RU33827U1 - Nuclear reactor vessel - Google Patents

Abstract

A nuclear reactor vessel made in the form of a welded structure consisting of a shell of a branch pipe zone, a shell of a core and a bottom, characterized in that all structural elements are made of titanium-based alloy with welding for homogeneous materials in relation to the elements attached to the body.

Description

The utility model relates to nuclear engineering, in particular, to the structural elements of high pressure tanks, and can be used for the manufacture of the body of a nuclear power reactor of water-water type (WWER) for nuclear power plants, mobile nuclear power plants.

The utility model can also find application in the creation of low-power vessel reactors with a water coolant for transport (ship) power plants. The prerequisites for this are the small dimensions of power plants, their simplicity and reliability, as well as extensive operational experience.

The relevance of the utility model consists in maintainability and the possibility of disposal of the reactor vessels of the water-water type of stationary and transport nuclear power plants that have worked out their life.

The VVER design, in which water serves both as a moderator and a coolant, is a case variant, when the entire active zone is placed in a single, robust case, designed for a pressure of 10.0 - 20.0 MPa, excluding volumetric boiling of water at energetically acceptable values its temperature (270-320 ° C).

The casing is one of the most important and critical elements of the VVER design. Its dimensions and physicomechanical properties of materials affect the reactor power, the main parameters of the primary coolant (temperature and pressure), provide the possibility of reliable operation of the reactor installation and nuclear power plant as a whole for a long period (30-40 years). The sealed volume created by the hull and the lid, together with other equipment of the primary circuit, is, in addition, an essential element of the radiation safety of the environment, and when used for marine power plants, an element of ensuring the radiation safety of the crew.

During operation, the VVER case is constantly located in the neutron radiation field of the core, which leads to the degradation of the physicomechanical properties of the metal of which the case is made. The housing is subjected to periodically varying loads associated with fluctuations in the temperature and pressure of the coolant during normal operation, scheduled stops for refueling and the like.

It should also be borne in mind that only limited, periodic (during reactor shutdowns) monitoring of the current state of the vessel, especially its inner surface, is practically possible. A huge obstacle to performing routine monitoring and disposal after the end of its service life is the high level of induced activity of the material of the reactor vessels and, especially, austenitic

anticorrosive surfacing. Due to these reasons to the material

the housing and its design are subject to much more stringent requirements compared to pressure vessels used in other areas of technology.

According to the conditions of factory manufacturing and operation, the body material must have high strength, be radiation- and corrosion-resistant, ductile, and technological in welding.

Corrosion resistance is ensured by surfacing of austenitic stainless steel. In the practice of domestic reactor engineering, the steel used for the manufacture of the vessel is: 15X2EOMFA-A, 15X2V2FA-A (see Technical Specifications TU 108.765-78 “Billets from steel of the grades 15X2NMFA and 15X2EQVIOA-A for the hulls and covers and other components of the reactor plants, sheet 6, table 6. . 2, registered in Gosstandart 08/01/1978 under No. 1855521).

These materials have sufficient radiation resistance, are well welded and, with the appropriate selection of the water regime, are corrosion resistant.

However, the main drawback of these steels is the high activatability in the neutron radiation field due to nuclear reactions to Fe, Ni, Mo, Co, Cu, Nb and other elements with the formation of long-lived radioactive isotopes that are a source of hard γ-radiation. This makes repair work extremely difficult, creates

Intractable problems in the disposal and disposal of bulky equipment that has expired.

A well-known nuclear reactor vessel with a water coolant made of structural material and an inner protective layer in the form of a nickel-phosphorus coating (see USSR author's certificate No. 880146 of 06/18/1980, IPC G21C13 / 08, Chabak A.F., publication date 06/20/1999).

The implementation of the nuclear reactor vessel with a protective layer of Nickel-phosphorus coating increases the operational reliability of the vessel by increasing its corrosion resistance.

However, the main disadvantage of the nickel-phosphorus coating is its high activability in the neutron radiation field with the formation of long-lived isotopes and radionuclides with high y-radiation energy. This, in turn, increases the radiation hazard and dose loads on maintenance personnel during the repair and dismantling of spent reactor equipment.

The closest in technical essence and the achieved result to the claimed solution is a nuclear reactor vessel, consisting of nozzle zone shells, core and bottom shells connected by welding (see Balandin Yu.F. et al., "Construction materials of nuclear power plants, - M .: Energoatomizdat, 1984, p. 137).

surfacing. The specified steel has high mechanical properties in the initial state.

However, as a result of neutron irradiation, steel of this brand has a high level of induced radioactivity and a low decline after neutron exposure, and due to the accumulation of radiation damage, it has a reduced level of mechanical properties.

An analysis of known analogues shows that they all have common shortcomings: the high activability of iron-based structural materials used for the manufacture of nuclear reactor vessels in the field of neutron irradiation, as well as a low decrease in induced activity. This makes it difficult to extend the life of the equipment and requires significant costs for the disposal of equipment after the end of its life.

