JP2562384B2 - Installation method of thimble tube and lower nozzle in assembly work of nuclear fuel assembly - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a control rod guide tube and a large number of thimble tubes formed by fuel rods between an upper nozzle and a lower nozzle, which are aligned with each other by a predetermined distance by a supporting grid. More particularly, it relates to a method for assembling a plurality of thimble tubes by assembling a lower nozzle in an orthogonal state with respect to an assembling operation of a series of fuel assemblies.

[0002]

2. Description of the Related Art As shown in FIG. 12, a fuel assembly 5 in which a large number of thimble tubes 4 are connected in parallel between an upper nozzle 1 and a lower nozzle 2 by a plurality of support grids 3 is provided. , Already known. By the way, in the assembling work of the fuel assembly 5 as described above, the lower end surfaces of the many thimble tubes 4 are brought into contact with the upper surface 2a side of the lower nozzle 2 and fixed by a set screw, and The nozzle 2 is attached, but this work affects the straightness of the thimble tube 4 with respect to the lower nozzle 2 (that is, there is no inclination and is in an orthogonal state). Therefore, the following complicated procedure is followed. It is done carefully.

That is, in the first step, as shown in FIG. 8, a desired number of thimble tubes 4 are mounted side by side on a surface plate A by a required number of support grids 3 so as to be aligned with a predetermined spacing. The upper nozzle 1 of each thimble tube 4 is placed.
The upper end faces, which are the sides, are aligned so as to be flush with each other on the reference line.

In the second step, among the mounting holes 6 having a large number of screw holes 6a provided in the lower nozzle 2, the screw holes 6a of the other mounting holes 6 other than the four mounting holes 6 shown by the thick lines in FIG. Has
The adjustment bushing 7 as shown in FIG. 9 is threadedly fitted, and the set screw 8 of FIG. 10 is attached to the four mounting holes 6 of the lower nozzle 2 from the lower side and is attached to the end face of the lower side of the thimble tube 4. The lower nozzle 2 is temporarily fixed to the thimble tube 4 by being screwed into the screw mouth 4a.

In the third step, the adjusting bushing 7 is screwed from the lower side to adjust the position so that it is pressed against the lower end surface of each thimble tube 4, and then the set screw 8 is turned backward. By doing so, the lower nozzle 2 is removed.

In the fourth step, as shown in FIG. 11, the adjustment bushings 7 above the adjustment bushings 7 of the lower nozzle 2 are carefully adjusted so as not to rotate unintentionally. The head is placed on the upper surface 2 of the lower nozzle 2
When the welding work is completed, the lower nozzle 2 is fixed to the welded parts 9 at two locations through the shaft holes 7a of the adjustment bushings 7 that have been welded at the required number of locations, and the set screw 8 is attached. The lower nozzle 2 is temporarily fixed to the thimble tube 4 again by screwing to the attachment screw port 4a of the thimble tube 4.

In the fifth step, the adjusting bushing 7 is screwed into the screw holes 6a of the four mounting holes 6 and is screwed from the lower side, whereby the upper head of the adjusting bushing 7 is screwed. The lower nozzle 2 is removed again by adjusting the position of pressing against the lower end face of the thimble tube 4 in the same manner as in the above-mentioned fourth step and turning the set screw 8 in the reverse direction.

Next, in a sixth step, the adjusted adjustment bushings 7 (four pieces) are fixed by the welded portion 9 in the same manner as in the fourth step, and the lower nozzle 2 is entirely removed after the welding operation. The lower nozzle 2 is completely attached by fastening the thimble tubes 4 (24 pieces) with the respective set screws 8.

[0009]

According to the above-mentioned conventional method, the lower nozzle 2 is temporarily fixed in the second step, removed in the third step, and the lower nozzle 2 is temporarily fixed again in the fourth step. Further, since it is removed again in the fifth step and the lower nozzle 2 is permanently attached in the sixth step, the number of steps is large, and accordingly, considerable labor and working time (about 1.5 hours) are required. In addition, when the lower nozzle 2 is removed, unless the extremely careful work is performed, the adjustment bushing 7 with the bent position adjusted may unintentionally rotate, and the straightness of the fuel assembly may not be obtained. .

