FI117527B - Apparatus and method for blowing off steam - Google Patents

Description

117527 1 i

Apparatus and method for blowing off steam

The invention relates to apparatus and a method for blowing off steam in a nuclear power plant.

A so-called drainage pipe may be provided in the nuclear power plant, in particular the boiling hydroelectric power plant, through which steam may be blown out of the pressure chamber, in particular the reactor pressure chamber, if the pressure in the pressure chamber exceeds a predetermined value. Steam blown off via drain pipe conducts:. I; is placed in the coolant, where it condenses.

It is known from U.S. Patent No. 5,491,730 that, in a nuclear power plant, steam, i.e. steam in the pressurized state of the pressure vessel, is conducted from the reactor pressure vessel, if necessary, first through a condenser and subsequently allowed to flow through a drain tube to condensation chamber coolant. In order to distribute the temperature evenly in the coolant, means are provided for the steam or product produced through the discharge pipe; the fluid is evenly distributed in the condensation chamber. !

From the article "SWR 1000 - Der Siedewasserreaktor der Zukunft",. ?

Siemens Power Journal, 2/96, Siemens AG, Bereich Energieerzeugung, order number A96001-U90-A314, is known for an inno-20 tional safety concept for a boiling water reactor. In this boiling water reactor, the reactor pressure vessel is connected to the condensation chamber via a drain tube, so-called? ## *: · via a loose pressure discharge line. The lower end of the drain tube sinks •: *: into the coolant in the condensation chamber. Pressure Unloading Tubes • · * ·. ***. the outlet line is opened with a safety / safety valve if the pressure in the reactor pressure tank increases to * · ·. *. : Above 25 t.

After the steam has been blown off, the condensing chamber flows coolant to the lower end of the drain pipe. At the same time, as the final steam in the drainage tube cools down, vacuum is created in the drainage pipe so that the coolant is absorbed from the upper side of the liquid level of the coolant liquid from the condensation chamber. In this case, it may happen that the cold cooling medium is sucked up to the safety / safety valve and is then exposed to it; *: *; high heat load.

•. ···. It is an object of the present invention to provide a device and method for purifying steam, which effectively prevents i *** 35 coolant from being undesirably absorbed into the drain tube.

• · · • · • 117527 2

The object is solved in accordance with the invention with respect to the device, with the drain pipe terminating in the coolant in the chamber and the internal space of the drain pipe being permanently connected through a constant flow path to an aeration port which extends outside the coolant to the gas zone.

Through the connection from the interior of the drainage pipe to the gas or to the gas region containing the gaseous liquid, it is ensured that there is no unacceptably high vacuum in the drainage pipe. The pressure differences between the gas chamber and the interior space are immediately compensated through an open flow path 10 throughout. The drain pipe is therefore artificially vented. This effectively prevents the coolant from being absorbed into the drain pipe above the level of the coolant in the chamber.

An essential benefit is to create a flow path into an open flow path. In other words, it cannot be closed and no means are provided, such as valves, for closing the flow path. The venting of the drain tube is based on self-regulating physical pressure effects and is purely passive. Thus, no active devices requiring external control are necessary. In addition, the drain tube aeration device with an open flow path selected in this way does not require any maintenance as its functionality 20 does not require any moving parts. The flow path and the vent may simply be formed with a hole in the wall of the drain pipe.

Preferably, an aeration tube is provided along which the flow path passes. Hereby:: *: the steam flowing out of the drainage pipe through the aeration pipe or the gas flowing in through the aeration pipe can be controlled by a single flow technique. ·. : 25 times.

In a preferred embodiment, the flow path is configured so that the flow resistance of the vapor scavenging from the drain tube, the so-called drain flow resistor, is greater than the inlet flow resistance of the gas scavenging into the drain tube. Different flow resistance depending on the flow direction causes the smallest amount of steam to flow out through the flow path. This outflow steam is also called the vapor leakage stream.

