JP3535798B2 - Attachment structure of spring for fuel rod ammunition in fuel spacer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light water reactor fuel, and is used to maintain a state in which a required number of fuel rods are vertically spaced at a predetermined distance. Regarding the fuel spacer, a number of unit cells are defined by a frame plate composed of the outer frame plate and the inner frame plate, and fuel rods vertically inserted in these unit cells are elastically held at appropriate positions. The present invention relates to a structure for attaching a fuel rod holding spring to a frame plate, which is suitable for this purpose. 2. Description of the Related Art As a known fuel spacer for elastically holding a fuel rod F, there are two types of fuel spacers, a ring type fuel spacer 1 as shown in FIG. 2 and a lattice type fuel spacer 2 as shown in FIG. As shown in FIG. 2, the former ring-shaped fuel spacer 1 is provided on an outer frame plate 1a, and is internally fixed in a circumscribed state using a number of annular or polygonal rings 1b as inner frame plates. It was done. The representative ring-type fuel spacer 1 shown in FIG. 2 is the same as the one shown in FIG. 2B or, more specifically, as shown in FIG.
b, a pair of circumscribed plate portions 1c, 1c is sandwiched between them so that a symmetrical loop type spring 1d is provided. A plate-formed strip made of a Ni-based alloy having excellent strength and corrosion resistance is employed. When the loop type spring 1d is further described, the elastic piece portions 1e, 1e which are symmetrical to the outer circumscribing plate portions 1c, 1c joined as described above.
And a lantern-type bulging portion 1f connected to these lower ends, and the extending portions 1g and 1g at the upper end are fixed by welding portions 1h. Here, since the lanthanum-type bulging portion 1f is used in the furnace, since a two-layer flow of high-temperature water and steam collides from below, if it is simply formed on a plate, it will wear in its thick direction, and the spring There is a danger that the function as will be impaired, so that this is avoided. Incidentally, the lantern-type bulging portion 1f is formed integrally as a rectangular tube 1i as shown in FIGS. 3 and 4 (A), and similarly as shown in FIG. 4 (B). However, the stacking portion 1j formed so as to be involved is welded to the welding portion 1.
fixed by k, 1 m square cylinder as shown in FIG.
As shown in FIG. 4 (D), a stack of U-shaped bent pieces 1n and 1p fixed by welding portions 1q and 1r is used. In the case of such a ring-shaped fuel spacer 1, as shown in FIG. 2A, a fixing projection 1s for rigidly receiving a fuel rod F is provided at another place in the ring 1b. Therefore, the loop-type spring 1d is provided with the unit cell 1 mounted with phosphorus.
It suffices only to cause the symmetrical pieces 1e, 1e to bend with respect to t and 1t, respectively, and it is not necessary to provide the fixed projection 1s. On the other hand, in the lattice type fuel spacer 2 shown in FIG. 5, unlike the ring type fuel spacer 1 as is known, the above-mentioned bullet pieces 1e, 1e and the fixing protrusion 1 are provided.
The following hairpin-type springs having both members that fulfill the role of s must be used. [0005] That is, in the above grid type fuel spacer 2, as disclosed in FIG. 5 and FIG.
a, a vertical plate 2c and a horizontal plate 2d, which are grid plates 2b, are internally fixed in an intersecting manner with an inner frame plate to form a square unit cell 2e, and the grid plate 2b is divided into the unit cells 2e. An elastic spring 2f for elastically holding the inserted fuel rod F is attached. The spring 2f for elasticity has a hairpin-shaped outer shape as is known and is vertically mounted so as to sandwich one lattice plate 2b. The spring upper plate portion 2i and the spring lower plate portion 2j, which are respectively in contact with the lattice plate lower side surface 2h, have an elastic contact plate portion 2k that is bent toward one of the adjacent unit cells 2e1. In addition, a crawling plate portion 2p that is in contact with the side surface 2m opposite to the lattice plate and that is formed by bending a fixed projection 2n toward the adjacent unit cell 2e2 by a required number. Further, the lower end of the crawling plate portion 2p and the lower end of the elastic contact plate portion 2k are attached to the spring 2f for holding the same by simply turning the folded portion 2 as shown in FIG.
Instead of being connected continuously by q, a flat reinforcing cylindrical portion 2r having substantially the same configuration as the lanthanum-type bulging portion 1f of the ring-type fuel spacer 1 described above is provided. ) To avoid the risk of breakage due to wear by cooling water from the direction of arrow A in the case of the folded portion 2q. That is, as is clear from FIGS. 6 (A), 7 (C) and 7 (B), the flat reinforcing cylindrical portion 2r is connected to the lower end of the crawling plate 2p and the elastic contact plate 2k.
The elastic contact side horizontal plate portion 2s and the crawling side horizontal plate portion 2t, each of which is arranged in a wide width from the lower end portion thereof, are connected to the elastic contact side horizontal plate portion 2s and the crawling side horizontal plate portion 2t. The rectangular passage 2w is opened by a pair of the vertical plates 2u and 2v provided. The elastic spring 2f constructed as described above can be understood with reference to FIG.
