RU2072571C1 - Device which removes heat from power production circuit - Google Patents

Abstract

FIELD: electric engineering, nuclear power plants and other objects which require natural ventilation. SUBSTANCE: device has ring-shaped collector which is mounted in coaxial to protection shield and shaped as cylinder with sphere cap. Lower part of collector has input holes, upper part has output holes which are connected to input ones through pieces of drafting columns in which air heat exchange units are located. They are connected to power supply circuit. Drafting columns are bent to follow cap shape. Their output areas have at least one deflector. EFFECT: increased reliability. 3 dwg

Description

 The invention relates to energy and can be used at nuclear power plants and other facilities where it is required to provide constant and reliable natural ventilation of the room, not responding to changes in wind direction.

 A device for removing residual heat from a high-temperature gas-cooled reactor (German patent DE 32 28 422 A1, CL G 21 C 15/18, 1984).

 The diagram of the device for removing heat from the energy circuit according to the specified patent consists of auxiliary heat exchangers integrated with the reactor in a common housing. The heat exchangers are connected via pipelines to external heat exchangers located in the lower part of the traction shafts. Traction shafts are partially integrated into the reactor containment shell and are evenly spaced around the shell circumference. Air inlets to each traction shaft are independent of each other. External heat exchangers are located above the heat exchangers so that it is possible to organize the movement of the coolant in the heat exchangers due to natural circulation, i.e. leveling pressure. At the exit of the traction shafts there are gates with which you can regulate the air flow.

 During normal operation of the energy circuit, the pipelines are closed by valves and the heat exchangers are cut off from the heat exchangers and are in standby mode.

 In emergency mode, after shutting down the reactor, heat continues to be generated in it, which must be removed from the energy circuit. In this case, valves, gates open, and the heat removal system comes into operation. Water in the heat exchanger is heated and evaporates, the steam through the upper pipe enters the external heat exchanger, there it transfers heat to the outside air and condenses. Condensate is drained through the bottom pipe into internal heat exchangers. Hot air through traction shafts goes into the atmosphere, thereby removing heat from the reactor.

 One of the drawbacks of the heat removal system under consideration is the unreliability of its operation with the complete loss of all external energy sources and wind exposure. In this case, the heat sink power of the device depends on the direction and speed of the wind. The protective shell in the area of the entrances to the traction shafts is a cylinder. As you know, with a transverse flow around the cylinder air flow around its circumference creates an uneven field of static pressure. The maximum value on the frontal part, the minimum in the zone of highest speed.

 Presented in FIG. 1-3 indicatrixes characterize the pressure field around a single cylinder streamlined by air flow for two air flow velocities Vв. 0.0 m / s, i.e. in the absence of wind, and Vc. 7.0 m / s at an undisturbed flow pressure of 1 bar. It can be seen that the pressure in the frontal part of the cylinder increases by 30 Pa, and in the aft and side zones decreases by 20 and 70 Pa, respectively. The pressure difference between the frontal and lateral points is 100 Pa, which is comparable to the temperature leveling pressure in the traction shaft.

 With an increase in wind speed, these differences will increase. The speed of the wind flowing around the protective shell of a nuclear power plant in an extreme case can reach 100 m / s.

 The inlet openings of the traction shafts of the heat removal system in the FRG invention under consideration are located around the circumference of the cylindrical containment and, obviously, the pressure at the entrances to the traction shafts will be different.

 The outlet openings of the shafts are below the upper point of the reactor containment. In the case of wind, the conditions for the flow around the outlet openings will be different than the conditions for the flow around the inlets, so the pressure field at the outlet of the air flow will differ from the pressure field at the inlet. When the wind rises in height of the traction shafts, a pressure differential occurs, in some shafts it is opposite in direction to the leveling pressure. As a result, the heat exchangers located in these mines will operate with reduced heat output.

 Thus, it is obvious that the heat dissipation system presented in this patent when all energy sources are lost can only work reliably in the absence of wind or in light winds.

 A device is known (French patent N 25 84228 from 01.07.85, class G 21 C 15/18, F 28 B 1/60), which is adopted as a prototype.

 In the device for removing heat from a three-loop energy circuit with a water-water reactor, the main elements are air capacitors located in three shafts located around the circumference of the containment. In this case, there are no special built-in heat exchangers and air condensers directly connected by pipelines to steam generators.

 Condensers are located above the steam generators, which allows you to organize the natural circulation of the coolant between the steam generators and condensers.

