Patent Application
20130160267
The invention relates to a method and a device for taking a sample from a steam generator. The steam generator is part of a nuclear power plant. The sample is taken from a deposit on a secondary side of a pipe base plate of the steam generator.
A steam generator as part of a nuclear power plant has a primary circuit and a secondary circuit. The primary circuit conducts cooling-water leads to the nuclear reactor. The secondary side leads to a steam turbine. In the steam generator, the thermal energy of the cooling water of the primary circuit is transferred into the secondary circuit by the water being supplied to the secondary side being converted into steam. The steam generator is an approximately cylindrical, vertically standing vessel which is divided into a top part and a bottom part by a horizontally extending pipe base plate. The bottom part is the primary region and is associated with the primary circuit and the top part is the secondary region and is associated with the secondary circuit. The secondary region has a plurality of U-shaped steam generator pipes, the interior of which communicates with the primary region. To this end, the steam generator pipes penetrate the pipe base plate in a sealing manner. The end face inlet and outlet openings of the steam generator pipes are situated exclusively on the bottom side, that is to say the primary side of the pipe base plate. The top side, that is to say the secondary side of the pipe base plate is consequently provided with a plurality of steam generator pipes with a diameter of approximately 20 mm spaced only a few millimeters apart and is associated with the secondary side of the steam generator.
During the operation of the nuclear power plant, deposits from the secondary-side steam circuit are formed on the top side of the pipe base plate. The secondary side is therefore the deposit-bearing top side of the pipe base plate on the secondary side, on which the deposits are deposited in the direction of gravity. Different cleaning methods are known for removing the mud-like deposits. The methods are carried out when the nuclear power plant is shutdown for inspection. For example, in the case of the known pipe bank cleaning process, a movable lance is introduced in the steam generator through a secondary-side hand hole, the lance being introduced into the so-called pipe banks between the steam generator pipes. The deposits are flushed out using liquid which emerges under high pressure at the other front end.
Along with mud-like deposits, however, it is also possible for hard or encrusted deposits which are as hard as glass to be formed on the secondary side. It is not possible to remove the deposits using the above-mentioned, known secondary-side spray cleaning methods. In order to find suitable cleaning agents, the precise type, character, composition etc. of the deposits have to be determined. To this end, it is necessary to take a sample of the deposits in order to analyze them in a laboratory. Part of the deposits, therefore, has to be removed in the form of a sample. A tool is necessary for this purpose. As the deposits only occur in one region in the interior of the bundle of pipes, it is not practical to take a sample with a tool through the manhole on the secondary side on account of the tight amount of space available. As a result of the hardness of the deposits, a sample of this type is also designated as a scratch sample.
It is accordingly an object of the invention to provide an improved method and a device for taking a sample in a steam generator which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type.
The method is carried out when the nuclear power plant has been shutdown for an inspection. First of all, at least one steam generator pipe is removed from the pipe base plate in order to expose a hot pipe bore which penetrates the pipe base plate. The corresponding removal of a steam generator pipe is known as so-called “drawing” and represents a conventional method. As a rule, in this connection, part of a portion of a certain steam generator pipe connecting to the pipe base plate is cut off and removed. Once the steam generator pipe has been removed, there therefore remains a hot pipe bore which closes off in a flush manner with the top and bottom side, that is to say the secondary and primary side of the pipe base plate.
The sealing and mechanical stabilizing of the remainder of the drawn steam generator pipe associated with the known “drawing process” does not take place until the method has been completed. The created connection between the primary side and the secondary side is closed again in this manner. The method is therefore carried out beforehand when the hot pipe bore is still freely accessible at the drawing position of the pipe base plate and makes a passage between the primary side and the secondary side of the pipe base plate possible.
According to an embodiment of the invention, a removal tool of a device for taking the sample is introduced into the hot pipe bore from the primary side of the pipe base plate, which is located opposite the secondary side which has the deposits. Part of the deposits is then mechanically removed by way of the removal tool. The removed deposits form the sample. The sample is conveyed through the hot pipe bore to the primary side and is removed out of the steam generator. The removal tool is then also removed out of the steam generator.
The removal tool is therefore part of the device according to the invention which is explained in more detail below. The removal tool and where applicable further parts of the device are introduced into the steam generator through the manhole of the steam generator, which is located on the primary side and therefore below the base plate.
The device is introduced no the steam generator in a remotely controlled manner using an existing dome test manipulator or by way of personnel. Otherwise, the control thereof, in particular that of the removal tool is effected by remote control. At the end of the method, the remaining part of the device is naturally also removed out of the steam generator with the removal tool.
