KR830001871B1 - Improved Pressurized Water Reactor - Google Patents

Abstract

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Description

Improved Pressurized Water Reactor

1 is a primary circuit diagram of a nuclear reactor with a pulsing or bleeding device according to the invention and having a vertical steam generator.

2 is a first circuit diagram of a nuclear reactor with a pulsing or bleeding device according to the invention and having a steam generator in an inverted U-shaped tube.

3 is a top view of a pressurizer with a pulsing or bleeding device according to the invention.

4 is a bottom view of a steam generator with a gas collection or blocking device according to the invention and having an inverted U-shaped tube.

The present invention generally relates to pressurized water reactors, each consisting of an external cooling loop having at least one pump and a vessel supporting the reactor core and connected to a primary circuit (PC) containing pressurized water, a suction box and an exhaust box. It includes a steam generator (SG) of the type having a primary pipe. The steam pressurizer is connected between the vessel and the steam generator SG by one heat pipe of the cooling loop. In this mechanical pressurizer, the water flowing from the primary circuit (PC) is heated to a temperature higher than the furnace core at the free steam level to maintain the circuit at a pressure above the saturated steam pressure at the furnace core to prevent non-driving (CVCC). In addition, these reactors have a chemical and volume control circuit (CVCC) branched from the cooling loop to regulate the amount of water in the primary circuit, taking into account the chemical state and expansion of the water in which boric acid is dissolved. The control circuit (CVCC) removes water from the cold pipe of the primary circuit between the pump and the reactor to transfer it to another building separate from the reactor building, and to provide a barrier against cold pipe and leakage of the other control circuit (CVCC). It is reinjected into the pump assembly and the auxiliary spray system in the steam chamber of the pressurizer. Usually this system is closed when the main spray system is in operation, ie when the pump of the primary circuit (PC) is in operation. During the processing of the control circuit CVC, the water is cooled and relaxed to an absolute pressure of approximately 2 bar under hydrogen atmosphere so that partially dissolved gas can be generated.

Condensable gases formed in the water by radioactivity during the normal operation of the reactor or released from the fuel element are dissolved in water and treated in this way.

After opening the vessel and shutting down, it is necessary to pulsate or bleed the primary circuit where the gas is present at various high points in order to start the reactor again. Local pulsing has generally been used, but they are not all at their peak and are artificially operated without nuclear power during some pressure and thermal cycling. Thus, in order to accelerate this operation, it is advantageous to have a pulsing or leading system that ensures the blocking of all high points and is operable during reactor restart and power generation. However, consider that in relation to an accident at the Three Mile Island plant in April 1979, conventional pulsing systems are inadequate, where the core cooling failure is caused by the reaction between the fuel cell metal and water. This resulted in many condensable gases. If gas could have been discharged, natural convection of condensate from the steam generator and boiling water from the core would have greatly reduced the core's overheating and its risk.

Instead, this condensable gas accumulates in the high section of the circuit and closes the circulation of water or steam as soon as the pump stops. In addition, at many points, gas pockets do not return the necessary water because the operator cannot determine the state of the circuit. Thus an accident occurs in the vertical steam generator in the reactor, where the crosshead and primary circuit suction box formed by the heat supply pipe form a hot zone with the obvious possibility of pulsing and bleeding. Another pressurized water reactor has a steam generator having an inverted U-shaped primary tube connected to a combined suction and discharge box. Bubbles carried by the primary water in such steam generators enter the tube again and remain in the cooling box under pumping. When the pumping stops, the accumulated gas will re-emerge in the tube and also block the natural circulation.

Thus, the primary object of the present invention is to provide the primary circuit of a pressurized water reactor with the abrupt removal of gas to protect the natural circulation.

A second object of the present invention is to simplify restart after opening the primary circuit. It is desirable to slightly modify the arrangement of the primary circuit here.

And according to the present invention, the pressurizer is used as a collecting member of the gas to the warmer portion of the primary circuit by the system of the rising pipe connecting the hot point of the circuit to the inner space of the pressurizer, and the pressurizer also has an exhaust system connected to the cooler at the top. The water condensed in the cooler falls to the pressurizer by gravity.

