JPS58189582A - Nuclear fuel assembly - 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 The present invention relates to a nuclear fuel assembly used in a nuclear reactor, and in particular,
The present invention relates to nuclear fuel assemblies suitable for use in boiling water reactors.

The technology for generating large amounts of thermal energy by nuclear fission in nuclear reactors has been around for a long time and is now well known. This energy is dissipated as heat within the elongated nuclear fuel rods. A plurality of fuel rods are divided into groups to form separately removed fuel assemblies. A large number of such fuel bundles are arranged in a matrix of rows and columns to form a nuclear reactor core that itself sustains the splitting reaction. The core is typically encased in a fluid, such as light water, that acts as a coolant to extract heat from the nuclear fuel rods and as a neutron moderator.

A typical fuel assembly consists of seven rows of elongated, slightly spaced rods supported between upper and lower tie plates.
They are arranged in seven columns or l rows and Xl columns. Examples of such types of fuel assemblies are shown in U.S. Pat. 7, J! r O
, Ko 7S, O J, 4IA 4, 116 and O a, t.
Oko, Tetsu J issue #4 is described in the detailed description.

In the fuel assembly of a typical boiling water m-feng reactor, 64 (one rod is 4II) forming a matrix of l rows and Xl columns.
Either all the rods are fuel rods, or seven or more are non-fuel water moderator rods and the remainder are fuel rods. A common problem in the typical deaf-type boiling water reactor fuel assemblies mentioned above in the U.S. permit list is that the central region of the nuclear fuel assembly has a low deceleration rate, which may improve the sound quality. It's something we don't know.

To increase the moderator flow rate, the fuel rods in the central region of such fuel assemblies have been replaced with seven or more elongated water moderator rods. If you ask me, the above US patent OJ, gOλβ
As stated in the VS Specification, water moderator rod &/
and Vλ are used. However, the use of seven or more water moderator rods precludes the use of a total of six fuel rods, ie, seven fuel rods for each grid position in the fuel assembly. Therefore, a higher linear heat release rate may be required when using one or more water moderator loincloths between one or more fuel rods in a fuel assembly. do not have.

In the typical boiling water reactor fuel assembly described above, an outer channel was formed of a zirconium alloy known as Zircaloy. The outer flow channel is structurally unsupported in a direction transverse to its longitudinal axis &C-perpendicular cross-section. Under various reactor operating conditions, this outer flow channel is slightly deformed due to creep. Therefore, attempts are currently being made to extend the life of the outer flow channel by using thicker outer flow channels to resist creep deformation. but,
Increasing the wall thickness increases parasitic absorption in the core, resulting in increased fuel cycle costs.

Many fuel assemblies currently used in boiling water reactors have lift handles bolted to the upper tie plate for handling and moving the fuel assembly in a vertical position. Accordingly, the weight of each fuel assembly, including the weight of its outer stream, is transferred from the lift handle via a plurality of fuel rods, commonly referred to as connecting rods.

The tie rod includes special end plug fittings that pass through the upper and lower tie plates of the fuel assembly and engage lock nuts. Such connecting rods are subjected to stresses during handling operations, which may cause failure of the fuel rods.

It is therefore a principal object of the present invention to provide a fuel assembly suitable for use in a boiling wood reactor, through which a liquid moderator flows separately from the coolant.

To this end, the present invention provides a nuclear fuel assembly having a cladding surrounding a plurality of fuel rods that together define an outer flow channel, in which a cruciform wall structure consisting of spaced apart chevron plates is provided within the cladding. are arranged to divide the nuclear fuel assembly into a plurality of separate fuel zones and create a moderator flow path for cool neutron moderator through the gaps between the chevron plates. This is a characteristic feature.

The invention will become more readily apparent from the following description of preferred embodiments thereof, shown by way of example only in the accompanying drawings, in which: FIG.