As claimed in the invention, the taking of the sample on the secondary side is affected from the primary side through the pipe base plate or an exposed hot pipe bore. In the case of known nuclear power plants, the hot pipe bore has a diameter, for example, of 19 mm. The pipe base itself has a thickness of approximately 640 mm between the primary side and the secondary side or the top side and the bottom side.
Obviously, it is possible, for example, once the steam generator pipe has been drawn and prior to introducing the removal tool, for a visual inspection of the top side to be effected, for example by a known endoscope which can be introduced through the hot pipe bore from the primary side. In this way, for example, the secondary side can be inspected in order to determine the thickness and the form of the deposits and in order to select a suitable removal tool. As a rule, a range of the most varied of removal tools that can be used are available for selection in the device.
As there is now access through the hot pipe bore, the conveying of the sample through the hot pipe bore to the primary side is effected in a simple manner.
The method or the device is defined below also by characteristics which refer to the center longitudinal axis of the hot pipe bore, This is only to be understood for the purposes of clarity: The device itself has the characteristics independently of the hot pipe bore also with reference to a center axis inherent to the device. In the same way, the explanations with reference to the center longitudinal axis, however, explain the functionality when using the device in a simplified and consequently intelligible manner, They refer to an assembled state of the removal tool. A so-called assembled state of the tool or of the device is provided when the latter is introduced into the hot pipe bore for carrying out the actual removal operation, the carrier, for example, is therefore fixed.
The device can have a carrier which carries the removal tool. The carrier together with the removal tool then forms a manipulator arm. In a preferred embodiment of the method, the carrier and the removal tool or the manipulator arm with the removal tool are introduced in advance into the hot pipe bore from the primary side, e.g. until the tool protrudes out of the bore on the secondary side in the region of the deposits. The carrier is then fixed in the hot pipe bore. With the carrier fixed, the removal tool is then moved in relation to the carrier in order to remove the sample from the deposit. The fixing of the carrier in the hot pipe bore is effected here, as a rule, with reference to a center longitudinal axis of the hot pipe bore in the axial, radial and circumferential direction. The advantage here is that a defined operating point or a defined securement for the removal tool is created by the fixed carrier. Proceeding from the position, the tool can be moved in a controlled and targeted manner in relation to the fixed carrier and consequently to the pipe base plate and the deposits in order to remove the sample.
In an advantageous embodiment, the removal tool—in the assembled state—is rotated about a drive axis which extends parallel to the center longitudinal axis of the hot pipe bore in order to remove the sample. A sample can be taken in a particularly good manner by a rotating tool. The removal tool is then, for example, a rotating milling or grinding head. The rotation parallel to the center longitudinal axis of the hot pipe bore is particularly simple to carry out because, for example, for this purpose it is possible to use a drive shaft, which carries the removal tool in a rigid manner and rotates about a drive axis parallel to the center longitudinal axis of the hot pipe bore.
In a preferred development of the method, with reference to the center longitudinal axis, the drive axis is adjusted in the radial direction and is advanced in the circumferential direction in order to remove the sample. in this way, it is possible for the circumferentially circular removal tool to be introduced initially through the bore concentrically with respect to the center longitudinal axis. When it then projects beyond the bore, it can be moved eccentrically and consequently can project beyond the edge of the bore such that it is able to engage the deposits.
Therefore in other words, for example, the above-mentioned rotating miffing or grinding head as the removal tool, proceeding from a position in which the drive axis coincides with the center longitudinal axis of the bore, is advanced, that is to say adjusted, in the radial direction from the center longitudinal axis onto the deposit until a desired depth of penetration into the deposit is achieved and the removal operation begins. The tool is then advanced in the circumferential direction in a circular manner by the drive axis circling the center longitudinal axis at a constant radius. After one complete revolution, a ring-shaped region of the deposit is taken as a sample and the removal tool can, for example, be adjusted a little further in the radial direction into the deposit. The tool is then advanced again by 360° in the circumferential direction, the drive axis circling the center longitudinal axis again at a greater radius. Both adjustment and advance can be selected in this connection as stepless parameters in order to adapt the removal operation in an optimal manner to the deposits. An adjustment can additionally be made in the axial direction of the center longitudinal axis of the bore in order to remove deposits which are greater in height than the height of the removal tool.
The device can also have a collecting container for the sample. As a rule, the collecting container is arranged such that in the assembled state it is located in the vicinity of the deposit to be removed. In a preferred embodiment, once the deposit has been removed, the sample is accommodated in a collecting container of the device and is then conveyed together with the collecting container to the primary side. The collecting container is, for example, emptied on the primary side or is removed entirely out of the steam generator together with the components of the device.
