JP2616887B2 - Apparatus for determining the mounting condition of the channel box of a nuclear fuel assembly - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for judging whether a channel box is mounted on a nuclear fuel assembly.

[0002]

2. Description of the Related Art In a nuclear power plant, a fuel assembly irradiated with radiation (hereinafter, also referred to as an "irradiated fuel body") is pulled out of a reactor core and periodically inspected for appearance. For example, in the case of a boiling water reactor, when conducting such a periodic visual inspection, the Zircaloy channel box was removed from the fuel assembly, and after the inspection, the channel box was reinstalled and fixed securely to the fuel assembly main body with fastener bolts. To the core. If the channel box is not installed properly, the water flow circulating upwards at high speed during reactor operation may cause rattling or floating, which may cause serious problems in safe operation. The worst case of the fastener bolt falling out may occur.

Conventionally, whether or not the channel box is correctly mounted is determined by visually checking the underwater fuel assembly located 3 to 4 meters below. The visual determination method is shown in FIG. A) Typical representative fuel assembly 1 shown in A) (referred to as "step I-type fuel assembly")
A description will be given in relation to the upper structure of the first embodiment. Generally, fuel assembly 1
Has a generally rectangular channel box 2 surrounding its body, and a corner post 4 is provided at each of the four corners of a generally rectangular upper tie plate 3 located in the channel box. A pair of opposite corner posts are covered by a generally triangular clip plate or bracket 5a, 5b secured to the corresponding corner of the top opening edge 9 of the channel box, and one of the clip plates ( For example, 5b) is provided with through holes 6 for fastening bolts for mutually fixing the channel box and the corner post. The fuel body is provided with a bail or a fuel handle 7.
Comprises a lateral handle portion 8a, generally located above the level of the opening edge of the channel box, and a clip plate 5a,
A pair of legs 8b fixed to the upper tie plate 3 adjacent to the corner posts 4 not covered by 5b. In some cases, the leg portion 8b is provided with a lateral projection 8c indicating the mounting position direction of the fastener bolt.
In the conventional visual judgment method, a judge usually pays attention to the relative height position of the top of the exposed corner post with respect to the opening edge of the channel box, and judges the mounting state of the channel box according to a known standard in a normal mounting state. Was.

[0004]

In recent years, a new type of fuel assembly (referred to as "step II type fuel assembly") shown in FIG. 5 (B) has been developed, while replacing the conventional step I type fuel assembly. is there. In such a new fuel assembly, the corner post is formed integrally with the leg 8b of the fuel handle,
It has become difficult to use the conventional corner post visual determination method. On the other hand, there is a drawback that the determination of the state of mounting the channel box visually from a remote place is uncertain and low in reliability.

An object of the present invention is to provide an apparatus which can reliably and efficiently determine the mounting condition of a channel box for both a step I type fuel body and a step II type fuel body.

[0006]

SUMMARY OF THE INVENTION In view of the above objects, an apparatus for determining the mounting of a rectangular channel box on a nuclear fuel body having an upper tie plate with a fuel handle comprises an elongated tubular housing member, A meter assembly operatively associated with the meter and including an elongated measuring rod movably axially telescopic within the housing member; and a lateral positioning base plate secured to the tubular housing member. the base plate is provided with a slot-like opening for receiving a fuel handle insertion freely, base plate, the water <br/> flat opening top edge of the rectangular channel box in a state that receives fuel handle into the slot-like opening those It has a lower surface in contact with it. When the slot-shaped opening of the base plate receives the fuel handle, the axis of the measuring rod is shifted laterally from the fuel handle, and the lower surface of the base plate is in contact with the top edge of the opening of the channel box. When the measuring rod is extended at, the measuring rod abuts any portion on the horizontal top surface of the upper tie plate without hitting the fuel handle. Thus, by comparing the measured value of the separation distance between the opening top edge of the rectangular channel box and the top surface of the upper tie plate of the nuclear fuel assembly with a known standard value, it is possible to determine the degree of attachment of the channel box.