A novel and improved fuel assembly 30 constructed in accordance with the principles of the present invention is shown in FIGS.
is illustrated. The fuel assembly JO includes an elongated, impermeable outer flow channel 3- preferably made of a zirconium alloy commonly known as Zircaloy.

The outer flow channel 32 extends substantially along the entire length of the fuel assembly 30 and structurally interconnects the upper yoke J bow and the lower casting or base 36.

It is preferable that the yoke 3 and the base 34 are made of matte stainless steel used in nuclear reactors.

The lower end Jg of the outer flow channel 32 provides a reliable structural interaction between the outer flow channel 3λ and the base body 36 without having to go beyond the envelope formed by the lateral outer diameter dimension of the outer flow channel 3U above it. To enable coupling, it is formed radially inward with a reduced lateral outer diameter dimension (O/Fig. 172, Male 1 Fig.).

The outer flow channel 3 extends at the lower end 3g to an elongated joint DA which has a reduced lateral dimension and extends around the periphery of the base body 36 and extends axially, i.e. in an up-down direction.
It is connected to the base 34 by means of a tongue-and-groove connection, which is formed by assembling the (Oko/Figure). The lower end 3g of the outer flow channel 3 also rests on a shoulder formed to extend laterally or radially inwardly around the periphery of the base body 34. Once in position on the shoulder lI and opposite the coupling part 0, the lower end Jt of the outer flow channel 32 has three screw threads on each side formed through the coupling part 0 of the base body 34. In a state where the screws are engaged with the five openings,
By passing three setscrews through the three openings 6 formed through the metal retaining rod or collar 5 and through the three openings JO formed below the outer flow channels 3, It is attached to the base body 36 and hangs thereon. In this way, each of the reference sides of the lower end 3t of the outer flow channel 3λ can be structurally interconnected to the seven base bodies 36. The outer one of the three openings jO provided along each side of the lower end Jt of the outer flow channel JJ controls the relative g tension between the lower FILE and the base 36 of the outer flow channel. An elongated or oval opening for receiving a punch. Therefore, it is preferable that the outer setscrews among the plurality of set screws are tightened a little less than the center setcrew so that relative expansion occurs.

According to an important feature of the invention, the outer flow channel 3λ
Attached to the side of the bow at the center of its length are t rigid, spaced apart structural reinforcing ribs 60, which may be welded or otherwise attached. Attach to the inner walls of the three flow channels by any convenient means.

The lowermost end of the reinforcing rib 10 is the lower end 31 of the flow channel Jλ.
It ends slightly above the reinforcing rib 4 (oni/figure).
The upper end of 0 terminates near the longitudinal upper end of the flow channel 3λ (OS diagram, Okoko diagram). The upper layer of the reinforcing rib 60 has three elongated notches 6 formed in the yoke 3'1.
Each of the six notches is designed to fit within λ, and these six notches communicate with a plurality of openings that pass through a U-shaped reinforcing portion 66 that is integrally formed on the yoke ridge. The opening 6 is formed through the upper end of each reinforcing rib 60.
These openings are designed to align with
A lock pin 70 in the shape of a letter is received, and the yoke 3II is fixed to the reinforcing rib 6° and the flow channel here, and is structurally connected to each other.

According to a further important feature of the present invention, the seven L-shaped or chevron-shaped plates constituting the cross-shaped wall structure have reinforcing ribs 401 welded at their lateral outer ends, and are located in the center. A defined moderator flow path, that is, a water cross path 7q is formed inside. This crossroad provides a closed flow path along the length of the fuel assembly 30 for the subcooled neutron moderator.

The lowermost end 74 of the crossroad 7-tei is located near the lower end Jt of the flow channel 3λ (Oni/figure), and the uppermost end 7K is located near the upper end of the flow channel here (Oko diagram). In order to control the flow rate and flow velocity of the moderator flowing through the crossroads 7q, it is preferable that a plurality of moderator current limiting devices 0 formed in an integral number ζ be provided at the lowest end 76 of the crossroads 7da. In this embodiment, the elongated portion at the lowest end of the chevron-shaped plate 7λ is bent inward, and comes into contact with an adjacent elongated portion of the opposing chevron-shaped plate 7 that is also bent inward. There is. To form the current limiter go, the elongated contact edges of the chevrons 7 may be welded.

