JP2004219102A - Conservation method for jet pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conservation method for jet pumps by which increase of fabrication process is suppressed and lowering of damage potential of jet pump beams can be attained. <P>SOLUTION: In conservation work, a retainer is removed so that jet pump beams 15 with thick ends 19 of the beam can be newly attached. By thickening the beam ends 19 for the withdrawal of the retainer, machining for providing a dent in the middle of the bottom of the jet pump beam 15 becomes unnecessary and generation of stress in the jet pump beam 15 can be reduced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a jet pump for flowing a coolant through a core of a boiling water reactor, and more particularly to a method for maintaining such a jet pump.
[0002]
[Prior art]
In a boiling water reactor, a recirculation system is provided in a pressure vessel. At this time, a jet pump is used as a pump. Here, FIG. 7 shows an example of a recirculation system of a nuclear reactor equipped with such a jet pump. In this figure, reference numeral 2 denotes a jet pump.
[0003]
The jet pump 2 is installed in the reactor pressure vessel 1 and injects pressurized water fed from a reactor recirculation pump 3 outside the reactor into a lower plenum 4 from a nozzle. It has a role of sending to the area 6.
[0004]
Next, details of the jet pump 2 will be described with reference to FIG. Here, the jet pump 2 serves as a riser pipe 7 for guiding the pressurized water into the furnace, an elbow 8 for changing the direction of the pressurized water, an inlet mixer 9 having a nozzle, and a connection section between the riser pipe 7 and the inlet mixer 9. A transition piece 10 and a diffuser 11 for jetting pressure water passing through the inlet mixer 9 to the lower plenum 4 are provided.
[0005]
Further, a jet pump beam bolt 12 for further pressing the upper surface of the inlet mixer 9, and a jet pump beam 15 which fits into a groove 14 provided in the arm portion 13 of the transition piece 10 and applies a downward load to the jet pump beam bolt 12. It has.
[0006]
At this time, as shown in FIG. 9, the jet pump beam bolt 12 has its male screw 16 screwed into the jet pump beam 15 having the female screw hole 17 and welding the keeper 22 to the plate 23 on the upper surface of the jet pump beam 15. The rotation is stopped by.
[0007]
At this time, the jet pump beam bolt 12 is mechanically fastened to the elbow 8 by a retainer 18 attached to the elbow 8 by a retainer bolt 21.
[0008]
Here, the jet pump beam 15, the jet pump beam bolt 12, the keeper 22, the plate 23, and the like may be collectively referred to as a jet pump beam assembly 24.
[0009]
Incidentally, the jet pump beam 15 is subjected to a strong tightening force for suppressing the lifting of the inlet mixer 9 due to the fluid reaction force, and hence a large stress is applied. Has a high damage potential.
[0010]
Therefore, in order to reduce the damage potential, the jet pump beam may be replaced as a maintenance work. For this reason, the first method (for example, replacing the jet pump beam and the jet pump beam bolt by widening the retainer) (for example, , Patent Document 1) and a second method of replacing only the jet pump beam (for example, see Patent Document 2) have been proposed as conventional techniques.
[0011]
On the other hand, apart from these, as a third technique (for example, see Patent Document 3), it has been proposed as a conventional technique to increase the thickness of the end portion of the jet pump beam and reduce the stress generated in the jet pump beam. Have been.
[0012]
[Patent Document 1]
JP 08-201566 A
[Patent Document 2]
JP-A-10-282289
[Patent Document 3]
JP 09-133781 A
[Problems to be solved by the invention]
The above prior art does not consider the existence of the retainer, which increases the number of processing steps in the maintenance work and reduces the possibility of the jet pump beam being damaged by the maintenance work, that is, the damage potential of the jet pump beam. There was a problem in the reduction of
[0016]
Here, of the above prior arts, the first method is to increase the thickness of the end of the jet pump beam in order to reduce the damage potential of the jet pump beam. It is necessary to provide a dent to avoid interference with the retainer in the part, or increase the depth of the groove provided in the arm part of the transition piece to escape the retainer, so that the number of processing steps is increased It will be lost.