 Traction shafts have inlet openings at the bottom, and gates are located in the upper part, which allow controlling the flow of heated air. Mine inlets are independent of each other.

 The heat removal device operates similarly to the device described above.

 When the energy circuit is operating in nominal mode, the air condensers are disconnected from the steam generator and are in standby mode.

 In emergency mode, the valves on the pipelines open and the steam from the steam generator flows through the pipeline to air condensers, where it condenses and flows through the pipeline again to the steam generator. The air in the mine heats up and creates leveling traction.

 This system is also not exposed to wind. Changing the direction and speed of the wind will change the pressure in the mine and thereby change the heat removal capacity from air condensers, depending on its location on the containment.

 From the foregoing it is clear that for reliable operation of the heat removal system it is necessary to ensure the same conditions at the entrance to the air condensers and the exit from the traction shafts, regardless of the direction and speed of the wind.

 Thus, heat removal devices from the energy circuit are widely known, comprising air-cooled heat exchangers connected to a heat source through steam lines, and condensate exchanger outputs are connected by pipelines to a heat source. Heat exchangers are installed in traction shafts located around the perimeter of the containment, and at a height at which the hydrostatic pressure difference is greater than the hydrodynamic losses. Traction shafts organize the flow of cooling air due to the temperature leveling difference.

 The disadvantage of such devices is the dependence of the efficiency of heat removal from air heat exchangers on the direction and speed of the wind.

 The objective of the invention is to increase the reliability and efficiency of heat removal from the energy circuit of nuclear power plants during emergency operation, regardless of wind direction and speed.

 The objective is achieved in that in the device for removing heat from the energy circuit, containing installed around the perimeter of the protective shell, made in the form of a cylinder with a sphere-shaped dome, traction shafts with inlet and outlet sections and air heat exchangers connected to the energy circuit, new is that it equipped with an annular collector concentrically mounted on the shell, in the lower part of which intake openings are made, and in the upper part outlet openings that are in communication with the inlet sections of traction shafts, while the latter are symmetrically bent along the contour of the dome and a deflector and / or deflectors are installed at their output sections.

 The essential features for this device is that it is equipped with an annular collector, with the help of which a constant uniform air draft in the mines is provided, independent of changes in the direction and speed of the wind, since the pressure of the wind is equalized in the cavity of the collector in communication with the inlet sections of the traction mines fields.

 The presence of deflectors allows you to increase the speed of pressure equalization in the manifold and increase the rate of suction of heated air.

 In FIG. 1 shows a containment with traction shafts, a longitudinal section; in FIG. 2 protective shell, top view; in FIG. 3 pressure indicatrices in the manifold and deflector when blowing the protective shell model at a scale of 1: 200 with an air flow at a speed of 10 38 m / s.

 The heat removal device from the energy circuit contains air-cooled heat exchangers 1 located in the traction shafts 2, which are located around the perimeter of the protective shell 3, made in the shape of a cylinder with a sphere-shaped dome.

 Heat exchangers 1 are connected via steam lines 4 to heat sources 5, the condensate output of heat exchangers 1 is connected by pipelines 6 to heat sources 5.

 At the entrance to the traction shafts 2 and after the heat exchangers 1, sliders 7 are installed, the opening of which ensures the inclusion of the device in operation. The gates 7 can perform the function of regulating the power of the heat removal device.

 In the energy circuit as a heat source 5, a steam generator is used, which is connected by pipelines to the reactor 8.

 Along the perimeter of the protective shell 3 when blowing it with the wind creates an uneven pressure field. This unevenness changes the pressure drops along the height of the traction shafts 2 depending on their location along the perimeter of the shell, which can reduce the power of individual heat exchangers 1 and the entire heat removal device as a whole. Therefore, it is necessary to ensure the same conditions at the inlet sections 9 to the traction shafts 2, regardless of their location along the perimeter of the containment. In this invention, the same conditions at the entrance of sections 9 to the traction shafts 2 are provided by installing a common collector 10.

 The common manifold 10 is a closed annular corridor located concentrically around the perimeter of the protective sheath 3. Air into this manifold 10 enters through the intake holes 11 made in its lower part. In the volume of this collector 10, the pressure drops equalizing around the perimeter of the shell when it is blown by the wind are equalized, and therefore at the inlet of sections 9 to the traction shafts 2, which are in communication with the outlet openings located on the upper part of the common manifold 10, the pressure value has one and the same same value i.e. the common collector provides the same conditions at the entrances 9 to the traction shafts 2, regardless of their location on the containment.