According to another important aspect of the invention, the water crossroads 7q, together with the inner walls of the flow channels 3, divide the fuel assembly 30 into elongated discrete fuel quadrants or zones g along its length. To divide. A plurality of sealed passageways ff4< formed through the water crossways 7da provide coolant flow between the separate fuel zones gλ. Is the sealed passage ga a crossroads?
4LL are distributed 9 to provide equalization of coolant pressure between adjacent units of the individual separate elongate fuel bundles or subassemblies 16. These fuel handles g6 are separately arranged in separate valley fuel zones gλ of the battery. A preferred method for forming the sealing passage gda is to deform the perforations or cutouts on the facing surfaces of the chevron-shaped member 72 in the area of the sealing passage ge inward toward the crossroads 7da of water, and to form the perforations The edges of the edges abut each other to form a roughly cylindrical passage (see Fig.
OV~7 figure, Oko/~Yuko figure). Thereafter, one or more circumferential welds seal the abutting edges of the perforations of the chevron plate 7.2 to form the sealed passageway 5. The sealed passage 1 is
rF4 allows fuel bundle coolant flow between adjacent fuel bundles 31 while preventing intermixing of the fuel bundle coolant flow with the super cooled neutron moderator flowing through the central water crossroads. .

Each fuel bundle ri (off-2 figure, o-san~j figure, 17~
Figure 5, Figure 5) shows the upper tie plate 9,
It includes a lower tie plate connection and a plurality of elongated fuel rods 94 disposed between both tie plates. In a preferred embodiment, each fuel bundle S includes 16 fuel rods vb4c arranged in rows of Xe, each fuel rod 96
has an upper end plug ioo and a lower end plug ioo. Each fuel bundle 16 also includes a plurality of spacer grids Vt spaced axially along its length by suitable means such as energized spacer capsule fuel rods.
For illustrative purposes, only one is shown in the ono diagram). Spacer·
The exact number and shape of grids 9S should be selected according to the unique thermal, hydraulic, nuclear, and mechanical properties of the particular fuel bundle j4 and fuel assembly 30.

According to yet another important feature of the invention, the upper tiebrae)? - is constructed from a series of thin metal rods or strips 109 joined together and formed by casting, machining, or any other suitable means.

Each of the 14 fuel rod grid positions has a fuel rod! A small cylindrical opening 104 is drilled or otherwise formed to receive the elongated vertical extension iot of the upper end plug 6/θθ in a slip fit. This slip fit between the upper tie plate tach and fuel rod 96 allows relative axial movement therebetween. In order to maintain the fuel rods q4 in the lower tie plate and to support the upper tie plate tach, a plurality of elongated compression springs (1) are connected to the upper end plug 1 in pressure contact with the underside of the upper tie plate 9.
It is arranged to cover the 0θ extension part 101.

At least one fuel rod t6 and TAB in each fuel bundle z4 is a connecting rod, and is used to interconnect the upper tie plate tλ and the lower tie plate q4 (and the plurality of fuel rods 94) together. This single connecting rod AA and 94B has an upper end plug 100mm, a threaded elongated vertical extension 101mm and /θjB, and the core extension has a locking nut // For alignment with λ, it passes through the opening toi in the upper tie plate 9.

The upper tie plate tacho also applies an unrestricted force 3 on the lateral or radial movement of the fuel bundle g6 to the relative axial direction of the cabinet with both the yoke 3II and the flow channel 3. That is, to enable vertical movement, it can be inserted into and out of one of the two bottle receiving openings integrally formed in the yoke J in a sliding fit. Designed to include an elongated G) vertical post or positioning bin/III.

