FI118279B - Protection building for a nuclear plant and method of pressure equalization between a condensation chamber and a pressure chamber in a nuclear plant - Google Patents

Description

1 118279

The present invention relates to a containment structure of a nuclear power plant, in particular a boiling water reactor plant, which has a pressure chamber and is filled with a coolant to a level with a coolant filling level. The invention further relates to a method for equalizing the pressure between such a condensation chamber of a nuclear facility and a pressure chamber.

A containment of this type is known, for example, from EP 0492899 A1.

In a nuclear power plant, in particular a boiling water reactor plant, the reactor pressure vessel is housed inside a containment building. The containment is intended to divide areas of environmental importance and is part of the security system.

The safety regulations of such a nuclear facility require that, in the worst case scenario, the effects of the incident should be limited to the site. To meet these high safety standards, there is, inter alia, a cooling system that • · · * · * * ensures that, in all operating conditions of the plant, the pressure remains within the permissible limits for which it is designed. Changes in pressure in the protective structure are due, for example, to leakage in the steam line. An essential element for controlling such a disturbance is a condensation chamber which is ·: * ·· fitted inside the containment. Its interior or interior volume is called; ***. also for pressure chamber. The condensation chamber is partly a filling of cooling water, which is supplied with steam from the pressure chamber under certain operating conditions. for condensation. Thus, the overpressure in the pressure chamber is reduced. If there is a vacuum in the pressure chamber, the pressure equalization between the pressure chamber and the condensation chamber will, for safety reasons, be an advantage, since the wall between the chambers is only designed for a certain pressure reduction.

One way to balance the pressure is to fit a non-return valve on the wall between the two chambers. Exceeding the specified pressure drop I · · "... 35 the non-return valve releases the flow path from the condensation chamber to the pressure chamber ** As soon as the pressure is equalized, the valve closes the flow path. However, there is a risk of collapse of the non-return valve sealing surface. so that a leak occurs between the pressure and the condensation chamber, however, such a leak adversely affects the operation of the pressure relief system.

5 In modern boiling water reactor types, such as SIEMENS

In the AG SWR 1000, care has been taken that hydrogen conducts into the condensation chamber. This prevents hydrogen, which may be formed under certain conditions of use, from accumulating in the containment and hindering the condensation of steam in or adjacent to the capacitors therefor. Therefore, in these modern reactor types, an absolute seal between the pressure and condensation chamber in normal operation is necessary, otherwise hydrogen overflow into the condensation chamber would not work.

The object of the invention is to ensure the safe operation of the safety system of a nuclear power plant, in particular a boiling water reactor.

According to the invention, the object is achieved by a containment structure of a nuclear plant, in particular a boiling water reactor plant, characterized in that the liquid line is connected by a flow technique to a single refrigerant in the condensation chamber, in particular at least one orifice.

In normal operation, the fluid line is at least partially filled with coolant * ..., in particular water, so that the flow path formed by it is closed by a siphon or u-shaped structure. · * ** When crossing between the condensation chamber and the pressure chamber, the coolant is squeezed out of the fluid line so that a pressure equalization can occur between the two chambers • · · ϊ., Ϊ 25 The decisive advantage of such a connection for both chambers ·: ** : It can sometimes be seen that, in normal operation, the flow path is completely sealed by the coolant so that no leakage currents between the two chambers can occur, which may interfere with the operation of the plant's pressure relief system: ·.

• · · · · · · · · · · · · · · · · · · · · · · ·, 30 There is thus a continuous exchange of coolant * · *. * 'Between the fluid line and the condensation chamber through the orifice. Thus, after the * *: '··, the fluid line has been opened, it automatically closes again when: [**: a large-scale pressure equalization has taken place between the two chambers.

·. ··. Thus, the liquid conduit formed in this way guarantees the liquid conduit • · ·.

35 don automatic and reversible opening and tight closure depending on the pressure conditions in both chambers. The operating mode of the fluid line is then purely passive, that is, pressure relief is possible without additional aids, and in particular without auxiliary energy. Due to its sturdy construction and the fact that the operating mode is only determined by the pressure conditions, high reliability is guaranteed. Control via the control point is not necessary.

In a preferred embodiment, the first mouth end of the fluid line extends to the gas gun of the condensation chamber, which in normal use is filled with coolant up to the fill level. This has the advantage that, when the flow path is open, there is a gas exchange between the two chambers. Thus, a more efficient pressure equalization is ensured without the larger quantities of coolant being flushed from the condensation chamber into the pressure chamber.