Preferably, on the lower surface of the base plate,
At least a pair of depending lower guides are fixedly secured adjacent to the slot-shaped openings, each of the lower guides being inclined toward the opening of the base plate so as to allow the base plate to approach the nuclear fuel assembly in the vertical direction. A guide bottom edge engageable with the horizontal handle portion of the fuel handle so that the slot-like opening receives the fuel handle.

Further, the lower end of the tubular housing is preferably located between the pair of lower guides of the base plate, and the bottom end of the tubular housing ends above the inclined guide bottom edge of the lower guide. In this way, there is no danger of the measuring rod being damaged by the fuel handle hitting the lower end of the tubular housing.

In addition to the first pair of lower guides described above, a second
A pair of lower guides may be provided, each of which is also inclined toward the opening of the base plate, and is provided on the horizontal handle of the fuel handle when the base plate approaches the nuclear fuel assembly vertically. It has a guiding bottom edge that can be engaged so that the slot-like opening receives the fuel handle. The first and second lower guide pairs cooperate to form guide chutes located on opposite sides of the slot-like opening in the base plate to further facilitate the introduction of the fuel handle into the slot-like opening in the base plate.

[0010] Further, the base plate is provided adjacent to the slot-shaped opening of the base plate and is spaced apart from the upper surface thereof.
A pair of fuel handles extend axially through the slot-like openings while the base plate is translated downwardly in a substantially horizontal position so that the lower surface of the base plate can properly abut the opening top edge of the channel box. Advantageously, a guide alignment means is provided, said pair of guide alignment means including a pair of lateral L-shaped guides supported on the base plate in opposition adjacent both ends of the slot-shaped opening. When the base plate is tilted beyond a predetermined tolerance level with respect to the opening top edge of the channel box, the legs of the fuel handle will strike one or both of the right-angled arm portions of each L-shaped guide.

Preferably, adjacent to the L-shaped guide, there is provided a pair of notches extending laterally in opposite directions from opposite ends of the slot-shaped opening, the notches being provided on the legs of the fuel handle. And has a shape complementary to the lateral projection indicating the mounting position direction of the fastener bolt.

[0012]

FIG. 1 is a perspective view of a measuring instrument assembly 10 (only the lower end is shown) and is attached to the measuring instrument assembly 10 and a part of the lower surface has an opening top edge at a diagonally opposite corner of the channel box 1. The judging device of the present invention, comprising a lateral positioning base plate 12 adapted to abut against the fuel 9, is shown in close proximity to the nuclear fuel assembly 1.
Referring to FIG. 2, the meter assembly 10, shown generally with the base plate 12 removed, includes an elongated tubular housing member 14, the length of the housing member 14 being adapted to accommodate a remotely located underwater irradiated fuel body. It should be long enough to reach, for example 4-6 m. In the case of a channel box mounting inspection of new fuel before irradiation, a shorter housing member may be used. At the top of the tubular housing member is mounted a suitable type of meter, for example a conventional dial gauge 16. The upper part of the housing member is provided with a handle grip 18 for facilitating the handling of the device according to the invention, and the measuring rod is manually operated through a slot 19 of a predetermined length in the length of the cylindrical wall of the housing member. The push-down lever 20 extends outward so that the operator's finger can be hooked.

With continued reference to FIG. 2, the internal structure of the meter assembly 10 is schematically illustrated in the non-depressed position of the measuring rod lever 20, with the measuring rod 22 being axially within the tubular housing member 14. It is provided to be able to move in the direction. The measuring rod 22 is always held upward between a spring receiving collar 24 fixed at an appropriate position in the length direction of the movable rod 22 and a fixed spring receiver 26 attached to an appropriate position on the inner peripheral portion of the housing member. A spring 28 for urging is provided. The fixed spring receiver 26 also serves as a guide for the measuring rod 22. The upper end of the measuring rod is pinned to a piston member 32, which is also fixedly attached to the push-down lever 20,
When the lever 20 is manually pushed down along the slot 19, the rod 22 moves downward so that its tip projects from the bottom end of the housing member.

