DE3624907C2 - Device for preventing a steam generator from overflowing - Google Patents

Description

The present invention relates to a device for Preventing a steam generator from overflowing and in particular to prevent the steam generator from excluding Lich is filled with the liquid phase, if one or several pipes inside should break where the fluid of the primary circuit circulates, some  has greater pressure than the liquid of the secondary circuit on.

The invention is in nuclear power plants for power generation usable and in particular in institutions that escape check for radioactivity from the container in the event of danger prevent the steam generator tubes from breaking. Although in the description below on a pressurized water reactor The invention is not based on this Reactor type limited.

For nuclear reactors with indirect heat transfer there are two main circuits for heat transfer: a primary circuit in which the primary exchange fluid the result of the nuclear reaction of the nuclear fuel Dissipates heat and transfers it to the secondary liquid, to generate heat, and a secondary circuit in which this secondary fluid circulates and in which of it generated steam is used to drive a turbine that is coupled to a power generator.

The cooling system of the reactor consists of several Circuits in parallel with the pressure vessel of the reactor are connected and each have a pump and a steamer have producers. The steam generator in which the primary liquid gives off heat to the secondary liquid vertically with natural circulation, with U-tubes and turned built steam traps: the primary liquid circulates inside the U-tubes and cools down while the Spei The generator's water flows outside of the pipes and into Steam is converted. An expansion tank is attached to one the branches of the primary circuit connected and enabled the control of the pressure.  

If the primary circuit breaks down, the emergency cooling system injects water to prevent damage Prevention of fuel to reduce the heat of decay to derive and to undercooling conditions in the reactor core to accomplish.

Under normal operating conditions is part of the off equal container filled with water, while the rest with Steam is filled.

The control of the water level in the expansion tank belongs to the facility for monitoring chemical Composition and volume of the primary coolant, taking a certain amount of the liquid from one of the derived cold branches and after a suitable chemi treatment is reintroduced into the primary circuit becomes.

The control of the liquid level in the compensation Container is therefore controlled by controlling the imbalance reached between the derived and the supplied amount.

The pressurized water that is the primary fluid forms, circulates through the core, being the through the nuclear reaction dissipates heat generated, the water ver leaves the pressure vessel and reaches the steam generator where it absorbs the heat absorbed into the generator's feed water emits steam for the door from this secondary liquid bine to generate. The pressurized water in the primary The circuit then becomes yours at the outlet of the steam generator the pressure vessel surrounding the reactor core is pumped.

The steam generated flows in the secondary circuit after Relaxation in the turbine in the condenser. The condensate  is then from the feed pumps to the steam generators pumped back.

In the event of a failure of the normal feeding system the emergency feed system is switched on to feed water to the Secondary side of the steam generator to feed the in the Reak dissipate heat generated by the gate core and the water stood to control the steam generator.

If one of the steam generator tubes should break because the pressure of the primary circuit is initially greater than that Pressure on the secondary side of the steam generator, then flows the primary coolant from the burst tubes in seconds intestinal cycle.

As a result of this loss of coolant, the level of the Expansion tank at a speed that from the through knife and depends on the number of burst tubes. To the pressure in the primary circuit drops immediately after the Expansion of the steam contained in the expansion tank.

If the pressure drop affects the refill capacity of the system tems to control the expansion tank level exceeds then the mass of the primary coolant continues to decrease, until due to the low pressure in the expansion tank Core shutdown signal is generated.

On the secondary side, the addition of radio active primary fluid an increase in radioactivity of the secondary coolant so that it responds to strong radiation de facilities report the damage.  

At this point the feed water flow becomes too the broken steam generator automatically throttled to the increase in level as a result of the leak to balance flowing liquid. As a result, a Imbalance between the flow velocities of the Steam and feed water. This makes it possible Lich to determine the generator in which the pipe break occurred.

The pressure drop in the primary circuit means that Emergency injection system is turned on and the main course was lines to the steam generators are shut off and emergency feed water is supplied to the steam generators.

Simultaneously with the shutdown of the reactor Flow of steam to the turbine interrupted: the steam is possibly via a system bypassing the turbine supplied to the condenser, or if no condensate it becomes gate is present, through the relief valves or the safety blow-out valves arranged in the steam lines are not.

