Upper bundle steam generator cleaning system and method

Information

  • Patent Grant
  • 6672257
  • Patent Number
    6,672,257
  • Date Filed
    Friday, July 14, 2000
    24 years ago
  • Date Issued
    Tuesday, January 6, 2004
    20 years ago
Abstract
An upper bundle steam generator cleaning, inspection, and repair system including a deployment support device receivable within the steam generator to raise a cleaning device, an inspection device, and/or a tool up to the upper bundles of the steam generator.
Description




FIELD OF INVENTION




This invention relates to an upper bundle cleaning, inspection, and repair system for a nuclear power plant steam generator.




BACKGROUND OF INVENTION




Steam generators convert heat from the primary side of a nuclear power plant to steam on the secondary side so that the primary and secondary systems are kept separate. A typical generator is a vertical cylinder consisting of a large number of U-shaped tubes which extend from the floor or “tube sheet” of the generator. High temperature and pressure fluid from the reactor travels through the tubes giving up energy to a feedwater blanket surrounding the tubes in the generator creating steam and ultimately power when later introduced to turbines.




Steam generators were designed to last upwards of forty years but in practice such reliability figures have proven not to be the case. The problem is that sludge from particulate impurities suspended in the feed-water forms on the tubes which greatly affects the efficiency of the generator and can even cause the tubes to degrade to the point of causing fissures in the tubes. If radioactive primary fluid within the tubes seeps into the secondary side, the result can be disastrous. Plugging or otherwise servicing such fissures is time consuming and results in expensive down time during which power must be purchased from other sources at a great expense.




There are known methods for cleaning the tubes proximate the bottom of the steam generator using flexible lances and the like which clean the tubes using water under pressure, but since a typical steam generator can be thirty feet tall, it is difficult to reach the sludge at the upper levels of the tubes using water jets. So, chemical cleaning is used but there are several disadvantages. First, chemical cleaning is very expensive (from $5,000,000 to $10,000,000 per application) and requires an extended outage. Also, some corrosion of steam generator internals by the solvents used will occur during the cleaning. In addition, large quantities of hazardous, possibly radioactive waste may be generated. Disposal of this waste is very expensive. For these reasons, although many utilities have considered chemical cleaning, few plants have actually implemented chemical cleaning.




On the other hand, there are severe technical challenges faced when considering alternate cleaning methods. A typical steam generator has approximately 50,000 square feet of heat transfer area. The tube bundle is about 10 feet in diameter and 30 feet tall but the access alley in the middle of the tube bundle is only 3.5 inches wide and is interrupted by support plates approximately every 4 feet. There are flow slots through the support plates but they are very small in size, typically 2.75 by 15 inches. In addition, the access into the steam generator is limited to a six inch hand hole. Finally, inter tube gaps are only 0.406 wide or smaller.




Thus, the inherent design parameters of a typical steam generator make it difficult to incorporate water jet sludge lancing techniques at the upper tube bundles even though these techniques are adequate to clean the tubes at the level of the tube sheet at the bottom most portion of the steam generator. See, e.g. U.S. Pat. Nos. 4,700,662; 4,980,120; 4,887,555; 4,676,201; and 4,769,085. Furthermore, the crowded interior space of a steam generator makes it very difficult to inspect and/or repair the individual tubes near the upper regions of the steam generator.




SUMMARY OF INVENTION




It is therefore an object of this invention to provide an upper bundle steam generator cleaning, inspection, and repair system.




It is a further object of this invention to provide such an upper bundle steam generator cleaning, inspection, and repair system which facilitates cleaning the generator from the top down thereby flushing deposits downward during the cleaning process.




It is a further object of this invention to provide such an upper bundle steam generator cleaning, inspection, and repair system which eliminates the need to use chemical cleaning techniques and overcomes the disadvantages inherent in chemical cleaning or which can be used in conjunction with chemical cleaning.




It is a further object of this invention to provide such an upper bundle steam generator cleaning, inspection, and repair system which adequately cleans the upper bundles of the steam generator using water under pressure even within the close confines of the tubes of the steam generator.




It is a further object of this invention to provide such an upper bundle steam generator cleaning, inspection, and repair system which successfully delivers sufficient water energy to remove scale and also distributes this energy in an efficient manner throughout the tube bundle.




It is a further object of this invention to provide such an upper bundle steam generator cleaning, inspection, and repair system which accomplishes cleaning remotely thereby overcoming the access restrictions of the steam generator as well as reducing exposure of personnel to radiation.




It is a further object of this invention to provide such an upper bundle steam to generator cleaning, inspection, and repair system which maximizes cleaning effectiveness with a minimum use of water.




It is a further object of this invention to provide such an upper bundle steam generator cleaning, inspection, and repair system which minimizes the number of equipment moves during the cleaning, inspection, and repair procedure thereby reducing cleaning and hence outage time.




It is a further object of this invention to provide such an upper bundle steam generator cleaning, inspection, and repair system which utilizes both a bulk cleaning, inspection, and repair head and a rigid lance for intertube inspection, cleaning, and repair.




It is a further object of this invention to provide such a system which has the capability to deliver inspection cameras; and drills, grippers, and welding or cutting devices and other tools even to the upper confines of the steam generator.




This invention results in the realization that even the upper bundles of a steam generator can be reliably inspected, cleaned, and repaired by deploying a telescoping or flexible arm up through the flow slots of the support plates of the steam generator; rotating the arm into place between the steam generator tubes; and deploying a tool such as a drill, grippers, or a welding or cutting device; providing number of cleaning nozzles; and/or a video camera and/or delivery and installing repair materials such as bars, brackets, or clamps to the individual tubes to be inspected, cleaned, or repaired.




This invention features an upper bundle steam generator cleaning, inspection, and repair system. There is a deployment and support device receivable within the steam generator including some means to raise and position a distal end of the device up to the upper bundles of the steam generator. There is a rotatable mechanism attached to the end of the deployment and support device and an arm attached to the rotatable mechanism. A cleaning device such as nozzles, an inspection device such as a camera, and/or one or more tools are attached to the other end of the arm.




