DE19838790A1 - Boiling water reactor fuel element with coolant swirling device - Google Patents

Abstract

A boiling water reactor (BWR) fuel element includes a swirling device, which forms spiral paths for imparting vortical flow to the upwards flowing coolant, and a debris collection system. A BWR fuel element includes (a) an axial swirling device which is arranged in the bottom of the bottom closure plate and which has vanes positioned around a central hub for imparting an upwards vortical flow to the upwardly flowing coolant; (b) a vertical open-ended cylindrical body which extends upwards in the bottom closure plate to a predetermined point at the downstream side of the swirling device and through which the vortex of debris-laden coolant flows upwardly; and (c) a debris collection section which is located between the outer surface of the bottom of the cylindrical element and the inner surface of the bottom closure plate and which collects sunken debris after it has passed outwards from the top of the cylindrical body. Independent claims are also included for similar fuel elements.

Description

The present invention relates to a fuel assembly in a boiling water reactor is attached. In particular, the invention relates to a fuel assembly at which can be prevented that dirt or waste particles (debris), which are in the Mixed coolant, penetrate into the interior of the fuel assembly.

A fuel assembly, which is mounted in a boiling water reactor comprises a plurality of fuel rods 2 and at least one water rod 3, which are housed in a cylindrical channel box. 1 At the upper and lower ends of the fuel element, an upper train or end plate 4 and a lower train or end plate 5 are attached. At the upper end plate 4 and the lower end plate 5 , the upper and the lower ends of the fuel rods 2 and the water rod 3 are fixed by end caps 6 and bottom end plugs 7 , respectively. Further, to the water rod 3, a plurality of spacers 8 at regular intervals in the axis Rich processing of the water rod 3 is mounted, such that the fuel rods 2 are not held by these spacers 8 only, wherein they are in lines or rows, but the Fuel rods 2 can also be prevented from bending at the same time.

Fig. 56 is a plan view showing an example of a network or matrix portion 9 of the lower end plate 5 which is designed to hold the lower end plugs 7 . This matrix section 9 contains cylindrical sections 10 , into which the bottom end plugs 7 for holding the fuel rods 2 and the water rod 3 are inserted, as well as flow holes 11 through which coolants pass in the form of a flow which rises from bottom to top.

Fig. 57 shows a longitudinal sectional view shown in that state in an enlarged view, wherein the lower end plugs are inserted into the matrix section 9 10. As illustrated in FIG. 57 by arrows, a coolant "a" flows to the fuel from the lower portion thereof, flows through the flow surface 11 of the lower cover plate 5 , and then flows toward the upper portion of the fuel, thereby the heat coming from the fuel rods 2 is dissipated.

The exchange is made during a periodic inspection of the nuclear reactor of the fuel assembly by opening the cover of the reactor pressure vessel. During this periodic inspection there is a possibility that metallic particles such as metal wires used in the inspection work into the reactor pressure vessel can fall into it. There is also the possibility that the Structural material of the reactor itself due in part to oxidation or from it other reasons, and that the peeled particles in the reactor pressure vessel can fall into it.

Since the dirt or waste particles such as these metallic particles, the flaked or peeled particles or other similar particles usually have only a small amount of waste, these waste particles can be passed along and together with the coolant flow into the reactor core, and it can Part of the dirt particles pass through the lower cover plate 5 and flow into the fuel assembly. This causes the disadvantage that some of the dirt particles are trapped in the fuel assembly, or other disadvantages may arise. A method has therefore already been developed by means of which dirt particles can be prevented from getting into the fuel assembly (see, for example, US Pat. No. 5,390,221).

In Fig. 58 an example of the structural configuration of a constructed according to the conventional method, dirt or waste catching means is shown. This dirt trap is constructed such that a twisted plate 13 is provided in an inlet section for the coolant, which opens in the center of the lower end of the cover plate 5 attached to the lower end, that a cylindrical ring 14 , which for guiding the coolant " a "is used, is provided above the twisted or twisted plate 13 such that it surrounds the upper side of the twisted plate 13 , and that above the ring 14 a filter 15 is arranged for filtering out. As a result of this structure, the dirt or waste particles that have flowed into the lower end plate 5 together with the coolant "a" are provided with a stirring motion component, that is, with a circulation component. In the dirt trap, the dirt and waste particles, which have a higher density than the coolant "a", are separated and passed to the outside of the ring 14 , which is arranged on the downstream side of the rotated plate 13 .

In the conventional dirt trap constructed as described above direction, the swirling force caused by the rotated plate is low, so that the dirt and waste particles are not always removed to a sufficient extent can. Furthermore, there is another problem that the pressure loss is large.

The present invention relies on overcoming the above problems from. Accordingly, it is an object of the present invention to provide a fuel assembly that is able to create dirt particles efficiently with little pressure loss capture in order to achieve that an inflow of dirt particles in the Fuel element together with the coolant can be prevented and thereby normal operating state of the fuel assembly is effectively ensured.

This object is achieved with the in claim 1 and / or one of the other ordered claims resolved features.

Advantageous embodiments of the invention are specified in the subclaims.

According to one aspect of the present invention, the above is for solving mentioned task created a fuel assembly in a reactor core section Reactor pressure vessel of a boiling water reactor is arranged and a plurality of Fuel rods, an upper pull or end plate and a lower pull or end plate, each holding the upper and lower ends of the fuel rods, a plurality  of spacers arranged at intervals between the two end plates are and serve the distances between each arranged adjacent to each other Hold fuel rods from the plurality of fuel rods, and a channel box has, in which the plurality of fuel rods is accommodated, wherein the coolant flows into the fuel assembly from the underside of the lower end plate and for this purpose is designed to point towards the side of the fuel rods in the fuel assembly moving increasing. The fuel element is characterized in that it is a Stirring or swirling device, which in the lower portion of the lower End plate is arranged along the axis direction of the fuel assembly and a has central hub and a plurality of blades surrounding the central hub are arranged around and serve to move towards the side of the fuel rods increasing coolant moving towards an upward vortex flow to lend. There is also a cylindrical body in the lower end plate is arranged vertically and an upper end portion and a lower end portion has that each open. The cylindrical body extends up to a predetermined altitude on the downstream side of the stirring or Ver whirling device. The coolant contains dirt or waste particles that migrate upward as they move along the inner peripheral surface of the zylin move the body in a vortex shape. There is also a dirt or waste collection section present between an outer surface located on the lower side of the cylindrical body, and an inner surface of the lower end plate is formed and is used to collect waste particles, the waste particles from flow out the upper end portion of the cylindrical body and thereby to Be brought down.

According to this aspect of the present invention, an annular, Waste catching hook element is provided which is coaxial with an upper portion of the inner peripheral surface of the cylindrical body is arranged and from the inner The peripheral surface of the cylindrical body protrudes downward and serves to prevent the waste particles in the coolant from moving upward  can.

According to the present aspect, it is preferred in one embodiment above the cylindrical body a second cylindrical body, which is approximately the same has the same diameter as the first-mentioned cylindrical body, with a predetermined vertical distance, the second cylindrical body abge by means of a mounting wall on the inner surface of the lower end plate is supported.

Such a configuration is in accordance with this aspect of the present invention provided that the cylindrical body has a lower cylindrical portion on which the Swirler is attached and includes an upper cylindrical portion, which is coaxial with the lower cylindrical portion and which is a plurality of Has slits formed on the peripheral wall portion of the upper cylindrical ab section near its upper end portion are formed spirally or obliquely.

According to this aspect of the present invention, the cylindrical body is in an alternative embodiment with a lower cylindrical portion on which the swirler is attached, and an upper cylindrical portion provided which is coaxial with the lower cylindrical portion and one Having a plurality of round holes formed on the peripheral wall portion of the upper one cylindrical portion are formed near its upper end portion.

According to this aspect of the present invention, it is further preferred that outer cylindrical body present, concentric with a fixed radial gap is arranged to the cylindrical body in the lower end plate and one upper end portion extending toward the upper end portion of the cylindrical Body extends so that it is fixedly connected to this, as well as a lower End portion which is fixed to the inner surface of the lower end plate is mounted. The gap between the cylindrical body and the outer cylindrical  Body is blocked here, and the cylindrical body has a plurality of Slits on an upper peripheral wall portion of the cylindrical body are spiral or oblique. This will remove the dirt particles move out through the slots in the space between the cylindrical body and the outer cylindrical body.

According to this aspect of the present invention, there is also a guide body is present, the waste particles fall down and essentially a kronenför shape and has an opening in its central portion. This leadership body is arranged so that it inner and outer peripheral portions of an edge of the surrounds the upper end portion of the cylindrical body, thereby causing the upward directional flow of the coolant flowing along the inner peripheral wall of the cylin body flows upward to divert into a flow that is on the outer Peripheral surface side of the cylindrical body flows downward.

According to a further aspect, the above-mentioned object is achieved the present invention, a fuel assembly is created in a reactor core section of a reactor pressure vessel of a boiling water reactor is arranged and a A plurality of fuel rods, an upper tension or end plate, the upper ends the fuel rods holds a lower tension or end plate, which the lower ends of the Fuel rods holds a plurality of spacers spaced between the two end plates are arranged and to maintain the distances between each adjacent fuel rods are designed from the plurality of fuel rods, and a channel box containing the plurality of fuel rods, with coolant flows into the fuel assembly from the lower end of the lower end plate and is designed or guided so that it is towards one side of the fuel rods moved in the fuel assembly. The fuel element is characterized in that it contains a stirring or swirling device, which is in a central position of the lower portion of the lower end plate is provided and a central hub as well has a plurality of blades around the central hub  are arranged and serve the coolant, which is towards the side of the Fuel rods moved upward, an upward vortex flow to lend. Furthermore, a plurality of dirt or waste particle traps provided above the swirling device in the lower end plate, wherein each of the waste particle traps protrudes in a direction opposite to that of the Swirling-induced vortex-shaped flow is such that seen in the lateral cross section, they essentially form the shape of an L.

To achieve the above object, according to another aspect, the Present invention, a fuel assembly created in a reactor core section a reactor pressure vessel of a boiling water reactor is arranged and the plurality of fuel rods, an upper tension or end plate, the upper ends of the fuel rods holds, a lower tie plate that holds the lower ends of the fuel rods, a plurality of spacers spaced between the two End plates are arranged and to maintain the distances between each mutually adjacent fuel rods are designed from the plurality of fuel rods, and comprises a channel box in which the plurality of fuel rods are accommodated, wherein coolant from a lower end portion of the lower end plate in the fuel inflow is designed to move towards the side of the fuel rods to move upwards in the fuel assembly. The fuel assembly stands out characterized in that it has a cylindrical element which in the lower Section of the lower end plate is provided and extends along the axial direction extends of the fuel assembly. The cylindrical member has a plurality of spirals flow paths, each on the top end faces and the bottom side end faces of the cylindrical member are open such that each other un dependent and spiral flow paths are formed. Each of the spiral Flow paths are at predetermined flow path positions with concave ribs provided, act on the centrifugal forces caused by the in the spiral stream flowing coolant. The concave grooves run perpendicular to the direction of flow in the spiral flow paths  flowing coolant.