The supply of emergency feed water to the steam generators and the emergency injection on the primary side enable one Absorption of the decay heat of the reactor, and the injection of water in the primary circuit also has an increase the level in the expansion tank and consequently the pressure result.

After a malfunction has been determined, the loading operator first remove the damaged steam generator lock.  

After switching off the steam generator, the Pri circulation to a temperature below the saturation temperature according to the pressure of the damaged steam generator cooled, the pressure of the operational steam generator decreases. At this point the flow of emergency cooling water of the primary circuit are shut off, with the This way the pressure of the primary circuit is reduced and the Leakage flow through the broken pipe is turned off.

The temperature in the primary circuit, the level in the compensation Containers and in the broken steam generator stabilize then, and the uncontrolled leakage of radioactive rivers As a result, liquidity is ended.

As mentioned above, the measures which the operator after breaking a steamer The generator tube must carry out the escape of Radioak Stop activity in the area, something complex because of it include:

• - Determine the type of accident
• - Identify and isolate the damaged steam genes rators
• - Reduce the temperature and pressure of the Pri circulation until pressure equalization is reached, so that the leakage current from the broken pipe ge can be stopped.

Because of the complexity of these operations, cannot concluded that the operator is able to to prevent the damaged steam generator from overflowing. Such conditions cause the liquid to leak out the safety valves and / or overflow valves of the  Steam generator with the risk that this Ven block yourself in the open position because they are not designed to deliver a liquid phase.

The invention has for its object the possibility diagnosis and control of an accident to improve the operator. According to the invention The following measures are planned:

• A) Installation of a device in the steam generator for Showing an excessive level around the area between the normal operating level and the upper side of the steam generator to cover one clear diagnosis and monitoring of the course of the Enable damage event;
• B) Installation of a protective device against a complete filling the steam generator to a full of the steam generator and steam lines if one or more pipes of the steam generator should break what would be possible at random.

The main objectives of the invention are:

• 1) Prevent the leakage of the radioactive liquid into the environment by being in the primary container ter is included;
• 2) Limit the escaping radioactivity that weh after the damage was remedied by the vapor phase is transported;  
• 3) providing an appropriate amount of borate water, cool around the core using the emergency injection system and keep it in an uncritical state indefinitely to be able to, with the leaked liquid in the sump the primary container is enclosed;
• 4) Short-term detection of the accident and the dam steam generator and keeping the Water level;
• 5) Monitor all secondary fluid losses in normal operation of the system by connecting the over barrel with a closed tank;
• 6) Maintain operability even in the case a simultaneous exit from more than one Steam generator;
• 7) Ensuring the functionality of the overflow pipe res both when closing and when opening in the case any failure of a mechanical or electrical component.

The device for preventing the steam from overflowing producer essentially consists of a line for each Steam generator, which is a liquid phase of each steam generator derive and feed to the pressure compensation overflow tank.

There are two check valves in each overflow line arranged in parallel.  

In addition, a shut-off valve is located upstream from the parallel valves provided that the war tion of the control valves and shutting off the lines in the In case of an undesired opening of the control valves possible light.

The flow rate of the lines to prevent the is completely filled by the steam generator simultaneous throughput of the pressure compensation safety valve tils and vice versa not affected.

The control valves can be operated manually or automatically Reaching the water level can be operated by the to instruments installed for this purpose is measured.

After the device is turned on, it can be used Water level on the secondary side of the steam generator in one Keep area to keep steam from entering the outlet lines of the device for preventing overfilling to keep as low as possible.

Further details, advantages and features of the invention result from the following description and the drawing, to those not described regarding the disclosure of all Details are expressly referred to. Show it:

FIG. 1 is a simplified flow diagram reactor of a pressurized water which can be equipped tung with the inventive Einrich but being single Lich, the prior art is shown (see. "Standard Handbook for Mechanical Engineers", 8th ed., Mehraw Hill, 1979, Pp. 9-34 to 9-35),

Fig. 2 shows the known system of Figure 1, but several rhe parallel steam generator are seen easily.

Fig. 3 shows a combination of ge in Figs. 1 and 2 showed components with the addition of the inven tion inventive device.

In Figs. 1 and 2, a conventional plant gene zei, a pressure vessel 1 is shown, containing the fuel elements comprising a plurality of core 2, which generate heat in 3 depending on the position of the control rods. The one generated in core 2 . Heat is transported through the primary liquid or the primary coolant, which enters through the inlet 4 into the pressure vessel and leaves it through the outlet 5 .