In one embodiment, the deployment and support device includes a first boom coupled by a rotatable connector to a second boom, the first and second boom and the rotatable connector being insertable into an access port of the steam generator and into a lane separating two rows of tube members so that the second boom falls within the lane.




The rotatable mechanism preferably rotates the arm both horizontally and vertically within the steam generator. In one embodiment, the arm includes a set of telescoping members; and in another embodiment the arm is made of a flexible material. Alternatively, only the distal end of the arm may be made of the flexible material.




In another embodiment, the deployment and support device includes an elongated body feedable through an access in the'steam generator shell proximate the tube sheet of the steam generator. The elongated body is flexible in one configuration to bend into position for extension up to the flow slots in the support plates of the interior of the steam generator, and yet rigid in another configuration for positioning and supporting cleaning, inspection, or tool devices up through the steam generator proximate the upper tube bundles of the steam generator. There is also some means for driving the elongated body up through the support plates and for retracting the elongated body back down through the support plates.




The elongated body may be a rigid chain, a pair of rigid chains, a number of bendable links, a number of rigid links, or a material self-biased to form a tube.











DISCLOSURE OF PREFERRED EMBODIMENT




Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:





FIG. 1

is a schematic, partially cut away view of a typical steam generator of a nuclear power plant;





FIG. 2

is a schematic view of the deployment subsystem used to deploy and support various cleaning heads at different levels within the steam generator shown in

FIG. 1

;





FIG. 3

is a schematic view of the bulk cleaning head subsystem of this invention used to direct water from the flow slots of the tube support plates of the steam generator;





FIG. 4

is a schematic view of the bulk cleaning head subsystem of

FIG. 3

shown in place within a flow slot directing water between rows of tubes;





FIGS. 5A-5C

are top plan views of the methodology of cleaning the various sectors of one level of a typical steam generator using the bulk cleaning head system shown in

FIGS. 3-4

;





FIG. 6

is a schematic view of the various components of the bulk cleaning head subsystem depicting the mechanisms which effect spray pitch control and swinging of the spray nozzle arm;





FIGS. 7A-7D

are schematic views of the rigid lance cleaning head subsystem of this invention used which is inserted in between the tubes thereby directing water under pressure in between the tubes of the steam generator from between the tubes;





FIGS. 8A-8C

are schematic views of the rigid lance of

FIGS. 7A-7C

shown in place at one level of a steam generator;





FIG. 9

is a schematic view showing typical tube support plate coverage utilizing both the bulk cleaning head subsystem and the rigid lance according to this invention;





FIGS. 10A-10D

are schematic views showing the various positions for inspecting, cleaning, and descaling tube bundles using the rigid lance of

FIGS. 6-7

;





FIG. 11

is a schematic three dimensional view of the support subsystem of this invention for maintaining a particular cleaning head in position during the application of high pressure fluid to the cleaning head;





FIGS. 12A-12C

are schematic front views showing the support subsystem passing through and ultimately engaging a support plate of a typical steam generator;





FIG. 13

is a schematic view of the process system of this invention for supplying water and video hook ups to the cleaning heads of this invention;





FIG. 14

is a schematic view of a control subsystem of this invention used to deploy and manipulate the cleaning heads of this invention within the steam generator during cleaning;





FIG. 15

is a schematic view of the telescoping arm subsystem of this invention deploying a drill assembly;





FIG. 16

is a schematic view of the telescoping arm subsystem of

FIG. 15

deploying a gripper assembly;





FIG. 17

is a schematic view of the telescoping arm subsystem of

FIG. 15

deploying a saw assembly;





FIG. 18

is a schematic view of the telescoping arm subsystem of

FIG. 15

deploying a welder;





FIGS. 19-22

are schematic views of different embodiments of the flexible lance subsystem of this invention;





FIG. 23

is a schematic view of the flexible lance subsystem deployed within a steam generator in accordance with the subject invention;





FIG. 24

is a schematic view of the deployment system of this invention which employs an elongated body flexible in one configuration and fairly rigid in another configuration;





FIG. 25

is a schematic view of a rigid chain embodiment of the elongated body shown in

FIG. 24

;





FIG. 26

is a schematic view an embodiment including back to back rigid chains according to this invention;





FIG. 27

is a front view of a typical chain linkage;





FIG. 28

is a front view of a rigid chain used in the deployment system of this invention;





FIG. 29

is a front view of two rigid chains placed back to back in the deployment system of this invention;





FIGS. 30 and 31

are schematic views of another type of rigid chain used in the deployment system of this invention;





FIG. 32

is a schematic view of still another type of rigid chain used in the deployment system of this invention;





FIG. 33

is a schematic view of a spring biased rigid chain according to this invention;





FIG. 34

is a schematic view of a magnetically biased rigid chain according to this invention;





FIG. 35

is a schematic view of a rigid chain incorporating both a magnet and a spring;





FIG. 36

is a front view of another type of rigid chain according to this invention;





FIG. 37

is a schematic view of a series of rigid links with a single articulation recess according to this invention;





FIG. 38

is a schematic view of a series of rigid links having dual articulation recesses according to this invention;





FIG. 39

is a schematic view of a self-biased mast used in the deployment system according to this invention;





FIG. 40

is another view of the self-biased mast of this invention including drive means; and





FIG. 41

is a schematic view of a deployment system according to this invention which employs both a mast material and a rigid link structure.












FIG. 1

schematically shows steam generator


10


which includes heat transfer tubes


12


separated into sections by tube support plates


14


,


16


,


18


,


20


,


22


,


24


and


26


. Each tube support plate includes a number of flow slots


28


and


30


as shown for first tube support plate


14


.




The Westinghouse model W44 and W51 steam generators comprise the largest steam generator market segment and the dimensions of the W51 are similar to the W44. The W44 steam generator utilizes 116″ diameter tube support plates spaced evenly at 51″ above the tube sheet. There are two 6″ diameter hand holes such as hand hole


36


at each end of the 3½″ blow down lane


38


at the tube sheet


32


level. Each tube sheet support plate has three flow slots measuring 2-2¾by 15″ spaced at 4″ inches on each side of the center tie rod


40


. The flow slots are aligned with respect to each other so that there is a clear “line of sight” vertical passage from the blow down lane


38


to the U-bends


41


of the tubes above the top tube support plate


26


.