According to another important feature of the invention, the upper tiebrae)?
41 is fuel rod q! includes a plurality of fuel rod locating apertures LλV disposed at each fuel rod grid location for receiving the elongated vertical extensions L of the lower end plugs 10 of the
Figure 11, O/g~-〇 Figure). Two connecting rods? 4A and T
AB has lower end plugs 10 and 10B including threaded elongated vertical sections 1h and 4B, respectively, and the cough extension passes through the opening /Jf in the lower tie plate 9. ) Go through and lock nut/noko (o/9~-
0), allowing the entire fuel bundle 16 to be raised, lowered and handled as one. The locking nut (Figure f, 2o) holds the elongated vertical extension of the spacer force rod in engagement with the lower tie plate when the spacer force fuel rod is used. Vine used for.

The lower tie plate ta has a plurality of openings formed therethrough for diverting fuel bundle coolant, and is formed along the outer periphery of the lower tie plate 9 to allow fuel bundle coolant to be diverted along the length of the fuel rods. It includes a plurality of elongated vertical notches /Jθ providing a flow path. The q chamfered notches formed in and rising from the bottom of the lower tie plate cage have 13 elongated notches formed integrally with the base 36 and extending upwardly from the base. Contains a vertical support /41o with chamfered sides,
Thirteen notches are supported by the support (O/
Figure, 171 figure, off 4 figure, fang/figure). In this way, the lower tie plate q extension is made up of the fuel band /L/
i4 is spaced above and supported by the substrate.

According to yet another aspect of the present invention, the three upper yokes (off-2 figures, 15 figures, off-? figures and fangs, 2- figures) have a generally square body or frame/column. It has an integrally formed elevating handle /jO that extends diagonally across and projects upwardly. This body part isλ has as small dimensions and mass as possible in order to minimize the fluid pressure drop there. Lifting handle/jO is direction indicating protrusion/j4
(and is designed to engage a lifting mechanism for vertically raising, lowering, and handling the fuel assembly 30. The bin receiving openings extend from the three corners of the body portion It is formed by penetrating two protrusions /jt that are integrally formed so as to extend inwardly in the middle diameter direction along a diagonal line.Through the openings //4 in the protrusions ist, the three fuel bundles g6 By coupling everything together, yoke J4Z moves the fuel bundles 16 together, minimizing the amount of loading from one fuel bundle g6 to the other that might otherwise occur.

Yoke 3 further includes a plurality of elongated, laterally extending bumpers 160. The bumper contacts a similarly shaped bumper on an adjacent fuel assembly to reduce the spacing and fluid gap between adjacent fuel assemblies.
dgap) t-In order to minimize the gap, it is formed integrally with the main body. Yoke 3# is further connected to the main body /j
It has 6 mounting posts that are integrally formed on the body. A long and thin screw hole 16 is formed in this mounting post/todoroko, and a spring assembly/44 and a holding bolt/4g are formed in the hole.
(Figure 2). Holding bolts/4g are formed through the bidirectional plate 1741 and the mounting plate or angle/74, respectively, in order to hold the spring assembly/64 in a fixed state with the mounting boss)/4. A pair of openings / 0
and/designed to pass through the wolfberry. Bidirectional leaf springs 17 are connected to corresponding leaf springs in the fuel assemblies 14 in contact with the fuel assemblies in order to maintain spacing between adjacent fuel assemblies and to transfer loads from one fuel assembly to another. It is designed to make contact. An elongated vertical bumper/7K (off view, Oyuyu view) is disposed diagonally opposite to the mounting post/6-.
7g is designed to transfer the load from spring assembly /4& to the upper internals of the reactor, thus preventing any significant movement due to such loads being applied to the fuel assembly 30. A plurality of suitably shaped notches are provided at the upper ends of the flow channels (inside view, off view and outboard view) to receive the radially outwardly projecting portions of bumper/40 and spring assembly/46. -0411 should be provided.