According to a further aspect, the above-mentioned object is achieved the present invention, a fuel assembly is created in a reactor core section of a reactor pressure vessel of a boiling water reactor is arranged and a A plurality of fuel rods, an upper tension or end plate, the upper ends the fuel rods holds a lower tension or end plate, which the lower ends of the Fuel rods holds a plurality of spacers at intervals between the two end plates are arranged and serve the intervals or distances between adjacent fuel rods from the plurality of fuel rods ten, and includes a channel box in which the plurality of fuel rods are accommodated is. Here, the coolant is from the lower end portion of the lower Ab end plate flows into the fuel assembly, designed or guided such that it ascending towards the side of the fuel rods in the fuel assembly. The Fuel element is characterized in that it has a plurality of vertical Direction elongated flow restricting plates which are arranged such that they are in the lower end plate from a lower central portion of the same extend upward and along the circumferential direction with respect to the axial direction of the fuel assembly are bent. The fuel assembly also contains the flow path blocking plate, which at the upper end positions of the flow limiting Plates is provided such that the coolant moving up to the Flow path blocking cover or plate bounces so that it is achieved the coolant down toward the inner peripheral surface side of the dispersed lower end plate. There is also dirt or waste Particle capturing section is provided, which a plurality of itself in the vertical Direction extending grooves and on the inner peripheral surface or Circumferential surface of the lower end plate is provided.

As described in detail above, according to the present invention, the very advantageous effect can be achieved that prevents dirt or waste  Particles that flow together with the coolant flow into the fuel assembly can. This allows the intact and normal condition of the fuel element coatings or fuel rod coatings are reliably maintained.

The invention is described below using exemplary embodiments with reference to the drawings described in more detail.

Fig. 1 shows an overall view, partially in section, of a fuel of the present invention is illustrated element according to a first embodiment,

Fig. 2 is an enlarged schematic sectional view, in which the lower end plate shows a fuel assembly according to a second embodiment of the present invention is illustrated,

Fig. 3 shows a schematic, enlarged sectional view illustrating the lower end latte of a fuel assembly according to a third embodiment of the prior invention,

Fig. 4 is a schematic, enlarged sectional view in which the lower end plate shows a fuel assembly according to a fourth embodiment of the present invention is illustrated,

Fig. 5 shows a schematic, enlarged sectional view illustrating a lower end plate of a fuel assembly according to a fifth embodiment of the present invention,

Fig. 6 is a schematic enlarged sectional view showing the lower end plate shows a fuel assembly according to a sixth embodiment of the present invention is illustrated,

Fig. 7 is a schematic, enlarged sectional view in which the lower end plate shows a fuel assembly according to a seventh embodiment of the present invention is illustrated,

Fig. 8 is a schematic, enlarged sectional view in which a lower plate from the final shows a fuel assembly according to an eighth embodiment of the present invention is shown,

Fig. 9 is a schematic, enlarged sectional view in which the lower end plate shows a fuel assembly according to a ninth embodiment of the present invention is shown,

Fig. 10 is a schematic, enlarged sectional view in which the lower end plate shows a fuel assembly according to a tenth embodiment of the present invention is shown,

Fig. 11 shows a schematic, enlarged sectional view, in which the lower end plate of a fuel assembly according to an eleventh embodiment of the prior invention is illustrated,

Fig. 12 shows a schematic, enlarged sectional view of a lower plate-Ab circuit of a twelfth embodiment of the measure in accordance with the present invention, the fuel element is illustrated,

FIG. 13A is a lateral, enlarged section view, in a cylindrical body unit in a lower end plate according to a thirteenth example of execution of the present invention is shown,

FIG. 13B shows an enlarged perspective view shown partially in cross section, illustrating a portion of the cylindrical body unit of Fig. 13, in accordance with the viewing of one axial side of the cylindrical body unit,

Fig. 14 shows a schematic, enlarged sectional view in which the lower end plate of a fourteenth embodiment of the measure in accordance with the present invention, the fuel element is shown,

FIG. 15A is a graph showing the rate, the relationship between the drop separation which is obtained by using the conventional dropping means using the ver turned plate, and the waste separation rate illustrated, which is achieved when using the waste catching means according to the fourteenth embodiment,

FIG. 15B is a graph showing the loss, the ratio between a Druckver, which is caused when using the conventional, equipped with the twisted plate th waste catching means, and displays the pressure loss, caused catching means in use of the provided in the fourteenth embodiment, waste ,

Fig. 16 is a schematic, enlarged sectional view in which the lower end plate shows a fuel assembly according to a fifteenth embodiment of the present invention is illustrated,

Fig. 17 shows an enlarged, partially shown in cross-section perspective view of a portion of a cylindrical body unit according to a sixteenth embodiment, and as viewed from the axial direction of the cylindrical body unit,

Fig. 18 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a seventeenth embodiment of the present invention is illustrated,

FIG. 19A is a graph showing the rate, the relationship between the drop separation which is obtained when using the conventional, equipped with the twisted plate th waste catching means, and waste separation rate shows that achieved game when using the dropper according to the seventeenth Ausführungsbei,

FIG. 19B is a graph showing the relationship between the pressure loss which is caused when using the conventional, equipped with the twisted plate waste catching means, and the pressure loss caused when using the waste catching means according to the seventeenth embodiment,

Fig. 20 is a schematic, enlarged sectional view in which the lower end plate shows a fuel assembly according to an eighteenth embodiment of the present invention is illustrated,

Fig. 21 is a schematic, enlarged sectional view in which the lower end plate shows a fuel assembly according to a nineteenth embodiment of the present invention is illustrated,

Fig. 22 shows a schematic perspective view in which a waste particles to the falling-bringing guide body according to the nineteenth example of execution is shown in more detail,

Fig. 23 shows a schematic, enlarged sectional view showing a twentieth embodiment of a forming modification of the provided waste catching plate guide, for example in the nineteenth from is illustrated,

FIG. 24 is a schematic enlarged sectional view showing a modification of a waste plate provided in the nineteenth embodiment, showing a twentieth embodiment;

Fig. 25 shows a schematic, enlarged sectional view showing a twentieth embodiment of a forming modification of the provided waste catching plate guide, for example in the nineteenth from is illustrated,

Fig. 26 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a twenty-first Ausführungsbei game of the present invention is illustrated,

Fig. 27 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a twenty-second Ausführungsbei game of the present invention is illustrated,

Fig. 28 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a twenty-third Ausführungsbei game of the present invention is illustrated,

Fig. 29 overall view, partly in cross section showing a fuel assembly which is in accordance with a twenty-fourth embodiment of the present invention,

FIG. 30A is a graph showing the rate, the relationship between the drop separation which is obtained using the conventional, ver with the rotated plate designated waste catching means, and the decrease rate of separation is obtained when using the drop catcher device according to the twenty-fourth embodiment,

FIG. 30B shows a graph showing the loss, the ratio between the Druckver, which is caused when using the conventional, provided with the rotated plate drop means, and the pressure loss is caused game when using the waste device according to the twenty-fourth Ausführungsbei,

Fig. 31 is an overall view, partly in cross section showing a fuel assembly, which is a modification of the twenty-fourth embodiment of the present invention,

Fig. 32 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a twenty-fifth Ausführungsbei game of the present invention is illustrated,

Fig. 33 shows a sectional view cut along in Fig. Line XXXIII-XXXIII shown 32,

Fig. 34 shows a schematic enlarged sectional view showing a lower end plate of a fuel assembly according to a twenty-seventh execution example of the present invention is illustrated,

Fig. 35 shows a sectional view cut along a in Fig. Line XXXV-XXXV shown 34,

Fig. 36 is an overall view, partly in cross section showing a fuel assembly according to a twenty-seventh embodiment of the prior invention lie

Fig. 37 shows a sectional view cut along a direction shown in Fig. 36 line XXXVII-XXXVII,

Fig. 38 shows a schematic, enlarged sectional view in which a lower ex-circuit plate of a fuel assembly according to a twenty-eighth exporting approximately example of the present invention is shown,

FIG. 39A is a view seen in the direction which is illustrated in Fig. 38 having a structure shown at the line XXXIXa arrow

Fig. 39B is a view seen in the direction illustrated by an arrow indicated on the line XXXIXB in Fig. 38;

Fig. 40 shows a partially ver in cross section and partially schematically illustrated größerte view in which the lower end plate is illustrated a fuel assembly according to a twenty-ninth embodiment of the present invention,

Fig. 41 shows a sectional view cut along in Fig. Line XXXXI-XXXXI shown 40,

Fig. 42 is a sectional view that is taken along in Fig. Line XXXXII-XXXXII shown 40,

Fig. 43 is an enlarged perspective view showing a portion of a in Fig. Waste catching member shown 42,

Fig. 44 is an overall view, partially in cross section, illustrating a fuel assembly according to a thirtieth embodiment of the present OF INVENTION dung shows

Fig. 45 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a thirty-first embodiment of the present invention is shown,

Fig. 46 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a thirty-second Ausführungsbei game of the present invention is illustrated,

Fig. 47 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a thirty-third Ausführungsbei game of the present invention is illustrated,

Fig. 48 shows a schematic, enlarged sectional view are shown in the portions of the lower end plug in a fuel assembly according to a thirty-fourth embodiment of the present invention,

Fig. 49 shows a schematic, enlarged sectional view showing portions of the lower end plug in a fuel assembly according to a thirty-fifth imple mentation of the present invention is illustrated,

Fig. 50 shows an enlarged view in which a portion of a lower end plug shown in a fuel assembly according to a thirty-sixth embodiment of the present invention,

Fig. 51 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a thirty-seventh Ausführungsbei game of the present invention is shown,

Fig. 52 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a thirty-eighth Ausführungsbei game of the present invention is shown,

Fig. 53 shows a schematic, enlarged sectional view in which the lower end plate of a fuel assembly according to a thirty-ninth Ausführungsbei game of the present invention is shown,

FIG. 54A shows an enlarged, perspective view of a rib-like shape according to a fortieth embodiment of the present invention,

FIG. 54A and 54C show partial sectional views are illustrated taken along in FIG. 54A-lines XXXXXIVB XXXXXIVB or XXXXXIVC XXXXXIVC-cut,

Fig. 55 shows a longitudinal sectional view of a fuel assembly,

Fig. 56 shows a plan view of a network or matrix portion of the lower end plate of the fuel assembly shown in Fig. 55,

Fig. 57 is an enlarged sectional view showing a portion of the lower end plate in a conventional fuel assembly, and

Fig. 58 is an enlarged sectional view showing a portion of the lower end plate of a fuel assembly with a conventional waste trap attached to the lower end plate.

Exemplary embodiments of the present invention are explained below with reference to FIGS. 1 to 54. Here, parts and components that are the same as those in the conventional fuel assembly are provided with the same reference numerals also used in FIGS. 55 to 57.