· * · *; The outflow resistance is preferably determined by the so-called edge * • *. point. At the junction of the edge, the effective flow cross section in the downstream direction is reduced relative to the effective flow cross section in the opposite inward flow direction.

• * · • · * · • · · 117527 3

If an even greater difference is desired between the outflow and inlet flow resistance, a flow restrictor is preferably provided, comprising a circulation means for providing negativity to the filing steam and coupled to the flow path. By means of the circulating means, the pressurized steam 5 is brought into rotation, particularly when it enters the flow path.

As a result, its axial flow rate decreases, and the outflow resistance becomes substantially greater compared to the flow resistance of the inward, non-negative, purely axial flow.

In a preferred embodiment, the flow path is implemented such that the outflow vapor condenses upon direct or indirect contact with the coolant. This prevents unnecessarily high pressure in the chamber.

The drainage pipe may further be connected to the drainage pipe both above and below the liquid surface level of the coolant.

However, the aeration pipe is preferably connected to a drain pipe below the level of the coolant liquid. The aeration tube is thus at least partially conducted through the coolant. The outflow steam is therefore already condensed in the aeration tube because it is indirectly contacted by the coolant through the wall of the aeration tube.

In this connection, the aeration tube preferably passes at least partially it *: · wrapped around the drain tube to provide a very stable and * · long flow path through the coolant.

• «· ·. * ··. The aeration opening is preferably directed downwards towards the coolant 25. The aeration tube is directed towards the aeration opening, particularly downwards, because the outgoing steam comes in direct contact with the coolant, *, thereby releasing its heat into the coolant ** ·· * and condensing.

In a very preferred embodiment, the drain tube is surrounded by a protective tube. This embodiment illustrates the parallel implementation of the drain pipe * ··, so that the protective pipe can take up the function of the drain pipe in the event that the drain pipe breaks.

*. ···. Preferably, the sheath is provided with a hole through which the aeration pipe is routed at a predetermined distance, in particular such that there is a margin to allow the shield and the drain pipe to be pushed. 117527 4 Inside each other without hitting the aeration tube. The protective tube typically moves relative to the drain tube during thermal loads.

For this purpose, in order to keep the leakage area between the protective pipe and the aeration pipe, which is formed as a hole, as small as possible, a lid 5 is preferably provided on top of the leakage opening.

The drainage pipe preferably connects to the condensation chamber and / or the tidal basin of the hydroelectric power plant.

Steam blasting as a method is solved according to the invention. and by subsequently evacuating the pressure in the chamber above the coolant, because of. In this method 15, the coolant is completely prevented from being absorbed into the outflow pipe above the level of the coolant in the chamber.

Other preferred embodiments of the method are disclosed in the dependent claims. Accordingly, the method has the same advantages as the device.

The embodiments of the invention will now be illustrated in greater detail by means of a drawing. Equal features in the figures? tt * j * with uniform reference numbers.

• · *: Figure 1 is a roughly simplified representation of boiling water

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. * ··. ·! *: Figure 2 shows the drain pipe and the safety / safety brick attached to it, • · Figure 3 shows an enlarged view of Figure 2 with a circle representing the nozzle and the edge 4-6 shows different positions of the aeration tubes in the drain tube, • · »Figure 7 shows the drain tube surrounded by the protective tube, Figure 8 shows an enlarged representation of the circle in Figure 6. ♦ ··. and the · · [· * Figure 9 illustrates arrangements related to the flow limiter when the flow *: * · 35 is limited to the inside of the drain pipe and extends as far as the vent pipe ♦ **.

5 1 1 7527

As shown in Figure 1, a central reactor pressure vessel 4 is disposed in the boiling hydroelectric power plant pressure vessel 2. designated as pressure chamber 9. The tidal basin 8 and the condensation chamber 6 are separated from each other and the pressure chamber 9 by partitions 10.

