EP0799385B1 - Device for limiting the volumetric flow of a pressurized fluid - Google Patents

Description

The invention relates to a device arranged in a nuclear power plant for limiting the Volume flow according to claim 1.

Document FR-A-2 356 029 shows a limiting device with a Swirl generating element and one perpendicular to Main axis extending inflow component.

In nuclear power plants the one Have system of lines and containers in which a fluid under pressure is carried or collected it is important for safety reasons in the case of a Leakage in the system causes the volume flow to escape and / or to keep the mass flow of the fluid as low as possible. This plays especially with nuclear power plants, where the fluid has a certain hazard potential has, for example, a chemically reactive substance, a hot vaporized liquid or radioactive contaminant Cooling water is. To the emerging volume flow, for example, if a line breaks completely, To keep the cross-sections as small as possible kept small, Venturi nozzles inserted, downstream Quick-acting fittings are used as well as pipe burst protection built-in. All of these measures affect the Part of the way the industrial plant works normal operation, require additional monitoring and maintenance work or involve the risk of failure in the event of a leak in the system.

The object of the invention is therefore a passive device to limit the volume flow in one of one to specify a pressurized fluid flowable system in a nuclear power plant, which can also be added to the system as part of a retrofit and when a leak occurs in the system, in particular the break of a line, the outflowing volume flow if possible keeps low.

According to the invention, the object is achieved by a device according to claim 1.

Through an inflow component perpendicular to the main axis occurs in the event of a leak or break in the flow channel a flow of the pressurized fluid in the direction the main axis. The fluid also gets a tangential one Velocity component in a plane perpendicular to the main axis. Because of this tangential speed component, which gets bigger towards the main axis and one Pressure drop leading to the main axis, the volume flow limited or reduced in the direction of the main axis. This limitation or reduction of the volume flow through Swirl generation also occurs, for example, when there is an outflow of Water through the drain opening in a bathtub. To the The main axis forms an area of low pressure, in particular Vacuum, in the steam under saturation pressure or low-density steam or gas flows, causing the Volume and mass flow of the fluid can be reduced. By connecting the swirl generating element with the Flow channel is a redirection of flow from one Flow direction in a plane perpendicular to the main axis in a flow direction parallel to the axis of the flow channel guaranteed. The axis of the flow channel and the The main axis of the device are preferably identical, at least largely parallel to each other.

The inflow component preferably has an inflow opening which is spaced from the major axis. Hereby is a tangential flow perpendicular to the main axis achievable with low pressure loss.

To create a swirl, especially a tangential one Speed component, has the swirl generating element fixed twist scoops that are vertical in one plane are arranged to the main axis. These swirl blades are preferably arranged on a circle and steer the initially flow directed radially onto the main axis into a flow tangential to the circle. The swirl generation element can alternatively in the inflow component have at least one inlet channel that is tangential a circle with a center on the main axis or an axis parallel to it runs.

The swirl generating element is preferably in a container arranged of the system at which the flow channel ends. This will result in a break or leak in the Flow channel an outflow of fluid from the container through the swirl generating element into the flow channel. The inflow opening can be essential in the container further from the main axis, which is preferably with the axis of the flow channel coincides, be spaced apart as one Wall of the flow channel. The distance of the inflow opening and possibly a swirl blade from the axis preferably larger than the diameter of the flow channel. By arranging the swirl generating element in one Container is also guaranteed to be independent of the local Location of the break or leak in the flow channel a limitation and reduction of the volume flow and the Mass flow from the system is guaranteed. Also is even the cross section of the flow channel exceeding the size of the device a subsequent input or attachment to the flow channel possible.

The device preferably has a cross-sectional constriction element to narrow the cross section of the flow channel. The cross-sectional constriction element is fluid connected to the swirl generating element, so that a flow of the fluid in the direction of flow at a First leak the swirl generating element and then the cross-sectional constricting element flows through. Since the volume or Mass flow one from a container through a flow channel escaping fluid through the cross section of the flow channel is determined and also with a smaller cross section becomes smaller, the cross-sectional constriction element ensures an additional reduction in volume flow a leak or break in the flow channel. The cross-sectional constriction element is preferably designed so that it is in the mouth of the flow channel in the container can be inserted.

Between swirl generation element and cross-sectional constriction element is preferably a diffuser, in particular a Radial diffuser arranged, which is an enlargement of the Flow cross-section of the device from the cross-sectional constriction element to the swirl generating element. The flow cross section of the swirl generating element is preferably larger than the cross section of the flow channel, so that during normal operation of the system, in particular a cooling system of a nuclear power plant, the additional Flow pressure losses from cross-sectional constriction element and swirl generation element by the additional Pressure recovery in the diffuser is at least compensated, i.e. the normal volume flow through the device is not is changed.