In Fig. 1 a first embodiment of the present invention is shown. Fig. 1 shows an overall view, partially in cross-section, in which the structure of a fuel assembly illustrated in accordance with the present embodiment. This fuel assembly comprises a plurality of fuel rods 2, each of which stratification by a Be or cladding tube is formed, and at least one water rod 3, whereby the fuel rods 2 and a water rod are housed in a cylindrical channel box 1 3 the least. At the upper and lower ends of this focal element, an upper pull or end plate 4 and a lower pull or end plate 5 are attached. On the upper end plate 4 , the upper ends of the fuel rods 2 and the water rod 3 are fastened by upper end plugs 6 , whereas the lower ends of the fuel rods 2 and the at least one water rod 3 are fastened to the lower end plate 5 by means of lower end plugs 7 . Furthermore, a plurality of spacers or spacer grids 8 are attached to the water rod 3 at predetermined intervals in its axial direction. By this spacer 8 , the focal rods 5 are held, where they are in rows. Furthermore, the fuel rods 2 are prevented from bending by these spacers 8 .

In the above structure, according to the present embodiment in that portion, a coolant inlet hole 5 is in the a for the coolant inlet guide, the lower end plate 5 is opened in the center of the lower portion, a vertical cylindrical body 21 provided, which in vertical direction and is arranged coaxially in the lower end plate 5 . The cylindrical body 21 extends upward from a lower end portion of the lower end plate 5 to substantially the middle portion of the end plate 5 . The cylindrical body 21 has an upper end portion and a lower end portion, each of which is open.

In a lower portion of the inner region of this cylindrical body 21 , a spiral blade unit or blade arrangement or blade arrangement 22 is arranged, which serves to impart an upward vortex flow to the coolant "a". This spiral blade unit 22 has a central hub 23 , which is arranged along a vertical direction, for example the axial direction of the fuel assembly, and a plurality of blades 24 , which are provided at equal intervals around the central hub 23 . Each of the blades 23 has, for example, a substantially helical twisted shape. The outer edge portions of the respective blades 24 are connected to the inside surface of the cylindrical body 21 by welding or the like such that the cylindrical body 21 is positioned on the downstream side of the spiral blade unit 22 . Further, an inner surface of the lower portion of the lower end plate 5 extends in a wedge shape, its diameter gradually decreasing toward the lower end portion of the lower end plate 5 . In contrast, the outer surface of the cylindrical body 21 has substantially the same diameter as the smallest diameter portion of the inner surface of the lower end plate 5 . As a result, a dirt collecting portion 25 is formed on the outside of the lower portion of the cylindrical body 21 and on the inner wall surface of the lower end plate 5 , in which the dirt particles, which together with the coolant "a" in flow into the inner region of the lower end plate 5 , fall down and are consequently collected there.

In this construction, the refrigerant 'a' into the cylindrical body 21 flows through the refrigerant inlet hole 5 a of the region below the lower end plate 5 into it, as is illustrated by an arrow. In the lower portion of the cylindrical body 21 , the spiral blade unit 22 is provided, so that the coolant "a" that has flowed into the cylindrical body 21 is forcibly imparted a stirring component through the blades 24 of the spiral blade unit 22 and the coolant thus moves upward in the cylindrical body 21 with vortex-shaped movements.

Even if waste particles are mixed in the coolant "a", the centrifugal force caused by the swirling movement of the coolant "a" causes the dirt or waste particles to have a higher density than the coolant "a" , move toward the outer periphery in the cylindrical body 21 such that the waste particles move upward while swirling along the inner surface of the cylindrical body 21 . The waste particles moving upward along the inner surface of the cylinder reach and flow out of the upper end of the cylindrical body 21 so that the waste particles are pushed outward in the radial direction of the cylindrical body. Here, the speed of the upward movement of the coolant "a" outside the cylindrical body 21 is slow, so that the waste particles which have been pushed out of the cylindrical body 21 do not move upward, but fall outside the cylindrical body 21 and consequently, are collected in the waste collecting section 21 .

In this embodiment, therefore, the coolant that flows into the lower end plate 5 , a vortex-shaped flow is impressed by which the dirt or waste particles can be prevented from entering the fuel assembly, and thus the intact and normal condition of the Cladding tubes or the fuel rods and water rods are maintained. Since, in the present exemplary embodiment, the device for forcing a vortex-shaped flow of the coolant "a" is formed by the spiral blade unit 22 , which consists of the central hub 23 and, for example, three or more blades 24 , the swirling component or vortex movement component is the one Coolant "a" is impressed, reinforced, and thus the rate of separation of the waste particles from the coolant "a" can be improved, compared with the conventional structure shown in Fig. 58, in which a plate once twisted through single twisting of a plate is used. Therefore, the ability to trap waste particles can be improved. Furthermore, since the blade angle of the blades 24 can be made small in this structure of the spiral blade unit 22 compared to the conventional structure in which the twisted plate is used, the degree of blocking the flow path through which the coolant "a" flows, and the area of the body with which the coolant comes into contact can be reduced, so that it is possible to reduce the pressure loss. Further, in view of the structural design, due to the fact that the respective outer edge portions of the respective blades 24 are firmly connected to the inner surface of the cylindrical body 21 , the number of fixed portions between the spiral blade unit 22 and the cylindrical body 21 increased so that the structural strength of the assembly containing the spiral blade unit 22 and the cylindrical body 21 is improved. As a result, even after prolonged use of the fuel element and even in a case where a connection area should separate, the spiral blade unit 22 is still firmly connected to the cylindrical body 21 via the other connection portions. It is therefore possible to avoid the occurrence of structural adverse effects or functional adverse effects with a view to achieving the generation of eddy currents even when a connecting section is separated. For example, it is possible to prevent vibrations of the spiral blade unit 22 and the cylindrical body 21 from occurring due to the disconnection of the connecting portion.

A second embodiment of the present invention will now be explained with reference to FIG. 2. FIG. 2 shows a schematic, enlarged sectional view, in which the section of a fuel assembly according to the second exemplary embodiment containing the lower end plate is shown. As shown in FIG. 2, the basic structure of the vortex-flow enforcing device in this embodiment is substantially the same as that in the above-described first embodiment. However, a cylindrical body 31 provided around the spiral blade unit 22 is provided with a mesh structure containing a large number of wires assembled in the form of a mesh. The spiral leaf unit 22 is also arranged here in the lower end plate 5 of the fuel assembly according to the present exemplary embodiment. With this structure, the coolant "a" that has flowed into the cylindrical body 5 also flows through the mesh-shaped wall of the cylindrical body 2 to the outside of the cylindrical body 5 . As a result, the area or cross-sectional area of the flow path of the coolant is increased and, consequently, the pressure loss can also be reduced.

A third exemplary embodiment of the present invention is explained below with reference to FIG. 3. Fig. 3 shows a schematic, enlarged sectional view, in which the portion of the fuel assembly containing the lower end plate is shown according to the third embodiment. As shown in FIG. 3, a cylindrical body 41 is provided in this exemplary embodiment, which is produced with a mesh structure or lattice shape as in the second exemplary embodiment explained above. However, the peripheral wall 41 a of the upper portion of the cylindrical body 41 , which is positioned above the spiral blade device 22 , is provided with indentations, so that sawtooth-shaped portion, seen in longitudinal section, are formed. Each of the sawtooth-shaped portions extends toward the inner peripheral side and the outer peripheral side of the cylindrical body 41 . With this structure, since the cylindrical body 41 is provided with the mesh structure, the pressure loss when the coolant "a" flows in the cylindrical body 41 is reduced. Further, if the waste particles contained in the coolant "a" which has been given a vortex flow by the spiral blade unit 22 due to the centrifugal force are pressed against the inner surface of the tooth-shaped upper portion of the cylindrical body 41 , the Waste particles on the inner surfaces of the tooth-shaped peripheral wall 41 a of the cylindrical body 41 additionally caught. Therefore, the rate of trapping waste particles can be further increased in this embodiment.

A fourth embodiment of the invention will now be described with reference to FIG. 4. FIG. 4 shows an enlarged, schematic sectional view, in which the section of the fuel assembly containing the lower end plate according to the present exemplary embodiment is shown.

In addition to the design of the fuel assembly according to the first exemplary embodiment explained above, this exemplary embodiment contains an annular, dirt particle-catching hook element 49 , which serves to prevent a further increase in the dirt or waste particles present in the coolant “a”, and this coaxially of the cylindrical body 21 is arranged such that the hook member 46 protrudes from the inner peripheral surface side near the upper end portion of the cylindrical body 41 . This hook member 46 has a flat annular body portion 46 a which communicates with the inner circumferential surface of the cylindrical body 21 in contact, and a projecting portion 46 b which projects from the annular body portion 46 a down, so that it the inner Circumferential surface of the cylindrical body 21 is opposite. As a result, a corner space 47 formed in the form of a recess is formed between the flat annular body portion 46 a, the projecting portion 46 b and the inner peripheral surface of the cylindrical body opposite the projecting portion 46 b.

In addition to the waste particle removing zone described in the first embodiment explained above, in the present structure, the waste particles having a higher density than the coolant become when they are along the inner surface of the cylindrical body 21 move upward while being pressed against the inner peripheral surface of the cylindrical body 21 by the centrifugal force, caught in the recessed corner space 47 between the cylindrical body 21 and the hook member 46 . This allows the waste capture rate to be increased even further.

In Fig. 5 shows a fifth embodiment of the present invention is shown. Fig. 5 is a schematic enlarged sectional view, in which the lower end plate containing section of the fuel element is shown according to the present embodiment. In this embodiment, the cylindrical body 51 has a lower cylindrical portion 41 a, which is connected to the spiral blade unit 22 , a conical or wedge-shaped or tapering portion 51 b, which is coaxial from an upper end portion of the lower cylindrical portion 51 a out runs in such a way that it tapers upward, and a small-diameter portion 51 c, which runs coaxially and cylindrically from the upper end portion of the tapered portion 51 b, the diameter of the small-diameter portion 51 c is smaller than the diameter of the lower cylindrical portion 51 a. With this structure, in addition to the waste disposal function described in the above-described first embodiment, the waste particles that coexist with the coolant "a" in the form of a vortex flow along the inner surface of the cylindrical body 51 ( 51 a, 51 b, 51 c) move upward, perform their passage movement while being pressed closer to the inner peripheral wall of the small diameter portion 51 c of the cylindrical body 51 . When the particles of waste then begin their Falling movement, whereby they separate from the th upward dishes flow of the coolant "a", the waste particles on the upper area 52 of the waste collection portion can of having, due to the small diameter portion 51 are caught 25 widened b then the waste particles are sent to the waste collecting section 25 . The waste capture rate can thus be further improved.

A sixth embodiment of the present invention will be explained below with reference to FIG. 6. Fig. 6 shows a schematic, enlarged sectional view, in which the portion of the fuel assembly containing the lower end plate is illustrated according to the sixth embodiment. This exemplary embodiment has a fuel assembly as the first exemplary embodiment explained above, wherein a second cylinder 57 is additionally provided, which has an upper end section and a lower end section, which are each open. The second cylinder 57 has a diameter that is smaller than the diameter of the cylindrical body 21st The cylinder 57 is arranged coaxially at the upper end portion of the cylindrical body 21 and communicates therewith. Since the diameter of the second cylinder 57 is smaller than the diameter of the cylindrical body 21 , an annular gap 58 is formed between the upper end portion of the cylindrical body 21 and the lower outside of the second cylinder 57 .

