JPS61124891A - Spacer in fuel aggregate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a spacer used as a fuel assembly stopper for a boiling water nuclear reactor to reduce pressure loss of coolant.

(Prior Art) Generally, in a fuel assembly for a boiling water reactor, as shown in Fig. 98, a large number of fuel rods a, one or two quarter rods b arranged in the center, and a t8x8 square arrangement. The upper and lower end plug portions are connected to an upper tie plate t1 and a lower tie plate t.

The fuel rods A are inserted and supported through a honeycomb-shaped white plate, and normally seven spacers S2 are arranged in the middle to hold the fuel rods A at a predetermined distance from each other.
There is a channel box C2 outside this fuel bundle,
Coolant flows into the interior of the structure from the lower side through the lower tie plates t,' and rises therein.
The friend spacer S that holds between the many fuel rods axlWA is formed in a lattice shape with a plurality of vertical and horizontal dividers 1 and a plurality of vertical and horizontal dividers 2 as shown in No. 911)g. , the outer periphery is surrounded by a side plate 3, and each divider 1 is provided with the required number of narrow fixing protrusions 4 (S-shaped bends) IF for rigidly supporting the fuel rods,'! ! A rectangular cylindrical elastic body 5 (lantern spring) made of a nickel-based alloy plate spring is attached to each intersection of the vertical, horizontal and vertical pars 2 to elastically support the fuel rod.

(Problems to be Solved by the Invention) Conventional spacers for holding fuel rods are equipped with a large number of fixing protrusions 4 and cylindrical elastic bodies 5 as described above.
The projected area in the axial direction of the fuel rods is large, leading to a large pressure loss of the coolant, and the presence of the intersections of the vertical, horizontal and vertical dividers -1 and -2 causes agitation of the inflowing coolant, causing damage around the aggregate. Film boiling occurs on the surface of the fuel rods in areas where thermal-hydraulic output fluctuations are large, making it impossible to improve the minimum critical power ratio (MCPR), which is a measure of the thermal safety of the fuel assembly. Therefore, the present invention does not require the frame 11jla formed by the divider and par as described above, but instead
By combining these elements, the pressure loss of the coolant is small, and the membrane mt on the fuel rod surface can be suppressed.
The purpose is to improve the safety of fuel assemblies and to provide a spacer that can be reduced by pump power.

(Means for Solving the Problems) Based on the above object, the first K feature of the present invention is that a window hole of a required size is formed in the center of one side of the circumferential surface of a single circular tube cord. At the same time, there are multiple arcuate protrusions τ on the opposite side of the circumference.
The four circular cords t are provided at required intervals.
Each window hole τ is made to face and abut on the inside, and the four protrusions of one annular or frame-shaped elastic member are respectively fitted into each window hole to form a basic assembly. The fuel rods τ, which are arranged vertically and horizontally in groups and inserted into each circular element of the whole assembly, are held by one protrusion of the elastic member and a plurality of arcuate projections, and the second A window hole of a required size is formed in the center of one side of the circumferential surface of a single circular f Engagement holes of a matching size are provided at required intervals vertically and horizontally, and the four holding holes of the circular tube element are brought into contact with each other facing inwardly, and one window hole is provided in each window hole. The protrusions on the four sides of the annular or frame-shaped elastic member are respectively fitted to form a basic assembly, and the required sets of the basic assembly are arranged vertically and horizontally, and the arc shape of the cylindrical element of one assembly is The fuel is inserted into each circular tube element of the whole assembly by engaging the protrusion rmm with the engagement hole of the circular tube element of the joint body and engaging the arcuate protrusion of the adjacent assembly with the engagement hole of one of the assemblies. The bar is characterized by being held by one protrusion of the elastic member and a plurality of arcuate protrusions.