The flat reinforcing cylindrical portion 2r is engaged with the lower notch groove 2x provided at the lower end edge of the lattice plate 2b, and the lattice plate 2
In the state in which the upper end of the elastic contact plate 2k and the upper end of the crawler plate 2p are engaged with the upper notch groove 2y provided on the upper end of the ring-shaped fuel spacer 1, It is attached to the lattice plate 2b by being fixed by welding means or the like in the same manner as the mold spring 1d. Accordingly, the above-mentioned elastic spring 2f is
As a result, the two-phase flow of high-temperature water and steam flows from below into each of the asymmetric plates during use in the furnace. By doing so, the elastic contact plate portion 2k is deformed by being pressed by the fuel rod F as illustrated in FIG. 8, so that the flat reinforcing cylindrical portion 2r, which is the lower end side of the spring 2f, is connected to the unit cell. 2e2, it not only has a risk of fretting between its lower end and the fuel rods F, but also causes a decrease in the cross-sectional area of the flow path of the cooling water. The disadvantage is that the pressure loss increases. From the above considerations, the above-mentioned difficulties are likely to occur in the case of the spring 2f for holding the grid-type fuel spacer 2, and as shown in FIG. It was also confirmed that no defect was generated in the case where the device was not provided with 2r but had only the folded portion 2q as shown in FIG. 6 (B). Further, the ring-shaped fuel spacer 1 does not use the symmetrical loop-type spring 1d as described above,
It was also confirmed that the same problem as that of the grid type fuel spacer 2 occurs when the f-type is used and the lower portion is formed in a lanthanum type as described above. SUMMARY OF THE INVENTION The present invention relates to a fuel rod having a ring-shaped or lattice-shaped fuel spacer as described above, and a fuel rod having a lanthanum-shaped reinforced square cylindrical portion at the lower end thereof. Regarding the retaining spring, when the retaining spring is attached to the frame plate composed of the spacer outer frame plate and the inner frame plate in the fuel spacer, the flat reinforcing cylindrical portion is simply engaged with the locking lower notch groove as in the conventional example. Rather, the rectangular through hole of the angular reinforcing cylindrical portion is engaged with a locking projection formed by drilling a pair of vertical slits at the lower edge of the frame plate. The fuel rod holding spring is attached to the frame plate, which causes the angular reinforcing cylindrical portion to be unintentionally bent by the flow of cooling water, and as a result, the angular reinforcing cylindrical shape with respect to the fuel rod. Undesired fretting of the part may occur, and It is an object of the present invention to solve the problem that the output as fuel of a light water reactor decreases due to an increase in pressure loss. According to the present invention, in order to achieve the above object, a large number of spacer unit cells are defined by a frame plate composed of a spacer outer frame plate and an inner frame plate. In the fuel spacer, a fuel rod holding spring elastically in contact with the fuel rod fitted and inserted into the spacer unit cell is sandwiched and attached, and the fuel rod holding spring is provided on one side of the spacer plate on one side of the spacer unit cell. And the other side plate portion asymmetrically disposed on the framed unit cell side of the frame plate and the lower end portions of the one side plate portion and the other side plate portion. One side horizontal plate part and the other side horizontal plate part extended side by side
The fuel cell includes a reinforced square cylindrical portion having a horn-shaped opening formed by a pair of vertical plates formed by connecting the one side horizontal plate portion and the other side horizontal plate portion. The rod holding spring engages the square through hole of the square reinforcing cylindrical portion with a pair of vertical slits formed at the lower edge of the frame plate and the remaining locking projection, and Each of the vertical plate portions is engaged with the pair of vertical slits, and the upper end portions of the one side plate portion and the other side plate portion are engaged with the cutout grooves formed on the upper edge of the frame plate. An object of the present invention is to provide an attachment structure for a fuel rod elastic holding spring in a fuel spacer, which is fixed in a state where it is fixed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to FIG. 1A. Referring to FIG. 1A, a spacer outer frame plate 3a corresponding to the previously described outer frame plates 1a and 2a and a ring as described above are described. A large number of spacer unit cells 3c are defined by a frame plate 3A composed of an inner frame plate 3b corresponding to the grid plate 1b and the lattice plate 2b. The fuel spacer 3 is formed by sandwiching and attaching the fuel rod retaining spring 3B in contact therewith. The above-mentioned spring 3B for holding fuel rods includes a side plate portion 3d provided on one spacer unit cell 3c1 side of the frame plate 3A and a spacer unit cell 3c2 adjacent to the frame plate 3A.
And the other side plate portion 3e disposed asymmetrically with the one side plate portion 3d and the lower end portions of the one side plate portion 3d and the other side plate portion 3e. The one side horizontal plate portion 3f and the other side horizontal plate portion 3g, and a pair of vertical plate portions 3h and 3i in which the one side horizontal plate portion 3f and the other side horizontal plate portion 3g are connected to each other, are rectangular. Reinforced cylindrical portion 3 having a square opening 3j having a square or other shape.
k, and the square reinforcing cylindrical portion 3k has substantially the same configuration as the above-described conventional flat reinforcing cylindrical portion 2r. The present invention has a feature in a structure for attaching the above-described square reinforcing cylindrical portion 3k to the frame plate 3A of the fuel spacer 3 and has a feature at the lower end edge 3m of the frame plate. Is a pair of vertical slits 3n as disclosed in FIG.