It is particularly advantageous to design the device as a construction Unit with swirl generating element, diffuser and cross-sectional constriction element to manufacture, because this makes it easy Retrofitted a flow channel in a system can be.

In a system in which the pressurized fluid from a container into the flow channel It is advantageous if the cross-sectional constriction element flows into it has a swirl destruction element. This causes the swirl generating element Swirl generated again largely during normal operation destroyed, so that almost no pressure loss occurs. The Swirl destruction element preferably has corresponding fixed and curved blades. Alternatively, too a swirl destruction element downstream of the flow channel be provided, which is rotationally symmetrical to the main axis or an axis parallel to it and at least one tangential Outlet channel, for example with a circular one Cross section. This also means that during one normal operation of the system a destruction of that by the Swirl generating element ensures swirl generated.

The system is preferably a cooling system a nuclear power plant holding a reactor pressure vessel has, in which the pipeline opens. In the event of a break the pipeline is limited and reduced volume and mass flow of the Fluids. Compared to a system without the device is one Reduction of the leaking fluid to half or even possible down to less than 1/10. The device can in the course retrofitting from inside the reactor pressure vessel in the pipeline to be inserted. An arrangement of the swirl generating element, of the diffuser and the cross-sectional constriction element is done so that during normal operation of the cooling system, at most little additional Flow pressure losses occur.

FIG 1

eine Vorrichtung in einem System zur Führung eines unter Druck stehenden Fluides in einem Längsschnitt,

FIG 2

einen Querschnitt der Vorrichtung gemäß FIG 1 entlang des Schnittes II-II und

FIG 3, FIG 4

je eine weitere Ausführungsform der Vorrichtung in einem Längsschnitt.

The devices and a use of the device are explained in more detail with reference to the exemplary embodiments described in the drawing. Show it:

FIG. 1

a device in a system for guiding a pressurized fluid in a longitudinal section,

FIG 2

a cross section of the device of Figure 1 along the section II-II and

3, 4

each a further embodiment of the device in a longitudinal section.

1 to 4 each have the same reference numerals same meaning.

1 shows in a longitudinal section a section of a container 6, a reactor pressure vessel 6a, a system through which a pressurized fluid, in particular water or water vapor, flows. The detail representation shows the line end 9 of a flow channel 2, a pipeline 2a, which opens into the line end 9 into the reactor pressure vessel 6a. The pipeline 2a is, for example, a condensate-carrying pipeline 2a with a diameter of 200 mm for the emergency condenser of a boiling water nuclear reactor plant. During normal operation of the nuclear reactor plant, the fluid flows from the pipeline 2a into the reactor pressure vessel 6a. The device 1 has a swirl generating element 4 with swirl blades 10, which are arranged on a circle 11 in a plane perpendicular to a main axis 3a of the device 1. An inflow opening 15, which is spaced apart from the main axis 3a, is formed between two adjacent swirl blades 10. In the area of the inflow openings 15, the wire-generating element 4 forms a circular disk-shaped inflow component 14 which extends essentially perpendicular to the main axis 3a. The radius of the circle 11 is more than twice as large as the radius of the circular pipeline 2a. A diffuser 7, in the form of a radial diffuser, adjoins the swirl generating element 4 and narrows on its outside to the inside diameter of the pipeline 2a. A cross-sectional constriction element 5 in the form of a Venturi tube connects to the diffuser 7. The smallest inner diameter of the cross-sectional constriction element 5 is approximately 62.5% of the inner diameter of the pipeline 2a. The device 1 with the swirl generating element 4, the diffuser 7 and the cross-sectional constricting element 5 forms a structural unit which is introduced into the pipeline 2a from the inside of the reactor pressure vessel 6a, so that the swirl generating element 4 remains in the reactor pressure vessel 6a and the cross-sectional constriction element 5 projects into the line end 9. Due to the arrangement of the swirl vanes 10 shown in FIG. 2 on a circle 11 with a curvature in the direction of the tangent to the circle 11, the fluid flowing from the reactor pressure vessel 6a into the swirl generating element 4 when a break occurs in the pipeline 2a tangentially contains a speed component to the circuit 11. During normal operation of the boiling water nuclear reactor plant, in which the fluid flows from the pipeline 2a into the swirl generating element 4, the device 1 causes no or only insignificant additional flow resistances. The height of the swirl generating element 4 of about 30 mm and the radius of the circle 11 of about 600 mm are chosen so that the outflow cross-sectional area of the device 1 is significantly larger than the inflow area given by the cross-sectional area of the pipeline 2a. The additional pressure recovery of the diffuser compensates for the additional pressure losses generated by the other elements. As a result, the volume flow of the fluid is not impaired during normal operation of the boiling water nuclear reactor system. The narrowing of the cross section of the pipeline 2a by the cross-sectional constriction element 5 is approximately 39%. If additional flow pressure losses are permissible, this narrowest cross-section can be reduced even further, for example to 27% of the cross-sectional area of the pipeline 2a, if the additional pressure loss coefficient ζ is _also 1 or 19% of the cross-sectional area of the pipeline 2a if ζ is _also 3.