The device, therefore, has a removal tool which serves for removing part of the deposits in a mechanical manner as a sample. The removal tool can be introduced from the primary side of the pipe base plate into an exposed hot pipe bore of the pipe base plate, or can be guided through as far as up to the secondary side thereof or to the deposit at that location.
In a preferred embodiment, the device has a carrier which can be fixed in the hot pipe bore. The removal tool is then able to be moved in relation to the carrier. The carrier and the removal tool form a manipulator arm.
In a preferred embodiment, the device has a damping element which is arranged on the outer periphery of the carrier and can be supported against the inside wall of the hot pipe bore. In the assembled state, the damping element supports the carrier on the inside wall of the hot pipe bore. It therefore damps the carrier in the hot pipe bore in the radial, axial and circumferential direction with reference to the center longitudinal axis of the bore. In a preferred embodiment, the damping element is an element which can be pressure-filled with a medium, in particular a sleeve which surrounds the carrier in a ring-shaped manner and can be filled with compressed air. On the inner side thereof facing toward the carrier, the sleeve can then have, for example, a sliding bearing such that the sleeve bears fixedly against the inner wall of the hot pipe bore by way of the outer periphery thereof, the carrier however slides on the inner periphery thereof, i.e. can be rotated about the center longitudinal axis of the hot pipe bore. For easier removal of the carrier out of the hot pipe bore, the medium can be actively sucked out of the sleeve in order to compress same. Fixing occurs, for example, by a rubber sleeve which can be filled with compressed air at a pressure of 10 mbar.
In a further preferred embodiment, in the assembled state when the removal tool is therefore guided through the hot pipe bore and lies on the secondary side of the pipe base plate, the removal tool can be rotated about a drive axis which extends parallel to the center longitudinal axis of the hot pipe bore in order to remove the sample from the deposit. In a further preferred embodiment, in the assembled state the drive axis is adjustable with reference to the center longitudinal axis in the radial direction and can be advanced in the circumferential direction, that is to say therefore circling about the center longitudinal axis in a circular manner, in order to remove the sample. In addition, the removal tool can also be adjusted axially with reference to the center longitudinal axis. In a preferred embodiment, the carrier has a drive shaft. The removal tool is fixedly connected to the drive shaft and the drive shaft can be rotated about a drive axis, the drive axis extending parallel to the center longitudinal axis. The drive axis can be adjusted and advanced in the radial and circumferential direction with reference to the center longitudinal axis.
The carrier can also be realized in multiple parts. In a preferred development of the embodiment, the carrier additionally has a feed shaft which can be rotated about the center longitudinal axis in the assembled state. The feed shaft includes a cylinder bore which is eccentric with reference to the center longitudinal axis and extends parallel to the center longitudinal axis, in which cylinder bore is mounted a cylindrical adjustment shaft which, in turn, is mounted in the feed shaft so as to be rotatable about an adjustment axis. The drive axis, in turn, is mounted in an eccentric manner in the adjustment shaft. The drive shaft can also be referred to as the milling shaft and the adjustment shaft can be referred to as the eccentric shaft.
The feed shaft, adjustment shaft and drive shaft are each rotatable independently of one another about their respective rotational axes, namely the center longitudinal axis, the adjustment axis and the drive axis. To this end, for example, each shaft has associated therewith its own drive which is controllable independently of the other drives. The drives are located, for example, in a drive unit underneath the pipe base which is fastened, in turn, for example, on an adapter plate. The adapter plate is held on the bottom side or primary side of the pipe base, for example, in an adjacent hot pipe position, that is to say in a position other than the position of the hot pipe to be penetrated. The drives have a remote control capability, that is to say they are operated by remote control.
In a preferred embodiment, the device includes a collecting container for the accommodation of the sample. In other words, the sample is brought into the device itself and can be removed out of the steam generator with the device at the end of the removal operation without any additional expenditure and from there can be forwarded or processed further.
The collecting container is located in a favorable manner on the carrier or manipulator arm in the vicinity of the removal tool. The collecting container is realized in particular on the carrier as an end-face indentation. As the hot pipe bore extends vertically and the carrier points upward by way of its end face, the sample removed by the removal tool is collected in the end-face indentation of the carrier purely by gravity. When the manipulator arm is drawn back out of the hot pipe bore, in this way the sample is taken with it.