The stem of the dial gauge 16 is inserted into the top opening end of the housing member 14, and is fixed to the housing member 14 with a set screw 30. The measuring element 34 of the dial gauge is arranged in a retracted state in which it comes into contact with the piston 32 and receives a spring urging force via the measuring rod 22 and the piston 32. Thus, lever 20
When the measuring rod 22 is driven downward by pressing down, the measuring element of the dial gauge also extends downward in contact with the piston 32.

Referring again to FIG. 1, the base plate 12, which is bolted to the lower end flange (not shown) of the housing member 14 of the meter assembly, allows the fuel handle 7 to be inserted through its length. Slot-shaped opening 36
have. Preferably, a pair of notches 38 extend in opposite directions laterally from both ends of the slot-shaped opening 36, corresponding to the projections 8c of the legs 8b of the fuel handle 7. The notch preferably has a complementary shape to the projection 8c.

Referring to FIGS. 1, 3 and 4, the base plate 12 has a pair of hanging lower guides 4 on its lower surface.
0 is provided. The lower end of the tubular housing 14 passing through the base plate is located between these lower guides 40. The lower guide 40 has a slot-shaped opening 36.
Preferably, it is oriented laterally adjacent to Each lower guide has a bottom edge 42 that slopes toward a slot-like opening 36 in the base plate. This bottom edge 42 allows the horizontal handle portion 8a of the fuel handle to move the base plate closer to the top edge of the opening of the channel box, even if the slot-like opening 36 and the fuel handle 7 are not aligned. , So that the slot-shaped opening receives the fuel handle. It should be noted that, as best seen in FIG. 3, the bottom end of the tubular housing 14 containing the measuring rod 22 ends above the inclined guide bottom end 42 of the lower guide. In this way, there is no danger of the measuring rod being damaged by the fuel handle hitting the lower end of the tubular housing. Preferably, another lower guide pair 44 is provided on the lower surface of the base plate, adjacent to the slot-like opening 36 and opposite the lower guide 40. Similarly to the lower guide 40, the lower guide 44 also has the slot-shaped opening 3.
The bottom guide 40 has a bottom edge inclined toward 6, but is smaller in size and shape than the lower guide 40 for weight reduction. The bottom edges of the lower pair of guides 40, 44 cooperate to form a guide chute 46 which facilitates the introduction of the fuel handle 7 into the slot-like opening 36 in the base plate.
It will be appreciated that the guide chutes, as viewed in FIG. 3, can easily achieve their alignment even when the longitudinal axis of the fuel handle legs are offset from side to side with respect to the slot-like opening 36.

The slot-shaped opening 3 of the base plate 12
A pair of guide alignment means 48 is provided on the upper surface adjacent to the opposite ends of 6. The purpose of the pair of guide alignment means 48 is to maintain the alignment and to maintain the vertical alignment when the fuel handle 7 passes through the slot-shaped opening 36 when the base plate 12 moves downward in a substantially horizontal state (FIG. 1). The horizontal orientation of the base plate with respect to the leg 8b is maintained, in other words, the longitudinal axis of the leg and the axis of the measuring rod 22 are kept parallel to each other so that the lower surface of the base plate is correctly seated on the top edge of the opening of the channel box. To make it happen. Each guide alignment means 48 includes a lateral L-shaped guide 52 supported by a support member 50 secured to the base plate. Each L-shaped guide 52 comprises arm portions 52a, 52b that are at right angles to each other. Guide arm portions 52a, 52 at both ends of the slot-shaped opening 36.
b are parallel to each other. As best seen in FIG. 4, the lateral separation of the arm portions 52a is slightly greater than the width dimension of the fuel handle, and the arm portion 52b is slightly greater than the distance between the legs of the fuel handle. Is good. Therefore, when the base plate 12 is tilted beyond a predetermined allowable level with respect to the horizontal opening top edge 9 of the channel box 1, the fuel handle legs 8 b move the arm portions 52 a, 5 of the upper L-shaped guide 52.
2b, so that a guided alignment of the base plate with respect to the channel box is achieved.