As discussed in the Background of the Invention above, there are known instruments for water-spray cleaning the areas between tube sheet


32


and first tube sheet support plate


14


at the bottom of the steam generator but the very close confines within the upper bundles of the steam generator make cleaning the tubes near the upper support plates


16


-


26


very difficult. See, e.g., U.S. Pat. No. 5,265,129.




In this invention, it was realized that there is an access path


34


from hand hole


36


along blow down lane


38


to the center tie rod


40


and then upwards through the aligned flow slots


28


,


30


, etc. in each support plate to the top portion


42


of the steam generator. And, it was realized that if a cleaning head or heads could be deployed to the top portion


42


of the steam generator, the generator could be cleaned from the top down thereby flushing deposits downward during the cleaning process. The technical challenge is to design cleaning heads which will fit within the close confines of the interior of the steam generator, to design cleaning heads which will still deliver water under sufficient pressure to thoroughly clean the tubes, and to design cleaning heads which will not become jammed inside the steam generator.




The upper bundle steam generator cleaning system of this invention, wherein an “upper bundle” is defined as those tubes within the steam generator above the first tube support plate


14


, includes four main subsystems or components: (a) the cleaning head deployment and support device shown in

FIG. 2

; (b) a bulk cleaning head affixable to the support/deployment device which directs fluid in between the tubes from the flow slots and includes means to change the pitch of the spray and to clean the tubes proximate an adjacent flow slot at the same level as shown in

FIGS. 3-7

; (c) a rigid lance also affixable to the support/deployment subsystem which extends in between the tubes and directs fluid from between the tubes as shown in

FIGS. 7-10

and (d) a support mechanism which releasably fixes and supports either type of cleaning head in place during spraying and also conveniently prevents equipment jams which could severely affect the cleaning process and cause down time. Each subsystem is discussed in turn.




The Deployment/Support Subsystem




The deployment subsystem


50


,

FIG. 2

, includes translation rail


52


, rail support


54


, rotation stage


56


, translation cart


58


, and vertical position subsystem


60


, including hydraulic cylinders


62


,


64


,


66


. Deployment subsystem


50


is the mechanism used to deploy a spray head vertically within the steam generator to the elevation of the tube support plate to be accessed. Vertical positioning subsystem


60


is mounted at the top of rotation stage


56


which in turn rides on translation cart


58


. Using motive means located outside the steam generator, the cart is caused to move down the blow down lane on rail


52


that is deployed through the hand hole.




This design is adapted from an existing design called the “Secondary Inspection Device (SID)” available from R. Brooks Associates of 6546 Pound Road, Williamson, N.Y., 14589 (see U.S. Pat. No. 5,265,129) and is a nine stage pneumatic cylinder currently used to transport a video camera up the blow down lane of a steam generator. Consequently, it is sized appropriately to pass through the hand hole and the flow slots of the steam generator. In its normal configuration, however, the secondary inspection device has several major shortcomings. The first of these is lack of control. The current control procedure is to increase cylinder air pressure to extend and reduce pressure to either retract or cease extending. Since the interstage seals permit significant leakage, it is frequently difficult to achieve a stable position. Also, since interstage friction plays a role in establishing an equilibrium position, anything which changes interstage friction, such as vibration, will cause the system to seek a new equilibrium position.




The other major short coming is an inadequate pay load capability. As a result of interstage seal leakage and small passages through the pressure regulator and supply hose, actual cylinder pressure can never be made to approach the pressure of the air supply and pay load is limited to about 5 pounds. Accordingly, this payload capability must be improved by a factor of 5-10 to support the cleaning heads of this invention.




A modification is made to incorporate cables inside the cylinders and a cable reel to control payout and takeup. Pressure inside the cylinders is maintained at a constant value, high enough to produce extension but held in check by the cable. Paying out the tension cable permits extension and taking up cable produces retraction. Cylinder pressure relief is provided for the retraction step. The cable reel is equipped with an encoder which would supply vertical position information. To improve the payload, internal pressure is increased, and cylinder weight decreased or both. Interstage seals are improved to greatly reduce leakage and pressurization is provided by water rather than air. Using water as a pressurization medium, internal pressures are several hundred psi are possible without creating an explosion hazard as would be the case with a compressible medium. Also, fabricating the cylinders from aluminum rather than steel reduces by about ⅔ the weight of the cylinders themselves. The control system is further discussed with reference to FIG.


14


.




The Bulk Cleaning Head Subsystem




Bulk cleaning head subsystem


70


,

FIG. 3

, is mounted on top cylinder


66


of deployment/support subsystem


50


,

FIG. 2

, and includes arm


72


extending from pivot support


74


. The bulk cleaning head subsystem of this invention shown in

FIG. 3

directs fluid in between the tubes from the flow slot. Bulk cleaning subsystem


70


extends along a flow slot such as flow slot


71


,

FIG. 4

, and directs fluid in between the tubes


78


,


80


from flow slot


71


. Arm


72


,

FIG. 3

, also rotates in the direction shown by arrow


82


to change the pitch orientation of the opposing nozzles


84


,


86


,


88


, and


90


to clean the length of the tubes in between two support plates and also the surfaces of the support plates. Nozzles


84


,


88


oppose nozzles


86


,


90


as shown in order to effect cleaning of the tubes on both sides of flow slot


71


and also to balance the thrust received by arm


72


due to the high pressure water delivered by the nozzles. Nozzles


86


and


90


are spaced appropriately to align with the spaces in between tubes


78


,


80


, FIG.


4


.




Arm


70


also swings over to the position shown in relief at


92


to clean the tubes proximate an adjacent flow slot without having to retract the cleaning head and deploy it up through the adjacent flow slot.




More particularly, as shown in

FIGS. 5A-5C

, arm


100


,

FIG. 5A

, is first orientated about flow slot


104


(typically the center flow slot of a three flow slot per side steam generator design) to spray water in sector


110


proximate flow slot


104


; the arm is then moved over within flow slot


104


to spray water in sector


108


,

FIG. 5B

; and finally the arm is caused to swing over to clean sector


112


,

FIG. 5C

, proximate flow slot


106


.