In view of the drawbacks of the above-mentioned conventional method, the present invention has been such that the welding work of the adjustment bushing 7 is performed so far by using the lower nozzle 2.
To remove the thimble tube 4 and remove the preconceived idea of pressing the welding torch from the upper surface side of the lower nozzle 2.
Then, the adjusted bushing 7 that has been adjusted in the lower nozzle 2 that is still attached to the thimble tube 4 is welded from the lower surface side thereof, and this allows the lower nozzle 2 to be repeatedly removed. We are trying to reduce work by eliminating work, shortening the total work time significantly (about 30 minutes). Further, by not performing the removing work, if the adjustment bushing 7 is adjusted, the welding for the rotation stop can be immediately performed, and the unintentional rotation of the adjustment bushing 7 is eliminated so that the reliability of the straightness can be improved. The purpose is to obtain a highly reliable fuel assembly.

According to a second aspect of the present invention, in addition to the first aspect of the present invention, when welding the adjusting bushing 7, a welding notch groove provided at an appropriate position of the attachment hole is used, and a welding torch is inserted therein. By doing so, it is possible to easily and surely aim at the welding spot, and the welding operation in an extremely narrow spot can be performed quickly and with high reliability.

[0012]

In order to achieve the above object, the present invention provides a plurality of thimble tubes at a predetermined interval on a surface plate by a required number of supporting grids. The first step of mounting and fixing so as to be aligned and aligning the upper end surfaces of the respective thimble tubes flush with each other, the lower opening having the set screw tightening seat, and the screw hole coaxially communicating therewith In the lower nozzle having a large number of mounting holes formed by the above, the adjustment bushing having the shaft hole penetratingly screwed into the screw holes in the desired large number of mounting holes described above at appropriate times. With the adjusting bushing in the required plurality of mounting holes with the adjustment bushing oriented toward the thimble tube, press the set screw that presses the set screw tightening seat from the lower side opening into the lower side of the thimble tube. It is screwed into the mounting screw provided on the end face. Then, in the second step of temporarily fixing the lower nozzle to the thimble tube, in this state, the plurality of adjustment bushings are screwed from the lower side of the lower nozzle so that the upper surface of the adjustment bushing abuts the lower side end surface of the thimble tube. A third step of adjusting, a fourth step of welding the adjusted adjustment bushings from the lower side to the lower nozzle in a rotation stop state by welding work from the lower side, and the set screw from the lower side opening of the mounting hole, Through the shaft hole of the welded adjustment bushing, the lower nozzle is screwed to the thimble pipe by being screwed to the mounting screw mouth of the thimble pipe and pressed against the set screw tightening seat, and the screw is already attached. The required plurality of setscrews are removed, and the adjustment bushing is screwed from the lower side opening into the screw hole of the mounting hole relating to the above-mentioned removed setscrew. The sixth step of bringing the surface into contact with the lower end surface of the thimble tube, and welding these adjustment bushings to the lower nozzle so as to prevent rotation by the welding work from the lower side, and then the set screw. From the lower side opening of the mounting hole, through the shaft hole of the welded adjustment bushing, by screwing into the mounting screw port of the thimble pipe and pressing it against the set screw tightening seat, the lower nozzle and the thimble pipe are connected. The present invention aims to provide a method of attaching a thimble tube and a lower nozzle in an assembly operation of a nuclear fuel assembly, which comprises a seventh step of screwing.