As the entire device is to be guided, for example, through a hot pipe bore of 19 mm in diameter, sliding bearings are used principally in the device in order to avoid, for example, bulky ball bearings. In this way, for example, the drive shaft, the adjustment shaft and the feed shaft are in each case mounted fitting into each other in a cylindrical manner by sliding bearings.
The removal tools, as a rule, are arbitrarily exchangeable, for example in the form of different milling and grinding heads or blades. The adjustment parameters of the removal tool with reference to the deposits are to be adapted to the tools and the type of the deposit in a corresponding manner, for example with reference to the speed of the removal tool, the adjustment e.g. within the range of between 0.1-3 mm or the feed speed, i.e. angular speed at which the drive axis circles the center longitudinal axis.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and a device for taking a sample in a steam generator, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Fig, 7 is a top view of a secondary side of the pipe base from
Referring now to the figures of the drawing in detail and first, particularly, to
The pipe base plate 10 has continuous hot pipe bores 20 with center longitudinal axes 21. In the secondary region 14, a U-shaped steam generator pipe 22, which penetrates the secondary region 14, connects to two of the hot pipe bores 20 each. During the operation of the nuclear power plant 2, primary-side cooling water traverses the primary region 12, the hot pipe bores 20 and the steam generator pipes 22. In the secondary region 14, as a result, secondary-side cooling water—which has also been removed during the inspection shutdown—is evaporated and forwarded to a non-illustrated steam turbine.
The pipe base plate 10 has, as a bottom flat side or under surface, a primary side 24 which faces the primary region 12 and an opposite secondary side 26 which faces the secondary region 14. As, with the upright steam generator 4, the secondary side 26 provides the bottom-side base of the secondary region 14, deposits 28 are deposited there during the operation of the nuclear power plant. Unlike soft deposits which are able to be removed by a known pipe bank cleaning method, the deposits 28 are hard deposits which can be as hard as glass and cannot be removed using the known mechanical, as a rule spray cleaning methods. A sample is then to be taken from the deposits 28 using the method as claimed in the invention.
As claimed in the invention, the sample is taken from the primary region 12 via a hot pipe bore 20 which penetrates the pipe base plate 10. As the primary and secondary circuit and consequently also the primary region 12 and the secondary region 14 are hermetically sealed off from each other, an access first of all has to be created. For this purpose, using a known method that is not explained in any more detail, one of the hot pipes 22 has to be partially removed, called “drawing” in professional jargon. A section 30 of the steam generator pipe 22, shown in
The drive shaft 40 is driven by a drive unit 42. As the removal tool 38 is mounted in a rigid manner on the drive shaft 40, the removal tool 38 is driven in this manner. The drive unit 42, in turn, is fastened on an adapter plate 44. The adapter plate 44 is fastened on the pipe base plate 10. This occurs, for example, by engagement in the hot pipe bores 20 adjacent to the active hot pipe bore 20, into which, for example, retaining pins are introduced in a clamping manner.
The drive unit 42 is connected by a control cable 46 to a control unit 48 which is arranged in the exterior 34 and which enables the control of all of the operations of the device 36 by remote control.
During the operation of the device 36, the drive unit 42 is actuated by the control unit 48 in order to control, in turn, the removal tool 38. The removal tool is moved to the deposits 28 or adjusted in order to remove part thereof in a mechanical manner. For this purpose, the drive unit 42 includes the most varied drives, gearing units and transmitters in order to control the removal tool 38—for example a milling cutter. For example, the rotation thereof and also the movement of the manipulator arm 43 is effected in the form of adjustment and feed movements.
The removed parts of the deposit 28 pass as a sample 50 into a collecting container 52 of the device 36, which is provided, for example, in the vicinity of the removal tool 38 on the drive shaft 40 or as an alternative to this, in the region of the drive unit 42.
By the dotted line,
The entire above-mentioned region can consequently be removed as a feed of the drive shaft 40 and consequently of the removal tool 38 is affected in the direction of the circumferential direction 66, which is symbolized by an arrow, by rotating the feed shaft 60 about the center longitudinal axis 21. By a rotation of the adjustment shaft 54 by less than 180° about the adjustment axis 58, even smaller adjustments can be effected in the radial direction with reference to the center longitudinal axis 21.
In
As an example,
| Number | Date | Country | Kind |
|---|---|---|---|
| 102010039413.0 | Aug 2010 | DE | national |
This is a continuation application, under 35 U.S.C. §120, of copending international application No. PCT/EP2011/061329, filed Jul. 5, 2011, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application DE 10 2010 039 413.0, filed Aug. 17, 2010; the prior applications are herewith incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2011/061329 | Jul 2011 | US |
| Child | 13770060 | US |