In this way, one complete side of the steam generator is cleaned while the cleaning head deployment and support equipment extends through one series of vertically aligned flow slots. So, the bulk cleaning head subsystem is deployed to top flow slot


25


,

FIG. 1

, within top support plate


26


and the cleaning operation depicted in

FIGS. 5A-5C

is accomplished (pitch changes made as necessary) and this process is repeated at each level of the steam generator down to the first tubes support plate


14


effecting top to bottom cleaning and thereby flushing deposits downward during the cleaning process. The other side of the steam generator is cleaned in the same manner.




Another aspect of this invention involves using specific nozzle alignment for bulk cleaning to maximize cleaning effectiveness with a minimum use of water. Specifically, the nozzles


84


,


88


etc. are aligned first on one side of the tube gap


79


, and then on the other side of the tube gap


79


to clean one side of the tubes and then the other. In testing, this procedure had a significant impact on the cleaning effectiveness and was instrumental in increasing the amount of sludge removed from the tube surfaces. Other testing variables included sludge type, nozzle pressure, nozzle flow rate, tilt speed, bulk cleaner location, nozzle design, and nozzle alignment. A prototype design proved that a bulk cleaning head directing water from the blow down lane can remove tube surface deposits and clean support plates and quatrefoils. Still another aspect of this the cleaning methodology of this invention involves slowly lowering the level of water within the steam generator as cleaning progresses top to bottom with the cleaning heads. In this way, additional agitation is provided and cleaning is enhanced as the nozzle jet spray strikes the surface of the water within the generator.





FIG. 6

schematically shows the prototype design of bulk cleaning head subsystem


120


. Nozzle arm


121


includes barrel portion


122


having opposing nozzles


123


,


125


,


127


,


129


, the pitch of which are varied by tilt gear


124


powered by tilt motor


128


by means of gear


131


. Swinging of arm


121


is accomplished by means of swing gear


138


powered by swing motor


130


through worm gear


133


. Water is supplied to nozzles


123


,


125


,


127


, and


129


through umbilical source


132


thorough water manifold


134


. Camera


126


provides the operator with alignment and inspection compatibility. Power for camera


126


, motor


130


and motor


128


is provided thorough umbilical source


132


.




The Rigid Lance




Rigid lance


200


,

FIG. 7A

, is another type of spray head mountable to deployment subsystem


50


,

FIG. 2

, and is used to direct fluid in between the rows of tubes from between the tubes. Lance portion


205


,

FIG. 7A

, rotates as shown in

FIGS. 7B and 7C

to a position as shown in

FIG. 8A

extending between tube row


207


. In this way, lance


205


,

FIG. 7A

, is positioned in line with the top cylinder of the support subsystem during deployment up through flow slot


210


,

FIG. 8B

, where it is then rotated in the direction shown by arrow


214


by lance drive motor


212


to extend between a particular row of tubes. Then, jet nozzles


216


, (

FIGS. 8B and 8C

)


218


,


220


, and


222


direct fluid from high pressure water source


224


to the tubes.




As shown in

FIG. 9

the areas of tubes not cleaned using bulk cleaning head subsystem


70


which sprays water from a flow slot are cleaned using lance


205


which can be inserted between rows of tubes. At the upper most end of rigid lance


200


,

FIG. 7A

is bullet nose piece


201


which can be manually inclined slightly as shown by arrow


108


to snake its way up through the flow slots regardless of minor slot misalignment or flexibility of the telescoping cylinder assembly of the deployment/support device shown in FIG.


2


. Bullet nose


201


is deflected with the use of one cable tether which works against an offset spring. By rotating the head around its vertical axis with the rotary stage, the nose deflection can be orientated in any direction. Since the rigid lance subsystem cleaning head will be traveling into regions from which significant amounts of sensory data must be obtained, it is essential that the head be outfitted with several eyes


182


,


184


to keep the operator up to date on its whereabouts and the status of the inspection and cleaning activities.




To enable the operator to align the bullet nose


201


with the next flow slot as the head traverses up to the tube sheet support plate of interest, one CCD video camera is mounted within the head and aimed upwards as shown for camera


184


. If appropriate, two video cameras would be mounted in horizontal opposition in the head to enable viewing down the no tube lane and at the tubes immediately adjacent thereto. To provide viewing capability in the intertube lanes, video probes can be mounted on the lance tip


209


shown in FIG.


7


D. CCD chips are positioned to enable inspection of the crevice areas and observation of the water jetting operations. The cables for these videos probes are routed through the rotary stage on the blow down lane cart and out the hand hole. To simplify the user interface, the signals would be multiplexed to a remote operator station where the video image of choice can be displayed. As indicated in

FIG. 7C

, if slightly reduced coverage of the intertube lanes is not acceptable at the tube sheet support plate, the recess


211


in the head formed by the offset as shown can serve to hold an optional tooling module


213


shown in

FIG. 7B

to suit the task at hand. For example, a sample holding bin can be mounted at this point so that tube scale could be reliably transported out of the steam generator for analysis.




In general, the intertube lance of this invention accomplishes visual inspection, crevice cleaning, tube descaling, tube sheet plate flushing, corrosion sampling, and foreign object search and retrieval. Lance


205


must be as long as possible but cannot exceed the vertical spacing of the tube sheet support plates or else it can not be rotated from the vertical. Since the radii of both the W44 and the W51 generator tube sheet plates are greater than the vertical spacing of the tube sheet plates, there is an area shown in

FIG. 9

that the rigid lance cannot reach at the furthest point from the no tube lane. The total percent area that is within the reach of the rigid lance, however, is estimated to be over 85% for the W44 and over 80% for the W51.




Lance


200


,

FIGS. 7A-7C

is a slender 2½″ diameter housing inside which is mounted a rotary drive (not shown) to position the rigid ¼″ arm


205


. Water jets at the tip of the lance are orientated so that they direct debris back toward the flow slots in the no tube lance since there is no reliable means to move debris from the periphery of the tube support plate.