[0017]
Next, in the second method, since the jet pump beam is simply replaced, the stress generated in the jet pump beam cannot be reduced. Therefore, a problem arises in reducing the damage potential of the jet pump beam. is there.
[0018]
On the other hand, the third method only increases the thickness of the end of the jet pump beam from the beginning, and has nothing to do with the reduction of the damage potential of the jet pump beam due to the maintenance work.
[0019]
An object of the present invention is to provide a jet pump maintenance method capable of reducing the damage potential of a jet pump beam while suppressing an increase in the number of processing steps.
[0020]
[Means for Solving the Problems]
The above object is achieved by removing a retainer at a lower portion of the jet pump beam during maintenance work and newly installing a jet pump beam having a thicker end according to the thickness of the removed retainer.
[0021]
In addition, the object is to remove at least a part of the retainer at the lower part of the jet pump beam during maintenance work, and to increase the thickness of the end of the beam according to the thickness of at least a part of the removed retainer. This can also be achieved by installing a new one.
[0022]
At this time, the above object is achieved even when the thickness of the end of the newly mounted jet pump beam is set to be 75% or more and less than 100% of the dimension of the groove of the transition piece.
[0023]
Also, at this time, the above-mentioned object is achieved even if the operation of removing the retainer is performed in the reactor pressure vessel, and the operation of removing the retainer is performed by removing the inlet mixer from the reactor and performing the operation in the pool. The above-described object is achieved even when the program is executed.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method for maintaining a jet pump according to the present invention will be described in detail with reference to the illustrated embodiment. First, FIG. 1 shows a jet pump beam 15 according to the first embodiment of the present invention and its surroundings. It is sectional drawing.
[0025]
At this time, also in this embodiment, since the overall configuration of the jet pump 2 is the same as that of the conventional one, the same description will be given in the following description of the embodiment with reference to FIGS. Description will be made using reference numerals.
[0026]
In FIG. 1, the jet pump beam 15 is first bent in a bow shape by a jig (jet pump beam tensioner) (not shown) and deformed in a direction in which the lower surface is concave and the upper surface is convex. By transmitting the force to the inlet mixer 9 via the jet pump beam bolt 12, the lifting of the inlet mixer 9 is prevented.
[0027]
At this time, the jet pump beam 15 also transmits the above-described elastic repulsion to the transition piece arm 13 by fitting into the groove 14 provided in the transition piece arm 13.
[0028]
Also in this embodiment, the positional relationship between the jet pump beam 15, the jet pump beam bolt 12, the transition piece arm portion 13, and the inlet mixer 9 and their interlocking relationship are the same as in the prior art. This is different from the conventional one.
[0029]
First, as is apparent from FIG. 1, the first difference is that the retainer 18 in the prior art shown in FIG. 9 is removed during the maintenance work and is not present. Second, the absence of the retainer 18 causes the jet pump beam 15 having a thicker end than in the prior art to be newly attached for maintenance work.
[0030]
At this time, as is apparent from FIG. 1, since the retainer 18 is removed and does not exist, the bottom of the jet pump beam 15 is not cut off and added to the groove 14 provided in the transition piece arm 13. It can be seen that the jet pump beam 15 having a thicker end is attached without processing.
[0031]
Therefore, the first of the above differences, that is, the point in FIG. 1 in which the retainer 18 in the prior art of FIG. 9 is removed will be described. Here, the removal of the retainer 18 is performed at the time of the maintenance work of the jet pump. At this time, there are two types, a method of removing the inside of the reactor pressure vessel 1 and a method of removing the inlet mixer 9 in the pool. However, in this embodiment, a method of removing the reactor inside the reactor pressure vessel, which is considered to be relatively difficult to realize, will be described.
[0032]
FIG. 15 shows a procedure for removing the retainer 18 at this time. When the removal operation is started, first, as a retainer widening operation 150, the widening device 32 shown in FIG. 10 is used, and as shown in FIG. Is widened (spread).