With this structure, the waste particles moving upward along the inner surface of the cylindrical body 21 can be discharged through the annular gap 58 during their upward movement, so that the waste particles can quickly flow into the waste collecting section 25 . As a result, the degree of preventing waste particles from entering the fuel assembly can be further improved. On the upper side of the cylindrical body 21 , three or more cylindrical bodies can be stacked, which have a gradually decreasing diameter.

In Fig. 7, a seventh embodiment of the present invention is shown. Fig. 7 shows a schematic enlarged sectional view, in which the portion of the fuel assembly containing the lower end plate according to this embodiment is illustrated.

In this embodiment, a second cylindrical body 59 is provided above the cylindrical body 21 , which is present according to the first embodiment explained above, which has substantially the same diameter as the cylindrical body 21 and which is coaxial with the cylindrical body 21 and with a fixed vertical distance from it is arranged. This second cylindrical body 59 is held in such a way that the second cylindrical body 59 is connected to the inner surface or wall of the lower end plate 5 via a horizontal mounting wall 60 which extends from the inner surface of the lower end plate 5 in a horizontal manner extends up to the second cylindrical body 59 . With this structure, the coolant "a" and the waste particles contained in the coolant "a" and which move upward, moving in a vortex shape along the inner surface of the cylindrical body 21 due to the swirling motion component, toward the outer peripheral side by the distance provided between the upper end portion of the cylindrical body 21 and the second cylindrical body 29 . The coolant "a" and the waste particles, which are led to the outer peripheral side, are reliably prevented from moving upward by the horizontal mounting wall 60 , so that they flow into and are caught in the waste collecting portion 25 . The waste particles caught in the waste collecting section 25 fall down due to their high density, so that the waste particles are no longer absorbed in the main flow of the coolant "a". In this embodiment, the waste particles can therefore be caught and retained even more reliably.

In FIG. 8, an eighth embodiment of the present invention is shown. Fig. 8 shows a schematic, enlarged sectional view in which the lower end plate containing section of the fuel element is illustrated according to the present embodiment. In this embodiment, the internal structure of the lower end plate 5 , the structure of the cylindrical body 61 , the positional arrangement of the spiral blade unit, etc. of the fuel assembly are modified according to the above-described first embodiment. As shown in Fig. 8, the cylindrical body 61 according to this embodiment has a lower cylindrical portion 61 a, which has a substantially constant diameter, and an upper cylindrical portion 61 b, which is coaxial from the lower cylindrical portion 61 a runs to this. The upper cylindrical or tapered portion 61b is tapered such that the diameter of the upper cylindrical portion 61b gradually increases toward the upper portion of the upper cylindrical portion 61b , that is, toward the downstream side . At the portion of the peripheral wall of the lower cylindrical From section 61 b of the cylindrical body 61, which corresponds to the height position of the bottom of the waste collection section 25, a plurality of hole-like windows (window holes) 71 is formed with mutual spacings in the circumferential direction.

Furthermore, a hook-shaped protruding portion 72 is arranged above the cylindrical body 61 , which protrudes from the inside surface of the lower end plate 5 into the open upper end portion of the cylindrical body 61 , ie into the upper conical portion 61 a. This hook-shaped projecting portion 72 has a cylindrical, coaxial (in particular with the components 61 a and 61 b) shape that is bent such that the portion 72 covers the space above the peripheral edge of the upper end portion of the upper conical portion 61 b , so that this space has an annular or bead-like shape. The tip-side or outer end side of the hook-shaped protruding portion 72 gradually decreases in diameter toward the lower end of the portion 72 , which thus has a smaller diameter than the peripheral edge of the open upper end portion of the upper conical portion 61b . The front end portion of the hook-shaped projecting portion 72 is designed so that it can be inserted into the upper cylindrical or conical portion 61 b. Furthermore, the spiral blade unit (spiral blade unit) 22 is arranged on the upper conical section 61 b, so that the spiral blade unit 22 is arranged higher than the hole-like window 71 .

In this structure, the coolant "a" that contains the particles of waste flows, first in the lower cylindrical portion 61 a of the cylindrical body 61, after which the coolant is impressed by the spiral blade unit 22, a vortex-shaped flow and the coolant then along the inner surface of the upper conical section 61 b moved upward. That portion of the coolant flow containing the waste particles strikes the hook-shaped protruding portion 72 that protrudes from the inside surface of the lower end plate 5 , so that this portion of the coolant flow along the outer peripheral surface or outer wall of the hook-shaped protruding portion 72 is guided towards the outer peripheral side (outer wall) of the upper conical section 61 b, in which the waste particles fall into the waste collecting section 25 . Then the waste particles enter through the hole-like window 71 into the interior of the lower cylindrical portion 61 a and then migrate again up into the interior of the lower cylindrical portion 61 a, so that the vortex-shaped flow pattern is impressed through the spiral blade unit 22 . In this way, the waste particles consequently undergo a circular movement in which they migrate through the interior of the cylindrical body 61 and along the outside thereof. In this game Ausführungsbei is consequently a large amount of waste particles in the lower end plate 5 limited and captured, so that consequently the extent of the introduction of the waste particles in the fuel assembly can be improved or reduced accordingly.

A ninth exemplary embodiment of the present invention is shown in more detail with reference to FIG. 9. Fig. 9 shows a schematic, enlarged cross-sectional view, in which the portion of the fuel element containing the lower end plate is illustrated according to this embodiment. In this embodiment example, waste trap nets 73 are provided above or on the hole-like windows 71 in the lower cylindrical portion 61 a of the cylindrical portion 61 , which is arranged in the lower end plate 5 of the fuel assembly according to the eighth embodiment described above. In this embodiment, those waste particles that circulate in the case of the eighth embodiment in the lower end plate 5 can be caught by the nets 73 . As a result, the waste particles can be held in the waste collecting section 25 .

A tenth embodiment of the present invention will be explained below with reference to FIG. 10. Fig. 10 shows a schematic, enlarged sectional view, in which the d 92005 00070 552 001000280000000200012000285919189400040 0002019838790 00004 91886ie the lower end plate-containing portion of the fuel assembly according to the present embodiment is illustrated. In this embodiment, a cylindrical body 81 has a lower cylindrical portion 81 a to which the spiral blade unit 22 is attached, and an upper cylindrical portion 81 b that is coaxial with the lower cylindrical portion 81 a. On the peripheral wall portion of the upper cylindrical portion 81b , which is close to the open upper end portion of the upper portion 81b , a plurality of slits 84 are formed spirally or obliquely. The spiral or oblique orientation of these slots 84 coincides with the vortex direction or vortex flow direction of the coolant "a", which is set in vortex motion by the spiral blade unit 22 . Other elements of this embodiment are substantially the same as the corresponding elements in the first embodiment. According to this structure, the waste disposal function, which has already been illustrated and explained with reference to the first exemplary embodiment, can be achieved. When the waste particles are displaced by the spiral blade unit 22 in the vortical flow pattern and thus move upward as they b together with the coolant "a" along the inner surface of the upper cylindrical portion 81 moving in a vortex shape, the waste particles are in this case from the the upper cylindrical portion 81b of the cylindrical body 81 is discharged to the outside through the spiral slots 84 , the swirl direction or direction of which corresponds to the swirling direction or the direction of the waste particles. In this example, it is therefore possible to reduce the amount of penetration of the waste particles into the fuel assembly.

An eleventh exemplary embodiment of the present invention is explained in more detail below with reference to FIG. 11. Fig. 11 shows an enlarged longitudinal sectional view, in which the portion of the fuel assembly containing the lower end plate is illustrated according to the present embodiment. In this embodiment, instead of the slits 84 provided in the structure according to the tenth embodiment explained above, there are a plurality of round holes 85 formed so that they are arranged in a zigzag pattern on the peripheral wall portion of an upper cylindrical portion 81 b1 of a cylindrical body 81 A are positioned, which is close to the open upper end portion of the cylindrical body 81 A. In this structure, the waste Parti will angles in the same manner as in the above described tenth Ausführungsbei play a vortex-shaped flow path through the spiral blade unit 22 is impressed, and move the waste particles along the inner surface of the upper cylindrical portion 81 b1 upwardly, they perform a vortex-shaped movement together with the coolant "a". The waste particles are then discharged to the outside from the upper cylindrical portion 81 b1 of the cylindrical body 81 A through the round holes 85 which are positioned in a zigzag arrangement. Therefore, the degree of preventing the entry of waste particles into the fuel assembly can be improved.

In Fig. 12, a twelfth embodiment of the present invention is shown. Fig. 12 shows a schematic, enlarged sectional view, in which the lower end plate-containing portion of the fuel assembly according to this embodiment is illustrated. In this starting example, the fuel assembly is provided with a cylindrical body unit 91 which includes the cylindrical body (inner cylindrical body) 81 having the slits 84 shown in Fig. 10 and an outer cylindrical body 96 which is concentric with the inner cylindrical Body 81 is mounted in the lower end plate 5 and defines a fixed radial gap to the inner cylindrical body 81 . The upper end portion of the outer cylindrical body 96 extends toward the upper end portion of the inner cylindrical body 81 and is fixedly connected thereto. The lower end portion of the outer cylindrical body 96 is fixedly attached to the inner surface of the lower end plate 5 . As a result, the gap that exists between the inner cylindrical body 81 and the outer cylindrical body 96 forms a waste collecting section 25 a.

With this structure, in the same manner as in the tenth embodiment described above, a vortex-shaped movement is imparted to the waste particles by the spiral-shaped blade unit 22, and the waste particles which perform a vortex-shaped movement together with the coolant "a" move along the inner one Upper surface of the upper cylindrical portion 81 b upwards. The waste particles are then discharged from the upper cylindrical portion 81 b of the cylindrical body 81 through the spiral slots 84 , the direction of which coincide with the vortex-shaped direction of movement of the waste particles, so that they are collected in the waste collecting portion 25 a, which by the Gap is formed between the inner cylindrical body 81 and the outer cylindrical body 96 . In this embodiment, the cylindrical body unit 91 has a double cylinder which is formed by the inner cylindrical body 81 and the outer cylindrical body 96 . This can improve the structural strength of the inner and outer cylindrical bodies 81 and 96 , so that it is possible to improve the support strength of the spiral blade unit 22 , the resistance to the vibrations caused by the vortex flow, and the like.

A thirteenth exemplary embodiment is explained below with reference to FIGS. 13A and 13B. FIG. 13A shows an enlarged cross-sectional view in which the cylindrical body unit is illustrated, which is disposed in this embodiment in the lower end plate of the fuel assembly. FIG. 13B shows an enlarged perspective view, which is shown partly in section and which illustrates the cylindrical body unit according to FIG. 13A, when viewed from the axial side of the cylindrical body unit or viewed obliquely from above. This embodiment example is constructed such that in the same manner as in the twelfth embodiment in the vicinity of the upper end portion of the inner cylindrical body 81 which forms part of the cylindrical body unit 91 of the double cylinder type, a plurality of spiral or inclined or oblique extending slots 84 is formed along the direction which corresponds to the swirling direction of the coolant "a". Further, along the inclined edge portion on the lower side of each of the slits 84 in the inner surface of the inner cylindrical body 81, there is provided a guide plate 97 which is substantially in the shape of an L as viewed in cross section of the cylindrical unit 91 and which is for Guide the coolant "a" and the waste particles to each of the slots, ie to the respective slots 84 .