The primary liquid or the primary coolant, which was heated when flowing through the core 2 , flows through a tube 6 into a steam generator 7 and in this through heat exchange tubes 8 , which contain the exchange of heat with that contained in the secondary side 9 of the steam generator 7 Allow water to generate steam.

The steam generated in the steam generator 7 flows through a pipe 10 to a turbine 11 , which is connected to a power generator 12 .

The primary liquid emerging from the steam generator 7 is pumped by a pump 13 through a pipe 14 to the inlet 4 of the pressure vessel 1 .

The pressure vessel shown in Fig. 1 has only one primary circuit, although the number of these circuits obviously depends on the size of the system. A Druckbe container 15 is connected to one of the primary cooling circuits, so that the primary pressure can be kept practically constant by acting as an expansion tank.

In Fig. 1, an intermediate piece 27 is also shown, with which the emergency cooling water can be injected into the core 2 in the event of a fault in the primary circuit. To the primary circuit, a tank 16 is connected, which serves to condense and cool the steam which escapes through the overflow valves 18 and safety valves 19 connected to the expansion tank 15 .

The tank 16 is provided with overpressure protection disks 31 .

The secondary side 9 of the steam generator 7 is separated from the primary coolant by the heat exchange tubes 8 .

The generated steam passes through a pipe 10 into a turbine 11 , where it expands, and then condenses in a condenser 20 . The condensate obtained in this way is pumped back by a pump 22 through a pipe 21 to the secondary side of the steam generator 7 .

In Fig. 2, a simplified circuit diagram of the connec tions between the steam lines 10 of the three steam generators 7 is shown.

The following components are shown in FIG. 2:

• - the relief valves 222 of the steam line 10 ;
• - The safety valves 23 of the steam line 10 ;
• - The shut-off valves 24 of the steam lines 10 ;
• - Feed water lines 21 ;
• - The shut-off valves 25 of the feed water lines 21 ;
• - The emergency feed water supply lines 26 , which supply the steam generator 7 with water if the normal feed water system fails to derive the decay heat generated in the core 2 and to control the water level of the steam generator 7 .

Fig. 3 is a simplified diagram of the device according to the Invention.

To the secondary side 9 of each boiler 7 is an overflow pipe 28 connected to the served in the case of bursting 8 to prevent complete filling of the steam generator 7 of a heat exchange tube. The overflow line 28 connects the secondary side 9 of the damaged steam generator 7 via the relief line 17 of the safety valves 19 of the expansion tank 15 to the overflow tank 16 of the expansion tank 15 .

Two control valves 29 are arranged in parallel in each line, and a shut-off valve 30 is provided upstream of the valves 29 arranged in parallel in order to isolate and maintain the line 28 in the event of an accidental opening of the control valves 29 .

Although it is shown in the drawing th and above-described embodiment by a preferred embodiment of the invention acts, serves this is only to explain the invention and can in Numerous modifications within the general knowledge without leaving the basic idea of the invention becomes.

Claims (5)

1. Device for preventing the overflow of a steam generator ( 7 ), consisting of a tube bundle in which a primary liquid circulates, a lower area in which the liquid phase of a secondary liquid is contained, an upper area in which the vapor phase of the secondary liquid is contained , wherein the secondary liquid consists of water, and means for supplying and discharging the primary liquid or the secondary liquid, characterized in that the upper loading area of the steam generator ( 7 ) is provided with means for measuring the level of the liquid phase, and with an overflow line ( 28 ) for each excess amount of the liquid phase is provided, which opens into an overflow tank ( 16 ) which is connected in parallel to an expansion tank ( 15 ). 2. Device according to claim 1, characterized in that the overflow line ( 28 ) for the excess liquid is provided with an interruption device ( 29 ) which can be actuated by the device for displaying the level of the liquid phase inside the steam generator. 3. Device according to claim 2, characterized in that the overflow line ( 28 ) has at least two parallel arms, which are each provided with an independent interruption device. 4. Device according to claim 3, characterized in that the overflow line ( 28 ) is provided upstream of the parallel arms with an additional shut-off valve ( 30 ). 5. Device according to one of the preceding claims, characterized in that the primary fluid from pressure there is water.