DE3518174A1 - Heat removal system for removing afterheat from the primary cell of a high-temperature reactor - Google Patents

Abstract

In order to remove afterheat from the primary cell (2) of a high-temperature reactor, the reactor pressure vessel (1) is surrounded at a distance by a heat absorbing system which essentially absorbs the afterheat by thermal radiation and contains a medium which guides the absorbed heat to a cooler arranged outside the primary cell. Heat pipes (3) are used as heat absorbing system, their heat absorbing side (4) being arranged inside the primary cell (2) and their heat dissipating side (6) being arranged outside the primary cell (2). As an alternative to this, it is also possible to arrange riser pipes which are filled with an evaporable coolant and open outside the primary cell into a steam drum. The steam drum is connected to a condenser in which the steam formed during the absorption of the afterheat is precipitated. Downcomers lead from the steam drum to the riser pipes. The coolant is thus conducted in the circuit. <IMAGE>

Description

Heat dissipation system to dissipate residual

heat from the primary cell of a high temperature reactor The invention relates to a heat dissipation system for dissipating residual heat from the primary cell of a High-temperature reactor, the reactor core of which is housed in a reactor pressure vessel is. For residual heat removal, the reactor pressure vessel is surrounded by a heat absorption system, the residual heat from the reactor pressure vessel essentially through thermal radiation records. The heat absorption system contains a medium that is used to dissipate residual heat serves. The residual heat is stored in a cooler located outside the primary cell submitted.

With the heat removal system, both in a high temperature reactor the operational heat loss as well as the residual heat can be dissipated in the event of an incident and at the same time the concrete structures of the primary cell and in particular that of the primary circle inclusion to protect the pressure vessel from impermissibly high temperatures. Essential is that the heat dissipation device is a distance of about 0.5 m to the pressure vessel having, so that it remains freely accessible for an examination.

For the high-temperature reactor in modular design, see Society for high temperature reactor technology GmbH, "high temperature reactor module for process heat generation", Technical report ITB-78.2634.1, 1981, are state-of-the-art with water Forced flow surface cooling systems, e.g. pipe coils welded onto plates or a pipe wall made of vertically arranged pipes is used, which is on the primary cell wall are attached and serve as operating and emergency cooling systems. The core generated residual heat stored in the core and the surrounding structures and through inherent heat transport mechanisms passed to the pressure vessel wall and from there primarily transferred to the surface cooling system by thermal radiation. In the surface cooling system the heat is absorbed by a quantity of water circulated via pumps and these are recooled by heat exchangers. If the active components fail, in particular the pumps, damage to the reactor system over a longer period of time Unavailability of the surface cooling system cannot be ruled out.

The inherent heat transport is therefore only within the reactor realized by myself.

Inherent systems for heat dissipation in one Nuclear reactor have so far only been designed for the event of a loss of coolant accident a pressurized water reactor or fast breeder, core melting by cooling to prevent the Raktordruckbehäters or after a core melting the melt to cool down in appropriate chilled collecting devices.

For example, in U.S. Patent 3 935 063 described cooling system in the core and outside on the reactor pressure vessel Attached heat pipes that serve as a replacement emergency cooling system. The condensation sides the heat pipes are in a room below the reactor pressure vessel, after the occurrence of an accident by opening a valve via a storage tank with a evaporable liquid must be flooded. By evaporation of this liquid the heat dissipated from the reactor remains in the primary cell.

Beyond the further dissipation of this heat from the primary cell nothing is known. Alternatively, a closed cycle is possible at where the condensation sides of the heat pipes are the primary side of a tube bundle heat exchanger form. The design of the secondary side of this heat exchanger is not specified. By selecting the operating medium of the heat pipes it is achieved that these heat pipes only then Dissipate heat when the temperature of the reactor pressure vessel rises above the normal operating value in the event of a malfunction.

Another application of heat pipes as an emergency cooling system is from DE-OS 25 25 554 known. This is a corecatcher that goes through heat pipes is cooled.

An inherent cooling system consisting of an open or closed The water cycle is described in DE-OS 20 35 089.

This is also a cooled corecatcher.

The concept of basic safety for the pressure-bearing parts of the primary circuit of a nuclear reactor requires these parts to be retested. These exams also include an ultrasonic test in each case, which is only available in the case of a freely accessible Surface of the part to be tested is possible. Because of this, one is right on The cooling system arranged on the surface of the reactor pressure vessel is no longer feasible. A cooled corecatcher has the necessary distance to the pressure vessel, however its ability to remove residual heat only comes into play after core melting. A core melt is with one However, due to high temperature creator the constructive execution.

The additional requirement for an inherent cooling system for one A high-temperature reactor in modular design is that between the cooling system and the pressure vessel a distance is maintained, the accessibility for testing the reactor pressure vessel guaranteed. This necessary distance is about 0.5 m. Furthermore, it is required that this cooling system transports the heat from the primary cell and also with normal Operating conditions can work. Activation in the event of a malfunction is thus superfluous and there is the possibility of using the inherent cooling system as a normal operating cooling system to use.