In this structure, the waste particles is impressed on a vortex-shaped movement through the spiral blade unit 22 and move the waste particles which perform together with the refrigerant 'a' a vortex-like motion, along the inner surface of the upper cylindrical portion 81 b upwards. In addition to the waste disposal function explained in the twelfth embodiment, the waste particles that have reached the position of the slots 84 are then guided by the guide plates 97 to the slots 84 so that they gently drish from the inside to the cylinders Body 81 are moved outwards. The capture of the waste particles can therefore be carried out with a higher efficiency.

With reference to FIGS. 14 and 15, a fourteenth embodiment of the invention is described in more detail below. Fig. 14 shows a schematic enlarged sectional view, in which the portion of the fuel element containing the lower end plate according to the present embodiment is illustrated. From this exemplary embodiment is designed such that the cylindrical body unit 81 A in the same way as in the fuel assembly according to the twelfth embodiment has a double cylinder structure which is formed by the inner cylindrical body 81 A and the outer cylindrical body 96 . In this embodiment Further, a plurality of round holes 85, which have the same diameter, the slots instead of 84 formed such that they the inner zylin-cylindrical body 81 is located A in a zigzag arrangement on the peripheral wall portion of the upper cylindrical portion 81 b1 , as is also the case with the eleventh embodiment. Furthermore, in this embodiment, a central hub 23 A of the spiral blade unit 22 is extended to the upstream side of the blades 24 compared with the hub in each of the above-described embodiments. With this structure, a swirling flow or movement is imparted to the waste particles by the spiral blade unit 22 in the same manner as in the twelfth embodiment, so that the waste particles move upward while moving along with the coolant "a" in a swirling motion the inner surface of the upper cylindrical portion 81 b1. The waste particles are then discharged from the upper cylindrical portion 81 b1 of the cylindrical body 81 A through the round holes 85 , which are seen in a zigzag arrangement before, so that they are collected in the waste collecting portion 25 a, which is through the gap between the inner cylindrical body 81 A and the outer cylindrical body 96 is defined.

FIG. 15A is a graphical representation of the relationship between the waste separation rate or waste particle removal rate achieved using the conventional waste trap shown in FIG. 58 and provided with the rotated plate and the waste separation rate or waste particle removal rate, respectively Use of the waste collection device according to the fourteenth embodiment is achieved. Fig. 15B is a graph showing the relationship between the pressure loss caused by using the conventional waste trap shown in Fig. 58 and provided with the rotated plate and the pressure loss caused by using the waste trap according to the fourteenth embodiment becomes. The characteristics shown in Figs. 15A and 15B have been obtained based on the results of experiments carried out by simulating the flow rate of the coolant used in an actual boiling water reactor, the shape of the waste particles, and the like. The graphs show the relationships regarding the waste separation rate and the pressure loss in the structure according to the present embodiment and the structure according to the conventional structure, respectively. In the conventional structure, a plate rotated by 90 ° is mounted in a cylinder, as shown in Fig. 58. Furthermore, in the upper section of the cylinder, a guide body for the falling waste, not shown, is arranged, which corresponds to the filter. In contrast to this, in the present exemplary embodiment, the spiral-shaped blade unit 22 , which has a structure with three blades or wings, is fitted in the inner cylindrical body 81 A, the central hub 23 A being extended in the direction of the upstream side of the blades 24 and the waste collection section 25 a is formed by the space between the inner cylindrical body 81 A and the outer cylindrical body 96 , which together form a double cylinder body. In addition to the unit decor with dark avoid imposing differences between the rotated plate and the spiral blade is thus to be noted that also the portion of the structure of the waste collector 25 a caused in this embodiment, influences play a role.

As shown in Fig. 15A, the waste separation rate in this embodiment is about 2.7 times that in the conventional structure. However, as shown in FIG. 15B, in this embodiment, the pressure loss ratio is also increased compared to that in the conventional structure. It is believed that this fact is due to the fact that the waste collection section 25 a is in the form of a gap between the two cylindrical bodies 81 A and 91 which is designed as a double cylinder in the body unit 91 A, the waste collection section 25 a having no coolant outlet openings and thus represents a blocking or blocking structure. However, it can be assumed that the waste collecting section 25 a, due to its blocking structure, ensures that the waste particles can never flow out together with the coolant "a", so that the waste collection rate is improved.

Further, in this embodiment, since the central hub 23 A is extended toward the upstream side of the blades 24 , there is no excessive mixing in the other part of the coolant "a" located in the middle portion of the inner cylindrical body 81 A moved in a vortex. Therefore, the waste rate can be further improved. Furthermore, it is possible to extend the central hub 23 A such that the height of the upper section of the central hub 23 A is arranged essentially at the same height as the lowermost inner peripheral surface or the lowermost edge of the lowermost round holes 85 .

A fifteenth exemplary embodiment of the present invention is explained in more detail below with reference to FIG. 16. Fig. 16 shows an enlarged sectional view, in which the lower end plate containing section of the fuel element is illustrated according to the present embodiment. This embodiment is constructed such that, in the same manner as in the construction according to the fourteenth embodiment of the fuel assembly, a plurality of round holes 85 A are formed so as to zigzag on the peripheral wall portion of an upper cylindrical portion 81 b2 of the inner one cylindrical body 81 B are positioned. However, the diameter of the round holes 85 A is not fixed. The diameters of those round holes which are positioned on the upper side, ie on the downstream side of the upper cylindrical section 81 b2, are in this case designed to be larger, whereas the diameters of those round holes which are on the lower side, ie on the upstream side of the cylindrical portion 81 b2 are arranged, are small. As a result, the diameter of the round holes 85 A varies. In this structure, a certain time period is required of large waste particles before these 81 A to reach the position of the peripheral wall of the inner cylindrical body due to its inertia, the position of the peripheral wall of the inner cylindrical body wohinge gen small waste particles 81 B simply and quickly reach . Since the distance over which the waste particles reach the cylindrical wall starting from the spiral blade unit 22 varies depending on the size of the waste particles, the diameters of the round holes are 85 A at these positions of the cylindrical peripheral wall of the inner cylindrical body 81 B, in which the respective waste particles reach this peripheral wall, depending on the respective sizes of the respective waste particles. As a result, the waste particles can be caught with a high degree of efficiency.

A sixteenth embodiment of the present invention will be explained below with reference to FIG. 17. Fig. 17 is an enlarged, perspective and partially sectioned view showing a section of a cylindrical body unit according to the sixteenth embodiment of the present invention, and as viewed from the axial direction of the cylindrical body unit, ie when viewed obliquely. This embodiment is constructed in such a manner that in the cylindrical body unit 91 C having a double cylinder structure according to the twelfth to fifteenth embodiments explained above, the upper connecting portion 98 through which the inner cylindrical body 81 C and the outer cylindrical body 96 A are connected to each other, is formed with a mesh-like or lattice-like shape. In Fig. 17, a case is shown where the slots 84 are provided. However, the same structure can also be used in a case where the round holes 85 are used.

With this structure, the waste particles are separated from the coolant "a" that has flowed from the inner cylindrical body 81 C into the waste collecting portion 25 a formed by the gap between the inner and outer cylindrical bodies 81 C and 96 A. The freed from the waste particles coolant "a" then flows through the existing at the upper end and a mesh-like structure Ver connecting section 98 to the outside. This smoothes the flow of the coolant "a", thereby improving the waste trapping rate. At the same time, the pressure loss can be reduced, which is due to the increase or increase in area of the flow path for the coolant "a".

A seventeenth embodiment of the present invention will be described below with reference to FIGS. 18, 19A and 19B. Fig. 18 shows a ver enlarged sectional view, in which the portion of the fuel assembly containing the lower end plate is illustrated according to the present embodiment. This embodiment has a cylindrical body unit 91 D which has a double cylinder structure as in the above-mentioned twelfth to fifteenth embodiments. Furthermore, the fuel assembly in the present embodiment is provided with a coolant flow path 99 formed between the lower end portion of the outer cylinder 96 B and the lower end plate 5 . This coolant flow path 9 can be formed, for example, by reducing the length by which the outer cylinder 96 B hangs down, so that a space is formed between the lower end of the outer cylinder 96 B and the lower end plate 5 . The coolant flow path 99 can also be formed, for example, by connecting the outer cylinder 96 B and the lower end plate 5 to each other and forming holes near the lower end of the outer cylinder 96 B.

With this structure, the coolant "a", which together with the waste particles flows through the round holes 85 (or the slots 84 ) into the waste collecting portion 25 a formed between the inner and outer cylindrical bodies 81 A and 96 B, flows along the Coolant flow path 99 to the outside of the outer cylindrical body 96 B. In this case, the flow rate and the flow rate of the coolant "a", which has flowed through the round holes 85 in the waste collecting section 25 a, in comparison with the flow rate and Flow rate of the coolant "a" flowing upward from the inner cylindrical body 81 A is low, so that the waste particles are collected in the waste collecting portion 25 a and only the coolant "a" without any waste particles from the outer cylindrical body 96 B flows outwards.

In this embodiment, not only the waste disposal function that is under Reference to the twelfth to fifteenth embodiments explained above has been achieved, but it also ensures that the pressure drops can be reduced because the flow path for the coolant is increased.

Figure 19A is a graphical representation of the relationship between the waste separation rate or waste excretion rate achieved using the conventional waste catcher shown in Figure 58 and rotated plate and the waste separation rate or waste disposal rate used the waste trapping device according to the seventeenth embodiment is achieved. Fig. 19B is a graph showing the relationship between the pressure loss caused by using the conventional rotary plate type waste trap shown in Fig. 58 and the pressure loss caused when the waste trap according to the seventeenth embodiment is used . The characteristic values shown in Figs. 19A and 19B were obtained in the same manner as those in the fourteenth embodiment on the basis of the results of experiments which simulated the flow rate of the coolant used in an actual boiling water reactor in the form of Waste particles and the like have been carried out. The graphs show the results of both the waste separation rate and the pressure loss with respect to the structure according to the present embodiment and the conventional structure. In the conventional structure, a plate rotated by 90 ° is mounted in a cylinder as shown in FIG. 58. Furthermore, a guide body (not shown), which serves to guide the falling waste and corresponds to the filter, is arranged in the upper section of the cylinder. In contrast to this, in the present exemplary embodiment, the spiral-shaped blade unit 22 , which has a structure with three blades or wings, is arranged in the inner cylindrical body 81 A, the central hub 23 A is extended in the direction of the upstream side of the blades 24 and it is the waste collection section 25 a formed by the space between the inner cylindrical body 81 A and the outer cylindrical body 96 B, which form a body of the double cylinder type. Further, the coolant flow path 99 is formed between the lower end portion of the outer cylinder 96 B and the lower end plate 5 .