According to a second aspect of the present invention, a plurality of required thimble tubes are mounted and fixed on the surface plate by a required number of support grids so as to be aligned with each other at a predetermined interval, and the upper side of each thimble tube is fixed. A first step of aligning the end faces flush with each other, a plurality of mounting holes formed by a lower side opening having a set screw tightening seat, and a screw hole coaxially communicating therewith, are provided, and
In the lower nozzle in which a part of the set screw tightening seat is partially cut out in the radial direction to form a welding notch groove, a shaft hole is provided at appropriate time in the screw holes in the desired large number of mounting holes. With the adjustment bushing screwed in and with the upper surface of the lower nozzle oriented toward the thimble tube, press the adjustment bushing into the set screw holes through which the adjustment bushing is not screwed, and press it into the setscrew seat. The second step of temporarily fixing the lower nozzle to the thimble tube by screwing the corresponding set screw to the mounting screw port provided on the lower side end face of the thimble tube, and the lower side of the lower nozzle in this state. From the third step of adjusting the upper surface of the adjusting bushing so as to abut the lower end surface of the thimble tube by screwing the plurality of adjusting bushings from above, and adjusting the adjusted bushing from the lower side to the welding torch of the mounting hole. Bottom side The fourth step of welding the welding notch groove, which is the outer peripheral side of the screw hole of the nozzle, by welding work by inserting it from the mouth into the notch groove for welding, and the set screw. The lower nozzle is screwed onto the thimble tube by screwing it from the lower side opening of the mounting hole through the shaft hole of the welded adjustment bushing to the mounting screw mouth of the thimble tube and pressing it against the set screw tightening seat. 5th step of stopping and removing the required plurality of screws that have already been screwed, and adjusting bushing is screwed into the screw hole of the mounting hole of the removed screw from the lower side opening. Then, the sixth step of bringing the upper surface of the adjustment bushing into contact with the lower end surface of the thimble tube, and these adjustment bushings,
By welding work by inserting a welding torch into the lower nozzle from the lower side of the mounting hole into the welding notch groove from the lower side,
After being welded to the bottom of the welding notch groove on the outer peripheral side of the screw hole of the lower nozzle so as to prevent rotation, the set screw is inserted from the lower opening of the mounting hole through the shaft hole of the welded adjustment bushing. And a seventh step of screwing the lower nozzle and the thimble tube by screwing them into a mounting screw mouth of the thimble tube and pressing them against a set screw tightening seat. The content of the method is to attach the thimble tube and the lower nozzle to the body assembling work.

[0014]

In the first step, the upper end surfaces of the thimble tubes are aligned flush with each other, so that the lower end surfaces of the thimble tubes are in an uneven state corresponding to the non-uniform lengths of the thimble tubes. . In the second and third steps, the lower nozzle is temporarily fixed to the thimble tube by inserting and screwing the set screw into only the required plurality of attachment holes, and the lower nozzle is screwed into other than these attachment holes. When the adjusting bushing is screwed from the lower side of the lower nozzle, the adjusting bushing abuts against the lower end surface of the thimble tube, thereby positioning (adjusting) each adjusting bushing.

In the fourth step, the adjusted adjustment bushing is welded from the lower side of the lower nozzle in the temporarily fixed state, so that the adjusted adjustment bushing is fixed at the desired adjustment position in the rotation stop state. .

In the fifth and sixth steps, the lower nozzle is fixed by a set screw by using a required plurality of welded adjustment bushings, and by this, the lower nozzle is screwed for temporary fixing until then. Even if the set screw is removed, the temporarily fixed state is maintained, and the adjustment bushing is screwed into the screw hole of the mounting hole, and by screwing it, it is pressed against the lower end face of each thimble tube. Adjustment work will be possible.

In the seventh step, the adjusting bushing can be welded from the lower side of the lower nozzle and fixed so as to be in the rotation stop state, and therefore, the temporarily fixed state can be maintained throughout the entire process. There is no need to remove the lower nozzle. Of course, with respect to the adjustment bushing for completion of welding, the fixing screw is screwed into the thimble tube through the mounting hole using the shaft hole, so that the main mounting of the lower nozzle is completed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of attaching a thimble tube and a lower nozzle according to the present invention will be described below in detail with reference to the drawings. The same members as those in the conventional example are designated by the same reference numerals.
The first step of claim 1 is substantially the same as the first step of the conventional example, and as shown in FIG.
A plurality of (thirty) required thimble tubes 4 which are on the upper side and are kept aligned in a state of being separated by a predetermined distance by the support grid 3 are arranged so that the upper end surfaces of the thimble tubes 4 are flush with each other. Therefore, the lower end surface of the thimble tube 4 becomes uneven according to the length of the thimble tube 4.