The inflow opening 15 and the swirl blades 10 are from an axis 3 of the flow channel 2 as far away as possible appropriate. It is more than twice the radius of the Pipeline 2a from the main axis 3a, which with the axis 3 of the Flow channel coincides, spaced. With a normal one Operation of the nuclear reactor plant, in which the fluid from the Pipeline 2a flows into the reactor pressure vessel 6a pressure recovery through the swirl generating element 4, slightly disturbed at most. Due to the curvature of the fixed swirl blades 10 leaves the in the reactor pressure vessel 6a fluid flowing into the swirl generating element 4 almost without twist. The swirl generating element 4 carries however essential for the reduction and limitation of the Volume flow and mass flow in the event of a line break the pipe 2a at. In this case it contains from the Reactor pressure vessel 6a flowing fluid predominantly tangential flow direction. As a result of the conservation of angular momentum the tangential velocity component increases of the outflowing fluid largely inversely proportional to the distance from the main axis 3. This applies in particular to low friction effects. The increase in tangential Velocity and the kinetic energy of the outflowing Fluid is caused by a decrease in static pressure Accompanied in the direction of the main axis 3. The pressure drop is around the greater the smaller the distance from the main axis 3. With a sufficiently large initial twist, that in the swirl generating element 4 is generated, even compared to the Negative pressure. Near the Main axis 3 is thus at an outflow Liquid vapor under saturation pressure or for escaping Steam or escaping gas corresponding to steam or gas of low density.

The already through the cross-sectional constriction element 5 greatly reduced outflow cross-section of the fluid in the Pipeline 2a thus has a mass flow density that towards the main axis 3 is getting smaller. The outflowing Volume flow or mass flow is thus determined by the Swirl generating element 4 generated swirl in addition to that Reduction due to the narrowing of the cross-section continues to be significant decreased. This reduction or limitation of the volume flow as a result of additional swirl generation, for example even if water flows out of one Bathtub on, this outflow is the slower, the stronger the vortex that forms in the drain pipe.

For a nuclear reactor plant with a pressure of about 70 bar in Inside the reactor pressure vessel 6a and the one connected to it Pipe system and an ambient pressure of The volume flow can break about 1 bar if the pipeline breaks 2a by using the device 1 to approximately one Limits tenths of the value without the device 1 would exit.

3 shows a further embodiment of a device 1 shown. The device 1 has a swirl generation element 4 with fixed swirl blades 10. To the swirl generation element 4 closes as shown in FIG 1 a diffuser 7 and a cross-sectional constriction element 5. The cross-sectional constriction element 5 points around the axis 3 of FIG Pipeline 2a around a displacement body 13, between the and the inner wall of the pipeline 2a swirl vanes 12 are arranged, which form a swirl destruction element 8 belong. The device 1 is analogous to 1 into the line end 9 a pipeline 2a opening into the reactor pressure vessel 6a inserted. In this case, however, the pipeline is 2a a pipeline into which during normal operation the nuclear reactor plant from the reactor pressure vessel 6a pressurized fluid flows. The swirl generation element 4 is dimensioned so that in normal operation no limitation of the volume flow in the cross-sectional constriction the pipe 2a takes place. By in the direction of flow downstream during normal operation Swirl destruction element 8, the swirl generated is largely destroyed again and the static pressure regained.

In the event of a break in the pipeline 2a with an increase in the tangential speed and thus the swirl a limitation of the volume flow and the mass flow the swirl generation and the narrowing of the cross section in the Pipeline 2a.