Both the tidal basin 8 and the condensation chamber 6 are filled with coolant f, particularly water, up to the level n of the liquid, and above the coolant f are respectively a gas space 8a or a gas space 6a containing gas or gaseous material. The coolant f acts as an emergency cooler and relieves pressure in the pressure vessel 2 in the event of a malfunction if the pressure in the pressure chamber 9 exceeds a predetermined value. This is the case, for example, when the steam pipe breaks inside the pressure vessel 2. For example, a flow pipe 11 from the tide pool 8 to the reactor pressure vessel 4 is provided for vigorous flow and emergency cooling of the reactor pressure vessel 4.

Figure 1 shows two alternative or complementary alternatives for implementing the drain tube 12. In the first alternative -20a, the drainage pipe 12 is connected to the coolant f of the trough 8 and, in the second alternative, the drainage pipe 12 is connected to the coolant 1 of the condensation chamber 6.

The drain pipes 12 are in each case flow-connected to the reactor pressure reservoir 4. They can be closed by means of a safety / safety valve 14. Her pai- • · · ·. * ··. they rise above a critical value in the reactor pressure vessel 4, the safety / relief valve 14 opens so that steam is blown out of the reactor pressure vessel 4

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through drain pipe 12, it flows at end piece 16 • · '.V.' of drain pipe 12 from the outlet openings 17 to coolant f and condenses there.

** ·· * The safety / safety valve 14 closes when the pressure in the reactor pressure vessel 4 again falls below a predetermined value. During blow-off, the drainage tubes 12 are completely filled with steam. After closing the safety / safety valve 14, the coolant f flows through the end outlet openings 17 * to the drain pipe 12. Because steam is still present in the drain pipe 12. * ··. cools and condenses, creating a vacuum in the interior of the drain tube 12, * ·.

that the coolant f is absorbed in the drain pipe 12 up to a level of ··· above the liquid level n in the condensation chamber 6 or: ** · 35. At the same time, the coolant f will, under these conditions, pass up to the safety / discharge valve 147527, which is now exposed to cold coolant f after hot steam and thus to high thermal loads.

As shown in Figure 2, the drain pipe 12 is guided from the pressure vessel 9 first horizontally through the septum 10 and then joins, for example, the tide 5 in the water basin 8. Immediately before the drain pipe 12 enters the trough 8 ° and extends perpendicularly down to the coolant f up to the level n of the fluid. At the lower end of the drainage pipe 12, an end piece 16 is placed perpendicular to the drainage pipe 12 perpendicular to the drainage pipe 12. The end piece 16 comprises a plurality of outlet openings 17 from which steam may flow out of the drain pipe 12 or coolant f may flow into the drain pipe 12.

An aeration opening 18 is provided at the top of the drainage pipe 12, which runs horizontally above the level n of the liquid surface 15. aeration tube 20 and nozzle 22.

The air outlet pipe 20 extends from the underside of the drain pipe 12 towards the coolant f perpendicularly downwards so that the outflow J; · * · The steam eventually condenses towards the surface of the coolant medium f. Il- • · · * • · '; the mast opening 18 is located in the tidal pool 8 with the gas gun 8a, for example * «* ·. ·· *. about 1 m, especially 0.3 m, higher than the level of the liquid surface n of the cooling medium f. Since the aeration tube 20 and the aeration opening 18 are * ** open for two-way flows, they can alternatively be called j 1. or a vent.

Figure 2 shows the drain tube under normal operation of the nuclear power plant, that is, when the safety / safety valve 14 is closed.

30 Under normal operating conditions, drain pipe 12 is filled in tidal basin • · · 8 to coolant level n. As soon as the safety / safety valve 14 opens, the steam flows through the drain pipe 12 and presses the liquid in the drain pipe 12 through the outlets 17 in the end piece 16 to the tidal basin 8. Figures 4-7 show a liquid like this: '* · 35 surface filling level, which after discharge of steam and closing of safety / safety valve 14 in drain pipe 12 is not usually exceeded.