FIGS. 10A-10D

show the orientation of the lance with respect to the head during deployment and various cleaning operations.

FIG. 10A

shows lance


205


aligned with head


215


for deployment and raising the cleaning head to the tube sheet support plate of interest;

FIG. 10B

shows a downward sweeping action of lance


205


to flush debris towards flow slot


217


;

FIG. 10C

depicts lance


205


sweeping back and forth for descaling the tubes; while

FIG. 10D

depicts lance


205


in position for inspecting the under side of tube support plate


219


.




The Support Mechanism




Although the vertical deployment and support system will be laterally supported on the bottom of the tube sheet, it is necessary to provide lateral support at the top proximate the deployed spray head as well. During cleaning of the upper spans of the steam generator, the vertical deployment and support system will be extended up to 25 feet. Sideloads will be applied during lance insertion into and retraction from the tube bundle as well as during jet sweeping operations. The upper lateral support subsystem of this invention is shown in FIG.


11


and provides mechanical engagement with and disengagement from a tube support plate such as tube support plate


250


and requires no additional actuators.




As shown in

FIG. 12A

, upon approaching the tube support plate


250


of interest, the pay load


252


(one of the spray heads discussed above) is lifted slightly to allow fingers


254


and


256


to open as shown in FIG.


12


B. Magnets


258


and


260


assist indexing to a position shown in FIG.


12


B. With fingers


254


and


256


in the open position, further extension of the vertical deployment system will rotate the fingers into the locked positioned as shown in FIG.


12


C. Cleaning operations are then conducted using the vertical motion of the upper most cylinder of the deployment/subsystem shown in

FIG. 2

with the lateral support system locked and the cylinders below stationary. Disengagement is accomplished by a reversing the procedure. The lower cylinders are retracted which will pull down on the lateral support system pivot pin


262


and friction on the pads which bear against the flow slot cause the finger assemblies to rotate into the position shown in

FIG. 12B

as the lower cylinders are retracted. The retraction of the independent upper cylinder would then cause the fingers to fold into the stowed positioned as shown in FIG.


12


A and permit passage through the flow slots to a new deployment location.




Retrieval is a concern where any equipment is deployed into the inner regions of the steam generator. Emergency retrieval according to this invention is accomplished by tension on the cylinder extension control cable which is attached to the second stage cylinder. If the fingers are in the stowed positioned as shown in

FIG. 12B

, when emergency retrieval is initiated, no interference will occur. If the fingers are in the ready position as shown in

FIG. 12B

, contact with each tube support plate on the way down will simply rotate them inwardly sufficient to pass through the flow slot. If the lateral support system is engaged as shown in

FIG. 12C

, when emergency retrieval is initiated, sufficient tension will be applied to the cable to overcome the friction associated with the lateral support system contact with the tube support plate. If the pay load is completely down and resting on the fingers, contact with the next support plate during retraction rotates the fingers inward and lifts the payload to the stowed configuration of FIG.


12


A.




Other Subsystems




There is shown in

FIG. 13

process subsystem


300


which supplies high pressure water to the jets of each spray head, low pressure water to the vertical deployment system cylinders, air and electric power as needed and video feedback from the cleaning system. Process subsystem


300


also provides for suction from the steam generator to maintains a stable level during lancing and it will filter that water sufficiently for recirculation to the water jet spray nozzles of the cleaning heads. The majority of the process system will be located in trailer


302


outside of the containment building and is very similar to that employed for tube sheet sludge lancing today. High pressure water is supplied to the nozzle jet of each cleaning head via high pressure pump


304


, low pressure water is supplied to the deployment/support subsystem cylinders by low pressure pump


306


and air electric, and video signals are transmitted via lines


308


,


310


and


312


respectively. Suction pump


314


maintain a stable level during lancing and filters


316


and


318


filter the water from pump


314


sufficiently for recirculization to the water jet spray nozzles via high pressure pump


304


.




The control subsystem


340


shown in

FIG. 14

provides the means of controlling all process system functions as well as those of the vertical deployment/support systems and intertube access rigid wand subsystems. All major system actuations are under closed-loop control with position feed back from encoders. A computer interface as shown at


342


provides control as well as position and function information. Relative motions, such as jet sweeping in the tube gaps as depicted by arrow


344


, rotation of the cleaning head as depicted by arrow


346


, raising and lowering of the cylinders of the deployment/support subsystem as depicted by arrow


348


and translational movement of the deployment subsystem as depicted by arrow


350


to affect cleaning according to the methodology depicted in

FIGS. 5A-5C

is programmed for automatic execution. The control console also includes a monitor for the video system. The intertube access system must enter the 0.406″ gaps and utilizes a Welch Allyn video probe, customized to 0.250″ diameter.




Cleaning, Inspection, and Repair Subassemblies




As shown in

FIG. 15

, telescoping arm


402


may be attached via rotating joint


400


to the upper most hydraulic cylinder


66


of the deployment and support device shown in FIG.


2


. Rotating joint


400


may be similar to the elbow joint shown in the '129 patent. On the distal end of telescoping arm


402


is drill assembly


404


for drilling operations about the upper tubes and the tube support plates such as shown for support plate


26


and tubes


12


. Rotating joint


400


rotates arm


402


horizontally as shown by arrow


403


and also vertically as shown by arrow


405


. Support mechanism


248


, also shown in

FIG. 11

, maintains upper hydraulic cylinder


66


in a fixed relationship with respect to the flow slot of plate


26


. While telescoping arm


402


and drill assembly


404


are being raised into position up through the flow slots in the support plates, telescoping arm


402


and drill assembly


404


are aligned coincident with upper hydraulic cylinder


66


of the deployment and support device shown in FIG.


2


. Once the desired level within the steam generator is reached, rotatable mechanism


400


articulates arm


402


vertically upward as shown by arrow


405


and the individual telescoping elements of telescoping arm


402


then extend in the direction of arrow


407


.