As such, some areas of the primary circuit as well as areas constructed by the presser pulsate their gases in the direction of the vapor space of the presser.

And this can have several advantages. That is, it is possible to create a new free level with the possibility of vibration and failure due to hydrogen action to recognize the state in the circuit using other pulsing or bleeding systems without passing through the pressurizer. The need for maintenance in an area less accessible than the top of the pressurizer adds valves while the risk of accidents and pressure is eliminated, and the large buffer volume configured by the pressurizer slows the sudden phenomenon and the gas discharge system from the pressurizer This is certainly necessary because it is connected to a pipe capable of moving the gas, and in part the discharge system replaces the valve on the pressurizer by connecting a vapor volume to the mechanical discharge member of the pressurizer.

The following describes a gas collection or blocking system directed to the press and a system for removing the gas from the press.

A very important high area is made up of the container cover top and the covering of the instrument attached thereto. Practically, this Youngyoung's aeration pipe cannot spread over the top of these shells. The pipe is thus located near the top of the sheath or sheath or cover of the central mechanism. The outlet of the other sheath optionally has a deflection skirt that limits the upward flow of bubbles in the sheath. This pipe follows the upward passage to the pressurizer and can be branched at a lower position in the coldest region of the pressurizer corresponding to the temperature at the top of the vessel or at a higher position of the same volume. In the first case, due to the loss of the pressure head in the cooling loop, some water flows from the pipe to normal and bubbles are transferred to the pressurizer. This pipe has a small diameter (for example 20-40 mm).

In the second case, the water equilibrates below the free level of the pipe, which is substantially level with the level in the pressurization, while very little vapor from the pressurizer condenses in the thermally isolated pipe. This pipe diameter will be larger, preventing water from flowing in or in danger associated with thermal shock.

In both cases the vent pipe may or may not be connected to the vessel cover during operation.

The other high area is constituted by the suction box of the steam generator.

In a pressurized water reactor (PWR) with a vertical steam generator, the suction box is higher than the top of the pressurizer. The riser of the pressurizer is improved in such a way that the riser pipe connects the high point of the box (or its supply crosshead) to the vapor space of the pressurizer. As in the container cover, the pipe has a free level, and the gas can pass towards the pressurizer. In addition, because the micro gas is located downward, it is not necessary to pulsate the discharge box of the steam generator, but when the pulp is stopped, the gas is raised to the suction box and pulsed.

In the case of a pressurized water reactor with a steam generator of an inverted U-shaped tube, the gas bubbles carried by the primary water and sucked into the suction box of the steam generator are introduced toward the tube plate formed at the top of the box and then pass through the tube. However, this attempt is partially suspended and can be passed through to the pressurizer. It was pointed out that there was a maximum bubble near any generating line of the inlet pipe adjacent the upper generating line.

Fine water flow from this relevant area can be echoed by a baffle forming a scoop and passed into the cap in the box, the top of the cap being connected to the press.

According to another arrangement, it is possible to use a symmetrical flow of water to assist the rotational movement, the axis of rotational movement being the hemispherical wall of the box rather than the tube plate, the bubble being concentrated in the axial region and contacting the wall by the cap. do.

It is also possible to replace a large diameter pipe (e.g. 365 mm) connecting the presser to one of these loops with a smaller diameter pipe (e.g. 200 mm) connecting the presser to each of the hot boxes. Such pipes can be placed as high as possible on the wall of the box, absorbing air bubbles reflected by the baffle system in the upward passage. At relatively large diameters, however, penetration must occur at the junction between the tube and box walls, which is very difficult to achieve. Conversely, a tube with a small diameter can be introduced obliquely between the bottom of the tube sheet and its side without any significant mechanical disadvantages. In this way, it can be seen that the present invention enables the use of small diameter pipes, especially in the suction box and pressurization period of the steam generator. This pipe can then be connected to the gas accumulator cap in the box.

However, for such nuclear power with inverted U-shaped steam generators, it is important to pulsate the discharge box where gas is likely to accumulate. It was also found that in normal operation the pressure in the box is about 15 m lower than the vapor space of the pressurizer. Thus, the possibility of directly airing to the pressurizer without the gas returning to the U-shaped tube exists only when the pump is running at a slower speed. It is also not possible to raise the pressurizer by 15 meters because the connecting pipe is not long enough.