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Fig. 3 is an enlarged view of the circular portion around nozzle 22 in Fig. 2. 3, the air outlet pipe 20 and the nozzle 22 are welded through welding points 24 to the outer wall 25 of the drain pipe 12. The air outlet pipe 20 communicates with the interior 5 only through a nozzle 22 disposed in the center of its interior. The nozzle 22 extends up to the interior 19 and comprises an inner opening formed therein as an edge junction 23.

The edge interface is defined in "Meiers Lexikon 4

Technik und exakte Naturwissenschaften ", Bibliographisches Institut AG, 10 Mannheim 1969, vol. 1," a nozzle-shaped outflow aperture formed to form an inwardly directed, sharp-edged tube piece in a circular wall opening. "

According to Fig. 3, the edge junction 23 is formed so as to be directed obliquely towards the inner wall 27 of the drain tube 12 as seen in the flow direction 26 of the arrow-off steam. The side 22 of the nozzle 22 facing away from the filing steam thus protrudes further into the interior space 19 than the opposite side and away from the outgoing steam.

The nozzle walls 28 are bevelled at their ends in the region of the junction 23 and taper sharply towards each other. In contrast, the nozzle 22 comprises nozzle walls 28 with a nozzle wall 28 rounded by an outer opening outside the bore tube 12 and opposite the edge junction 23.

·: · Geometrically made - sharp-edged and junction j ··; formed into an inner opening and a rounded outer opening - to achieve that, * ·· ·. ** ·. that the vapor flow resistance of the steam flowing out of the drain pipe 12 is approximately, "* 25 times four times the flow resistance of the gas flowing from the gas gun 8a into the drain pipe 12.

Figures 4 and 5 show alternative embodiments in which the aeration opening 18 is connected via aeration conduit 20 to a discharge conduit 12 below the liquid level n of the coolant liquid f. According to Fig. 4, the aeration conduit 30 20 is formed L-shaped. and, at its lower end, connects to the interior space of drain pipe 12 ··· According to Figure 5, aeration pipe 20 is first wound in coolant region f around drain pipe 12 and is directed upwardly to the gas gun 8a above plane n. In addition, the flow path inside the coolant f:: ** · 35 is lengthened so that the outgoing steam cools * * · more deeply and condenses in the vent pipe 20.

117527 8

Fig. 6 illustrates a preferred variant in which the vent pipe 20 is connected to the drain pipe 12 above the level n of the liquid through the nozzle 22. The nozzle 22 is similar to the nozzle 22 depicted in Figure 3. The aeration tube 20 first runs away from the drain tube 12 horizontally with the drain tube 12, and then makes a bend downward toward the coolant f. The outgoing steam is therefore guided from the aeration tube 20 along a certain flow path so that the steam is blown obliquely towards the surface of the coolant f where it can release heat and condense. t

Compared to the embodiments illustrated in Figures 4 and 5, this embodiment has the advantage that the aeration tube 20 is always filled with gas from the gas space 8a.

According to Fig. 7, the drain tube 12 is possibly coaxially surrounded by a protective tube 30, which assumes the function of the drain tube in the event that the drain tube 12 possibly breaks. Air n exhaust? the conduit 20 is formed similar to the aeration conduit 15 illustrated in Fig. 6 and is guided through an opening 32 in the conduit 30 and is secured to the drain conduit 12.

Fig. 8 is an enlarged sectional view of a portion of the opening 32. From this, a portion of the outer wall 25 of the drain tube 12, to which both the vent pipe 20 and the nozzle 22 are attached, can be detected. Sa-20 also shows a portion parallel to the drainage tube 12, a protective tube 30 coaxially disposed around the drainage tube 12. The air supply pipe 20 is guided in through an opening 32, for example longitudinal; a full groove, through the conduit 30 so that there is a distance therefrom. climate

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. ··. the inlet conduit 20 is also guided through the conduit conduit 30 so that there is room for movement.