Note that the zero point of the dial gauge 16 of the measuring instrument assembly 10 is determined by referring to the top opening edge 9 of the channel box as a reference level and the top surface of the upper tie plate 3 of the fuel body when the channel box is correctly mounted. Measurement point 4
Preferably, it is adjusted to the height position of 5. The operation of adjusting the zero point of the dial gauge 16 is obvious to those skilled in the art, and thus the description thereof is omitted. Thus, at the time of measurement, the pointer of the dial gauge 16 indicates the deviation from the standard separation distance L (see FIG. 3) in the vertical direction between the reference level, the top edge 9 of the opening and the top surface of the upper tie plate, and indicates the zero point. , That is, when there is no deviation or within the allowable range, it can be understood that the channel box is correctly mounted.

The method of using the judgment apparatus of the present invention will be described. In a state where the tubular housing member 14 is supported by both hands,
It is lowered toward the irradiated fuel body located in the water. While the lower guide of the base plate 12 is applied to the horizontal handle portion 8 a of the fuel handle 7, the base plate is guided so that the slot-shaped opening 36 receives the handle 7. Subsequently, the base plate is gradually lowered so that the notch 38 passes through the lateral projection 8c of the handle leg 8b. If the base plate is tilted about its longitudinal axis, the leg 8a of the fuel handle 7 will hit one of the arm portions 52a of the upper L-shaped guide 52 and if the base plate is aligned with its longitudinal axis. If tilted about a vertical axis, the legs 8a of the fuel handle 7 will hit one of the arm portions 52b of the upper L-shaped guide 52, thus the base plate relative to the top horizontal opening of the channel box. The horizontal alignment state is maintained.

When the base plate 12 is further lowered,
The lower surface contacts the top edge 9 of the horizontal opening of the channel box 1 (see FIGS. 3 and 4). Then, the measuring instrument assembly 1
The measurement rod 22 in the housing member 14 of FIG.
Will be located just above the top surface of. In this state, the measuring rod push-down lever 20 is pushed down so that the lower end of the measuring rod comes into contact with an arbitrary point on the top surface of the upper tie plate, for example, a point 45 (see FIG. 3). The reading of the dial gauge 16 at this time is obtained. If the reading deviates from the standard separation distance within a predetermined allowable range, it indicates that the channel box is correctly mounted on the nuclear fuel body. After confirming the proper mounting condition of the channel box, the fastener is passed through the through hole 6 of the clip plate 5b and screwed into the screw hole of the corner post, and the channel box is fixed to the fuel body and returned to the core.

[0021]

Since the present invention is configured as described above, it has the following effects.

Measuring the distance between the opening top edge of the channel box and a predetermined location of the bail of the fuel body by using a measuring instrument assembly including a dial gauge, and comparing the dial gauge reading with a reference value; Thus, the degree of attachment of the channel box is determined, so that the reliability is higher than that of the conventional visual method, and it can be used for both new and old step I-type fuel bodies and step II-type fuel bodies. In the present invention, the top edge of the opening of the channel box is employed as the reference level for measurement, but another portion of the channel box may be employed.
However, the top edge of the opening with the least product error is optimal.

[0023]

[Brief description of the drawings]

FIG. 1 is a perspective view of a determination device of the present invention, showing a state in which the determination device is brought close to a fuel assembly.

FIG. 2 is a vertical sectional view showing a measuring instrument assembly constituting the determination device of the present invention in a non-pressed position.

FIG. 3 is a partially omitted schematic view showing a use state of the apparatus of the present invention, and shows a state in which a lower end of a measurement rod is in contact with a point to be measured on a top surface of an upper tie plate. FIG. 3 is a view taken along line III-III of FIG.

FIG. 4 is a plan view taken along line IV-IV in FIG. 3, showing a state in which a base plate is correctly in contact with a top opening edge of a channel box.

