JPS62126387A - Mounting joint for combustible absorbing rod - Google Patents

Abstract

Mounting joint for combustible absorption rods comprises a deformable fixture to fit a socket into a hole of an absorption rod support plate, so that the fixture is deformable by an external force to remove the absorption rod from the support plate. -

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to nuclear reactors and, more particularly, to a unique one-inch storage joint for combustible absorption rods that facilitates the removal and collection of spent combustible absorption rods.

9 Kodama In a typical nuclear reactor, the reactor core comprises a number of fuel assemblies, each consisting of an upper and a lower nozzle, and a plurality of lateral nozzles extending between the nozzles. and a plurality of transverse gratings spaced axially along the guide simple.

Additionally, each fuel assembly is comprised of a plurality of elongated fuel elements, or fuel rods, which are laterally spaced from each other and from the guiding simple and arranged in a lattice between upper and lower nozzles. Supported by Each of these fuel rods contains fissile rods and provides sufficient neutron flux into the reactor core to maintain a high fission rate and thereby maintain a large release of nitro niobium in the form of heat. They are grouped into organized sequences so as to cause Liquid coolant is pumped upward through the core to extract some of the heat generated in the core and perform useful work.

Since the heat release rate in the reactor core is proportional to the fission rate, which is also determined by the neutron flux in the reactor core, the heat release control ij at reactor startup, operation, and shutdown depends on the neutron flux. Achieved through change. Generally, this is done by absorbing excess neutrons using control rods containing neutron absorbing material. In addition, the guide thimble is
In addition to being a structural element of the fuel sound collector, it provides a passageway for the insertion of neutron-absorbing control rods within the reactor core.

The level of neutron flux, and therefore the thermal power of the core, is typically regulated by the insertion and withdrawal of control rods from the guide simple.

Additionally, overdesigning the amount of neutron flux into the core at reactor start-up may result in sufficient reactivity to sustain core operation for extended periods of time as the neutron flux depletes over the life of the reactor. It is common practice to do so. In view of this practice, in some applications of nuclear reactors, a combustible absorption rod, i.e. a combustible poison rod, is inserted within the guiding simple of the fuel sound collector consisting of a guiding simple of the other three fuel collectors. Control rods within the core help maintain the core's reactivity, or neutron flux, constant over the life of the core. These combustible absorption rods, like the control rods, contain neutron absorbing material. These poison rods differ from control rods primarily in that, during use in the reactor core, they are maintained in place within a guide simple. The overall advantages of using a burnable poison rod in place in the core of a nuclear reactor are described in US Pat. No. 3,361,857 by Rose and US Pat. 51
No. 0,398.

The 18-month fuel cycle, as opposed to the more common 127-month fuel cycle, has been increasingly used in nuclear reactor operations. The need for cargo collection has become an important element in overall reactor fuel management. Traditionally, when a 12-month fuel cycle is used, the combustible absorber rod assembly is only required for the first cycle, and t; f =
The spent combustible absorber rod assemblies could be stored together with the spent fuel waste. In the 18γ fuel cycle, the combustible absorber rod assemblies were 3 cycles are also required.Therefore, more used combustible absorption rod assemblies are generated than spent fuel collections 61←, so all of the used combustible absorption rod assemblies are They cannot be stored within the fuel assembly, which means that the combustible absorber rods must be collected to save space in the spent fuel pool.

The structure of the cluster assembly of combustible absorber rods is convenient for collection because the upper end of the combustible absorber rods is fastened to the bottom plate, or support plate, of the cluster assembly by means of a screw connection that is fixed in place. is not suitable. In order to remove the flammable absorption rod from the support plate, it is necessary to separate the flammable absorption rod from it, which must be carried out remotely while the irradiated assembly is submerged in water. It's not an easy task.

Therefore, during the application of the combustible absorption rods to the fuel assembly of the reactor core, the combustible absorption rods are securely anchored in the required position within the guide simple, and the single-layer combustible absorption rods are placed in the used gorge to absorb the spent fuel. What is needed is an alternative means for attaching combustible absorption rods to support plates that allows for easy removal to aid in effective collection of pools.

The present invention provides a push-out mounting joint for combustible absorption rods designed to meet the above needs. The modifications to the combustible absorber rod assembly required to meet the requirements of the push-out mounting joints of this invention are likely to be less expensive than traditional threaded connections.
However, many of the benefits derived from the 1-inch joint according to the present invention are obtained from used combustible absorbent 6 achieved when collecting rods
Most importantly, this attachment joint I- allows the used combustible absorption rod to be removed from the support plate without the hassle of having to cut the combustible absorption rod remotely. Instead of cutting off the combustible absorption rod, a suitable tool, i.e., alternatively deforms the connected connecting part of the upper end of the combustible absorption rod, which has been cut through the opening in the support plate (through this opening) Removal of the used combustible absorption rod is carried out from above by simply pressing down on said upper end using a tool that separates the combustible absorption rod from the support plate (within which the combustible absorption rod is inserted and fixed in the support plate of the assembly).