Due to the distance between the aeration pipe 20 and the protective pipe 30, a so-called leakage opening 34 is formed which should be closed. Therefore, it is covered by a cover 36. The cover 36 is constructed in two parts, the first part being a perforated plate-shaped guard ring 38, which is fixed to the aeration tube: .i 30 to 20. The second part is formed as a kind of cover or cover cloth. - * * · * \ 'Σ 39, and in particular in the form of a perforated plate and attached to the protective tube 30. The protective cover 39 is visible in the outermost regions of the cut. ···. formed L-shaped and overlaps with a guard ring 38 disposed between the guard cap 39 and guard tube 30.

Figure 9 illustrates, as an alternative embodiment, a flow restrictor 40 partially positioned inside the drain tube 12 and 117527 9 which extends to the aeration tube 20. By means of the flow limiter 40, a clear distinction is made between the inlet and outlet resistances of the gas flowing into the drain pipe 12 or of the vapor filing away from the drain pipe 12. The flow limiter 40 is thus connected to the flow path. Thus, in this embodiment, the flow path consists of a flow limiter 40, aeration tube 20, and aeration opening 18 not shown in Figure 9.

The flow limiter 40 comprises a rotary member 42 by means of which the steam is brought into a vortex or twist flow and subsequently introduced into aeration tube 20. There, the negative vapor flows along the longitudinal axis 48 in the direction of the tube 10. The rotation member 42 includes a single, largest feature, disk-like inflow component 44, at the outer end of which the steam flows in, the negatively-engaging means 46, for example vortex vanes, are disposed. In the vapor flow, where the steam first flows radially into the disc-shaped inflow components 44 along the longitudinal axis 48, the negating member 46 is rotated so that the disc-shaped inflow components 44 are provided with a helical or . The rotation member 42 expands in the direction of the longitudinal axis 48 in the form of a diffuser 50.

Preferably, the flow restrictor 40 further controls a cross-section reduction element 52 coupled to the flow path at the connection of the circulating member 42, which may, for example, be in the form of a venturi tube.

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:. ·. If the flow limiter 40 is implemented in this way, it has the advantage that it. ···! provides a very high flow rate for the steam flowing out of the drain tube 12 • «'V'. 25, on the other hand, the gas flowing in through the aeration tube 20 can flow into the drain tube 12 on the side of the flow restrictor 40 almost freely. The operation of the flow limiter 40 is based on * ··· the formation of a helical flow and a sharp increase in the rotational speed of the helical flow as a result of the reduction in the cross section. At the same time, the static pressure around the rotation 30 about the longitudinal or longitudinal axis 48 decreases. Depending on the flow conditions, this • ♦ · area may cause underpressure.

The effective flow cross section of the off-stream steam is in the mid- • · ·, * ··. due to escape forces, small and limited to the outer cross-section of the aeration tube 20 at a distance of t? There is no steam flowing in the • * · <: * ·· 35 areas around the longitudinal axis 48. As a result of the reduction in the effective flow cross section, i, which is further enhanced by the cross-section reduction element 117527 10 52, the flow limiter 40 provides a very high flow resistance to the filing steam. Instead, in the upstream direction, the gas may flow into the drain tube 12 as a purely axial flow into the drain tube 12, approximately free of the flow limiter 40 without obstructing the circulation member 42. Thus, by means of the flow limiter 40, a clear distinction is made between the flow resistance and the flow resistance.

The invention distinguishes itself by the advantage of a maintenance-free aeration or deaeration device which prevents the coolant remaining in the drain pipe 12 after the steam has been blown away from being drawn into the drain pipe 12 unauthorized. In addition, the geometry of the aeration system ensures that a clear distinction is made between the flow resistance and the flow resistance. Therefore, in the event that the steam is blown away, only a small amount of steam flows out through the aeration opening 18. On the other hand, after the steam has been blown off, a large amount of gas from the gas gun 8a flows through the vent 18 to the discharge pipe 12. The invention is also distinguished by the advantage of not having active or movable parts.