Gripper assembly


406


,

FIG. 16

may also be attached to telescoping arm


402


for retrieving objects about the upper bundles of the steam generator. Cutting may be accomplished by saw assembly


408


,

FIG. 17

, attached to telescoping arm


402


or by an Electrode Discharge Machine (EDM) head for performing various operations attached to arm


402


. Saw assembly


408


may beta reciprocating saw providing a sawing action as shown by arrow


409


.




Telescoping arm


402


,

FIG. 18

, may also include welder assembly


410


for performing welding operations within the steam generator. Welding may be performed using an electric arc technique or by using a laser beam delivered to the welding site by an optical fiber.




It is very important that any device which extends upwards of 30 feet within the steam generator and then outward between the individual tubes does not become jammed or otherwise disabled within the steam generator. Accordingly, arm


412


,

FIG. 19

is a flexible lance made of graphite or some other suitably flexible material so that the arm is pliable enough to be withdrawn from within the interior of the steam generator. In another embodiment, arm


413


includes two sections


414


and


415


as shown. Arm section


414


may be very flexible while arm section


415


may be somewhat more rigid. Arm


414


may be extendible outward in the direction shown by arrow


417


through the use of telescoping cylinders or an equivalent mechanism or it may be pivotable with respect to arm section


415


in the direction shown by arrow


419


for compact deployment through the flow slots of the steam generator. In another embodiment, it may be desirable to fabricate arm section


415


of a more flexible material, and arm section


414


or a more rigid material. Arm section


414


may include cleaning nozzles


421


, video camera


423


, and/or drill assembly


404


,

FIG. 15

, gripper assembly


406


,

FIG. 16

, saw assembly


408


,

FIG. 17

, and/or welder


410


, FIG.


18


. [should describe in more detail]




In another embodiment, arm


412


,

FIG. 21

, may be attached to rotatable mechanism


400


through the use of offset mechanism


416


used to position arm


412


among the tube bundles. Offset mechanism


416


may be adjustable in the direction shown by arrow


417


to move arm


412


once boom


66


is locked in place via support mechanism


248


.




In another embodiment, shorter arm


418


,

FIG. 22

is used as shown in

FIG. 23

to clean, inspect, or repair the tubes about the shorter tubes lanes. Arm


412


,

FIG. 19

, is used to clean, inspect, or repair tubes about the longer tube lane of the steam generator, and arm


413


with arm sections


412


and


414


are used to clean, inspect, and repair tubes about the deepest portions of the tubes lanes within the steam generator. See FIG.


23


.




Thus, the system of this invention facilitates cleaning, inspection, and repair or rework of the upper tube bundles. Gripper assembly


406


,

FIG. 16

, may be used to hold a welding rod or a bar or bracket, while welder assembly


410


,

FIG. 18

is used to weld an individual tube. Camera


423


,

FIG. 20

, may be used to inspect and monitor the work in process.




Alternative Deployment Subsystems




Although deployment subsystem


50


,

FIG. 2

may be used to deploy the various cleaning, inspection, and repair devices shown in

FIGS. 3

,


6


,


7


, and


15


-


22


, other deployment subsystems may be used since the boom and telescoping cylinders combination (

FIG. 2

) which in its collapsed state is only 18 inches tall and which must still extend up to 30 feet is difficult to design, manufacture, and control. Moreover, this design requires that the boom


70


be placed inside the steam generator.




In contrast, the invention of this application includes an elongated body


480


,

FIG. 24

feedable through hand hole


482


from outside steam generator


484


. Elongated body


480


is flexible enough to bend into position to travel upwards as shown at


486


and also rigid in another configuration as shown at


488


for positioning a cleaning head/inspection and/or repair device up through the steam generator to reach the upper tube bundles.




There are some means


492


for driving elongated body


480


up through the support plates, and for retracting body


480


,

FIG. 24

, back down through the support plates.




In a preferred embodiment, elongated body


480


,

FIG. 24

, is a “rigid chain”


500


,

FIG. 25

driven by motor


502


and drive assembly


503


as it unfurls from stack


504


in container


506


. Turn shoe


508


directs rigid chain


500


to turn upwards carrying inspection/cleaning/repair head


510


to the upper bundles of the steam generator. Rigid chain


500


is flexible enough to make the bend shown at


508


but is also rigid enough to extend upwards after bend


508


and support cleaning and inspection equipment about the upper tube bundles some 30 feet from bend


508


.




Other elongated bodies, however, are possible and are within the scope of this invention so long as they are flexible in on configuration to bend into a position for extension up through the flow slots and rigid in another configuration for positioning and supporting cleaning head/inspection devices up through the flow slots in the support plates of the steam generator. The various embodiments are discussed as follows.




Rigid Chains




In on embodiment, there are two rigid chains


520


and


522


, FIG.


26


. Rigid chain


522


is constructed to bend in only one direction as shown in


524


while rigid chain


520


is constructed to bend only in the opposite direction as shown at


526


. When placed back-to-back, the combination is rigid enough to be deployed upward supporting a cleaning head/inspection/and/or repair device up through the flow slots in the tube support plates


528


,


530


,


532


, etc. Rigid chain


520


is deployed in annulus


534


while rigid chain


522


is deployed in annulus


536


. Then, both chains are driven by drive


538


through guide shoes


540


and


542


respectively. Video/cleaning fluid/power umbilical


544


is tensioned by tension arm


546


.




As shown in

FIG. 27

a typical non-rigid chain


550


is free to bend in two directions. Rigid chain


552




a


,

FIG. 28

, however, is free to bend in only one direction. When two such chains


552




b


and


552




c


,

FIG. 29

, are placed back to back, a rigid structure is formed from an assembly flexible in one configuration—namely, each chain by itself.




Another rigid chain is shown in FIG.


30


. Each link


560


is hollow to carry video


562


, cleaning spray


564


, and power


566


umbilicals. Pin


568


engages the adjacent link to prevent rotation of the links with respect to each other. Pin


568


also retracts to allow bending of link


572


with respect to link


560


.




In this embodiment, a pin drive


573


,

FIG. 31

is used to push the engagement pins in after the 90° turn is made providing a rigid support. The pin drive also pulls the engagement pins out upon retraction of the rigid chain back down through the flow slots of the support plates of the steam generator. Pin drive


577


can be as simple as set of leaf type springs that bear against the top of the pin


577


, engaging it in the hole, when pushed from the direction shown by arrow


575


. When pin


579


is pulled back, in the direction shown by arrow


581


, the leaf springs bear under the pin head, disengaging it from the hole in the links.