[0033]
The widening procedure at this time is as follows. First, as shown in FIG. 14, a rope 30 is passed through the suspending tool 29 of the widening device 32, and the bogie 31 used for the work is suspended in the reactor pressure vessel 1. Then, as shown in FIG. 10, the widening device 32 is positioned by the jet pump beam bolt 12, and the fixing bolt 33 is rotated by a tool having a socket wrench at the tip of a long pole, and the jet pump beam The widening device 32 is seated on the top 15 and fixed.
[0034]
After confirming with the underwater camera or the like that the attachment 34 of the widening device 32 is hooked on the bent portion 20 at the tip of the retainer, the attachment operation bolt 35 is rotated to move the attachment 34. By this operation, the width of the retainer 18 can be widened as shown by a solid line in FIG.
[0035]
Next, as a retainer extending operation 151, a bent portion 20 at the tip of the retainer is mechanically extended as shown in FIG. 3 by using a nail extending device 37 shown in FIG.
[0036]
The procedure for extending the retainer at this time is as follows. First, the rope 30 is passed through the hanging member 36 of the claw extending device 37, and the retainer is suspended from the bogie 31 into the reactor pressure vessel 1. Next, the claw extending device 37 is similarly positioned by the jet pump beam bolt 12, and the claw extending device 37 is seated on the jet pump beam 15. Thereafter, the bent portion 20 at the tip of the retainer is sandwiched between the upper claws 39 and the lower claws 40 by the hydraulic cylinder 38, and in this state, the upper claws 39 and the lower claws 40 are pulled upward by the hydraulic cylinder 41. By this operation, the bent portion 20 at the tip of the retainer can be linearly extended as shown by a solid line in FIG.
[0037]
Next, as the retainer cutting operation 152, the cutting device 43 shown in FIG. 12 is used, and as shown in the front view of FIG. 4 (a) and the side view of FIG. 4 (b), around the retainer bolt 21 of the retainer 18 Cutting is performed mechanically or by another method at a cutting position 26 having a size of φ25 mm to φ35 mm.
[0038]
The procedure for cutting the retainer at this time is as follows. First, the rope 30 is passed through the suspending tool 42 of the cutting device 43, and is suspended from the bogie 31 into the reactor pressure vessel 1. Next, the cutting device 43 is similarly positioned by the jet pump beam bolt 12, and the cutting device 43 is seated on the jet pump beam 15. After that, the hole saw 46 is rotated by one or more gears 45 by the air motor 44. By this operation, the retainer 18 around the retainer bolt 21 can be cut circumferentially as shown in FIG. For cutting, a means such as electric discharge machining can be used.
[0039]
Next, as a retainer removing operation 153, the retainer 18 is gripped using an apparatus such as an air plier (not shown) and removed from the inside of the reactor pressure vessel 1, and then, as a bolt collecting operation 154, the bolt rotation shown in FIG. The retainer bolt 21 remaining in the inlet mixer 9 is recovered using the device 48.
[0040]
The procedure for collecting the retainer bolts 21 at this time is as follows. First, the ropes 30 are passed through the hanging members 47 of the bolt rotating device 48, and are suspended from the bogie 31 into the reactor pressure vessel 1. Next, the bolt rotating device 48 is positioned by the jet pump beam bolt 12, and the bolt rotating device 48 is seated on the jet pump beam 15. Then, the socket 51 is rotated counterclockwise by one or more gears 50 by the air motor 49 to loosen the retainer bolt 21 and collect the retainer bolt 21 in the socket 51. By this operation, the retainer bolt 21 can be collected.
[0041]
By the above procedure, the retainer can be removed. At this time, as an alternative to mechanically extending the bent portion 20 at the tip of the retainer, there is also a method of removing the retainer 18 with the jet pump beam 15 removed. A method may be used.
[0042]
By the way, in this embodiment, as described above, the retainer 18 is removed in the reactor pressure vessel 1 without removing the inlet mixer 9, but the inlet mixer 9 is removed and moved to a pool or the like, where it is illustrated. It is also possible to remove the retainer 18 using a jig or tool that is not used.
[0043]
Next, a second difference will be described. Here, the second difference is that the bottom of the jet pump beam 15 is not cut off, the groove 14 provided in the transition piece arm 13 is not additionally processed, and The jet pump beam 15 having a large thickness of the portion 19 is to be mounted.