Uf--This invention provides a support plate with one end of the combustible absorption rod removable for use in a cluster assembly comprising a support plate and at least one combustible absorption rod. a mounting joint that connects to (a) a spigot defined in the end of the combustible absorption rod; and (1) at least one hole in which a support plate is fitted to receive the spigot. (c) connected to the means for defining at least one hole and the spigot;
The attachment means is deformable in order to mutually engage and fix the insertion part to the support plate disposed in the hole, and the insertion part is removed from the hole to remove flammable absorption from the support plate. said attachment means being also re-deformable upon application of a predetermined axial force to the insert in order to remove the rod;
Discloses a r=t joint for a combustible absorption rod having a length of 11 hours. In addition, the housing 1 [means is used to remove the old core portion (11a
It is growing.

More particularly, in a preferred embodiment, the attachment means in the accommodation joint include a hollow annular wall extending axially outwardly from the plug receptacle of the combustible absorption rod and a conical cone connected to the hole in the support plate. and means for defining a shaped recess in the support plate. The recess funnels outward from the hole to a maximum diameter that is greater than the diameter of the hole.

Also, the annular wall of the insertion part is deformed to match the shape of the four parts. Furthermore, the spacing portion for preventing rotation of the insert within the bore includes means for defining a recess in the support plate that is connected in eccentric relation to the four parts, and a portion of the annular wall that is deformed into the eccentric recess. There are 11 cities.

In a modified embodiment, the attachment means of the attachment joint are provided with means for defining a concave vortex in the hole of the support plate, and the annular wall of the spigot is adapted to match the shape of this groove. transformed. In another variant embodiment, the storage means include a solid portion 11f extending axially outwardly from the insert at the upper end of the combustible absorption rod and beyond the hole in the support plate.
a L, there. Remove the collar from the solid part of the insertion part 1
・[This collar has an outer diameter larger than the outer diameter of the hole.

Further, a concave groove is formed in the solid portion, and the collar has a portion that protrudes clearly in order to be attached to the solid portion.

The above-mentioned advantages and effects of the present invention and further advantages and effects thereof will become apparent to those skilled in the art after reading the following detailed description along with the drawings showing one embodiment of the invention. Dew.

The sales outlet! In the following description, the same reference numerals indicate the same or equivalent parts throughout the drawings. In addition, in the following explanation, "front", "rear", [left], "right",
Terms such as "upper" and "lower j" are words of convenience and should not be understood as limiting terms.

Referring to FIG. 1 in the drawings, 1+j, the fuel assembly is shown generally by 2o in vertically shortened form in front view. This fuel collector 20 is of the type used in a pressurized wooden reactor (PWR), and basically consists of a lower core plate (not shown) in the core region of a nuclear reactor (not shown). A lower end structure for supporting the fuel assembly 2°, that is, a lower nozzle 22, and a plurality of guide pipes, that is, guiding simples 24 that project upward from the lower nozzle 22 and extend in the longitudinal direction. We are prepared. Furthermore, this fuel set 14s20 includes a plurality of transverse grids 2 axially spaced apart from each other along the guide thimble 24.
6 and an organized array of 41Il long fuel rods Z8, supported one by one and laterally separated from each other by the lattice 26. The fuel assembly 20 also includes an instrumentation pipe 30 located at its center and a guide simple 2.
4 has an upper end structure, ie, an upper nozzle 32, which can be attached to the upper end 24 of the nozzle 4.

Due to this arrangement of the parts, the fuel v:t a = body 20 forms an integral unit which can be normally accessed without depleting the constituent parts.

As described above, in the fuel assembly 20, the fuel f'l rods 28 in the arrangement are arranged along the longitudinal direction of the fuel sound collector 20.
They are held in series separated from each other by juxtaposed grids 26. Each fuel rod 28 includes nuclear fuel pellets (not shown), and the ends of the fuel rod 28 are closed by an upper end plug 34 and a lower end plug 36.

A fuel barrel composed of nuclear-intrusive material is responsible for generating the reaction output of the PwR. In order to extract the heat generated in the core and perform useful work, liquid moderation/cooling such as 7K or boron water is pumped upward through the fuel assembly 20 of the core. Sent.

u2.111 In order to make more effective use of uranium fuel and reduce fuel costs in L and PWR operations, it is necessary to
It is desirable to make one life as long as possible. To achieve this goal, it is common practice to create an excess of reactivity in the core and provide means to keep the reactivity relatively constant over the life of the core. There is.