 In addition, it is necessary to ensure the same conditions at the output sections 12 of the traction shafts, which are created by installing in the volume 13 of the deflector 14 and / or deflectors, which are two concentric shells of round or square section, and a protective umbrella.

 In this case, the traction shafts are curved along the dome contour and the upper openings of the sections 12 of the traction shafts 2 extend into the total volume 13 of the deflector 14. A variant is possible in which the traction shafts may have separate deflectors.

 A device for removing heat from the energy circuit works as follows.

 During normal operation of the nuclear power plant, when the coolant heated in the reactor 8 is transferred by pumps 15 to the steam generators, and the steam generated in the steam generators is supplied through the steam lines 16 through the stop valves 17 to the turbine to generate electricity, the heat removal device is in standby mode, i.e. heat exchangers 1 filled with steam. When this gate 7 are in the closed position. In this case, a small amount of steam is supplied through the pipeline 4 from the steam generator to the air heat exchanger 1, which is necessary only to compensate for heat losses due to the thermal conductivity of the device material, air leaks, and radiation. The steam condenses in the heat exchanger and the condensate is drained through line 6 back to the steam generator.

 In the event of an accident in the event of a blackout of the station, valves 17 on the steam lines 16 are turned off, the turbine shuts off, the pressure in the steam generator rises, the valves open 7. Cold air flows from below into the common manifold 10, which equalizes the pressure along the inner perimeter and provides the same conditions at the inlet sections 9 for all heat exchangers 1. The cold air coming from the common collector to the heat exchangers cools the outer surface of the tube of the heat exchangers 1 and condenses the steam entering the pipe through the pipe rovodam 4 of steam generators. Condensate due to the height difference between the heat exchangers 1 and the steam generators or with the help of pumps is drained back to the steam generators through pipelines 6. Heated air through open gates 7, traction shafts 2 and the deflector 14 goes into the atmosphere. When operating in this mode, regardless of the direction and speed of the wind, the power of the heat exchangers is the same.

 In the presence of wind along the height of the traction shafts, an additional positive pressure arises and thereby increases the heat removal capacity from air heat exchangers 1.

 To substantiate the operability of a system consisting of a common collector, traction shafts and a deflector, experimental studies were conducted on a model of the main building of a nuclear power plant, made on a scale of 1: 200.

 In FIG. Figure 3 shows the experimental pressure indicatrix in a common collector and deflector when blowing a protective sheath with an air stream at a speed of 10 38 m / s. From FIG. 3 it can be seen that in the volume of the common collector and deflector around the entire circumference, regardless of the direction and speed of the wind, the same pressure value is provided, and thus the same conditions are created at the entrances to the air heat exchangers and at their exits.

 In addition, experiments showed that, along the height of the traction shaft, in the presence of a deflector and a collector, a traction pressure occurs, which is 0.35 ± 0.03 of the dynamic air pressure.

 Thus, due to the combination of distinctive features, the proposed device for removing heat from the energy circuit has a new property leading to the achievement of a new positive effect, which consists in ensuring the reliability of the system regardless of the direction and speed of the wind and in increasing the cooling capacity due to the additional pressure drop in the wind .

 The introduction of a heat removal device from the energy circuit allows eliminating or limiting unauthorized releases of radionuclides into the environment during emergency conditions, and maintaining the equipment of the reactor coolant circuit during design and beyond design basis accidents.

 The introduction of a heat removal device from the energy circuit will increase the safety of the reactor installations of power units and nuclear power plants by maintaining safety barriers (fuel cladding, density of the coolant circuit, maintaining the required amount of steam and water in the steam-water path without additional recharge) in case of accidents with complete blackout of the nuclear power plant and, even if the coolant circuit breaks.

Claims (1)

 A device for removing heat from the energy circuit, containing installed around the perimeter of the protective shell, made in the form of a cylinder with a sphere-shaped dome, traction shafts with inlet and outlet sections and air heat exchangers connected to the energy circuit, characterized in that it is equipped with a ring-shaped collector concentrically mounted on the shell , in the lower part of which there are intake openings, and in the upper part of the outlet openings, which are in communication with the input sections of the traction shafts, last symmetrically curved along the contour of the dome and on their days off areas fitted vent and / or deflectors.

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