency can be solved by reducing the size of nuclear power plants, simplifying and accelerating the repair and replacement of equipment.

 A nuclear power plant is known, including a protective shell, a hall with a crane, a concrete massif with a fuel holding pool, a room, a reactor shaft, revision and transportation, a light-water tank reactor, equipment and pipelines (see, for example, [2]).

 The loop layout of the first circuit allows compactly filling the concrete mass below the reactor hall, ensuring the minimum diameter of the containment. The most unreliable equipment of the first circuit of the said nuclear power plant - each pump is placed in a separate room, is serviced by a reactor hall crane.

 Repair and replacement of each pump are carried out independently and in parallel with other works, thereby simplifying, reducing the time to complete these works.

 However, the presence of circulating pipelines of the first large-diameter loop limits the safety of this nuclear power plant.

 A nuclear power plant is known, including a protective shell, a hall with a crane, a concrete massif with a fuel holding pool, rooms, reactor shafts, revisions and transportation, a light-water reactor, equipment and pipelines, a device for transporting pumps (see, for example, [4]).

 The installation is more secure by reducing the number of circulation pipelines of the primary circuit and combining two pumps and one steam generator into a single unit of primary equipment.

The loop layout, the reduction in the number of loops and equipment of the primary circuit of this nuclear power plant can reduce its volume compared with the volume of existing nuclear power plants with light-body reactor reactors of the same power by 30%
On each steam generator, two sealed pumps are installed below. Repair and replacement of pumps are carried out using a reactor hall crane and transportation devices (hoisting, tilting). The lower placement of the pumps complicates and lengthens the work on their repair and replacement.

 The presence of circulating pipelines of the first circuit of large diameter limits the safety of this nuclear power plant.

 A nuclear power plant is known, including a containment, a hall with a crane, a concrete massif with a fuel storage pool, rooms, reactor shafts, revisions and transportation, a light-body integrated reactor with first-second circuit heat exchangers and horizontal pumps, the pipes of which are located above the core, piping piping heat exchangers of the first or second circuits, a device for transporting pumps (see, for example, [5]).

 Horizontal pumps, pipes and piping piping heat exchangers of the first or second circuit are located in a common room in the middle of the reactor shaft.

 The diameter of the common room allows repair and replacement of pumps, as well as installation (dismantling) of piping piping heat exchangers of the first or second circuit during their repair and replacement.

 The diameter of the common room is greater, the larger the size of the pump. That is, the greater the power of the reactor, the larger the size of the pump, the larger the disassembly of the pump, the larger the diameter of the common room. Above the common room, the diameter of the reactor shaft is determined by the dimensions of the reactor lid, below - the diameter of the reactor vessel.

 Behind the wall of the common room in the nuclear power plant is a fuel holding pool. This is done to reduce the size of the nuclear power plant. The fuel holding pool is connected to the reactor shaft (above the reactor cover) with a channel filled with water for transporting fuel assemblies under a layer of water during fuel overload.

 In addition to the fuel holding pool, in the concrete array around the reactor shaft there are inspection, transportation, equipment, and other mines.

 Thus, the larger the diameter of the common room, the larger the size of the concrete mass, the larger the size of the nuclear power plant, and, consequently, the lower its efficiency.

 For the installation (dismantling) of pumps, a special transportation device is required, which is located in the same common room and, therefore, interferes with the work with pipes and piping piping heat exchangers of the first or second circuits, complicates the organization of parallel work, complicates and lengthens the repair and replacement work the specified components of the reactor.

 The task to which the invention is directed is to reduce the size, as well as simplify and speed up the repair and replacement of pumps and heat exchangers of the first or second circuit and, consequently, increase efficiency while maintaining a high level of safety of a nuclear power plant with a light-weight integrated reactor.

 To solve this problem, a nuclear power plant, including a containment, a hall with a crane, a concrete array with a fuel storage pool, equipment rooms, reactor shafts, revision and transportation, a light-weight integrated reactor with heat exchangers of the first and second circuits, horizontal pumps, nozzles located above the core, piping piping heat exchangers of the first or second circuits, a pump transportation device, equipped with separate rooms for each pump, connecting the reactor shaft and the common peripheral room and located below the fuel storage pool, revision shafts, and also below the room in the reactor shaft with pipes and piping pipelines, while separate and common peripheral rooms are equipped with guides for transporting pumps, at the junction of separate and common The peripheral premises are rounded.

The set of restrictive essential features of the claimed invention is proposed in the following wording:
"A nuclear power plant, including a containment, a hall with a crane, a concrete array with a fuel storage pool, equipment rooms, reactor shafts, revisions and transportation, a light-body integrated water reactor with heat exchangers of the first or second circuit, horizontal pumps, pipes located above the core, piping piping specified heat exchangers, a device for transporting pumps. "

 The specified set of essential features of the prototype is not proposed by chance. It is the integrated layout of the primary circuit that makes it possible to increase the safety of the next generation of nuclear power plants with light-water reactor vessels. At the same time, the nozzles of the pumps and heat exchangers of the first or second circuits are located above the active zone, which simplifies the conservation of the active zone under the bay at the maximum possible accident (rupture of the primary circuit or reactor pipe).

 Due to the fact that the equipment of the entire primary circuit is assembled in one building, the tasks of simplifying and speeding up the repair and replacement of this equipment, organizing independent and parallel work, allocating the corresponding rooms and devices, and placing them in the protective shell of the nuclear power plant are gaining great importance.

 When repairing and replacing components of a reactor, it is necessary to use the reactor hall crane to the maximum extent possible.