The aperture is preferably arranged below the fill level, and in particular so that the aperture is guaranteed to be covered with refrigerant under all relevant operating conditions. This ensures that there is always sufficient coolant supplied to the liquid-15 line to achieve a safe and tight seal. The aperture fitting thus preferably takes into account fluctuations in the fill level.

In order to allow gas to flow from the condensation chamber gas gun through the fluid line into the pressure chamber, the flow resistance of the coolant flowing through the opening through the fluid line is greater than the flow resistance of the coolant flowing from the liquid line into the pressure chamber. Thus, it is guaranteed that, when the preset maximum internal pressure is exceeded in the condensation chamber, the amount of coolant flowing through the orifice to the liquid v line is less than the amount flowing into the pressure chamber. Thus, in this case, the liquid line forms the gas flow path 25 from the gas weapon of the condensation chamber. In addition, the flowing gas causes the coolant flowing through the orifice to flow into the fluid line, ** ·. either. The flowing gas thus makes sure that the gas flow path remains constant in spite ··· Paana after filing counter the coolant.

yt The orifice of the condensation chamber connecting the condensation chamber and the pressure chamber is preferably located inside the condensation chamber • · ** "* below the filling level height. *: The siphon-like region of the conduit is positioned deep enough into the condensation chamber so that the siphon-like region is filled with coolant even when a maximum external overpressure of 35 is generated.

• · • · • φ * 4 118279

Thus, the fluid line is fitted to the condensation chamber relative to the condensation tube such that when pressure builds up in the pressure chamber, the liquid line remains closed at least as long as the flow path from the pressure chamber to the condensation chamber through the condensation tube is opened. The siphon-like region 5 should then be positioned deep enough in the condensation chamber so that the liquid conduit remains closed even in the event of sudden overpressure and the associated passage of the water column in the liquid conduit. Such a measure ensures that the fluid line only opens when the condensation chamber is pressurized, but remains closed when the pressure chamber is pressurized.

10 The vertical distance between the siphon-like area and the other mouth end of the fluid line in the pressure chamber is suitably measured such that the fluid line is closed by the refrigerant until a maximum inlet pressure is created in the condensation chamber. The maximum vertical pressure allowed is thus adjusted along the vertical length of the liquid line.

Preferably, the fluid line has a first branch disposed inside the condensation chamber, which is connected via a siphon-like region to a second branch which passes at least partially through the wall between the condensation chamber and the pressure chamber. This has the advantage that leakage between both chambers is also impossible in the event of a possible fluid line break.

In addition, there is preferably a replacement plan for increasing the safety of the fluid line.

The object of the invention is further achieved by a method for equalizing pressure between a nuclear power plant, in particular a boiling water reactor plant, a condensing chamber and a pressure chamber, wherein the liquid line comprising the siphonous region is between the condensation chamber and the pressure chamber. in normal use:: ··· at least partially filled with refrigerant, and thus at maximum inlet; ** ·. when the pressure in the condensation chamber is exceeded, the fluid line is automatically released, and the method is characterized in that the liquid line exchanges coolant with the condensation chamber via a flow connection, in particular through at least one opening.

* · '* “* The advantages and particular embodiments described in connection with the containment are, of course, transferable to the process. Other preferred embodiments of the method are disclosed in the dependent claims.

··· .1. An embodiment of the invention will now be described in more detail with reference to the drawing. In Fig. 1, Fig. 1 is a roughly simplified, schematic representation of a containment structure, Fig. 2 is a schematic sectional view of a pressure chamber and a condensation chamber having a fluid line in normal operating mode, with the same pressure between the condensation chamber and the pressure chamber 3. Figure 2 shows when the pressure in the pressure chamber is increased, Figure 4 shows the figure 2 when the internal pressure in the condensation chamber is increased, Figure 5 shows the figure 2 when the maximum inlet pressure in the condensation chamber is reached, and Figure 6 shows Figure 2 cutting when the fluid line is open and the internal overpressure is at maximum.

1, the reactor pressure vessel 4, the condensation chamber 6 and the flow basin 8 are housed within the containment building 2. The remaining interior space of the containment building 2 is called the pressure chamber 10. The containment building 2 is specifically designed for a boiling water reactor , high safety standards.

The condensation chamber 6, the flow cavity 8 and the pressure chamber 10 are separated by massive concrete walls 12, the flow cavity 8 being open upwardly into the pressure chamber 10. The flow cistern 8 contains coolant, in particular water, * · · v; which is introduced in the event of a failure to cool the reactor pressure vessel 4.