As shown in FIG. 19A, the waste separation rate in the case of the present embodiment is about 2.4 times that in the conventional structure. In addition, the ratio between the pressure loss in the present embodiment is reduced to about half (1/2) compared to the pressure loss in the conventional structure, as shown in Fig. 19B. It is assumed that the reason for this is that the waste collection portion 25 a formed by the gap between the inner and the outer cylindrical body 81 A and 96 B of the doppelzylindrigen body unit, but that portion in the waste collection 25 a of the cooling medium flow path 99 is formed so that the coolant "a" can flow out smoothly from the outer cylinder 96 B along the coolant flow path 99 .

An eighteenth exemplary embodiment of the present invention is explained in more detail below with reference to FIG. 20. Fig. 20 shows a schematic enlarged sectional view, in which the portion of the fuel element containing the lower end plate according to the present embodiment is illustrated. This exemplary embodiment is constructed in such a way that a guiding body 100, which is falling down, is attached to the cylindrical body 21 of the fuel element according to the first, fifth, tenth and eleventh exemplary embodiments explained above. In Fig. 20, a structure is shown, which is mainly due to the design according to the first embodiment. However, the structure in the present exemplary embodiment is such that it can also be based mainly on the design according to the fifth, tenth or eleventh exemplary embodiment, the guide body 100 guiding the falling waste also being attached in this case.

In this embodiment, the falling waste guide body 100 is formed substantially in a crown shape which is open at the center thereof and is formed to have both the inner and outer peripheries of the upper end edge of the cylindrical body 21 and surrounds its upper side. The waste guide body 100 is made with a predetermined gap around the upper portion of the cylindrical body 21 by means of a clip or the like (not shown). This guide body 100 consequently consists of a flat ring portion 100 a, which is arranged above the upper end edge of the cylindrical body 21 , and two provided as a pair of inner and outer cylindrical, depending portions 100 b and 100 c, by the inner and outer peripheral edge of the ring section 100 a hang down or are guided downwards such that they run essentially parallel to the inner and the outer peripheral surface of the upper end edge of the cylindrical body 21 . By doing so, the flow direction of the rising coolant flow "a" flowing upward along the inner peripheral surface of the cylindrical body 21 is reversed into a flow flowing downward on the outer peripheral surface of the cylindrical body 21 .

According to the present structure, the waste particles that move upward in a vortex shape along with the coolant "a" along the inner peripheral surface of the cylindrical body 21 are guided to migrate to the outer peripheral wall of the cylindrical body 21 and downward, which by the section of the cylindrical body 21 attached to the upper forehead guide body 100 is effected. The waste particles are thus collected in the waste collecting section 25 .

A nineteenth embodiment of the present invention will be described below with reference to FIGS. 21 and 22. This exemplary embodiment represents a modification of the guide body 100 which guides the falling waste and is provided in the eighteenth exemplary embodiment. FIG. 21 shows a schematic sectional view of the structure of the guide body 100 , while FIG. 22 shows a schematic, enlarged perspective view, which illustrates the internal structure of the falling waste guide body 100 in more detail.

This embodiment is designed so that, as in the Fig. 21 and 22, there is provided a plurality of waste receiving plates 101 in the downward flow path c through the gap between the inner peripheral surface of the outer cylindrical depending portion 100 of the crown-shaped guide body 100 and the outer peripheral wall of the upper end portion of the cylindrical body 21 is defined. The waste collecting plates 101 here consist of a large number of, for example, tongue-shaped plates. The waste receiving plates 101 are located on the inner peripheral surface of the outer cylindrical hanging portion 100c and the outer peripheral surface of the cylindrical body 21 c of the inner peripheral surface of the outer cylindrical drooping portion 100 opposite, mounted in a projecting manner and in such a way that the Waste catcher plates 101 are each arranged in a mutual zigzag arrangement or offset from one another. Furthermore, the surfaces of the waste trap plates 101 are oriented to be perpendicular to the downward flow path.

In the conventional structure of the fuel assembly, in a case where the waste particles that have migrated upward along the inner peripheral surface of the cylindrical body 21 can pass through the guide body 100 to the outer peripheral portion of the cylindrical body 21 and accumulate in the waste collecting portion , these waste particles are again whirled up from the downward flow path section when, for example, the swirling component caused by the spiral blade unit 22 is large or when the density of the waste particles is small. In this case, the waste particles can flow out together with the main flow of the coolant "a".

In the design according to the present exemplary embodiment, however, this waste flow of the waste particles, which would be whirled up by the downward flow path, can be prevented by the waste collecting plates 101 . As a result, the waste rate can be improved.

Referring to FIGS. 23, 24 and 25 from a twentieth is subsequently exemplary implementation of the invention described in more detail. This embodiment relates to a modification of the waste collecting plates 101 provided in the nineteenth embodiment explained above. In FIGS. 23, 24 and 25 decor with dark tung moderately various modifications are illustrated respectively. In the modified embodiment shown in Fig. 23, the garbage catch plates 101 A, which protrude from the guide body 100 carrying the falling garbage and the cylindrical body 21 , are inclined upward, and are gradually higher and higher toward their tip-side and free end portions, respectively lie higher, ie run diagonally upwards.

In the modified embodiment shown in FIG. 24, each of the garbage plates 101 B is substantially L-shaped. Each of the garbage plates 101 B has a body portion that is substantially horizontal, with a tip end portion of the body portion bent upward so that each of the garbage plates 101 B is formed like a hook. In the modification shown in Fig. 25, each of the garbage plates 101 C is bent such that each of the garbage plates 101 C is in the shape of a semicircular arc. The arcuate inner surface of each of the garbage plates 101 C faces the guide body 100 guiding the falling garbage.

In the configurations of the modified embodiments explained above, ensure good waste collection.

A twenty-first embodiment of the present invention will be explained below with reference to FIG. 26. Fig. 26 shows a schematic enlarged sectional view, in which the portion of the fuel assembly according to the present embodiment containing the lower end plate is illustrated. In this embodiment, in addition to the configuration of the fuel assembly according to the seventeenth through twentieth embodiments explained above, a plurality of garbage traps or garbage ribs 102 are attached around the cylindrical body 21 . Overall, the garbage trap ribs 102 are essentially frog-shaped, each of the garbage trap ribs being substantially needle-shaped. The waste trapping ribs 102 are arranged in the vicinity of the outlet of the guide body 100 guiding the falling waste in the waste collecting section 25 .

With this configuration, the waste trapping function can be achieved, which is already in Ver Binding with the seventeenth to twentieth embodiment explained above has been described.

In the conventional design of the fuel assembly, the waste particles can be whirled up again and transported again along with the main flow path if, for example, the swirling component caused by the spiral blade unit 22 is large or if the density of the waste particles is low. However, in the structure according to the present embodiment, the waste particles can be held by the waste collecting ribs 102 without moving upward, so that the waste catching rate can be improved.

A twenty-second embodiment of the present invention will be described below with reference to FIG. 27. Fig. 27 is a schematic enlarged sectional view, in which the lower end plate containing section of the fuel element is illustrated according to the present embodiment. In this embodiment, in addition to the configuration of the fuel assembly according to the seventeenth through twentieth embodiments explained above, a plurality of annular, irregular portions 103 extending along the inner peripheral surface (peripheral wall) of the lower end plate 5 are in the vertical direction of the lower end plate 5 in a row.

The irregular sections 103 consist of concave ribs 103 a, which are arranged at regular intervals along the vertical direction, that is to say one another in the vertical direction.

With this structure, in addition to the waste trapping function described in the seventeenth through twentieth embodiments described above, it is achieved that in a case where the waste particles are again swirled out of the waste collection section 25 , e.g. B. can be caused by the spiral blade unit 22 swirling component or what can occur at low density of the waste particles, the swirled waste particles are captured by the concave grooves 103 a of the irregular portions 103 , which are provided on the inner peripheral surface of the lower end plate 5 . This can improve the waste capture rate.

A twenty-third embodiment of the present invention will be described below with reference to FIG. 28. Fig. 28 shows a schematic enlarged sectional view, in which the portion of the fuel element containing the lower end plate according to the present embodiment is illustrated. In this embodiment, each of the concave grooves 103b of the irregular portions 103 provided in the inner peripheral wall of the lower end plate 5 according to the twenty-second embodiment is provided with an inner peripheral edge portion and an outer peripheral edge portion. The width of the inner peripheral edge section is narrowed compared to the width of the outer peripheral edge section, ie smaller. With this structure, the trapping of the waste particles that could be whirled up as described in the twenty-second embodiment explained above can be effected with greater reliability, thereby further improving the waste trapping efficiency.

A twenty-fourth embodiment of the present invention will be explained below with reference to FIGS. 29, 30A, 30B and 31. Fig. 29 is an overall view of the fuel assembly, shown partly in cross-section according to this embodiment.

In this embodiment, the outer diameter "d" leading the falling waste and provided in the lower end plate 5 guide body 100 A so that it is smaller than the inner diameter "D" of the coolant inlet hole 5 a at the lower end portion of the lower end plate 5 . Accordingly, also the cylindrical body 21 A is formed with a smaller diameter than the coolant inlet laßloch 5 a of the lower end plate 5, so that the cylindrical body b 21 A to the coolant inlet hole 5a of the lower end plate 5 by means of an annular mounting member 5 detachably attached are can. Furthermore, the central hub 23 A of the spiral blade unit 22 is extended to the downstream side of the blades 24 , as is also the case in the fourteenth embodiment.

With this structure, the guiding body 100 A leading to the falling waste can be produced independently of the lower end plate 5 , and assembly of the cylindrical body 21 A including the guiding body 100 A on the lower end plate 5 is facilitated. As a result, the manufacturing costs in the manufacture of the fuel assembly are reduced. Furthermore, it is easy to replace the cylindrical body 21 A and the guide body 100 A guiding the falling waste, thereby facilitating maintenance.

In FIGS. 30A and 30B, the conditions for the waste trap rate (Fig. 30A) and the pressure loss (Fig. 30B) shown in relation to the conventional design and lying before embodiment. The graphs shown are based on data obtained as the results of experiments performed by simulating the flow rate of the coolant used in an actual boiling water reactor, the shape of the waste particles, and the like, as in the same manner in FIGS is the result of the case 15 and 19 shown in FIGS.. The conditions associated with the twisted plate, the spiral blade unit, and the like are the same as those already set forth with reference to FIGS. 15 and 19.

As shown in Fig. 30A, the waste separation rate in the present embodiment is increased to about 4.5 times compared to the waste separation rate in the conventional structure. Further 30B is seen from FIG. That the pressure loss ratio to approximately the 4/5-fold (four-fifths) as that in the conventional structure is decreased.

In Fig. 31 is a partial sectional view partially shown of a fuel assembly is Darge, which represents a modification of the twenty-fourth embodiment.

31 is as shown in FIG., 21 B, which has the structure shown in Fig. 29, the round holes 85 are formed according to the eleventh embodiment described above, in the cylindrical body.

In this structure, the cylindrical body 21B, which is provided with the round holes 85 may also be formed independently of the lower end plate 5, so that a simple producibility, a reduction in the production cost, simplification can be achieved exchanges etc.

A twenty-fifth embodiment of the present invention will be described below with reference to FIGS. 32 and 33. In this exemplary embodiment, in contrast to the respective exemplary embodiments explained above, the spiral blade unit 112 , which has essentially the same structure as the spiral blade unit 22 , is mounted directly on the lower firing plate 5 without using a cylindrical body.