[0044]
Here, according to FIG. 1, a jet pump beam 15 having a larger dimension H2 of the jet pump beam end portion 19 than in the case of the prior art is newly attached for maintenance work. At this time, it is apparent from FIG. As described above, since the retainer 18 has been removed and is not present, the jet pump beam 15 has a thick end 19 without notching the bottom of the jet pump beam 15 or performing additional processing on the groove 14 of the transition piece arm 13. It can be seen that the beam 15 is attached.
[0045]
Here, the thickness of the retainer 18 in FIG. 9 is represented by t as shown, and the thickness of the end 19 of the jet pump beam 15 at this time is represented by T1. If the thickness of the end portion 19 of the jet pump beam 15 in the embodiment of FIG. 1 is T2, simply, T2 = T1 + t.
[0046]
Moreover, at this time, the thickness T2 of the end portion 19 of the jet pump beam 15 can be obtained without notching the bottom of the jet pump beam 15 and performing no additional processing on the groove 14 provided in the arm portion 13 of the transition piece. T1 + t can be obtained.
[0047]
As a result, according to the embodiment, the bending stress, the shear stress, and the like generated in the vicinity of the end 19 of the jet pump beam can be significantly reduced by the maintenance work, so that the damage potential can be sufficiently reduced. it can.
[0048]
In addition, at this time, according to the above-described embodiment, since the shape of the transition piece 10 is not changed, no change is required in the connection relationship with the other components such as the transition piece arm 13, and the jet pump The replacement operation of the beam 15 and, consequently, the jet pump beam assembly 24 can be performed in the same manner as in the prior art.
[0049]
Further, according to this embodiment, after the maintenance work is performed, the retainer does not exist in the nuclear reactor, so that the retainer itself and bolts attached to the retainer itself due to vibration due to fluid flow during operation of the nuclear reactor. There is no risk of damage.
[0050]
Therefore, according to this embodiment, the possibility that loose parts are generated in the nuclear reactor, that is, the loose parts generation potential can be reduced, and this can greatly contribute to ensuring safe and stable operation of the nuclear power plant.
[0051]
At this time, by setting the dimension T2 to be less than 100% of the dimension T3 of the groove 14 of the arm 13 shown in FIG. 1, the shape of the transition piece 10 does not need to be changed, and additional processing is not required. A maximum increase in strength can be obtained.
[0052]
Therefore, it is desirable that the dimension T2 be less than 100% and be as close to the dimension T3 as possible. In practice, it is sufficient to set the thickness to 75% or more and less than 100%. Even when the end 19 of the jet pump beam 15 is thickened to this extent, the maintenance work is performed to sufficiently reduce the damage potential of the beam. be able to.
[0053]
Next, a second embodiment of the present invention will be described. Here, FIG. 5 is a cross-sectional view of the jet pump beam 15 of the jet pump 2 and its periphery in the second embodiment of the present invention, which also shows a state after the maintenance work has been performed. .
[0054]
The difference between the embodiment of FIG. 5 and the first embodiment described with reference to FIG. 1 is that the retainer 18 is not completely removed at the time of maintenance work, but only a part of the retainer 18 is removed. The point is that it is left as part 28.
[0055]
Therefore, in the second embodiment shown in FIG. 5, a processing procedure for removing a part of the retainer 18 and leaving it as the retainer remaining portion 28 will be described below with reference to FIG.
[0056]
Here, in the case of the second embodiment, first, as is apparent from FIG. 16, the retainer cutting operation 152 in the processing procedure of the first embodiment in FIG. 15 is changed to the retainer cutting operation 160, and The bolt recovery operation 154 has been eliminated.
[0057]
However, the other work 150 for widening the retainer, the work 151 for extending the retainer, and the work 153 for removing the retainer are the same as those in the second embodiment in FIG. 16 as in the first embodiment in FIG.
[0058]
Therefore, the retainer cutting operation 160 will be described below. In this case, after performing the retainer widening operation 150 and the retainer extension operation 151, the operation enters the retainer cutting operation 160, and first, cutting means such as mechanical or electric discharge machining is suspended from the carriage 31 into the reactor pressure vessel 1.