The condensation chamber 6 is also filled with coolant up to the fill level H by a coolant: **. In the condensation chamber, the coolant forms a water collection vessel 14, above which is located a gas area 16. The condensation chamber is closed in a gas-tight manner in the pressure chamber 10 and in the flow basin 8: ·. towards. It is, of course, connected to the pressure chamber 10 by a condensation tube 18 * ·· 30, however, the orifice 19 being submerged in the water collection vessel 14 * · * · "'at the depth M of the orifice.

• * ·. The left half of the figure shows a fluid line 20 comprising a first leg 22 and a second leg 24 connected to one another via a phial-like region 26. The fluid line 20 is thus substantially substantially U-shaped. The first mouth end 28 of the fluid line 28 is located at the end of the first leg 22 and extends to the gas gun 16. The siphonic region 26 extends into the wall 12 between the condensation chamber 6 and the pressure chamber 10. Inside this wall 12, a second leg 24 extends to the second mouth end 30 of the fluid line 20, which ends in the pressure chamber 10.

Below the filling level height H, the first leg 22 has a flow-like connection between the fluid line 20 and the condensation chamber 6 in the form of an opening 32. Through the opening 32, it is possible to continuously exchange coolant between the liquid line 20 and the condensation chamber 6. In order to ensure that coolant can be continuously fed through the opening 32 to the fluid line 20, the opening 32 is arranged at an immersion depth T1 below the fill level height H and sufficiently far from the latter. The opening 32 is arranged, for example, about 2 meters below the fill height H.

The fluid line 20 is formed and fitted inside the condensation chamber 6 so that it opens and closes automatically and reversibly 15 as soon as the internal overpressure APi exceeds the preset maximum inlet pressure APi (max) or respectively when a large amount of pa has occurred between the condensation chamber 6 and . The internal excess pressure APi is then defined as the positive pressure difference between the condensation chamber 6 and the pressure chamber 10. The internal pressure Pi of the condensation chamber 6 thus exceeds the external pressure Pa of the chamber 20. The maximum inlet pressure APi (max) is defined by the vertical distance A between the second mouth end 30 and the siphon region 26.

: The maximum inlet pressure APi (max) is set, for example, to 0.8 bar so that the vertical distance A is 8 meters. External pressure APa is understood to mean a positive pressure difference between the pressure chamber 10 and the condensation chamber 6 25. The external pressure Pa thus exceeds the internal pressure Pi. Under normal operating conditions, both chambers 6, 10 are exposed to approximately atmospheric pressure.

. · * ·. At the same time, the fluid line 20 is formed and arranged so that it is kept closed by the coolant at least up to a maximum external pressure APa (max). The maximum external pressure APa (max) is defined by the depth M. of the mouth of the condensate tube ... ... 30, which is approximately 3.5 meters, so that the maximum external pressure APa (max) is 0.35 bar. This means that when such external overpressure APa is generated, gas or vapor is discharged from the pressure chamber 10 through the condensation tube 18 into the condensation chamber 6 and condenses there. Thus, the external pressure Pa in the pressure chamber 10 is reduced.

In order to prevent the liquid line 20 from opening at such a maximum external pressure, the siphon-like region 26 is arranged below the immersion depth T2 7118279, for example about 4 meters. The immersion depth T2, including the length L of the protrusion by which the first leg 22 protrudes from the water collecting vessel 14, is preferably measured so that the fluid line 20 is not released even at the sudden external pressure APa and its associated water column overflow the difference between the water column in the sudden external pressure APa may be 2 times greater in the variable case than in the unchanged case. The length L is preferably 5 m. For purposes of illustration, magnitude ratios are not given in scale in Figure 1.

10 Such a fluid conduit 20, which is reversibly sealed with a refrigerant, has provided a passive, so-called '' hydraulic non-return valve ''. The fluid line 20 forms a pressure relief line. Its advantage is that it operates without moving parts and does not allow gas leaks as long as the internal overpressure APi is below the maximum inlet pressure APi (max). If the internal excess pressure APi 15 exceeds this limit, a connection is automatically established between the gas region 16 and the pressure chamber 10, through which gradual pressure relief is possible. As soon as the pressure equalization in both chambers 6, 10 is approximately reached, the fluid line 20 automatically closes again, resulting in a gas-tight separation of the two chambers 6,10.