Such means take the form of a cluster of combustible absorption rods 38 of reduced length, supported by a hold-down device 40 -m. As shown in FIG.
0 immovably supports combustible absorption rods 38 in guide simples 24 in several combustible rt4A fuel bodies 20 and thereby guide simples 24 in pond fuel assemblies (not shown).
Movable control rods (not shown) within the core assist in maintaining the neutron flux or reactivity within the core at a substantially constant level throughout the core's operating cycle.

Referring to FIGS. 2 and 3 in addition to FIG. 1, a hold-down device 40 supporting the combustible absorbent rods 38 in spaced juxtaposition includes a perforated flat lower support plate 42 (11a and This support plate 4Z fits into the upper nozzle 32 of the fuel assembly 6 ZO, and is mounted aZ on the adapter plate 44 of the upper nozzle 32. Furthermore, the holding device 40 is inserted into the center opening 48 of the support plate 42. a sleeve 46 having a lower end secured therein and extending upwardly therefrom; Further, a retainer coil spring 52 is arranged around the sleeve 46 and extends between the support plate 4Z and the upper retainer plate 50. 1;C
Therefore, the holding coil spring 52 is attached to the upper core plate (not shown).
(acting through the upper holding plate 50 that contacts this upper core plate), and this holding coil spring 52 presses the support plate 42 downward against the adapter plate 44 of the upper nozzle 32. It will be done. With this arrangement, the combustible absorption rods 3 mounted on the support plate 42 with f=I
8 reliably prevents coolant from flying out of the core due to flow force, and allows any thermal expansion of the combustible absorption rods 38.

nI5! Conventionally, each combustible absorption rod 38 has a threaded upper end, thereby connecting the combustible absorption rod 38 to the support plate 42.

Such a threaded connection makes it cumbersome to remove the combustible absorption rods 38 from the holding device 40 in order to collect them for storage when they reach a used state. there were. The extruded mounting joint of the present invention, generally designated 54 as shown in FIG. 1 and particularly FIGS. 4 and 5, overcomes and eliminates the complications described above. was invented in

4-9, a preferred embodiment of a push-out mounting joint for removably connecting the upper end 56 of each combustible absorption rod 38 to the support plate 42 is shown. Basically, the mounting joint 54 is attached to each combustible absorption rod 3.
a plug receptacle 58 defined in the upper end 56 of the plug receptacle 58 and a six 60 defined through the support plate 42 for receiving each receptacle 58 and interlocking the receptacles 58 within the six 60; Each combustible absorption rod 3 is fixed to the support plate 42 by
8, and mounting means, generally indicated at 62, for connecting 8.

In the preferred embodiment shown in FIGS. 6-9, the containment means 62 includes a thin-walled hollow annular wall extending axially outwardly from the spigot 58 on the upper combustible absorption rod 38. 64 and a conical recess 66 defined in the support plate 42 and connected to the 660 of the support plate 42.

As shown in FIGS. 8 and 9, the recess 66
from a diameter of 660 to a maximum diameter greater than the diameter of 660, funneling or sloping outward from 660. Before the attachment joints l~54 are formed,
The hollow annular wall 64 on the insert portion 58 has a substantially cylindrical shape, as shown in FIGS. 6 and 7.

After the 1-inch joint 5=i is completed as shown in FIG. 4r21 and FIG. Such interlocking, formed by the annular wall 64 deformed into contact with the conical quadrant 66, is achieved by a large diameter flange 68 formed at the upper end 56 below the spigot 58, which Support plate 4
2) and maintain a spigot 58 in the 660 of the support plate 42 to securely attach each combustible absorber P#:38 to the support plate 42.

However, by forcibly pushing out the insert portion 58 from the hole 60 of the support plate 42, the insert portion 58 is freed from the hole 60.
When a predetermined force is applied axially downward to the insert 58 in order to remove the annular wall 64, the annular wall 64 deforms again.

The center 70 of the deformed annular wall 64 is provided with a guide for receiving a suitable extrusion tool (not shown), which presses the insert 58 downwards and at the same time pushes the hex 60. The drawer is used to straighten the annular wall 64 sufficiently to permit extraction and removal of the combustible absorption rod 38 from the support plate 42.

In order to prevent the spigot 58 and therefore the combustible absorption rod 38 from rotating in the hole 60 of the support plate 4Z, the attachment means 62 of the mounting joint 1-54 are aligned with the axis of the combustible absorption rod 38 and 660. (It also includes a free center portion located at an eccentric distance.) It takes the form of a vortex or indentation 72 defined in the plate 42 and connected to the quadrature 66 and the IQ recess 66.An annular ri 64 is taken ([conical to complete the dicointo 54). When the annular wall 64 is deformed to
A small portion 74 at the peripheral edge 76 is press-fitted into the eccentric recess 72. In this way, the deformed annular wall 64 and the insert 58 are fixed against rotation with respect to the recess 66 and the hole 60. However, the small portion 74 of the annular 'i64 easily slips out of the recess 72 as the annular wall 64 is deformed during the removal of the combustible absorption rod 38 from the support W,42.