(Embodiment) Referring to the drawings, the embodiment will be described. In FIG. 1, ll is a single circular f element made of Zircaloy,
These four circular tube elements 11t are combined as described later to form a basic assembly 10, and this basic assembly 10it has 4 pieces in the vertical and horizontal directions.
Each pair is arranged in a square shape, and the outer periphery is made of the same material as side plates 1.
2, and is formed as a spacer consisting of 11 groups of 64 cylindrical elements in total.

Figure 1g2 shows one of the basic assembly 10, t5+, in which four circular tube elements 11 of unit τ are placed at the center of one side of each circumferential surface (the sides facing each other) with the required size. It is provided with a window hole 11ak, and on the opposite side of each circumferential surface, two upper and lower slits are formed on one circumferential surface, and this protrusion 11b fits into a ridge arc-shaped protrusion 11b that bulges outward. Seven engagement holes 11C are formed vertically at a required interval t and at an angular interval of 90 degrees left and right, but these protrusions 11b and engagement holes 11c are As seen in the developed view of Figure 4, one diagonal m of the basic assembly lO is located on one side (on the left side in the figure) of the diagonal IVII) A-A. The tube element and the two circular tube element halves are provided so that the arcuate protrusion 11b is on the top and the engagement hole 11c is on the bottom.

- 10,000, in one circular tube cord and two circular tube element halves located on the other side of the diagonal line A-A, the engagement hole 11C is on the top and the protrusion 11b
is placed so that it is at the bottom. And, group τnacho 4
The circular tube elements 11 have their window holes 11a cr;”in
Each window hole 11 alc is fitted with the four protruding corners of an elastic member 13 made of a thin plate material of nickel-plated metal ring, and the four cylindrical elements are assembled to face each other. 11 are combined, and the upper and lower portions of the abutting portions of each circular tube cable 11 are welded together to form a basic assembly 10, as shown in FIG.

In this way, four circular tube elements 11'7 and one elastic member 13
As a result, the required sets of basic assemblies 1O are arranged vertically and horizontally, and as shown in FIG. 11, and the protrusion 11b of the adjacent assembly is engaged with the engagement hole 11c of one assembly, so that all (16
The basic assemblies 10 of the set 1) are connected and assembled into a spacer as shown in Figure 1+.

Therefore, when each circular tube element 11t4c2 is inserted, the fuel rod is inserted into the elastic member 13 that protrudes into the circular tube element 11.
The circular tube is elastically supported from three sides by one protrusion and two arcuate protrusions 11c. A vertical slit 14 (Fig. 1) is provided in a part of the element 11, and the protrusion 15 on the water rod W is inserted into this vertical slit 14 from above, and the rod w2 is rotated with care to ensure that it does not pass through. , the protrusion 15 is engaged with the circular tube cord 11, and the water rod W is held in a predetermined position.

In addition, FIG. 6 shows a plurality of arcuate protrusions 11b'7 bulging inward on the circumferential surface on the opposite side of each window hole 11a of the four circular tube cords 11 constituting the basic assembly lOt. The inward protrusion 1 l b' and the elastic member 13
This shows a modified example in which the fuel rod is held by one of the protruding parts of the cylindrical element 11. The elastic member 13' of the ninth modified example is formed of a wire or a band into a planar frame shape having locking protrusions 13a''7 on all sides, and the elastic member 13' also has a cross vertical frame shape having locking protrusions 13a''' on all sides. The nine modified elastic members 13"τ shown in FIG. The window hole 11a provided in is in the shape of a slit.

Further, as an embodiment of the present invention, if at least one end of the cylindrical element is formed into a tapered or rounded shape, the pressure loss t can be further reduced.

Further, in the above example, Zircaloy τ is used as the material suitable for the circular tube element 11 and the side plate 12, and nickel-based alloy is used as the material suitable for the elastic member, but other materials may be used as long as they have the same effect.