20 Due to its robust and simple design, the '' hydraulic non-return valve 'is virtually trouble free and does not require maintenance. It '· *: requires no control technology or foreign energy. Maximum Inlet · * ·: The pressure APi (max) is adjustable by suitable dimensioning and adaptation of the fluid line 20. Thus, it is ensured that the pressure difference between the condensation chamber 6 and the pressure chamber 25 20 cannot substantially rise above the maximum overpressure APi (max) determined in this way. This is essential for the protection; ···. to ensure the integrity of the building 2, which means that it is ensured that the wall 12 between the condensation chamber 6 and the pressure chamber 10 is only loaded up to about the maximum inlet pressure APi (max). The walls • · ♦ 30 12 can therefore be formed accordingly.

The function of the "hydraulic non-return valve" formed by the fluid line 20 will be explained in greater detail with reference to Figures 2-6.

According to Fig. 2, the pressure between the condensation chamber 6 and the pressure chamber 10 is the same, the internal overpressure APi as well as the external overpressure APa being zero. With the same pressures in both chambers 6, 10, the 118279 level of the coolant in the fluid line 20 is the same as the fill level height H of the coolant in the condensation chamber 6.

Figure 3 illustrates a situation where, for example, the external overpressure APa is 0.2 bar. In this case, a height difference X of 2 meters is formed between the surface of the liquid column of branch 22 and the opening 22 of branch 22. Figure 3 illustrates a situation of sudden external overpressure APa where the filling level or water level in the first branch 22 rises 1 meter. Due to the opening 32, the fill level in the first leg 22 gradually decreases again to the fill level height H. 10 Since the external overpressure APa remains constant, the fill level in the second leg simultaneously drops to a height 2 meters below the fill level height H. This situation corresponds to a constant state. Thus, when external pressure APa is generated from the fluid line 20, coolant flows through the orifice 32 to the condensation chamber 6.

Figure 4 illustrates a situation where a positive internal excess pressure APi is, for example, 0.3 bar. Simultaneously, it is assumed that the internal pressure Pi increases in the condensation chamber 6 at a certain rate. The internal overpressure APi results in a height difference X between the filling levels in the first and second legs 22, 24. Due to the pressure rise rate, a constant state is not achieved and the filling level 20 in the first leg 22 is permanently below distance Y. Since the internal excess pressure APi is below the maximum internal pressure APi (max), the fluid line 20 remains closed.

* · ·: When the maximum inlet pressure APi (max) of Figure 5 is reached, *: * the height difference X corresponds to the vertical distance A so that 25 of the second orifice end 30 of the fluid line 20 are cooled to the pressure chamber 10.

·; ··· When the internal overpressure APi remains constant, 30 at one end of the mouth. as much coolant flows into the pressure chamber 10 as through the opening 32 to the first branch 22. This overflow of coolant can be neglected for the pressures 30 Pa, Pi in the pressure chamber 10 and the condensation chamber 6.

If the internal overpressure APi decreases again, less coolant is discharged from the second mouth 30 than through the opening 32 to the first leg 22. Therefore, the water level in the first leg 22 and the height difference y., 'X between the two water pillars decreases and falls below distance A value.

Conversely, if the internal overpressure APi continues to rise, then gas flowing through aperture 32 ***** will pass through the siphon-like region 26 to another branch 9 118279 and rise there. It then partially displaces the water in the second leg 24. Thus, the water column in the second leg 24 is effectively reduced so that it can no longer replace the internal overpressure ΔΡϊ. Therefore, additional gas flows into the second leg 24, which further reduces the water column.

Due to this self-reinforcing phenomenon, practically all water is blown out of the second branch 24 in a short time and already when the maximum internal overpressure APi (max) is slightly exceeded and the fluid line 20 is thus practically completely drained.

Figure 6 illustrates this condition when fluid line 20 is completely emptied at maximum inlet pressure APi (max). The pressure equalization between the chambers 6, 10 occurs by exchanging gas between the gas region 16 and the pressure chamber 10. As a result of the pressure drop, the gas reaches a certain flow rate, which results in the coolant entering through the opening 32 being dragged along. The volume flow rate of the gas is then approximately 15 orders of magnitude greater than the amount of coolant inlet flow into the fluid line 20 according to the exemplary embodiment. To achieve this, the inner diameters of the flow line 20 and aperture 32 are respectively selected.

As soon as the pressure between the two chambers 6, 10 is approximately equalized, the fluid line 20 is again filled with coolant 20 through the orifice 32 until the condition of Figure 2 is reached and the condensation chamber 6 is again gas-tightly separated from the pressure chamber 10.