It is necessary to provide a separate facility for pulsing the box under these conditions. The simplest installation consists of a riser connected to the box as high as possible and connected to a mechanical cold element with a level detector and an upper discharge valve towards the facility for the storage and treatment of the gas.

In addition, the collection and blocking of the gas in the suction and discharge boxes where the tube plates constitute the top would be helpful if the plate was bent downwards, thus helping the gas to pass through the tube along the edge rather than the one adjacent to the center. .

In the case of incomplete pearling, the gas is discharged only to the surrounding pipe as soon as the pump is stopped. It is also conceivable that the extension portions of the outlets of all the pipes are downward. This makes the upper part a trapping layer but it is difficult to construct such an extension.

The gas exhaust system from the barometer will now be described. The system used to cool the mixture of steam and gas returns the condensed water to the primary circuit and transfers the condensable gas and their residual steam to an intermediate pressure storage vessel located within the reactor containment building, where the radioactive gas is To eliminate the possibility of leakage.

The upper part of the pressurizer has a discharge fan into which the cooler is inserted, and condensed water flows back to the pressurizer under the action of gravity.

In its simplest form, the chiller consists of a riser that is not insulated from air and is guided to the mechanical storage member via an outlet hole and a shutoff valve. However, in order to prevent rapid and sudden outbreaks, cooling is originally done as cold water, for example spray installation of the pressurizer, which must be put back in the primary circuit.

The cooler can be coiled and the cooled water finally flows through the auxiliary spray system of the pressurizer, or the reciprocating ring which crosses from top to bottom by cooling water and from bottom to top by cooling water. Flow through a contact type auxiliary spray device having a contact configured by such a Raschig ring).

This cooling quantity roughly corresponds to the amount needed to condense the leaked vapor volume. This exact set can be controlled by a temperature probe located at the bottom of the cooler. High areas can be sufficiently cooled and low areas can be sufficiently heated.

And, it is preferable to basically fix the cooling water quantity and to adjust the amount of residual oil gas.

The instrumental storage member, which introduces gas and residual steam, provides a catalysis system for the oxidation of hydrogen and tritium to reduce the gas volume. The condensed water is discharged, for example from the valve junction towards the discharge line which collects the leak.

The allowable pressure and amount of the instrumental member are fixed in a manner which is producible against the release of hydrogen, for example, which substitutes for the oxidation of all fuel cans.

There is a regulated safety valve system that connects the pressurizer vapor volume to a mechanical discharge member with an internal spray system for condensing steam in the installation, and a pressurizer discharge device incorporating a remote control valve system.

This remote control valve is automatically activated when the spray system in the pressurizer is temporarily unsuitable to limit the pressure rise. The three mile island event indicates that the mechanical exhaust member was inadequate when opening a blocked valve.

It is very important for the instrument outlet to act as an instrumental storage member according to the invention and the gas outlet is connected here to operate preferentially and simultaneously cool in comparison with other valves in case of unexpected pressure rise.

This system then becomes equivalent to the auxiliary spray system and can prevent the filling of the mechanical discharge member. It is also desirable to check that this apparatus and the internal spray system according to the invention prevent the opening of other valves and have adequate cooling power.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

1 is a vessel (1) of a pressurized water reactor including a core (2), a vertical steam generator, a cold pipe (3) for introducing primary water into the vessel, a heat pipe (4) for discharging primary water, and a pressurizer (5). And a connection 6 with the pipe 4, a suction box 7 of the steam generator, a pipe group 8 for transferring heat to the secondary circuit, a steam generator discharge box 9, a pump 10, a primary The circuit supply pipe 11 and the primary circuit return pipe 12, the pipe 13 extracted from the pipe 3 for spraying to the pressurizer, the valve 14 for regulating it, and the like are shown.

The lifting pipe 15 having a separating flange connects one of the instrument casings 16 on the cover of the container 1 to the steam section of the pressurizer.