The object of the invention is therefore for a high-temperature reactor to create a heat dissipation system with the reactor pressure vessel, in which the residual heat not only inherently transferred within the reactor, but also within of the primary cell and out of the primary cell inherently to outside of the primary cell arranged coolers is transportable.

This object of the invention is achieved by two alternatives: a) through the use of heat pipes (claim 1), b) through the formation of a heat dissipation system with natural circulation for the cooling medium (claim 5).

The advantage of these two inherent heat dissipation systems is that justifies that there are no active components with a possible unavailability can be used. The only driving force for the dissipation of heat is inherent physical processes, such as gravity, buoyancy, evaporation and condensation processes are used. Another advantage can be seen in the fact that in particular when using heat pipes by subdividing the entire system a greater redundancy can be implemented in many identical subsystems.

The evaporation part is located near the heat pipes for the cooling medium within the primary cell and absorbs the heat there. The heat is released in the condenser part of the heat pipe, which is located outside the Primary cell is located.

From there, the heat is passed on via natural convection.

In a further embodiment of the invention, the heat pipes are with lateral Radiant fins provided and staggered. The primary cell wall is with an insulation provided, on which to the primary cell room a reflective sheet is located.

Through this film, the staggered arrangement of the heat pipes and the Radiant fins is a uniform heat load through internal radiation exchange possible between the individual surfaces. So that the heat pipes without entering the primary cell are interchangeable, it is provided that the heat pipes in the primary cell are permanently mounted Take up ducts. For replacement, the cladding tube is opened from the outside and the freely suspended heat pipe pulled.

For better heat transfer from the cladding tube to the heat pipe is a Filling the space with high-boiling liquids, especially liquid metal possible. With an outside diameter of the heat pipe of 100 mm and an evaporator length of 15 m can be a heat pipe with water / steam as the working medium at atmospheric pressure Dissipate around 2.5 to 5.5 kW of power.

Another possibility for realizing an inherent cooling system consists in the formation of the heat dissipation system according to the natural circulation principle, such as it is known from steam generator technology. The working medium, e.g. Water at atmospheric pressure, almost at boiling point, enters the riser pipes are located within the primary cell. By partial Evaporate of the working medium, the heat to be dissipated is absorbed. The difference in density between the downpipe and the riser side causes the cooling medium to circulate naturally in the system. Following the riser pipe, the liquid-vapor mixture enters a steam drum located outside the primary cell. There the steam is separated and precipitated, for example, in an air cooler and then flows into the steam drum return. The liquid is returned to the downpipe and a collecting container Risers fed.

With this solution, redundancy can also be achieved by that several of the systems described are operated in parallel. An interpretation of the system for the working medium water at atmospheric pressure results in a to be discharged Power of e.g. 700 kW at atmospheric pressure in the system a mass flow to be circulated of about 170 kg / sec with an amount to be evaporated of 0.3 kg / sec. As a driving force The pressure difference for the circulation is about 0.3 to 0.5 bar.

The invention is explained in more detail below on the basis of exemplary embodiments described.

The drawing shows in detail: Fig. 1: Heat dissipation system with heat pipe (schematic); Fig. 2: Partial cross-section of a heat dissipation system 1 according to section line II / II; Fig. 3: Heat dissipation system with natural circulation (schematic).

A heat dissipation system according to the first alternative of the invention is reproduced in a schematic representation in FIGS. 1 and 2. Fig. 1 shows a Reactor pressure vessel 1, which in the exemplary embodiment is designed as a steel pressure vessel is, and a heat pipe arranged therefrom within the primary cell 2 at a distance 3, its heat-absorbing side, the evaporation part 4, in front of one made of concrete outer cell wall 5 of the primary cell 2 runs.

The heat-emitting side of the heat pipe 3, the condenser part 6, is located outside the primary cell 2. In the exemplary embodiment, the heat discharged from the condenser part 6 via natural convection in the air.

The mode of operation of a heat pipe is also shown in FIG. 1. An enlarged section of the evaporation part 4 of the heat pipe is shown schematically reproduced.

The section shows that in the heat pipe 3 when absorbing the residual heat formed vapor of the cooling medium flows in the inner pipe part 3 ', while the liquid Cooling medium is guided in the outer pipe part 3 ″.

Fig. 1 shows the heat dissipation system only schematically on the basis of a individual heat pipe. When implemented, the reactor pressure vessel 1 surround a Variety of heat pipes. From Fig. 2 is the staggered arrangement of the heat pipes 3 can be seen. The heat pipes run in two different levels in front of the inside of the cell wall 5, with the heat pipes 3a of one level opposite the heat pipes 3b of the other level are offset from one another. The heat pipes 3 wear radially arranged ribs 7 to enlarge their heat-absorbing surface.