The technical task of the utility model is to create a monoblock nuclear reactor vessel from a low-activated structural material in which the active zone, supporting structures of control rods, and a steam generator are located, the main elements of which are made of titanium alloys.

The solution of this problem ensures the achievement of a new technical result, consisting in the rejection of the use of highly activated anticorrosive surfacing on the reactor vessel, the exclusion of the brazed joints of the titanium pipe system of the steam generator with the elements of the steel vessel. All this will ensure the cleanliness of the primary circuit of the power unit from corrosion products Fe, Cr, Ni.H, and, therefore, increase the decline rate

induced activity 5-6 times to a subtle value of 10 Br / kg

The technical result indicated is achieved by the fact that in a nuclear reactor vessel made in the form of a pork structure consisting of a shell of a pipe zone, a core of an active zone and a bottom, according to a utility model, all structural elements are made of an alloy based on titanium using h; materials in relation to the elements connected to the housing.

The presence of distinctive PrEcDeacs, namely, the performance of elements of a pork structure made of an alloy based on titanium., As well as the welding for homogeneous materials in the presence of connected joints, indicates the conformity of the claimed technical solution with the patentability criterion of “novelty.

In FIG. 1 shows a nuclear reactor vessel, a longitudinal section (image of a reactor vessel) and shown schematically, conditionally), in FIG. Figure 2 shows a graph of the decay of titanium-based sidava activity after neutron flux irradiation.

The nuclear reactor shell is surrounded by a pipe of zone 1, the ring of the core 2 and bottom 3. The nuclear reactor is made in the form of a vertical reactor with an elliptical Д1шш 3. The cylindrical part of the vessel consists of a continuous shell 2. Further up is the zone of pipes 1. Entrance and exit the coolant is located above the active zone, which allows to increase the size of the core of the active zone 2

more durable, without pipes and openings. With the aim of the bottom 3 of the reactor vessel is made elliptical, stamped, without welds.

The reactor vessel contains a minimum number of welds in accordance with the stick out technology and the calculation of the mass-dimensional characteristics of the ingots for the manufacture of the structure.

To the inner surface of the upper part of the nozzle zone 1, a ring that serves as a support for the reactor internals (not shown in the drawing). The upper part of the body is made in the form of a solid forged flange with holes for studs, on which: the body cover is attached. The housing cover is also made of titanium-based alloy.

The low power reactor vessel shown in FIG. 1 has an inner diameter of dvn. 1445mm., Diameter Dnars. 1645 mm, the height of the casing with the bottom 3 is 3362 mm, the weight of the shell of the pipe zone 1 is 11.5 tons, the weight of the shell of the active zone 2 is 8.5 tons.

After the manufacture of the elements, the designers bring them to mechanical processing with the preparation of iqpoMOK under. Then, pork annular seams are made for the mold; a. Then they weld the edements of the reactor attached to the vessel. Then, machining is carried out according to the inner and outer diameter of the housing to the desired dimensions. In conclusion, mounting special equipment and testing for internal pressure. The manufacture of this utility model in an industrial way is not

causes difficulties, involves the use of developed materials and standard equipment, which indicates the compliance of the proposed technical solution with the patentability criterion of "industrial applicability.

The aforementioned analogue of the nuclear reactor vessel made of steel grade 15Kh2MFA for calculating the decrease in activity after irradiation under conditions typical of a VVER-1000 reactor at a fluence of N / cm is significantly inferior to the titanium-based alloy after holding for more than 10 years (see Fig. 2).

A characteristic feature of the titanium-based alloy is the presence of a long incubation period of radiation resistance. Significant changes in the mechanical properties of a titanium-based alloy as a result of neutron irradiation at a temperature of 250 ° C begin after fluence N / cm

Due to the preservation of high plasticity after neutron irradiation, its low rate of decrease from neutron fluence and the absence of brittle fracture, a titanium-based alloy is applicable as a material for a low-power nuclear reactor vessel for stationary and marine nuclear power plants.

The use of an alloy based on titanium as a structural material as a body of a nuclear reactor allows:

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- abandon highly activated anticorrosive surfacing on the inside of the reactor vessel, subject to brittle fracture;

-exclude bimetallic adapters from the titanium pipe system of the steam generator to the elements of the body, if it is made of steel specified in analogues;

-to solve the problem of clogging with corrosion products of water purification filters of the primary circuit of an energy reactor;

-to ensure maintainability of the reactor vessel, including the replacement of structural elements.

The execution of the reactor vessel from an alloy based on titanium will ensure the environmental safety of the nuclear power plant and solve the problem of the disposal of radioactive waste and reduce radioactive pollution to the requirements of international norms and standards.

Claims (1)

The nuclear reactor vessel, made in the form of a welded structure, consisting of a shell of the pipe zone, the shell of the active zone and the bottom, characterized in that all structural elements are made of titanium-based alloy with welding for homogeneous materials in relation to the elements attached to the body.