(Effects of the Invention) As described above, in this invention, four circular tube cords are tied together by one elastic member to form a basic assembly, and the required sets of τ branches of this basic assembly are arranged side by side. However, since the fuel rod inserted into each circular tube element is held by one protrusion of the elastic member and a plurality of protrusions formed on the circular tube cord, there is no need to use many cumbersome lanterns like conventional spacers. There is no need to use springs or S-shaped fixing protrusions, the projected area in the axial direction of the fuel rod is reduced, the pressure loss of the coolant is reduced, and the pump power can be reduced. Since there are no lattice intersections, agitation of the coolant is prevented, and the space between the diagonal fuel rods is increased, making the fuel assembly thermally stable and improving the minimum power ratio. Furthermore, since the assembly of four circular tube cords is made into one unit, there are advantages such as the number of parts is small and the construction is simple and easy to manufacture. If the arcuate protrusions are engaged with the engagement holes of the cylindrical elements of the adjacent assemblies, and at the same time the arcuate protrusions of the cylindrical elements of the adjacent assemblies are engaged with the engagement holes of one of the assemblies, All the assemblies are connected to each other and become an integral part 9, so that the trouble of contacting the assemblies can be omitted.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the invention. FIG. 2 is an exploded perspective view of the basic assembly. Figure 3 shows one side of the basic assembly. Figure 4 is a developed view of the west side centered on the plane of the basic assembly. FIG. 5 is a side view showing how the circular tube elements of the assembly are connected to each other. FIG. 6 is a plan view of a modified example of the basic assembly. FIG. 7A is a perspective view of a modified example of the elastic member. FIG. 8 is a partially cutaway front view of the fuel assembly. FIG. 9 is a plan view of a conventional spacer. In the figure, lO... Basic assembly 11... Cylindrical element 11a... Window hole 11b, 1lb-... Arcuate projection 11C... Engagement hole 12...・Side plate 13...Elastic member

Claims (6)

[Claims] (1) A window hole of a required size is formed in the center of one side of the circumferential surface of a single circular tube element, and a plurality of arcuate protrusions are provided at required intervals on the opposite side of the circumferential surface, The four tube elements are brought into contact with each window hole facing inward, and the four protrusions of one annular or frame-shaped elastic member are respectively fitted into each window hole to form a basic assembly. None, the required set of the basic assembly is vertical,
1. A spacer for a fuel assembly, characterized in that fuel rods arranged horizontally and inserted through each circular tube element of the whole assembly are held by one protrusion of the elastic member and a plurality of arcuate protrusions. (2) A spacer in a fuel assembly according to claim 1, wherein the plurality of arcuate projections formed on the circumferential surface of the circular tube element are projections that bulge inward. (3) A window hole of the required size is formed in the center of one side of the circumferential surface of a single cylindrical element, while a plurality of outwardly bulging arcuate protrusions and the protrusions are formed on the opposite side of the circumferential surface. Engagement holes large enough to fit are provided at required intervals vertically and horizontally, and the four circular tube elements are brought into contact with each window hole facing inward,
The four protrusions of one annular or frame-shaped elastic member are respectively fitted into each window hole to form a basic assembly, and the required sets of the basic assembly are arranged vertically and horizontally in parallel, and one set is The arcuate protrusions of the circular tube elements of the body are engaged with the engagement holes of the circular tube elements of the adjacent assembly, and the arcuate protrusions of the adjacent assemblies are engaged with the engagement holes of one of the assemblies. A spacer for a fuel assembly, characterized in that a fuel rod inserted into each circular tube element is held by one protrusion of the elastic member and a plurality of arcuate protrusions. (4) A spacer in a fuel assembly according to claim 1 or 3, wherein the elastic member is formed of a thin plate material of a nickel-based alloy. (5) A spacer in a fuel assembly according to claim 1 or 3, wherein the elastic member is formed of a nickel-based alloy wire. (6) A spacer in a fuel assembly according to claim 1 or 3, wherein at least one end of the cylindrical element is formed into a tapered or rounded shape.