In another embodiment, the rigid chain concept includes link


600


,

FIG. 32

, joined to link


602


by pins


604


and


606


. Detent ball


608


on link


602


engages a detent recess


610


on link


600


. In this way, link


602


is normally locked with respect to link


600


but upon the application of a sufficient bending force (by pushing the chain through turn shoe


508


,

FIG. 25

) detent ball


608


will be dislodged from detent recess


610


thereby allowing link


600


to pivot with respect to link


602


providing a flexible configuration to bend into a position for extension up through the flow slots in the support plates of the interior of the steam generator. After the bend is made, the detent balls of one link again engage the detent recesses of an adjacent link to provide a rigid configuration for positioning and supporting inspection/cleaning devices up through the steam generator proximate the upper tube bundles.




The design shown in

FIG. 32

offers advantages over the paired rigid chain design shown in

FIG. 26

in that only one set of links is required and also offers advantages over the pin configuration shown in

FIG. 30

since a pin engagement/retraction drive is not required. Also, in the configuration shown in

FIG. 32

, the hollow interior of links


600


and


602


provide a passage for the umbilical subsystem which provides cleaning fluid to the nozzles, power to the tools (welder, grippers, etc.) and video signals to and form the video camera.




In another embodiment, rigid chain


620


,

FIG. 33

includes links


622


and


624


joined by ball and spring assembly


626


. Spring


628


biases link


624


to lock with respect to link


622


but upon the application of sufficient bending force (by pushing the chain through turn shoe


508


, FIG.


25


), the links rotate with respect to each other to make the 90° turn shown at


31


, FIG.


1


. The closest analogy to this embodiment is a series of tent poles engaged by an elastic “bungie” cord running through the center of the poles. After the 90° turn is made, the springs bias the links together providing a rigid configuration for deployment up through the steam generator.




In another embodiment, link


650


,

FIG. 34

includes rare earth magnet


650


while link


654


includes ferrous plate


656


. The magnet


652


of link


650


is attracted to ferrous plate


656


of link


654


thereby urging the links to remain locked together. A sufficient bending force, however, as with the designs shown in

FIGS. 32 and 33

, will allow the links to rotate with respect to each other but will then engage after bending of the chain. Rigid chain


660


,

FIG. 35

, is a combination of both the spring embodiments shown in FIG.


33


and the magnet embodiment shown in FIG.


34


.




In another embodiment, rigid chain


680


,

FIG. 36

, includes fairly lengthy links


682


,


684


, and


686


each having an extension


690


as shown for link


682


which prevents each adjacent link from rotating in one direction. These longer links minimize the total number of links required for the system.




Rigid Links




Another embodiment for elongated body


480


,

FIG. 24

which is flexible in one configuration and rigid in another configuration is a series of rigid links, FIG.


37


. Hollow rigid links


706


,


708


,


710


each include articulation recesses


703


and


704


between adjacent links


706


,


708


, and


710


. In this embodiment, the articulation recess is only on one side of each link. Pivot pin


712


and articulation recess


702


allow link


706


to rotate slightly with respect to link


708


in the direction shown by arrow


714


. Since each link can rotate slightly, the series of rigid links can make the bend required to traverse the blowdown lane of the steam generator (See

FIG. 1

) but then also extend upward through the flow slots and in this configuration the assembly is fairly rigid since “backbone” portion


716


prevents the individual links from bending in the direction shown by arrow


718


.




A similar design is shown on

FIG. 38

for rigid links


722


,


726


and


728


. In this case, each link


722


,


724


, and


726


comprises a hollow member joined to an adjacent link by elastomeric hinge element


730


. Here, there is an articulation recess


736


and


738


on each side of each elastomeric hinge element. The series of links can bend enough to be driven down the blowdown lane and then turn upwards to extend up through the flow slots. Straightening cable


732


which passes through orifice


733


formed in each link is used to lock the links in a rigid configuration. Water umbilical


734


and peripheral service lines


736


pass through the center of each link. These links may be made of any flexible plastic material.




Mast Embodiments




An alternative to the various rigid chain or rigid link embodiments described above is shown in FIG.


40


. Extendable mast


770


is made of a material normally self-biased to form a tube as shown at


762


even though it can be fed off a flat roll


764


. The material of mast


760


is typically a 0.010 spring-tempered stainless steel available from Spar Aerospace 9445 Airport Road, Brampton, Ontario, Canada. The natural aspect of the material is a 2″ diameter tube with plenty of overlap. The tube may be reinforced along its length by guide sleeves such as sleeve


764


as required.




As shown in

FIG. 40

, mast


760


guides water line


770


and peripheral service lines


772


and


774


encased by jacketing material


776


up through the flow slots of the steam generator. Motor drive


778


drives this embodiment of the deployment system up through the flow slots. Motor drive


778


includes counter rotating drums


780


and


782


each driving planetary guide roller arrangement


784


. As an alternative, two rolls of the mast material may be used to form a tube—each roll forming half of the tube with plenty of overlap for extra rigidity.




Combined Mast/Rigid Link Embodiments




The mast shown in

FIG. 40

may be used in conjunction with any of the rigid chains or rigid links described above including the rigid link embodiment


700


,

FIG. 37

as shown in

FIG. 41

for additional support as the rigid links are extended upward to the top of the steam generator. Mast storage drum


782


,

FIG. 41

includes the roll or rolls or mast material and turning shoe


784


feeds the rigid links from outside the hand hole of the steam generator aqd ultimately up through the flow slots in the successive series of support plates.




In any embodiment of the elongated snake-like body of this invention, whether rigid chain or rigid embodiments or the mast material embodiment, or combinations thereof, the boom and telescopic cylinders of the prior art shown in

FIG. 2

are eliminated and instead the elongated body is small enough so that it can be fed through the hand hole of the steam generator and through the flow slots in successive support plates. The body is also fully retractable to prevent any risk of any component of the system from becoming lodged in the upper regions of the steam generator. The body is flexible enough in one configuration to bend into a position for extension up through the flow slots in successive support plates and rigid in another configuration for positioning and support cleaning head/inspection devices up about the upper tube bundles.