Each 0-shaped lock bin 7Q is designed so that the receiver can be inserted through the aligned openings 4 and 41, with a hanging part at the outermost end. Includes elongated, almost straight lower legs. Lower leg lS
When the bow passes through the alignment opening 1 and Aft, the spring-formed upper leg ito moves in the direction of the lower leg it+ and tightens tightly, and the hanging portion /1- passes through the adjacent upper part of the reinforcing portion 44 of the yoke J bow. Because it is positioned in alignment with the vertical edge,
The lock bin 70 is maintained in a removably locked state with respect to the reinforcing IJ block base 0 and the yoke J41.

Substrate, yi (O/Figure 1. t3 figure, O/Tei~76 figure, 11
FIG. 1) includes an inlet/hole/90 having an inlet opening/9/ for receiving a flow of coolant or moderator. As is clear from FIGS. 3 and 116, the inlet nozzle/'10 has an eccentric structure, so that its center
and off-center of the fuel assembly 30, but the inlet opening /9/ is concentric with the base body 36 and the fuel assembly 3o. Inlet nozzle l? In order to form the eccentric channel θ, the material of the base body No. 3 forming the inlet nozzle ivo may be processed during or after the casting of the base body 36 to form the inlet nozzle/de. It is better to change the thickness around the area. Therefore,
During refueling of a nuclear reactor core, a 3° fuel assembly having a large lateral outside diameter is used in place of a spent fuel assembly having a small lateral outside diameter.

Disposed above the inlet nozzle/90 is the inlet nozzle/90 that receives the flow of coolant or moderator and directs it to the fuel bundle 16.
It is the Blenheim area that distributes to the center of the lower tiebrae 71 and water crossroads 7411. Inlet nozzle/re. The three legs/legs extending downwardly are inclined radially inward in order to align the base J4 and thus the fuel assembly 3o within the core internals and within the attachment structure in the fuel storage rack. - rfJj & sushita support/daO rising from base 34
has a chamfered surface iii /94 starting from a vertically extending elongated radial circular surface and ending at the top surface /9g. A cross-shaped base support member disposed at the center within the base body 36 and extending laterally - q supports/41' integrally formed with 〇〇.

Is the lower HL tie plate of one adjacent fuel bundle g4? It includes a pair of chamfered surfaces /9&, each designed to contact, seat and support a flattened notch /3λ in the bow. In addition, in order to provide room for the current limiting device 1go of the water crossroad 7da (male 1 figure) on the upper rTJtqt of the da supporter/4!0 arranged in the center, a long and narrow curved recess - The embodiment of the present invention described above can be modified in various ways. For example, the upper tie plate? In another embodiment of FIG. 1 (FIG. 110), a lateral or radial extension 1-0 integrally formed in the metal rod or strip 104I is used to extend the lateral or radial direction of the fuel bundle t6. Both the movement of the fuel bundle 16 and the circumferential rotational displacement of the fuel bundle 16 are further regulated or limited. Additionally, the flow channels 31 of the fuel assembly 30
Another embodiment of 1 (male figures 3 to 15) has a lower end jfl with a corresponding bent cross-sectional shape so as to enter the elongated groove formed in the base jAl with a bent cross-sectional shape.
is formed at the end in the axial direction. As in the embodiment shown in Figure 1, a rigid structure can be provided between the flow channel 3.21 and the base body 361 without having to go beyond the envelope formed by the flow channel 3.21 or the outer circumferential surface of the base body 361. To provide a tongue-and-groove connection, the lower end 3 ft is formed radially inwardly to have a lateral outer diameter dimension that is small compared to the lateral outer diameter dimension of the portion of the flow channel JJl above it. ing. The central water crossroad 7gl is formed at the lowermost edge 6 without having a moderator flow limiting device 10 (Fig. 111). Thus, the flat upper surface of the centrally located, chamfered support ttio is formed integrally with and rises from the laterally extending cross-shaped base support member oo'. 1 acts as a current limiting device that limits the flow rate and flow velocity of the moderator flowing through the crossroads 7 of water.