Next, in the second step, as shown in FIGS. 1 and 2, the lower side opening 6c having the set screw tightening seat 6b is shown.
And a plurality of mounting holes 6 formed by coaxially communicating screw holes 6a in the lower nozzle 2 corresponding to the number of thimble tubes 4, a desired number (20) of mounting holes 6 are provided at appropriate times. The adjusting bushing 7 is screwed into only the screw hole 6a in the mounting hole 6 as shown in FIG.
It is preferable that the upper surface of the lower nozzle 2 is not exposed from the upper surface 2a of the lower nozzle 2.

Further, in the second step, with the upper surface 2a of the lower nozzle 2 being directed toward the thimble tube 4,
Required number (4 pieces) without adjusting bushing 7 screwed
Of the mounting hole 6 of the thimble tube 4 by inserting and screwing the set screw 8 from the lower side opening 6c of the thimble tube 4 and the head portion 8b. The lower nozzle 2 is fixed to the thimble tube 4 in a temporarily fixed state by pressing it against the set screw tightening seat 6b of No. 6.

Here, 10 shown in FIG. 2 and FIG.
As is known, it shows the water flow hole of the lower nozzle 2, and in practice, the diameter of the lower side opening 6c in the mounting hole 6 is about 15 m.
The depth is about 10 m, and the depth is as small as about 10 mm. In order to perform the method of claim 2 described later in the illustrated example, the set screw tightening seat 6b of the mounting hole 6 is provided in a simple annular shape. In the illustrated case, a part of the groove is not shown in FIG.
1 is recessed, and therefore the set screw tightening seat 6b
Is divided into two arcuate bodies.

Next, in the third step, the adjusting bushing 7 screwed in the temporarily fixed state is screwed from the lower side of the lower nozzle 2, and its upper surface is adjusted so as to contact the lower end surface of the thimble tube 4, As a result, each adjustment bushing 7 is positioned.

Further, by welding the adjusting bushing 7 positioned in the fourth step from the lower side of the lower nozzle, the lower end peripheral edge of the adjusting bushing 7 as shown in FIG. The welded portion 12 is formed by welding to the nozzle 2, and the adjusting bushing 7 is fixed in a rotation-stop state.

Here, in order to perform the above-mentioned welding operation, the welding notch groove 11 is used in claim 2, and therefore, in the embodiment shown in FIG. 5, the welding torch is used. A positioning pin 13 protruding parallel to the welding torch B is inserted into the water flow hole 10 from the base D of the welding machine C having a protruding B (tungsten electrode), whereby the welding torch B is The welding torch B is just inserted into the notch groove 11 for welding, and the tip of the welding torch B is guided to the portion of the adjusting bushing 7 to be welded without labor.

In the fifth step, as shown in FIG. 6, the set screw 8 is screwed into the mounting screw port 4a of the thimble tube 4 through the shaft hole 7a of the welded adjustment bushing 7 described above. At this time, the head 8b of the set screw 8 is pressed against the set screw tightening seat 6b, and the lower nozzle 2 causes the thimble tube 4 to move.
Therefore, even if the set screws 8 (four pieces) used for the temporary fixing are removed at this time, the temporary fixing state is maintained.

Therefore, in the sixth step, a separately prepared adjusting bushing 7 is screwed into the screw hole 6a of the mounting hole 6 of the set screw 8 removed in the fifth step from the lower side opening 6c, and The adjustment bushings 7 (four pieces) are positioned by bringing the upper surface of the adjustment bushings 7 into contact with the lower end surface of the thimble tube 4 in the same manner as before.