Fig. 32 shows a schematic enlarged sectional view, in which the portion of the fuel assembly containing the lower end plate according to the present exemplary embodiment is illustrated. FIG. 33 shows a sectional view cut along the line XXXIII-XXXIII shown in FIG. 32.

In this embodiment, as can be seen from FIGS. 32 and 33, the spiral blade unit 112 , the diameter of which is larger than the diameter of the spiral-shaped blade unit in the first embodiment, directly by welding to the coolant inlet hole 5 a of the lower end plate 5th appropriate. Further, a plurality of hook-shaped waste catcher plates 114 are attached to that upper portion of the inner surface of the lower end plate 5 , which is positioned above the spiral sheet unit 112 .

Each of the hook-shaped garbage plates 114 protrudes in a direction opposite to the vortex-shaped flow caused by the spiral blade unit 112 . In this case, each waste trap plate 114 essentially has the shape of an L, as seen in the cross section of the fuel assembly. With this construction, the coolant "a" containing the waste particles, which has flowed in from the lower end of the lower end plate 5 , is also subjected to a swirling component by the spiral blade 112 , thereby causing a swirling flow, as in the same manner is also the case with the exemplary embodiments explained above.

In this embodiment, the coolant "a" is pressed against the inner surface of the lower end plate 5 , where the waste particles can be trapped by the hook-shaped waste catch plates 114 , which are arranged on the inner surface of the lower end plate 5 so that they oppose the vortex-shaped Stand current. Consequently, the waste catching function can also be achieved in this embodiment. In particular, in the present exemplary embodiment, the number of parts to be used can be reduced due to the omission of the cylindrical body, which leads to a simplification in terms of design.

A twenty-sixth embodiment of the present invention will be described below with reference to FIGS. 34 and 35. This embodiment represents a modification of the twenty-fifth embodiment. FIG. 34 shows a schematic enlarged sectional view, in which the portion of the fuel assembly according to the present embodiment containing the lower end plate is illustrated. FIG. 35 shows a schematic sectional view taken along the line XXXV-XXXV shown in FIG. 34.

In this embodiment, hook-shaped waste catching plates 114 A are arranged on the inner surface of the lower end plate 5 and each provided with a mesh-like or lattice-like structure. Each of the hook-shaped waste collecting plates 114 A consists of a frame section 114 a, which has the shape of an L, and a mesh section 114 b, which is attached to the outer surface of the L-shaped frame section 114 a.

In this structure, the coolant "a" is pressed against the inner surface of the lower end plate 5 due to the spiral blade unit 112 and passes through the mesh portions 114 b of the hook-shaped drop-catching plates 114 therethrough. The waste particles are each captured in the network sections 114 b of the waste collecting plates 114 . In this embodiment, the waste particles that have been through the network sections 114 b once captured will be pressed by the coolant "a" to the network portions 114 b, so that the waste particles catch plates hardly of the hook-shaped drop freely come 114 and pass into the flow. This makes it possible to improve the waste trapping ability.

A twenty-seventh embodiment of the present invention will be described below with reference to FIGS. 36 and 37. Fig. 36 is an overall view, partially in section showing the fuel assembly according to the present the embodiment. FIG. 37 is a sectional view cut along the line XXXVI-XXXVI shown in FIG. 36.

In this embodiment, as can be seen from FIGS. 36 and 37, the structure of the spiral blade unit is designed differently than the configurations of the spiral blade unit according to the first to twenty-sixth embodiments described above.

In the present embodiment, a spiral blade unit 117 is attached to the lower end of the lower end plate 5 A of the fuel element instead of using a conventional assembly guide such as the assembly guide 1 a shown in FIG. 1. The spiral blade unit 117 is provided with a plurality of arcuate blades or blades 125 that face the lower side of the fuel assembly or downward, each of which has a generally spirally twisted (twisted) shape, and a central one Provide hub 116 projecting upward from the central portion of blades 115 . This spiral blade unit 117 also has the function of serving as an assembly guide which is used to attach the fuel assembly to the boiling water reactor. In the lower end plate 5 A there are also provided a cylindrical body 21 A and a guide (guide body) 100 A guiding the falling waste, which are similar to the components shown in FIG. 29.

In this structure, the distance can be made longer 117 at the downstream located side of the spiral blade unit so that it becomes easier for the waste particles to flow 21 A along the inner peripheral surface of the cylindrical body. Therefore, the waste particles can flow to the outside of the cylindrical body 21 A more easily, thereby improving the waste trapping rate. Furthermore, the spiral blade device 117 also serves as the assembly guide, so that the number of parts to be used can be reduced and a structurally compact structure etc. can be achieved.

Further, in this embodiment, since the central hub 116 of the spiral blade device 117 is elongated as far as the downstream side or even further than the downstream end of the blades 115 , it is possible to have a turbulent in the central portion downstream of the spiral blade device 117 To prevent flow, and to increase the swirling force acting on the coolant "a". This can improve the waste capture rate.

A twenty-eighth embodiment of the present invention will be described below with reference to Figs. 38, 39A and 39B. Fig. 38 is a schematic enlarged sectional view showing the portion of the fuel assembly containing the lower end plate according to the present embodiment. FIGS. 39A and 39B each show views viewed in the directions indicated by the arrows on the lines XXXIXA and XXXIXB shown in FIG. 38. As can be seen from these drawings, is in this embodiment example, instead of the spiral blade unit 22 or 117 , which is used in the above-described embodiments, a cylindrical member 128 at the position of the coolant inlet hole 5 a of the lower end plate 5 is arranged. The cylindrical element 128 has a plurality of spiral flow paths 129 (for example three spiral flow paths 129 a, 129 b and 129 c). This cylindrical member 128 is mounted coaxially with the end plate 5 , the axis of the cylindrical member 128 being elongated in the vertical direction. The respective spiral flow paths 129 a, 129 b and 129 c are, as can be seen from FIGS. 39A and 39B, open on the upper and lower end faces of the cylindrical element 128 , so that they have mutually independent flow paths in the cylindrical element 128 form twisted or twisted embodiment. Furthermore, concave grooves 130 are formed in those sections of the spiral flow paths 129 a, 129 b and 129 c, which are acted upon by the centrifugal forces, which are perpendicular to the flow direction of the coolant "a". In this embodiment, a waste collecting portion 135 is further defined between the outer peripheral side of the cylindrical member 128 and the inner surface of the lower end plate 5 . With this structure, the coolant "a" flows into the plurality of spiral flow paths 129 a, 129 b and 129 c via the lower end surface of the cylindrical member 128 and is put into a vortex-shaped flow by the spiral flow paths 129 a, 129 b and 129 c so that it flows out of the upper end face or end face of the cylindrical member 128 into the inside of the lower end plate 5 . In this case, the waste particles are caught in the respective spiral flow paths 129 a, 129 b and 129 c in the respective concave grooves 50 , to which the centrifugal force acts. This prevents the waste particles from entering the fuel assembly.

Further, since those waste particles that have not been caught in the cylindrical member 128 are also expelled from the cylindrical member 128 in a state of being subject to the vortex flow, the waste particles flow toward the outer peripheral side of the cylindrical member 128 due to the centrifugal force so that they are collected by the waste collecting section 135 . In the present exemplary embodiment, therefore, the coolant "a" and the waste particles which are present in the coolant "a" are efficiently captured, in the same way as is also the case in the exemplary embodiments explained above.

A twenty-ninth embodiment of the present invention will be described below with reference to FIGS. 40 to 43. Fig. 40 shows an enlarged view, partly in section and partly schematically, illustrating the portion of a fuel assembly containing the lower end plate according to the present embodiment. FIG. 41 shows a sectional view cut along the line XXXXI-XXXXI shown in FIG. 40. Fig. 42 shows a sectional view cut along the line XXXXII-XXXXII shown in Fig. 40. Fig. 43 is an enlarged perspective view showing a section of a drop-catching element shown in Fig. 42.

As can be seen from these drawings, the structure of the lower end plate and the structure of the swirling flow generating unit in this embodiment are different from those in the above-described embodiments. In the present embodiment, the coolant inlet laßloch 140 a of the bottom closure plate 140, for example, a small diameter compared to the diameter of the refrigerant inlet hole 5 a in the above embodiments, and it is arranged coaxially in the coolant inlet hole 140a an opening or nozzle 141 . This causes the coolant "a" to move upward at high speed. Above this Mün opening or nozzle 141 , an annular base stand 142 is provided coaxially. On this base stand 142 , a plurality of vertically extending flow restriction plates or flow guide plates 143 are close together around the center line of the orifice 141 and the base stand 142 .

These flow restricting plates 143 are essentially bent in the shape of a V in the lateral cross section, as can be seen from FIG. 41. Furthermore, each of the flow restriction plates 143 may instead be bent into a substantially circular arc. The flow restricting plates 143 are bent with a uniform angle of curvature so that they form, so to speak, fixed blades or blades of an impeller.

Accordingly, in a case where the coolant "a" flows in the radial direction from the position of the center line of the nozzle 141 , the coolant flow is restricted to flow along the bending angle of the V-shaped shape, so that it creates a vortex flow. An umbrella-shaped flow path blocking cover 144 is attached to the tip and top ends of the flow restriction plates 143 and is positioned to be positioned substantially in the central portion of the lower end plate 140 . The lower surface of this flow path blocking cover 144 is bent from the central portion toward the peripheral edge in a dome shape so that the coolant "a" that has moved upward from the nozzle 141 now moves to the lower one surface of this the flow path blocking occurs cover 144, so that it becomes a gentle flow, which is distributed disper gierend toward the outer periphery, that is, toward the inner surface side of the lower end plate 140th Thus, when the coolant "a" becomes a distributed flow, a plurality of flow restricting plates 143 impart a vortex-shaped flow direction to the coolant "a". Arranged on the inner surface of the lower end plate 140 on the inner surface of the lower end plate 140 is a cup-shaped waste catcher 146 which has a plurality of concave grooves 147 which extend in the vertical direction, as shown in Figs. 42 and 43 . The garbage catcher 146 extends from the lower side or the lower end of the inner surface of the lower end plate 140 to the upper end thereof, as can be seen from FIG. 40. With this structure, the coolant "a" is introduced through the hole of the opening 141 into the middle portion of the lower end plate 140 , being given an increasing flow direction. Subsequently, the flow direction of the coolant "a" is changed because it strikes the cover 144 blocking the flow path. When the impinging coolant "a" flows out in the form of a downward-pointing radial flow, the flowing coolant "a" is impressed with a vortex-shaped flow pattern through the flow restriction plates 143 . Subsequently, the coolant "a" flows through the concave groove 147 of the waste trapping member 146 arranged on the inner surface of the lower end plate 140 and is thus directed to the fuel assembly. In this case, large particles of the waste particles contained in the coolant "a" are caught by the flow restricting plates 143 which are close to the opening 141 and held in the central portion of the lower end plate 140 . Further, small-sized waste particles of the waste particle flow flow out through the flow restricting plates 143 and down to the outer peripheral side, and the flow rate of the small-sized waste particles subsequently decreases. As a result, the small-sized waste particles are moved from the flowing state to the falling state. The small-sized waste particles are then separated from the swirling coolant "a" and captured in the recessed grooves 147 of the waste collecting element 146 . As explained above, in the present embodiment, the capture of the waste particles can be carried out efficiently.

