RU2279604C1 - Steam generator for reactor with liquid-metal heat-transfer agent - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: steam generator comprises housing, pipes for supplying water and discharging steam, heat exchange surface made of individual pipe banks mounted in the casing and secured in the pipe plates of supplying and steam collectors and arranged around the central pipe filled with inert gas that receives the supplying pipe. The steam and supplying collectors of the tube bank are mounted in the space filled with inert gas. The space is defined by casings secured to the outer sides of the additional pipe plates connected with the central pipe and interposed between the collectors with a spaced relation to the pipe banks.

EFFECT: enhanced reliability.

2 dwg

Description

The present invention relates to the field of power engineering and can be most effectively applied in nuclear reactors with a liquid metal coolant. The steam generator is designed to generate superheated steam due to heat removal from the liquid metal (for example, sodium) coolant, as well as to cool the reactor installation in normal operating conditions.

Steam generators are known that have various types of heat-exchange surfaces and are used in nuclear power plants with fast neutron reactors (RBN), for example BN-600 (Russia) (see: B.V. Kokorev, V. A. Farafonov. Steam generators of nuclear power plants with liquid metal heat carrier. - M.: Energoatomizdat, 1990).

The problem of this type of steam generator is the appearance of defects in the form of a branched network of cracks in the metal of the tube sheets of the collectors uniting the tube bundle due to high temperature stresses arising in the tube plate, since it is in contact with the liquid metal coolant on the one hand and with the working medium on the other (water vapor).

Also known are a Super Phoenix steam generator (France) and a steam generator (see: US Patent No. 4,307,685 to CL F 22 B 1/06; F 28 F 9/02, publ. 12/29/1981), consisting of a housing with a buffer a container filled with inert gas of at least one tube bundle located inside the housing. The upper and lower ends of the heat exchanger tubes are equipped with thermocompensation bushings for their passage through the side wall of the housing to reduce thermal stresses at the contact point of the heat exchanger tubes with liquid metal. These steam generators are devoid of the aforementioned drawback, since the steam and feed water collectors are removed from the steam generator body and there is no contact with the liquid metal coolant. However, during depressurization of the sleeve at the junction with the heat exchange pipe, liquid metal or products of its interaction with water flow out of the steam generator body, which can lead to serious consequences.

A direct-flow steam generator is known (see British Patent No. 1514831, class F 28 D 7/00, publ. 04/22/1976) liquid metal / water, consisting of a housing with a lid, to which one or more tube bundles are formed, formed of spiral or straight pipes and a supply pipe surrounded by a central gas-filled pipe. Steam collectors are located above the steam generator cover.

In the known steam generator there is no contact with the liquid metal of the tube plates of the steam manifolds. The water supply pipes are located in a cavity filled with an inert gas, which allows protecting their surfaces from contact with a liquid metal coolant, however the tube boards of the supply collectors and the outlet sections of the tube bundle filled with steam are in contact with it, which negatively affects the safety of the steam generator, that leads to:

- the occurrence of high temperature stresses on the tube plate, since on the one hand it is in contact with the liquid metal coolant, and on the other hand, with the working medium (water);

- the occurrence of pulsating temperature stresses in the place of passage of the tube bundle through the boundary of the liquid metal - inert gas due to the variable level of the liquid metal.

According to the largest number of common features and the achieved effect, the UK patent No. 1514831 is taken as a prototype.

The problem to be solved is the exclusion of contact between the liquid metal coolant and the feed and steam collectors, which improves the reliability of the steam generator.

The problem is solved due to the fact that in the steam generator for a reactor with a liquid metal coolant containing a casing, pipes for supplying feed water and steam, a heat exchange surface made of individual tube bundles placed in a casing, fixed in tube boards of steam and feed collectors and formed around a central tube filled with an inert gas, inside of which a supply pipe is located, the steam and feed manifolds of the tube bundle are located in a cavity filled with tnym gas, which is formed by sheaths covering the reservoir, wherein the covers are fixed on the outer surfaces of the additional tube plates connected to the central tube and disposed between the reservoirs with a gap relative to the latter.

The proposed design due to the fact that the steam and supply manifolds of the tube bundle are located in a cavity filled with an inert gas, which acts as a thermal barrier and protects their surfaces from contact with a liquid metal coolant, can significantly reduce temperature stresses in these power units and parts, control them tightness by changing the pressure in the cavity filled with an inert gas, thereby increasing the reliability of the steam generator.