In the final seventh step, these adjusting bushings 7 are welded to the lower nozzle 2 in a rotation preventing state by welding work from the lower side in the same manner as before, and then the set screw 8 is attached.
From the lower side opening 6c of the mounting hole 6 through the shaft hole 7a of the welded adjustment bushing 7 to the thimble tube 4
The lower nozzle 2 and the total thimble tube 4 are completely attached by screwing into the attachment screw port 4a. Further, in the method of claim 2, even in the seventh step, the welding operation of the adjustment bushing 7 is performed by using the welding notch groove 11 as described above.

[0028]

Since the present invention can be carried out as described above, according to the method of claim 1, the adjustment bushing is welded from the lower side of the lower nozzle. The process of temporarily fixing the lower nozzle and removing it twice is eliminated, thus reducing the work effort and reducing the work time to about 1
/ 3.

Furthermore, without removing the lower nozzle,
Since the welding work for the adjusted adjustment bushing can be immediately performed with the temporary fixing state, the adjustment bushing does not open unintentionally after the adjustment and before welding, and as a result, the fuel with excellent straightness can be obtained. The aggregate can be easily provided, which contributes to the quality improvement of the product.

Further, in the case of claim 2, claim 1
In addition to the effect of the above, by providing the notch groove for welding in the seat for tightening the screw, the welding torch can be inserted vertically with respect to the lower nozzle, and the welding spot is narrow. In addition, the tip of the welding torch can easily and accurately enter the desired welding location, and highly reliable welding can be performed quickly.

[Brief description of drawings]

FIG. 1 is a partial vertical front view of a lower nozzle used for carrying out a mounting method according to claim 1 of the present application.

FIG. 2 is a partial bottom view of the upper and lower nozzles.

FIG. 3 is a partial vertical cross-sectional front view of a state in which an adjustment bushing is screwed into the lower nozzle of FIG.

FIG. 4 is a partial bottom view of the upper and lower nozzles.

5 is a partial vertical sectional front view showing a state where the adjustment bushing of the lower nozzle of FIG. 3 is welded. FIG.

FIG. 6 is a partial vertical sectional front view showing a state where the lower nozzle of FIG. 5 penetrates the adjustment bushing welded to the lower nozzle and is attached to the thimble tube by a set screw.

FIG. 7 is a bottom surface explanatory view of the lower nozzle shown for explaining a method of attaching the thimble tube and the lower nozzle in the conventional assembly operation of the nuclear fuel assembly.

FIG. 8 is a partial cutaway front view showing a temporarily fixed state of the lower nozzle and the thimble tube, which is for illustrating the attachment method.

FIG. 9 is a vertical cross-sectional front view showing an adjustment bushing for illustrating the attachment method.

FIG. 10 is a front view showing a set screw for illustrating the attachment method of the same.

FIG. 11 is a perspective view showing a welding state of the adjustment bushing with respect to the lower nozzle for showing the attachment method.

FIG. 12 is a front view showing a fuel assembly for illustrating the attachment method same as above.

[Explanation of symbols]

 2 Lower nozzle 2a Upper surface of lower nozzle 3 Support lattice 4 Thimble tube 4a Mounting screw hole 5 Fuel assembly 6 Mounting hole 6a Screw hole 6b Set screw tightening seat 6c Lower opening 7 Adjusting bushing 7a Shaft hole 8 Set screw 11 Welding gap Notch groove 11a Bottom of notch groove for welding 12 Welded portion A Surface plate B Welding torch

Claims (2)