··· V · 1 The filling volume of the fluid line 20 as the pressures iT of both chambers 6, 10 are approached is determined by the flow resistance of the orifice 32. Here, the borehole 32 of the opening 32 may be altered or the number of openings 32 may be more than ··· meters. Pressures: "1 · 25 The amount of fluid equalization in the situation of Fig. 6 is decisively determined by the diameter of the liquid flow line, i.e. the inside diameter of the flow, whereby a larger halftone leads to a faster pressure equalization.

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Claims (13)

A containment structure (2) for a nuclear plant, in particular a boiling water reactor plant, having a pressure chamber (10) and, in normal use, a condensation chamber (6) filled with coolant to fill level (H) connected by a fluid line (20) comprising a siphonic region (26). characterized in that the fluid conduit (20) is fluidly connected to one of the refrigerants in the condensation chamber (6), in particular through at least one opening (32). A containment structure (2) according to claim 1, characterized in that the condensation chamber (6) comprises a gas region (16) above the filling level height (H), to which the first mouth (28) of the liquid conduit (20) extends. Shelter (2) according to Claim 1 or 2, characterized in that the opening (32) is arranged below the fill height (H) 15, and in particular in such a way that the opening (32) is covered with coolant. The containment structure (2) according to any one of the preceding claims, characterized in that the flow resistance of the coolant filing into the fluid line (20) through the opening (32) is higher than the flow resistance of the coolant flowing from the liquid line (20) to the pressure chamber (10). Ml v A containment structure according to any one of the preceding claims: T: (2), characterized in that the condensation chamber (6) is connected to the pressure chamber (10) through a condensation tube (18) having a second orifice (19) I ···. ; * · *. is fitted inside the condensation chamber (6) to a depth (M) below the fill level (H) below the filling level height (H) derived from the maximum allowable overpressure [APa (max)] in the pressure chamber (10), whereby the siphonous region (26) Fitted into the condensation chamber (6) sufficiently deep so that the siphon-like region (26) is filled with coolant even when a maximum external pressure [APa (max)] is generated. A containment structure (2) according to any one of the preceding claims, characterized in that the second siphon-shaped area (26) and the fluid conduit (20) are provided. the vertical distance (A) between the orifice head (30) in the pressure chamber is measured such that the fluid conduit (20) is closed by the coolant until a maximum internal pressure [APi (max)] is generated in the condensation chamber (6). A containment structure (2) according to any one of the preceding claims, characterized in that the liquid conduit (20) comprises a first branch (22) inserted into a condensation chamber (6) 11 11 8279 connected to a second branch (24) through a siphon-like region (26), and the second leg (24) extends at least partially within the wall (12) between the condensation chamber (6) and the pressure chamber (10). A method of equalizing pressure between a nuclear power plant, in particular a boiling water reactor plant, a condensation chamber (6) and a pressure chamber (10), wherein the liquid line (20) comprising a siphon-like region (26) between the condensation chamber (6) and the pressure chamber (10) wherein the fluid line (20) is automatically released when the maximum inlet pressure [APi (max)] is exceeded, the feeling 11 u that the fluid line (20) exchanges coolant with the condensation chamber (6) via a flow connection, in particular at least one opening (32). Method according to Claim 8, characterized in that the liquid line (20) connects the gas region (16) of the condensation chamber (6) to the pressure chamber (10). Method according to Claim 8 or 9, characterized in that, when the maximum inlet pressure [APi (max)] falls below, and as the balancing between the pressure chamber (10) and the condensation chamber (6) approaches, the refrigerant flows into the fluid line (20) and closes it again. 10 1 1 8279 A method according to any one of claims 8 to 10, characterized in that, when the maximum inlet pressure [APi (max)] is exceeded, less coolant flows through the orifice (32) to the fluid line (20) than to the pressure chamber (10). ..2 · 1 Method according to Claim 11 and Claim 9, characterized in that, when the maximum inlet pressure [APi (max)] is exceeded:: ··· gas is drawn from the gas gun (16) into the liquid line (20), whereupon the gas is drawn. according to the coolant through the opening (32). · · · A method according to any one of claims 8 to 12, characterized in that the fluid line (20) remains closed until the pressure chamber (10) has a maximum outer pressure [APa (max)], whereby the maximum outer pressure [**; When 1 APa (max)] is exceeded, the flow path between the condensation chamber (6) and the pressure chamber (10) is opened by the condensation tube (18). • · · • · * · * · »* • ·· * · · * ♦ · · 2 • · · 12 1 1 8279