3n is separated and cut out, so that the locking projection 3p is formed.
Is left behind. And the above-mentioned square reinforcing cylindrical part 3k
The vertical plate portions 3h and 3i can be fitted into the pair of vertical slits 3n and 3n by engaging the rectangular through holes 3j with the locking projections 3p. Therefore, even if the angularly reinforced cylindrical portion 3k is subjected to an external force such as to be inclined toward the fuel rod F side as described above, its movement is blocked by the locking projection 3p. The occurrence of the undesired bending is prevented. A notch groove 3r is cut in the upper end edge 3q of the frame plate in the same manner as in the conventional example, and the upper end portion 3s of the one side plate portion 3d and the other side plate portion 3e of the fuel rod elastic spring 3B are formed. The upper end 3t is engaged, and in this state, it is fixed as shown in FIG. 1D by means such as welding. According to the present invention, as described above, an asymmetric fuel rod holding spring is used for the fuel spacer, and a reinforced square cylindrical portion is provided below the spring. In the case where the fuel rod is provided, the spring for holding the fuel rod is mounted so as to be engaged with the locking projection formed on the lower edge of the frame plate of the fuel spacer. Even when receiving the flow of cooling water from below, it is possible to reliably prevent the locking protruding portion from being tilted, and as a result, the tilted locking protruding portion prevents the fuel rod from being tilted. Fretting can be reliably prevented, and an undesired increase in pressure loss of the cooling water due to the tilt can be prevented, so that it greatly contributes to improvement in output as a nuclear fuel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (A) is a schematic plan view showing a part of a fuel spacer according to the present invention, FIG. 1 (B) is a partial front view showing a frame plate thereof, and FIG. FIG. 3D is a partial bottom view in which the inner frame plate of the fuel rod holding spring mounted on the frame plate is cut away, and FIG. 4D is a vertical sectional side view of the fuel rod holding spring. FIG. 2A is a plan view showing a conventional ring-shaped fuel spacer, and FIG. 2B is a front view of the ring-shaped fuel spacer with a part cut away. FIG. 3 (A) is a vertical sectional side view showing a loop type spring in the ring type fuel spacer, and FIG. 3 (B) is a side view thereof. 4A is a bottom view of the ring-shaped fuel spacer shown in FIG. 3, and FIGS. 4B, 4C, and 4D are bottom views showing another embodiment. FIG. 5 is a plan view showing a conventional grid fuel spacer. FIG. 6A is a vertical sectional side view showing an example of the same grid type fuel spacer, and FIG. 6B is a vertical sectional side view showing another example. FIG. 7A is a partial front view showing a conventional lattice plate of the same as the above, and FIG. 7B is a partial bottom view showing the lattice plate of a spring for elasticity mounted on the lattice plate, cut away. . FIG. 8 is a vertical sectional side view showing a case where the flat reinforcing cylindrical portion of the above-mentioned bullet holding spring is in an inclined state. [Description of Signs] 3 Fuel spacer 3A Frame plate 3B Fuel rod holding spring 3a Spacer outer frame plate 3b Inner frame plate 3c Spacer unit cell 3c1 One spacer unit cell 3c2 Adjacent spacer unit cell 3d One side plate 3e Other side plate 3f One side horizontal plate part 3g The other side horizontal plate part 3h The vertical plate part 3i The vertical plate part 3j The square-shaped opening 3k The square reinforcing cylindrical part 3m The frame plate bottom edge 3n The vertical slit 3p The locking protrusion 3q Frame plate edge 3r Notch groove 3s Upper end 3t of one side plate Upper end F of the other side plate Fuel rod

Claims (1)

(57) [Claims 1] A large number of spacer unit cells are defined by a frame plate composed of a spacer outer frame plate and an inner frame plate, and the frame plate is fitted with the spacer unit cells. A fuel rod holding spring, which is elastically in contact with the inserted fuel rod, is sandwiched and attached to the fuel spacer, and the fuel rod holding spring includes a side plate portion disposed on one spacer unit cell side of the frame plate. The other side plate portion asymmetrically disposed on the side of the frame unit with the phosphorus unit cell side, and one side which is extended in parallel with each other from the lower ends of the one side plate portion and the other side plate portion, respectively. A horn-shaped reinforced cylinder having a horn-shaped opening formed by a horizontal plate and another horizontal plate, and a pair of vertical plates in which the one horizontal plate and the other horizontal plate are connected to each other. The fuel rod holding spring is provided with a square opening of the above-mentioned square reinforcing cylindrical portion, which is provided below the frame plate. A pair of vertical slits are formed on the edge and are engaged with the remaining locking projections, and each of the vertical plate portions is engaged with the pair of vertical slits, respectively. Attachment of a fuel rod elastic holding spring in a fuel spacer, wherein one side plate portion and an upper end portion of the other side plate portion are fixedly engaged with a notch groove formed in an upper end edge of the frame plate. Construction.