(57) [Claims] 1. A required number of thimble tubes are mounted and fixed on a surface plate by a required number of support grids so as to be aligned with each other at predetermined intervals, and the upper end surface of each thimble tube is a surface. The first step of aligning the same, the lower side opening having the set screw tightening seat, and the mounting hole formed by a large number of screw holes coaxially communicating with the lower side opening are provided at appropriate times in the lower nozzle. Adjusting bushings with shaft holes penetratingly screwed into the desired number of mounting holes, and with the upper surface of the lower nozzle pointing toward the thimble tube, the required plurality of mountings without screwing the adjusting bushings. The lower nozzle is attached to the thimble tube by screwing a set screw, which is located in the hole and presses against the set screw tightening seat from the lower side opening, into a mounting screw port provided on the lower end face of the thimble tube. Second to temporarily stop
Steps, a third step of screwing the plurality of adjustment bushings from the lower side of the lower nozzle in this state so as to bring the upper surface into contact with the lower side end surface of the thimble tube, and the adjusted bushings that have been adjusted. From the lower side by welding to weld the lower nozzle to the lower nozzle in a rotation stop state, and the set screw from the lower side opening of the mounting hole through the shaft hole of the welded adjustment bushing to the thimble pipe. The lower nozzle is screwed to the thimble tube by being screwed to the mounting screw mouth of No. 5 and pressed against the set screw tightening seat, and the required plurality of set screws that have already been screwed are removed. Step, and the adjusting bushing is screwed into the screw hole of the mounting hole for the removed set screw from the lower side opening, and the upper surface of the adjusting bushing is brought into contact with the lower side end surface of the thimble tube. And the extent, these adjustments bushings,
After welding to the lower nozzle so as to prevent rotation by welding from the lower side, set screw is attached from the lower side opening of the mounting hole through the shaft hole of the welded adjustment bushing. A thimble tube in an assembly operation of a nuclear fuel assembly, comprising a seventh step of screwing the lower nozzle and the thimble tube by screwing the threaded mouth and pressing the set screw tightening seat. And how to attach the lower nozzle. 2. A required number of thimble tubes are mounted and fixed on a surface plate by a required number of support grids so as to be aligned with each other at predetermined intervals, and the upper end surface of each thimble tube is a surface. The first step of aligning with one, a plurality of mounting holes formed by a lower side opening having a set screw tightening seat, and a screw hole which is coaxially communicated therewith, are provided through the set screw tightening seat. In the lower nozzle in which the welding notch groove is formed by cutting off only a part in the radial direction, the adjustment bushing with the shaft hole penetratingly screwed into the screw holes in the desired number of mounting holes described above at appropriate times. , With the upper surface of the lower nozzle oriented toward the thimble tube, in a plurality of required mounting holes in which the adjustment bushing is not screwed, and a set screw that is pressed from the lower side opening to the set screw tightening seat, Provided on the lower end surface of the thimble tube The second step of temporarily fixing the lower nozzle to the thimble tube by screwing it into the mounting screw port, and in this state, the plurality of adjusting bushings are screwed from the lower side of the lower nozzle, and the upper surface of the adjusting bushing is screwed onto the thimble tube. By the third step of adjusting so as to make contact with the lower end face and the welding operation in which these adjusted bushings are inserted from the lower side into the welding notch from the lower side opening of the mounting hole. A fourth step of welding to the bottom of the welding notch groove on the outer peripheral side of the screw hole of the nozzle so as to prevent rotation, and the set screw from the lower opening of the mounting hole to the shaft of the welded adjustment bushing. The lower nozzle is screwed to the thimble tube by screwing it into the mounting screw mouth of the thimble tube through the hole and pressing it against the set screw tightening seat, and the required plurality of screws that have already been screwed are fixed. Remove the screws In the fifth step described above, the adjustment bushing is screwed into the screw hole of the mounting hole for the removed set screw from the lower side opening, and the upper surface of the adjustment bushing is brought into contact with the lower side end surface of the thimble tube. The sixth step of making the adjustment bushings and the welding work of inserting the welding torch into the lower nozzle from the lower side of the attachment hole into the notch for welding from the lower side so that the adjustment bushing is brought into the rotation stop state. After welding to the bottom of the welding notch groove on the outer peripheral side of the screw hole of the lower nozzle, attach the thimble tube from the lower opening of the attachment hole through the shaft hole of the welded adjustment bushing after welding the bottom of the welding notch groove. A thimble tube in an assembly operation of a nuclear fuel assembly, comprising a seventh step of screwing the lower nozzle and the thimble tube by screwing the threaded mouth and pressing the set screw tightening seat. And below Method of attaching the nozzle.