 The current requirement for the consideration of a postulated accident with core melting, the requirement to protect the holding pool and the process of refueling fuel from external influences can be solved with a protective shell. The protective sheath can be double if necessary. It is impossible to solve the problem using only the set of essential features of the prototype specified in the restrictive part of the claims.

 To solve this problem, the set of essential features indicated in the restrictive part of the claims should be supplemented with the following set of distinctive features, namely, equipped with separate rooms for each pump connecting the reactor shaft and the common peripheral room, which are located below the fuel holding pool, revision shafts, and also below the room in the reactor shaft with pipes and piping piping; separate and common peripheral rooms are connected by guides for the pump transportation device; at the junction of the individual and the general peripheral premises, fillets are made.

As a result, the presented set of restrictive and distinctive essential features of the invention has an inventive step and allows
to provide independent and parallel repair and replacement of pumps, these most unreliable installation elements;
to provide independent and parallel repair of pumps and heat exchangers of the first and second circuits;
reduce the diameter of the room in the middle part of the reactor shaft with pipes and piping piping and place a fuel holding pool closer to the axis of the reactor shaft.

 In FIG. 1 shows a longitudinal section of the proposed nuclear power plant; in FIG. 2 is a section AA in FIG. one.

 The proposed nuclear power plant is arranged as follows: inside the containment shell 1 there is a reactor hall 2 with a crane 3, a concrete array 4, a fuel holding pool 5, equipment rooms 6, a reactor shaft 7, a revision shaft 8, a transport shaft 9, a light-water integrated reactor 10 with a cover 11, heat exchangers 12 of the first and second circuits, horizontal pumps 13, nozzles 14 of the pumps and pipes 15 of the heat exchangers of the first and second circuits located above the core 16, pipelines 17 of the piping of the heat exchangers of the first and second circuits, a device 18 with guides 19 for transporting the pump, separate for each pump rooms 20, a common peripheral room 21, rounding 22.

 Repair and replacement of pumps 13 is as follows. The reactor 10 stops and cools, the surfaces of the primary circuit are decontaminated, the cover 11 is removed, it is installed in the revision shaft 8, the core 16 is completely unloaded, the primary coolant is drained to a level below the pump nozzles 14. Then the pump 13 is dismantled, immersed on the devices 18 and transported along the guides 19 first to the intersection of the separate 20 and the common peripheral 21 rooms to the transport shaft 9. Next, the pump 13 is transported by a crane 3 to the reactor hall 2 and outside the nuclear power plant shell 1 by a known solution.

 The sizes of the individual 20 and the general peripheral 21 premises, as well as the fillets 22 are selected from the conditions of the possibility of carrying out these works.

 The new pump 13 is installed in the reverse order.

 Repair (search and suppression of current pipes, sections, etc.) of heat exchangers 12 of the first or second circuit is carried out as follows: reactor 10 is stopped and dampened, surfaces of the primary circuit are decontaminated, reactor cover 11 is removed, it is installed in revision shaft 8, drainage the primary coolant to a level below the nozzles 15 of the heat exchangers of the first or second circuits, opening the nozzles 15, and then searching and killing the current pipes, sections, etc. by a known decision.

 The heat exchangers 12 of the first and second circuits are replaced as follows: the reactor 10 is stopped and cools, the surfaces of the primary circuit are decontaminated, the reactor cover 11 is removed, it is installed in the inspection shaft 8, the core is unloaded 16, the primary coolant is drained to a level below the heat exchanger pipes 15 12 of the first and second circuits, opening the nozzles 15, a segment of heat exchangers 12, dismantling them from the reactor 10 using a crane 3 of the reactor hall 2.

 The diameter of the room in the middle part of the shaft 7 of the reactor, where the nozzles 15 and piping piping 17 heat exchangers of the first or second circuits are located, is selected from the condition of the possibility of carrying out these works.

 Separate rooms 20 provide independent and parallel repair and replacement of pumps.

 The room in the middle part of the shaft of the reactor 7 for work with nozzles 15 and piping 17 piping heat exchangers of the first or second circuits and separate rooms 20 of the pumps provide independent and parallel repair of pumps 13 and heat exchangers 12 of the first or second circuits.

 The placement of the pumps 13 in separate rooms 20, connecting the reactor shaft 7 and the common peripheral room 21 below the fuel storage pool 5 and revision shafts 8, allows to reduce the diameter of the room in the middle part of the reactor shaft 7 for pipes 15 and piping 17, placed closer to the shaft axis 7 reactor pool 5 fuel exposure, reduce the diameter of the concrete mass 4 and the protective shell 1.

 Thus, the present invention allows to reduce the size, simplify and speed up the repair and replacement of pumps and heat exchangers of the first or second circuits, and therefore, increase the efficiency of nuclear power plants with a light-weight integrated reactor with the same level of safety.

Claims (3)

 1. A nuclear power plant containing a containment, a hall with a crane, a concrete array with a fuel storage pool, equipment rooms, reactor shafts, revision and transportation, a light-body integrated reactor with heat exchangers of the first second circuit, horizontal pumps, pipes located above the core pipelines piping heat exchangers of the first second circuits, a pump transportation device, characterized in that it is equipped with separate for each pump room and connecting the shaft reactor and total peripheral space, and which are arranged below the fuel pool, the audit mines, as well as space in the reactor shaft with pipes and conduits of the heat exchanger of the first strapping second circuits.  2. Installation according to claim 1, characterized in that the separate and common peripheral rooms are provided with guides for the pump transportation device.  3. Installation according to claims 1 and 2, characterized in that at the junction points of the individual and the common peripheral rooms, fillets are made.

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