FIG. 5A is a perspective view of the upper structure of a step I fuel body, and FIG. 5B is a perspective view of the upper structure of a step II fuel body in which an upright leg and a corner post of a fuel handle are integrally joined. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nuclear fuel body 2 Channel box 3 Upper tie plate 4 Corner post 5a, 5b Clip plate 7 Fuel handle 8a Horizontal handle 8b Upright leg 9 Opening top edge 10 Measuring instrument assembly 12 Base plate 14 Tubular housing member 16 Dial gauge 22 Measuring rod 34 Measuring element of dial gauge 36 Slot-shaped opening 40, 44 Lower guide 45 Measured point 48 Guide alignment means 52 Upper L-shaped guide

Claims (10)

(57) [Claims] 1. An apparatus for determining the mounting of a rectangular channel box on a nuclear fuel body having an upper tie plate with a fuel handle, the apparatus being operatively associated with an elongated tubular housing member and a meter. A meter assembly including an elongated measuring rod capable of axially telescoping movement within the housing member and a lateral positioning base plate secured to the tubular housing member, the base plate receivably receiving a fuel handle. slot-like opening is provided, the base plate is in the open mouth top edge of the rectangular channel box in a state that receives fuel handle into the slot-like opening provided with a lower surface in contact, the horizontal opening the top edge of the lower surface of the base plate channel box When the measurement rod is extended while being in contact with the part, the measurement rod The axis is offset laterally from the fuel handle so that it touches any part of the upper tie plate horizontal top surface without hitting the A determination device, characterized in that a measured value of a separation distance from a top surface is compared with a known standard value so as to determine a mounting state of a channel box. At least one pair of lower guides hanging down adjacent to the slot-shaped openings are fixed to a lower surface of the base plate, and each of the lower guides is inclined toward the opening of the base plate, and is provided with a nuclear fuel. When the base plate is vertically approached to the assembly, the horizontal handle portion of the fuel handle can be engaged so that the slot-like opening has a guide bottom edge for receiving the fuel handle. The determination device according to claim 1. 3. A lower end of the tubular housing is located between a pair of lower guides of a base plate, and a bottom end of the lower end terminates above the inclined guide bottom edge of the lower guide. Item 2. The determination device according to item 2. 4. A second pair of lower guides is provided, each lower guide also being inclined toward the opening of the base plate, and upon vertical approach of the base plate to the nuclear fuel assembly, The first and second lower guide pairs each include a guide bottom edge engageable with a horizontal handle portion of the fuel handle such that the slot-shaped opening receives the fuel handle. 3. The determination device according to claim 2, wherein the determination device is arranged on both sides of the base plate and cooperates to form a guide chute which facilitates introduction of the fuel handle into the slot-shaped opening of the base plate. 5. A fuel handle axially extends through the slot-like opening while the base plate is translated substantially downward in a substantially horizontal state, adjacent to the slot-like opening of the base plate. A pair of guide alignment means is provided to enable the lower surface of the base plate to correctly contact the opening top edge of the channel box. Judgment device. 6. A pair of guide alignment means including a pair of lateral L-shaped guides supported on a base plate in opposition adjacent both ends of the slot-like opening, wherein the base plate is a top edge of the opening of the channel box. tilts beyond a predetermined acceptable level with respect to parts, determine a constant according to claim 5, characterized in that the legs of the fuel handle is adapted to impinge on one or both of the arm portions at right angles to one another of each L-shaped guide apparatus. 7. A pair of notches are provided adjacent to the L-shaped guide and extending laterally in opposite directions from opposite ends of the slot-shaped opening, the notches being provided in the legs of the fuel handle. 2. The determination device according to claim 1, wherein the determination device is provided and has a shape complementary to a lateral projection indicating a mounting position direction of the fastener bolt. 8. A measuring device is a dial gauge, determination of claim 1, characterized in that it is configured as feeler of the dial gauge to follow the movement of the measuring rod in constant contact state to the measurement rod apparatus. 9. The judging device according to claim 1, wherein the dial gauge is zero-adjusted so as to display the standard value when the pointer is at the zero point position. 10. The measuring rod and the measuring element of the dial gauge are constantly urged upward by a spring provided in the tubular housing member, and manually move the measuring rod downward against the urging force of the spring. 9. The determination device according to claim 8, wherein when pressed down, the tracing stylus of the dial gauge also extends downward.