In the modification shown in FIG.
The joint 54' has attachment means 62' in the form of a concave hole 78 in the 660 of the support plate 42, with an annular wall 64' on the spigot 58' matching the shape of the hole 78. It is transformed like this. Rotation is prevented by providing an eccentric member similar to that shown with respect to the previous preferred embodiment. A modification of the mounting joint 1-54'' is shown in FIG. 11. In this modification, the mounting joints Vj, 6
2" is the support plate 4 axially outward from the insertion part 58".
2, a solid portion 80 extending beyond the six 60, and an insert portion 5.
A collar 8 that slides over and fits over the 8" solid portion 80 and has an outer diameter larger than the outer diameter of the 660.
It takes the form of 2. A concave groove 84 is formed in this solid portion 80, and the collar 82 is connected to the insertion portion 58.
In order to attach the collar 8Z to the solid part 80 of
4. It has a portion 86 that protrudes into 4. Rotation is prevented in a manner similar to that shown in the previous preferred embodiment.

It will be appreciated from the foregoing description that this invention and its many attendant features may be used without departing from the spirit and scope of this invention or sacrificing its substantial advantages. It will be obvious that various modifications may be made in shape, construction and arrangement without any further modifications, and the embodiments described above are therefore merely preferred embodiments of the invention.

[Brief explanation of drawings]

FIG. 1 shows a fuel assembly with a cluster assembly of combustible absorber rods using the mounting joint of the present invention, shown in vertically collapsed form with portions removed for clarity. 2 is an enlarged front view 1f of the combustible absorption rod cluster assembly of FIG. 1 removed from the fuel assembly, shortened in the vertical direction and partially cut away.
fi, No. 312I is a plan view of the cluster assembly of combustible absorption rods along line 3-3 of No. 2121, and FIG.
In a cluster assembly of combustible absorption rods of No. 12I, the upper end of one combustible absorption rod and a part of the support plate of the cluster assembly surrounding the combustible absorption rod are attached to the support plate. A partial enlarged view showing in cross section a preferred form of the 1-inch joint according to the present invention that removably connects the absorption rod;
Figure 5 is a plan view of the mounting joint between the combustible absorption rod and the support plate along line 5-5 in Figure 4, and Figure 6 is before the formation of the l5Er joint connecting the combustible absorption rod to the support plate. A cross-sectional view of the mounting structure of the upper end of the flammable absorption rod in
Figure 7 is a plan view of the mounting structure for the upper end of the flammable absorption rod along line 7-7 in Figure 6, and Figure 8 is the support before forming the mounting joint that connects the flammable absorption rod to the support plate. Figure 9 is a cross-sectional view of the structure for mounting the support plate along the line 9-9 in Figure 8, and Figure 10 is a plan view of the structure of the support plate (= f joint). 11 is a sectional view similar to FIG. 4 and FIG. 10 showing another modification of the joint according to the present invention. In the figure, 20 :Fuel assembly 38;Flammable absorption rod 42:Support plate 54:Mounting joint 56:Upper end
58: Insertion part 60: 6 02:
Mounting means 64: Tubular wall 66: Recess 72: Recess Drawing cleanup (No change in content No change in report content of drawing) FIG, lOFI also 11 Procedural amendment (method) % formula % 1. Indication of incident 1985 Patent Application No. 214244 2 Name of the invention Mounting joint of flammable absorption rod 3 Relationship to the case of the person making the amendment Patent applicant name (711) Westinghouse Electric Corporation 4 Agent address 〒 100 Marunouchi Building 4, 2-4-1 Marunouchi, Chiyoda-ku, Tokyo] @ November 25, 1985 6, Subject of amendment (1) Drawing 7, Contents of amendment (1) Drawing originally attached to the application. (Figures 1 and 2) as engravings and attachments (no changes in content)

Claims (1)

Claims: for use in a cluster assembly comprising a support plate and at least one combustible absorption rod, the support plate having one end of the combustible absorption rod removable therein; a mounting joint connecting (a) a spigot defined in the end of the combustible absorption rod; and (b) at least one hole passing through the support plate for receiving the spigot. (c) mutually connecting the spigot to the support plate, the spigot being connected to the means for defining at least one hole and the spigot, the spigot being disposed in the hole; The attachment means is deformable for engaging and fixing, and the insertion means is provided with a predetermined axial direction on the insertion portion in order to remove the insertion portion from the hole and remove the combustible absorption rod from the support plate. said attachment means being also re-deformable upon application of force.