The ascending pipe 17 connects the upper end of the pipe 4 to the vapor section so that the pressurizer is at a sufficiently high position such that the separation surface of the steam and water formed in the pipe 15 and the pipe 17 is level balanced in the pressurizer. do. Also located above the pressurizer 5 is a condenser 18, which contains a coil provided by the pipe 12 via a control valve 20, and the heated water is pumped into the pressurizer. The outlet from the transducer with the control valve 19 is connected to the mechanical outlet member 22. And one of the pipes 23 connecting the pressurizer to the member 22 according to the prior art is shown. The member 22 is provided with a catalytic reaction recombination facility 24.

Figure 2 shows the relevant elements of a pressurized water reactor with a steam generator in an inverted U-shaped tube.

The difference from the above relates to the collection or blocking in the intake or discharge box of the generator. The suction box 7 is provided with a collecting pipe 17 connected as high as possible in the vicinity of the tube plate to the pressurizer, while the discharge box 9 contains a rising pipe 25 which is also connected as high as possible to the mechanism. It is guided to the type degassing cooling member 26 and flows upward by the pipe 27 with the valve 28 to the mechanism type gas storage member 22. The level detectors 29 and 30 installed in the member 26 allow the valve 28 to be controllable to maintain the free level in the member 26.

3 shows the top of a pressurizer with a bonded condenser. The main ferrule of this pressurizer 5 extends upwardly by a cylindrical body 35 of smaller diameter, which is provided with pulsing pipes 15 and 17. This condenser is configured as a basket-like member 36 just below the lid of the body 35, where the contact material 37 is configured as a contact element, such as a rasing ring.

Pipe 12 emerges above the lid to allow material 37 to be sprayed. Water is discharged from the bottom of the basket member 36 by the side grid 38. This allows opening from the pipes 15 and 17 to be re-injectable through the gap 38 during operation, while mixing little with the steam from the pressurizer.

The discharged gas is left at the top of the lid via the valve 21. The temperature in this material is monitored at several levels by the sensor 40, allowing to determine the thickness of the site where condensation takes place effectively, and to maintain appropriate limits by the control valves 20 and 21. .

FIG. 4 shows the bottom of the steam generator of the inverted U-shaped tube associated with FIG. 2, dispersing the gas that tends to accumulate in the box 7 and box 9 by using a curved tube plate 24 below. Let's do it.

Also shown is a baffle 50, which is carried by at least the primary flow introduced into the box 7 by the pipe 4 and can capture a portion of the bubbles that have aggregated along the generation line. The baffle 50 also forms a scoop over the outlet of the pipe 4 and is connected to the outlet of the pipe 17. The water caught by the scuff raises the bubbles and descends toward the main flow at one side of the outlet of the pipe 4 according to the arrow 51.

Pipes 17 and 25 enter the box by holes slanted on the tube plate and avoid the stress concentration areas formed by connecting the plate to the lower hemisphere. These inclined holes are stainless steel tubes welded to the inner cover of the barrel and to the actual pipe, since all walls in contact with the primary circuit must be stainless.

Thus, the pulsing or bleeding apparatus of the primary circuit according to the present invention can prevent the difficulty of gas removal occurring in the pressurized water reactor in a simple manner.

This allows the gas to form within it and continue the natural circulation of the primary circuit even if the primary pump has failed. The use of this device has side benefits, in particular the following:

That is, the gas removal problem no longer occurs during charging of the circuit, so that gains during downtime required by reactor repair or fuel replacement and gas accumulation in other areas of the circuit are eliminated, ensuring control when the cause is known. In the event of an undetected leak, it is possible to load water, accurately indicating the amount of primary water in accordance with the level criteria on the pressurizer, and limiting the reactor to a mechanical member provided at storage pressure for this purpose without an intermediate passage. Gains from the storage of the radiation gas into the zone;

Claims (1)

Reactor tubing, steam pressurizer with auxiliary heating to prevent boiling and to maintain pressure in the primary circuit, as well as the primary tubular type between the intake and exhaust boxes as well as the chemical and volume control circuits branching out of the primary circuit. A device for pulsing and bolling a primary circuit of a pressurized water reactor comprising at least one steam generator, etc., wherein the inside of the pressurizer includes a gas discharge pipe on which a cooling system is placed, which is incapable of condensing with steam discharged from the press And a condenser for condensing the mixture of gases, the condensed water being returned to the pressurizer.

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