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Claims (16)

Apparatus for blowing meadows away in a nuclear power plant, which has a drainage pipe (12) which terminates in a coolant (f) in a chamber (6, 8), characterized in that the inner space 5 of the drainage pipe (12) 19) interconnects via a flow route (18, 20, 22, 40) which is permanently held open by an aeration opening (18) which opens into a gas range (6a, 8a) outside the coolant (f). Apparatus according to claim 1, characterized in that it is provided with an aeration pipe (20), in which the flow route (18, 20, 22.40) likes. 3. Apparatus according to claim 1 or 2, characterized in that the flow route (18, 20, 22, 40) is formed such that the flow resistance of meadow flowing away from the drainage pipe (12) is greater than the flow resistance of gas flowing in. in the drainage pipe (12) from the gas region 15 (6a, 8a). 4. Apparatus according to claim 3, characterized in that the away flow resistance has been determined by means of the edge orifice (23). 5. Apparatus according to claim 3, characterized in that the away flow resistance has been determined by means of a flow limiter 20 (40) comprising a rotating means (42) for generating a spiral flow in the flowing meadow, which rotating means is coupled in the flow path (18). , 20.22, 40). • · ♦ .. Apparatus according to any one of claims 1-5, characterized in that the flow route (18, 20, 22, 40) has been controlled so that the flowing gas condenses when it comes into direct or indirect contact with the gas. coolant (f). Σ · ..: Apparatus according to any one of claims 2-6, characterized in that the aeration pipe (20) is connected to the drainage pipe (12) below the level (n) of the liquid surface (f) of the coolant. 8. Apparatus according to any of claims 2-7, characterized in that the aeration opening (18) is directed downwardly against the coolant (f) and the aeration. the tube (20) extends to the vent opening (18) in particular downwardly. **: ** 9. Apparatus according to any of claims 2-8, characterized in that the aeration tube (20) is at least partially helical about the drainage tube (12). · ** '117527 Apparatus according to any of the preceding claims, characterized in that the drain drain pipe (12) is surrounded by a protective pipe (30). 11. Apparatus according to claim 10, characterized in that an opening (32) is provided in the protective tube (30), through which the aeration tube (20) 5 has been guided to a predetermined distance, in particular to create a small clearance. 12. Apparatus according to claim 11, characterized in that it is provided with a leakage opening (34) according to the opening (32) between the protective tube (30) and the aeration tube (20) and a cover (36). Apparatus according to any of the preceding claims, characterized in that the drainage pipe leads to a condensation chamber (6) and / or a tidal basin (8) in a boiling water nuclear power plant. 14. A method for blowing off meadows in a nuclear power plant, where meadows are biases away via the drainage pipe (12) for a limited time to a coolant (f) in the chamber (6, 8), above which is a gas space (6a, 8a), and thereafter the pressure in the drainage pipe (12) is uniformly equalized with the pressure in the gas space (6a, 8a), characterized in that gas flows from the gas space (6a, 8a) via a flow route (18, 20, 22, 40). is permanently open into the drainage pipe (12) as a result of the rescuing vacuum. 20 15. A method according to claim 14, characterized in that the meadow, when blowing off meadow, flows away via the flow route (18, 20, ·: · 22, 40) from the drainage pipe (12) and at the same time a larger Current · · ·: is directed. ·. resistance than the next to the gas flowing in the opposite flow direction-! 1 · 1! accession. · 25 16. A method according to claim 14 or 15, characterized in that the flowing stream is condensed when it comes into direct or indirect contact with the coolant (f). · 1 • 1 ·. ^ * · 1 '.V * · 1 * · • · *** • · • ♦ 1 · 1 ♦ * ·· • .... * · · • · • 1 · 2.. "1 • ·" .iJ • · ··· 1 1 • »• · 2 • · ·