The base support member J00' is Voltco io (Okoda vA)
It has an elongated vertical opening -θ1 formed through the center in order to secure the opening. The inner diameter of the opening 20X is designed to be smaller than the outer diameter of the head lλ of the bolt λ10, which acts as a stop and support surface for fixing the flow channel 3λ1 in engagement with the basic body J4'. The elongated threaded end K/# of the bolt λ10 is designed to fit into the elongated threaded hole K/l in the center of the lock nut core B. Is Rocknut Core 4 a crossroads of water by appropriate means such as bathing? It may be attached at a predetermined position in the center of the lowermost end 741 of 41+. When the portco 10 is sufficiently tightened so that its threaded end 21 properly engages the threaded hole 2/l of the lockcolumn 16, the lower end jf of the flow channel JJ'
fl will be held tightly within groove 204.

[Brief explanation of drawings]

Figure 17 is a front view of a fuel assembly constructed in accordance with the principles of the present invention, the off view is an enlarged plan view of Figure O1, the off view is an enlarged bottom view of Figure O1, and the ori view is the line IV-IV in Figure 17. cross section,
Figure 15 is a sectional view taken along the V-v line of the ori diagram, and Figure O6 is the V of the O S diagram.
The l-Vl line cross-sectional view, the off view is the ■-■ line cross-sectional view of the ori diagram,
Figure 19 is a cross-sectional view of the Ori diagram along the ■-■ line, and Figure 19 is the V of the O diagram.
-■ line sectional view, OFF 0 figure is a partially enlarged sectional view showing a modified example of the upper tie plate, OFF figure 7 is a sectional view taken along line T1 in figure 17, 171 figure is a m-shoulder line sectional view of OFF figure 7, Figure 13 is a thin sectional view of Figure 172, and Figure 4' is a cross-sectional view of Figure 7.
-XIV- cross-sectional view, Off figure 3 is the XV-XV line cross-sectional view of Off figure 7, O figure 16 is the XYI - front view,
Figure 110 is an exploded perspective view showing the fuel bundle in a disassembled state, Figure 110 is a perspective view showing the fuel bundle in an assembled state without the grid spacer, and Figure 110 is a perspective view showing the bottom of the fuel bundle , 127 is an exploded perspective view showing the lower end of the flow channel and the base; Oko view is an exploded perspective view showing the upper end of the flow channel and the yoke at the top of the fuel bundle; FIG. Plane showing another embodiment of the base of the aggregate! #Front view, OJ4
Figure 1 is a cross-sectional view of Figure 3 on the ■-bean ■ line, and Figure 125 is 113.
FIG. 3 is a SI+ view showing the lower end of the flow channel and the substrate of the illustrated fuel assembly; In the figure, JO is a nuclear fuel assembly, 3 and 1 are flow channels, 7- is a chevron-shaped plate forming a cross-shaped wall structure, 74
1 and 741 are water cross paths (moderator flow paths), fJ is a fuel area, and 94 is a fuel rod. Patent Applicant: Westinghouse Electric Corporation Agent: So Wa Do Teru Figure 2, Figure 3, Figure 4, Figure 5, Figure 8, Figure 9, Child, 10, Rhinoceros, Figure 11, Figure 13, Atsushi, 14, and I, I, 17. Also, R3jlt) 15th figure, 16th figure, vines, 23rd figure, 24th figure, 25th figure, continued from the first page ■Inventor: Theodore Uniin Niland 1230 South Beltline Boulevard, Columbia, South Carolina, United States of America

Claims (1)

[Claims] In a nuclear fuel east coalescence having a cladding defining an outer flow channel and surrounding a plurality of fuel rods, a cruciform wall structure of spaced apart chevron plates is disposed within the cladding and the nuclear fuel A nuclear fuel assembly comprising dividing the assembly into a plurality of separate fuel zones and creating a moderator flow path for cold neutron moderator through the gaps between the chevron plates.