The essence of the proposed steam generator is illustrated by drawings, where:

figure 1 shows a steam generator;

figure 2 shows the remote element A of figure 1.

The steam generator consists of a cylindrical body 1, a partition wall 2, an upper cover 3 with cylindrical nozzles 4 for installing the required number of the same type, standardized heat exchanger tube bundles 5, a supply pipe 6 and a discharge pipe 7 of the liquid metal coolant and the gas cavity 8 of the steam generator body. The heat exchange tube bundle 5 is a vertical cylindrical heat exchanger and consists of heat exchange tubes formed spirally or rectilinearly and located in the casing 9, which is mounted in the upper part to the flange 10, designed for fastening the tube bundle to the nozzles 4 of the cover 3, nutrient 11 and steam 12 collectors with tube plates 13, in which heat exchange tubes, a feed water supply pipe 14 and an annular cavity for removing steam 15 formed by pipes 16 and 17 located between each other are fixed no axis of the tube bundle. On the outside (with respect to the flange 10) side of the tube bundle there is a feed water supply pipe 18 and a superheated steam pipe 19 from the annular cavity 15. Also, the heat exchange tube bundle 5 includes a gas separation cavity 20 filled with an inert gas. The gas cavity is formed by covers 21 and 22, which are hermetically connected to additional tube plates 23, which in turn are connected to a central pipe 24, around which a tube bundle is formed and inside which a feed water supply pipe 12 passes. Cover 21 in the upper part is hermetically connected to flange 10. The upper part of the gas cavity 20 ends with a fitting 25, to which a pulse line is connected to fix the pressure change in the gas separation cavity of the tube bundle.

The steam generator operates as follows. The liquid metal coolant from the inlet pipe 6 enters the annular cavity between the casing of the steam generator 1 and the dividing wall 2. Next, the coolant rises up under the cover of the casing 3 and is distributed through the cavity between the tube bundles and through holes in the casings 9 enters the heat exchange surface. Next, the coolant passes through the annular space of the heat exchange surface of the tube bundles 5, transferring heat to the working medium (water-steam), enters from them, turns around and enters the annular cavity and from it into the branch pipe 7.

Feed water from the pipe 18 through the pipe 14 is lowered into the lower part of the tube bundle at the entrance to the feed collector 11. From the feed collector, water enters the heat exchange pipes, rises, is heated to boiling point, evaporates and enters the steam collector 12 as superheated steam. From it enters the annular cavity 15, rises up and then through the pipe 19 to the consumer.

Due to the fact that the pipes 14 and 16, the collector 11 and 12 with the tube plates 13, and the nodes for welding the heat exchange pipes to them do not come into contact with liquid metal, since they are in the separation gas cavity 20, which plays the role of a protective and heat shield formed by covers 21 and 22, additional tube boards 23, the Central tube 24 and the pipe 17, the temperature stresses in them are significantly reduced. In addition, it is possible to control their tightness by changing the pressure in the separation gas cavity, the pressure in which exceeds the pressure in the gas cavity of the steam generator body.

As the operating experience of the BN-600 steam generator has shown, pipe boards with weld units for heat-exchange pipes are the determining components that affect the reliability and safety of the steam generator.

The proposed design due to the location of the steam and feed manifolds of the tube bundle and the annular section of the steam outlet in the cavity filled with inert gas, can significantly reduce the temperature stresses in these power units and parts, thereby increasing the reliability of the steam generator. In addition, this design does not allow contact of the working medium (water-steam) with liquid metal, such as sodium, during their depressurization, which increases the reliability of the entire installation as a whole. It is also possible to monitor the tightness of the steam and supply manifolds of the tube bundle and the annular section of the steam outlet by changing the pressure in the gas cavity, which reduces the time of detection of a defect in them and, accordingly, the time of localization of the leak and, therefore, increases the installed capacity utilization factor (KIUM) The most important economic indicator of a nuclear installation.

Claims (1)

A steam generator for a reactor with a liquid metal coolant, comprising a housing, pipes for supplying feed water and steam, a heat exchange surface made of separate tube bundles placed in a casing, mounted in tube boards of steam and feed collectors and formed around a central pipe filled with an inert gas inside which is the inlet pipe, characterized in that the steam and feed manifolds of the tube bundle are located in the cavity filled with an inert gas formed by rubbish covering the collectors and mounted on the outer surfaces of the additional tube plates connected to the Central pipe and located between the collectors with a gap relative to the latter.

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