[0059]
Next, as shown in the front view of FIG. 6A and the side view of FIG. 6B, the cutting means is used at a cutting position 27 between the retainer R portion 25 of the retainer 18 and the periphery of the retainer bolt 21. The retainer 18 is cut in a straight line, and the fork-shaped leg 18A of the retainer 18 is separated from the portion fixed by the retainer bolt 21.
[0060]
Then, after that, as a retainer removing operation 153, the retainer 18 is gripped using an apparatus such as an air plier (not shown) and removed from the inside of the reactor pressure vessel 1.
[0061]
Therefore, according to the second embodiment, the retainer bolt 21 remains fixed to the elbow 8 together with the retainer remaining portion 28 which is a part of the retainer 18, and it is not necessary to collect the retainer bolt 21. (FIG. 15) can be eliminated.
[0062]
By the way, in the second embodiment, as an alternative to mechanically extending the bent portion 20 at the tip of the retainer, there is a method of removing the retainer 18 with the jet pump beam 15 removed, and this method is used. Is also good.
[0063]
Also in this second embodiment, a part of the retainer 18 is removed in the reactor pressure vessel 1 without removing the inlet mixer 9, but the inlet mixer 9 is removed and moved to a pool or the like. It is also possible to remove the retainer 18 using a jig (not shown).
[0064]
Also in the second embodiment, the bottom of the jet pump beam 15 is not cut off, and the groove 14 provided in the transition piece arm 13 is not additionally processed. A jet pump beam 15 having a large thickness is mounted as in the first embodiment.
[0065]
That is, in the second embodiment as well, as shown in FIG. 5, the jet pump beam 15 in which the dimension H2 of the end portion 19 of the beam 15 is larger than that of the prior art is newly attached during maintenance work. Have been.
[0066]
At this time, as is apparent from FIG. 5, since a part of the retainer 18 has been removed and does not exist, the bottom of the jet pump beam 15 is notched or the transition piece arm is also provided in the second embodiment. It can be seen that the jet pump beam 15 having the thickened end 19 is attached to the groove 14 of the thirteen without additional processing.
[0067]
That is, in the embodiment shown in FIG. 5, the bottom of the jet pump beam 15 is not cut off, and the end of the jet pump beam 15 is not cut into the groove 14 provided in the arm 13 of the transition piece. This means that the thickness T2 of the portion 19 can be set to T2 = T1 + t.
[0068]
Therefore, also according to the second embodiment, the maintenance work can greatly reduce the bending stress, the shear stress, and the like generated near the end portion 19 of the jet pump beam, so that the damage potential can be sufficiently reduced. Can be.
[0069]
Moreover, according to the second embodiment, since the shape of the transition piece 10 is not changed, there is no need to change the connection relationship with other components such as the transition piece arm 13 at all. In addition, the replacement work of the jet pump beam assembly 24 can be performed without any difference from the case of the prior art.
[0070]
Here, the effects of the above embodiment will be listed as follows.
[0071]
According to the above-described embodiment, the jet pump beam 15 can be replaced with the jet pump beam 15 having an increased thickness at the end portion 19 without providing a dent at the center of the bottom surface of the jet pump beam 15. There is an effect that the generated stress of the pump beam 15 can be reduced.
[0072]
According to the above embodiment, the jet pump beam 15 can be replaced with the jet pump beam 15 having an increased thickness at the end portion 19 without providing a dent at the center of the bottom surface of the jet pump beam 15. There is an effect that processing of the beam 15 becomes easy.
[0073]
According to the above-described embodiment, it is possible to replace the jet pump beam 15 with the increased thickness of the end portion 19 of the jet pump beam without processing the groove portion 14 provided in the transition piece arm portion 13. This has the effect that the preventive maintenance work and the post-maintenance work of the jet pump 2 are facilitated.
[0074]
According to the above-described embodiment, since part or all of the retainer 18 is removed, the jet pump beam 15 having the increased thickness at the end 19 of the jet pump beam without providing a dent at the center of the bottom surface of the jet pump beam 15. Can be mounted, which can reduce the potential for generating loose parts in the nuclear reactor, and has the effect of ensuring safe and stable operation of the nuclear power plant.