In Fig. 2 is a schematic for a portion of the heat pipes 3 Embodiment of the heat dissipation system shown in which the heat pipes 3 in Ducts 8 are laid. The heat pipes 3 can be displaced in the cladding tubes 8 stored in such a way that they can be exchanged without entering the primary cell 2 to have to. The heat pipes 3 can be drawn into the cladding tubes 8 from the outside and take it out of the ducts again. The space between the heat pipe 3 and Cladding tube 8 is with a high-boiling liquid 9, in particular with liquid metal filled to improve the heat transfer from the cladding tube to the heat pipe.

On the cell wall 5 of the primary cell 2 is inside an insulation 10 is applied to protect the concrete structure of the cell wall 5.

The insulation 10 carries a heat-reflecting film 11.

Fig. S shows a heat dissipation system with natural circulation. With this heat dissipation system Form the system absorbing the residual heat riser pipes 12, which with a heat absorption are filled with boiling coolant.

The riser pipes 12 open into a steam drum 13, from which the resulting Steam flows off via a steam line 14 to a condenser 15. In the condenser 15 the steam is condensed and the condensate flows through a condensate line 16 back to the steam drum 13. A capacitor 15 is used in the exemplary embodiment Air cooler with natural convection.

Downpipes 17 lead from the steam drum 13 to the lower part of the riser pipes 12, so that a closed coolant circuit is created for the coolant. To the Collection and distribution of the coolant from the downpipes 17 to the riser pipes 12 are located in front of the inlet into the riser pipes 12 at the lowest point of the coolant circuit one or more liquid collectors 18 outside the primary cell 2.

In the exemplary embodiment according to FIG. 3, the steam drum 13 is still attached a pressure regulator connected. By means of a pressure compensation piston 19 the coolant circuit can be operated at atmospheric pressure. Instead of the pressure compensation piston 19 can also be a pressure piston for setting a pressure above atmospheric pressure use in the heat dissipation system. From a storage container 20 is after opening one Shut-off valve 21 to feed coolant into the downpipes 17.

The heat dissipation systems shown in Figures 1 to 3 work automatically.

External interventions are not required to dissipate the heat. So in both cases it is a question of completely inherent systems with which a further improvement in the safety of high-temperature reactors is achieved.

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Claims (7)

Claims heat dissipation system for dissipating residual heat the primary cell of a high temperature reactor with a reactor pressure vessel for the reactor core and a heat absorption system surrounding the reactor pressure vessel at a distance, the residual heat from the reactor pressure vessel essentially through thermal radiation receives and a medium for dissipating the residual heat to an outside of the primary cell arranged cooler contains, d u r ch g e k e n n n n z e i c h n e t that as Heat absorption system heat pipes (3, 3a, 3b) are used, the heat-absorbing Side (4) inside the primary cell (2) and its heat-emitting side (6) outside the primary cell (2) are arranged. 2. Heat dissipation system according to claim 1, characterized in e t, that the heat pipes (3) are guided within the primary cell (2) in a cladding tube (8) are, the space between the cladding tube (8) and heat pipe (3) with high-boiling point liquid (9) is filled and the heat pipe (3) is arranged exchangeably in the cladding tube (8). 3. Heat dissipation system according to claim 1 or 2, d a d v r c h gek e n n -z e i c h n e t that heat pipes (3) and / or cladding tubes (8) with radially extending Ribs (7) are provided to enlarge the heat-absorbing surface. 4. Heat dissipation system according to one of claims 1, 2 or 3, d a d u r c h g e -k e n n n z e i c h n e t that behind the heat pipes (3) or the ducts (8) in the primary cell (2) on the inside of the cell wall (5) a heat reflective Foil (11) is attached. 5. Heat removal system for removing residual heat from the primary cell of a high temperature reactor with a reactor pressure vessel for the reactor core and with a heat absorption system surrounding the reactor pressure vessel at a distance, the residual heat from the reactor pressure vessel essentially through thermal radiation receives and a medium for dissipating the residual heat to an outside of the primary cell contains arranged cooler, characterized in that as a heat absorption system arranged with a coolant filled with a coolant which can evaporate when absorbing heat are, the outside of the primary cell (2) open into a steam drum (13) with a Condenser (15) for precipitating the partially formed by absorbing the residual heat Steam is in communication and from the downpipes (17) for gravity conveyance for the return of the coolant to the riser pipes (12). 6. Heat dissipation system according to claim 5, d a d u r c h g e k e n n z e i c h -n e t that the coolant circuit is via a pressure compensation piston Atmospheric pressure is operable. 7. Heat dissipation system according to claim 5, d a d u r c h g e k e n n z e i c h -n e t that the coolant circuit by means of a pressure piston (19) at can be operated at a pressure above atmospheric pressure.