4 shows an alternative embodiment of the device 1, which extends along a main axis 3a. The Device 1 has a swirl generating element 4, which an inflow component 14 perpendicular to the main axis 3a with an inflow opening spaced apart from the main axis 3a 15 owns. The swirl generating element 4 is with a Cross-sectional constriction element 5 in a the reactor pressure vessel 6a of a nuclear power plant penetrating flow channel 2 introduced. On the swirl generating element 4 opposite end of the flow channel 2 is a to Main axis 3a rotationally symmetrical swirl destruction element 8 arranged, which is spaced from the main axis 3a has a tangentially arranged outlet channel 16. On the outlet channel 16 closes a not shown Pipeline 2a of the system. The device 1 is suitable preferably in newly constructed industrial plants, especially a nuclear reactor plant, or for retrofitting, in which the cable routing in the system can be changed. It is characterized by a special low flow pressure loss because both the Generation as well as the destruction of the twist without any special Swirl blades is reached. The inflow component 14 is essentially rotationally symmetrical to the main axis 3a and has one or more inlet channels Cross-section, which are arranged tangentially. The structure of the swirl destruction element 8 corresponds approximately the spiral casing of a centrifugal Pump. The inflow component 14 experiences a normal one Operation of the system, i.e. the nuclear reactor plant, only Static significantly reduced in the vicinity of the main axis 3a Pressures; the swirl destruction element 8, however, is designed for the full static differential pressure. A yourself in the swirl generation element 4 and the swirl destruction element 8 potential swirls forming with exception of the vortex core represents a largely swirl-free flow. Friction effects arise practically only on the inner walls of the swirl generating element 4 and the swirl destruction element 8. However, this is due to the relatively low Flow velocity in the area of the inner walls relative low. A calm is formed in the vicinity of the main axis 3a Flow zone, which is roughly the "eye of a typhoon" corresponds. In the event of a rupture, in the outlet channel 16 connecting pipeline 2a, in particular one Live steam line of a boiling water nuclear reactor plant, the escaping volume flow is approximately 120% of normal Volume flow limited.

The invention is characterized by a device which also retrofitted into a flow channel one under Pressurized fluid leading system is insertable. Here are in particular when a leak occurs in the system a break in the flow channel, a reduction or limitation of what emerges from the system as a result of the break Volume flow reached. The device has one Swirl generation element, and possibly also a diffuser and a cross-sectional constriction element. These components the device are designed so that during a normal Operation of the system, in particular a cooling system Nuclear reactor plant, an unfavorable influence on the flow of the fluid is avoided. A limitation of the volume flow in the event of a leak, the cross-section is narrowed by creating a swirl in a plane perpendicular to the Flow direction of the fluid in the flow channel. With a appropriate dimensioning of the components of the device For example, if a live steam line breaks a boiling water nuclear reactor plant at low Pressure loss of the emerging volume flow to approx. 150% of the normal operational volume flow can be limited. This corresponds to a reduction to about 75% of that without the device emerging volume flow. For a feed water pipe can limit the volume flow at a Break down to less than 50% of the normal operating volume flow can be achieved. This could cause stress Installations of the reactor pressure vessel significantly reduced, one Reduction of the rate of lowering of the level in the reactor pressure vessel achieved, as well as a smaller dimension be carried out by emergency cooling systems. Particularly advantageous is that the device as a structural unit manufactured and also in the course of retrofitting can be introduced. As a passive element, the Device on high reliability, so that opposite active devices the risk of failure as well as the The need for a periodic inspection is significantly reduced is.

Claims (11)

1. Device (1) arranged in a nuclear power plant for limiting the volumetric flow of a fluid from a container (6) in the event of the occurrence of a downstream leakage in a system connected to the container (6), which system has a flow channel (2), with a main axis (3a) and a swirl-generating element (4), which for the purpose of swirl generation in the fluid has an inflow component (14) extending substantially at right angles to the main axis (3a), whereby the fluid can only flow into the flow channel (2) through this inflow component (14).
2. Device (1) according to claim 1, whereby the inflow component (14) has an inflow opening (15) which is spaced apart from the main axis (3a).
3. Device (1) according to claim 2, where downstream of the flow channel (2) a swirl-destroying element (8) is provided, which is rotationally symmetrical to the main axis (3a) and has at least one tangential exit channel (16).
4. Device (1) according to one of the preceding claims, whereby the swirl-generating element (4) can be arranged in a container (6) of the system at which the flow channel (2) ends.
5. Device (1) according to claim 4, having a cross section narrowing element (5) to narrow the cross section of the flow channel (2).
6. Device (1) according to claim 5, where a diffuser (7), in particular a radial diffuser, is arranged between the swirl-generating element (4) and the cross section narrowing element (5).
7. Device (1) according to claim 6, where the swirl-generating element (4), the cross section narrowing element (5) and the diffuser (7) form a structural unit.
8. Device (1) according to one of claims 5 to 7, where the cross section narrowing element (5) has a swirl-destroying element (8).
9. Device (1) according to one of claims 1 to 7, where downstream of the flow channel (2) a swirl-destroying element (8) is provided, which is rotationally symmetrical to the main axis (3a) and has at least one tangential exit channel (16).
10. Use of the device (1) according to one of the preceding claims in a nuclear power plant, the device having a system through which a pressurized fluid flows, the system having a flow channel (2) designed as a pipeline (2a).
11. Use according to claim 10, whereby the system is the cooling system of a nuclear power plant with a reactor pressure container (6a) into which the pipeline (2a) opens.

Images