[0075]
【The invention's effect】
According to the present invention, it is possible to reduce the damage potential of the jet pump beam without increasing the number of processing steps, and as a result, it is possible to greatly contribute to improvement in reliability by maintenance work.
[Brief description of the drawings]
FIG. 1 is a partial enlarged view of a jet pump for explaining a first embodiment of a maintenance method of a jet pump according to the present invention.
FIG. 2 is an explanatory diagram showing a widened state of a retainer in the embodiment of the present invention.
FIG. 3 is an explanatory view showing a state in which a tip of a retainer is extended in the embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a cutting position of a retainer in the embodiment of the present invention.
FIG. 5 is a partially enlarged view of a jet pump for explaining a second embodiment of the jet pump maintenance method according to the present invention.
FIG. 6 is an explanatory diagram showing a cutting position of a retainer according to the embodiment of the present invention.
FIG. 7 is a schematic explanatory view of a recirculation system of a boiling water reactor.
FIG. 8 is a structural diagram showing an example of a jet pump.
FIG. 9 is a structural view showing an example of a jet pump beam assembly.
FIG. 10 is a structural diagram showing an example of a widening device used in an embodiment of the present invention.
FIG. 11 is a structural diagram showing an example of a claw extending device used in the embodiment of the present invention.
FIG. 12 is a structural diagram showing an example of a cutting device used in the embodiment of the present invention.
FIG. 13 is a structural view showing an example of a bolt rotating device used in the embodiment of the present invention.
FIG. 14 is a schematic state diagram for explaining a work situation in the embodiment of the present invention.
FIG. 15 is a flowchart of a retainer removing process according to the first embodiment of the present invention.
FIG. 16 is a flowchart of a retainer removing process according to the second embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 reactor pressure vessel 2 jet pump 3 reactor recirculation pump 4 lower plenum 5 arrow indicating pressure water flow 6 core area 7 riser pipe 8 elbow 9 inlet mixer 10 transition piece 11 diffuser 12 jet pump beam bolt 13 arm 14 Groove 15 Jet pump beam 16 Male screw 17 Female screw hole 18 Retainer 19 Jet pump beam end 20 Bend at retainer tip 21 Retainer bolt 22 Keeper 23 Plate 24
Jet pump beam assembly 25 Retainer R section 26 Cutting position (circular shape)
27 Cutting position (linear)
28 Retainer Remaining Part 29 Hanging Device 30 Rope 31 Car 32 Widening Device 33 Fixing Bolt 34 Attachment 35 Attachment Operation Bolt 36 Hanging Device 37 Claw Extending Device 38 Hydraulic Cylinder 39 Upper Claw 40 Lower Claw 41 Hydraulic Cylinder 42 Hanging Device 43 Cutting Device 44 Air motor 45 Gear 46 Hole saw 47 Hanging tool 48 Bolt rotating device 49 Air motor 50 Gear 51 Socket

Claims (5)

Remove the retainer at the bottom of the jet pump beam for maintenance work,
A method for maintaining a jet pump, characterized by newly attaching a jet pump beam having a thicker end according to the thickness of the removed retainer. At least part of the retainer at the bottom of the jet pump beam was removed during maintenance work,
A method for maintaining a jet pump, characterized by newly attaching a jet pump beam having a thicker end according to the thickness of at least a part of the removed retainer. In the method for maintaining a jet pump according to claim 1 or 2,
A method for maintaining a jet pump, wherein the thickness of the end of the newly installed jet pump beam is 75% or more and less than 100% of the dimension of the groove of the transition piece. In the method for maintaining a jet pump according to claim 1 or 2,
The maintenance method for a jet pump, wherein the operation of removing the retainer is performed in a reactor pressure vessel. In the method for maintaining a jet pump according to claim 1 or 2,
The maintenance method of a jet pump, wherein the operation of removing the retainer is performed in a pool by removing an inlet mixer from a nuclear reactor.

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