Accordingly, the instant invention in any embodiment achieves the seemingly mutually exclusive goal of providing a deployment device which can bend and which is also rigid enough after the bend to support a cleaning head or an inspection device at a distance up to 30 feet within the steam generator.




Although specific features of the invention are shown in some drawings and not others, this is for convenience only as some feature may be combined with any or all of the other features in accordance with the invention.




Other embodiments will occur to those skilled in the art and are within the following claims:



Claims
  • 1. An upper bundle steam generator cleaning, inspection, and repair system comprising:a deployment and support device receivable within the steam generator including means to raise and position a distal end of said device to the upper bundles of the steam generator; a rotatable mechanism attached to the distal end of said device; an arm attached on a first end said rotatable mechanism; and at least one of a cleaning device, an inspection device, and a tool on a second end of said arm.
  • 2. The system of claim 1 in which said deployment and support device includes a first boom coupled by a rotatable connector to a second boom, said first and second boom and said rotatable connector being insertable into an access port of a steam generator and into a lane separating two rows of tube members, said second boom within said lane.
  • 3. The system of claim 1 in which said arm includes a set of telescoping members.
  • 4. The system of claim 1 in which said arm includes a flexible section.
  • 5. The system of claim 1 in which said arm is fabricated from a flexible material.
  • 6. The system of claim 1 in which said arm includes two sections, a first section attached to said rotatable mechanism and a second section rotatably attached with respect to said first section.
  • 7. The system of claim 1 in which said cleaning means includes a plurality of nozzles disposed on said arm.
  • 8. The system of claim 1 in which said inspection device includes an inspection camera disposed on said arm.
  • 9. The system of claim 1 in which said tool includes a drill assembly.
  • 10. The system of claim 1 in which said tool includes a gripper assembly.
  • 11. The system of claim 1 in which said tool includes a saw assembly.
  • 12. The system of claim 1 in which said tool includes a welder assembly.
  • 13. The system of claim 1 in which said deployment and support device includes:an elongated body feedable substantially horizontally through a lower access in a steam generator shell proximate the tube sheet of the steam generator, said elongated body flexible in one configuration to bend into a position for extension vertically up through flow slots in support plates of the interior of the steam generator, and rigid when vertically disposed for positioning and supporting cleaning/inspection/tool devices up through the steam generator proximate the upper tube bundles of the steam generator; means for driving said elongated body vertically up through said support plates and for retracting said elongated body back down through said support plates; and means for guiding the elongated body to bend from said substantially horizontal orientation to the rigid vertical position.
  • 14. The system of claim 13 in which said elongated body is a rigid chain.
  • 15. The system of claim 14 in which said rigid chain includes a number of links, each pivotable with respect to an adjacent link in one configuration, said links including means for releasably locking adjacent links against pivoting in another configuration.
  • 16. The system of claim 15 which said means for releasably locking includes retractable pins for locking said links together when engaged, and for freeing said links when retracted.
  • 17. The system of claim 16 in which said means for driving includes means for automatically retracting and engaging said pins.
  • 18. The system of claim 15 in which said means for releasably locking includes detent balls on one portion of said links and complementary detent recesses on one portion of adjacent sets of links.
  • 19. The system of claim 15 in which said means for releasably locking includes a spring for urging one link to remain engaged with an adjacent link.
  • 20. The system of claim 15 in which said means for releasably locking includes a magnet for urging one link to remain engaged with a adjacent link.
  • 21. The system of claim 15 in which said means for releasably locking includes both a spring and a magnet for urging one link to remain engaged with an adjacent link.
  • 22. The system of claim 14 in which said rigid chain includes a plurality of links each having a hinge and a portion extending beyond said hinge for preventing movement of an adjacent link in one direction.
  • 23. The system of claim 13 in which said elongated body comprises a pair of rigid chains, each bendable in only one direction, each deployed into the steam generator by bending, the pair deployed back to back in the rigid configuration.
  • 24. The system of claim 13 in which said elongated body comprises a pair of rigid chains, each chain free to bend in one direction but rigid in the opposite direction.
  • 25. The system of claim 24 further including means for orientating said pair of rigid chains back to back thereby providing a rigid structure for positioning and supporting cleaning/inspection devices up through the steam generator.
  • 26. The system of claim 13 in which said elongated body includes a plurality of rigid links.
  • 27. The system of claim 26 in which said links each have a hinge and at least one articulation recess proximate said hinge for allowing movement of an adjacent link in only one direction.
  • 28. The system of claim 27 in which said links includes an articulation recess on each side of said hinge.
  • 29. The system of claim 13 in which said elongated body includes an extendable mast formed of a material self-biased to form a tube.
  • 30. The system of claim 29 in which said means for driving includes a pair of counter-rotating drums for driving said mast material engaged between said drums.
  • 31. The system of claim 13 in which said elongated body comprises a rigid chain supported by an extendable mast formed of a material self-biased to form a tube.
  • 32. The system of claim 13 in which said elongated body comprises a series of rigid links supported by a mast formed of a material self-biased to form a tube.
  • 33. The system of claim 13 in which said drive means includes a turning shoe for directing said elongated body from a position proximate the tube sheet to a position for extension upwards therefrom to the upper bundles of the steam generator.
  • 34. The system of claim 1 further including an offset mechanism for displacing said arm with respect to said rotatable mechanism.
RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 08/728,905 filed Oct. 11, 1996 now abandoned which is a continuation-in-part of U.S. patent application Ser. No. 08/239,378 filed May 6, 1994 (U.S. Pat. No. 5,564,371). This application is also related to U.S. patent application Ser. No. 08/682,645 which is a continuation-in-part application of Ser. No. 08/239,378.

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Continuations (1)
Number Date Country
Parent 08/728905 Oct 1996 US
Child 09/616481 US
Continuation in Parts (1)
Number Date Country
Parent 08/239378 May 1994 US
Child 08/728905 US