Furthermore, in this embodiment, the orifice 141 is provided to form a throttle device for throttling the inflowing coolant "a", so that in a case where the flow rate increases, the resistance value of the flow path is reduced. This makes it possible to improve the stability of the flow rate of the cooling medium that is directed to the fuel assembly.

A thirtieth embodiment of the present invention is described below with reference to FIG. 44. Fig. 44 shows an overall view, partly in section, illustrating the thirtieth embodiment of the fuel assembly according to the invention. This embodiment is designed such that, instead of the cylindrical body and the spiral blade unit, which are provided in the above-described embodiments as the vortex-forcing member, there is provided a flat, waste particle-removing plate 158 in which a plurality of them are disposed through holes 157 is formed, each having a small diameter. This waste particle removing plate 158 is mounted in the lower end plate 5 so as to be inclined with respect to the main flow direction (vertical direction) of the coolant "a", to thereby prevent the passage of the waste particles. Further, a protruding wall 160 protruding from the inner surface portion of the lower end plate 5 toward the waste particle removing plate 158 is provided at a position below the upper end portion of the waste particle removing plate 158 , that is, a position below an upper portion 159 , which is formed by the lower, inclined surface of the plate 158 and the inner surface of the lower end plate 5 . The gap formed between the inner surface of the protruding wall 160 , which is opposite to the inner surface of the lower end plate 5 , and the inner upper surface of the lower end plate 5 , constitutes a waste collecting portion 161 which serves to collect the waste particles from which remove the waste particles or the blocking plate 158 fall down.

In this structure, the coolant "a" flows from the bottom into the lower end plate 5 and passes through the small holes 157 which are provided in the plate 158 removing the waste particles. Furthermore, the coolant "a", which passes through the small holes 157 , passes through the network section 9 and flows into the channel box 1 . As a result, scrap metal elements or metallic waste elements such as metallic wires, etc., which have entered the system when, for example, engineering or construction work and the like have been carried out, are introduced into the lower end plate 5 together with the coolant flow "a". However, the metallic waste elements through which the waste particles eliminated plate 158 which is provided in the lower end plate 5 is trapped and up to the upper portion 159, the particulate eliminated by the inclined surface of the drop plate 158 and the inner surface of the lower end plate 5 is formed, transported by the fluid force or flow force exerted by the coolant "a".

Below the upper portion 159 of the inclined surface, the waste collecting portion 161 is provided so that a stagnant portion of the coolant flow "a" is formed. Due to this fact, for the metallic waste elements that have been transported to the upper section 159 , the effective force caused by the flow of the coolant "a" is reduced. As a result, the waste particles such as the metallic waste elements fall down and accumulate in the waste collecting section 161 .

Depending on the operating conditions of the boiling water reactor, the flow rate of the coolant "a" may become high and the small metallic waste particles may not fall down from the upper portion 159 of the inclined surface of the waste particle removing plate 158 in some cases. Even in the case of such metallic waste particles, however, they are accumulated in the waste collecting section 161 when the boiling water reactor is brought back into an operating state with a low output and consequently the flow rate of the coolant is reduced, or when the coolant flow is stopped at the time of a periodic inspection. In this embodiment, therefore, it is possible to prevent the waste particles from mixing into the fuel assembly, so that it is possible to keep the fuel rods in the correct and normal condition, as is the case with the above-described embodiments .

Referring to Fig. 45, a thirty-first embodiment of the present invention will be described below. Fig. 45 shows a schematic enlarged sectional view, in which the portion of the fuel element according to the present exemplary embodiment containing the lower end plate is illustrated. In this exemplary embodiment, instead of the waste particle-removing plate 158 of the fuel assembly, which is present in the thirtieth exemplary embodiment explained above, a waste-removing plate 162 is used, which, for example in longitudinal section, essentially has the shape of a V and in the lower end plate 5 is arranged. The waste particle removing plate 162 has a central portion positioned along the center line of the lower end plate 5 and one or two inclined portions which extend upward from the central position of the waste particle removing plate 162 toward the inner one Upper surface of the lower end plate 5 extends, wherein he or she runs inclined with respect to the center line of the lower end plate 5 . Accordingly, the lower inclined surfaces of the inclined portion of the waste particle removing plate 162 are formed such that the central portion of the lower inclined surfaces lies on the central axis of the fuel assembly, and that the projecting wall 160 A is substantially an annular shape as viewed in cross section transversely to the central axis, so that the waste collecting portion 161 A is arranged around the inner surface of the lower end plate 5 . The other structural sections are identical to those in the thirtieth embodiment. In this structure, the length of the inclined surfaces of the particles of waste-removing plate 162, ie, that distance through which the waste particles that have been captured by the waste particulate removing plate 162, 161 A are moved for collecting the waste particles in the waste collection portion, shortened and the waste collection rate can actually be improved.

Referring to FIG. 46, a thirty-second embodiment of the present invention will be described below. Fig. 46 is a schematic enlarged sectional view, in which the lower end plate containing section of the fuel element is illustrated according to the present embodiment. In this embodiment, instead of the provided at the thirty-first embodiment, the waste particulate removing plate having a lower surface (waste particles removed surface) 169 a of the fuel elements supported network section 169 formed such that, for example, they have substantially the shape of a V in the longitudinal section. Further, the flow holes 11 are designed to serve as the holes 157 of the thirty-first embodiment through which the coolant "a" passes. The waste particles removed surface 169 a has a central portion which is positioned along the center line of the lower end plate 5, and an inclined portion extending from the central position of the falling particulate removing surface 169 a upward in the direction to the inner surface of the lower end plate 5 , wherein it extends inclined with respect to the center line of the end plate 5 . Thus, the same effects as those in the thirty-first exemplary example can be achieved, the lower inclined surfaces of the inclined portion of the waste particulate removing surface 169 a so formed that the central portion of the lower inclined surfaces axis at the center of the fuel assembly is positioned, and that the protruding wall 160 A is substantially in the form of a ring when viewed in cross section perpendicular to the central axis, so that the waste collecting portion 161 A is arranged around the inner surface of the lower end plate 5 .

In this embodiment, the angle formed by the inclined surface is smaller than that in the thirty-first embodiment, but still the metallic waste particles are reliable, if only step by step, up to the upper points 159 A of the inclined surfaces due to the vibrations trans ported, which are due to the flow of the coolant. As a result, the same waste trapping effect as in the thirty-first embodiment can be achieved, and also a structural simplification can be realized due to the reduction in the number of parts to be used.

Referring to FIG. 47, a thirty-third Ausführungsbei is hereinafter game of the present invention will be described in more detail. Fig. 47 shows a schematic, enlarged sectional view in which the lower end plate containing portion of the fuel assembly shown in this embodiment. In the present embodiment, the fuel assembly has a protruding wall 160 B for forming a waste collecting portion 161 B in the lower end plate 5 , the protruding wall 160 B being different from that in the thirty-second embodiment explained above. The protruding wall 160 B is namely, seen in longitudinal section, essentially in the form of a leaf or blade profile. Since the projecting wall 160 B in this construction is configured in its longitudinal section essentially in the form of a blade or leaf profile, the vortex movement caused by the flow of the coolant "a" on the back of the projecting wall 160 B is is brought to a small value so that the waste collection rate of the waste collection section 161 B is further improved.

Referring to Fig. 48, a thirty-fourth embodiment of the present invention will be described below. Fig. 48 is a schematic enlarged sectional view showing portions of the lower end plugs in the fuel assembly according to the thirty-fourth embodiment of the present invention are illustrated. In this embodiment, are in the lower end plug 7 A, through which the lower ends of the fuel rods 2 are held on the lower end plate 5, respectively formed coolant flow paths 174th Each of the coolant flow paths is bent substantially at right angles so that the coolant flow "a" is conducted as a flow that moves up once and then flows to the side. Each outlet portion 175 of these coolant flow paths 174 is laid out such that it opens in the respective spaces above the flow holes 11 which are formed in the network portion 9 of the lower end plate 5 . Each of the outlet ports 175 of the coolant flow paths 174 is formed in a rectilinear shape when viewed in side view. The outlet sections can alternatively also be formed with a substantially V-shaped shape, L-shaped shape, S-shaped shape or crank shape or cranked shape.

In this structure, the coolant "a" moves from the area of the lower end plate 5 through the flow surface 11 in the network section 9 and through the coolant flow paths 174 in the lower end plug 7 A upwards. The shape of the cooling medium flow paths 174 is substantially at right angle with respect to the rich the flow of the coolant tung bent so as to be transported in a case where metallic debris in the coolant flow paths 174, long metalli specific waste elements, such as metallic wires do not step out of the flow paths 174 and are thus caught in the lower end plugs 7 A. By providing the coolant flow paths 174 in addition to the flow holes 11 , the fluid loss in the lower end plate 5 can also be reduced, whereby the flow rate of the coolant "a" flowing in the channel box 1 can be increased. As a result, the efficiency of heat generation by the fuel assembly can be improved.

Referring to FIG. 49, a thirty-fifth Ausführungsbei hereinafter game of the present invention will be described in more detail. Fig. 49 is a schematic enlarged sectional view, in which the lower end plate containing section of the fuel element is illustrated according to the present embodiment. In this embodiment, a network section 9 A of the lower end plate 5 is constructed such that it contains no flow holes in any section other than those of the holes 9 a supporting the lower end plugs, and that a coolant flow path 176 is formed in each of the lower end plugs 7 B which is bent such that it passes the coolant "a" in the form of a flow which rises once and then flows to the side. With this structure, the coolant "a" is guided so that it can only pass through the coolant flow paths 176 so that the waste trapping rate can be increased.

Referring to FIG. 50, a thirty-sixth Ausführungsbei is hereinafter game of the present invention explained in more detail. Fig. 50 shows an enlarged view illustrating a portion of one of the lower end plugs of the fuel assembly according to the present embodiment. In the present Ausführungsbei game, each of the lower end plugs 7 differs C of this embodiment from those in the above-described thirty-fourth or thirty-fifth embodiment, and otherwise no differences are present. The outlet portions 175 A of the coolant flow path 174 , which are formed in each of the lower end plugs 7 C, are consequently formed, for example, substantially in the shape of a V when viewed from the side. The outlet sections 175 A can alternatively also be designed essentially with an L-shaped shape, an S-shaped shape, a T-shaped shape, a cranked or cranked shape or in other similar shapes.

Referring to FIG. 51, a thirty-seventh Ausführungsbei hereinafter game of the present invention will be described in more detail. Fig. 51 is a schematic enlarged sectional view, in which the lower end plate containing portion is illustrated a fuel assembly according to the present embodiment. In this embodiment, a plurality of plates 187 preventing the introduction of waste particles are provided, which are alternately arranged in the interior of the lower end plate 5 . Here, a group of the introduction of waste particles preventing plates 187 a with predetermined gaps or intervals is attached to an inner surface portion of the lower end plate 5 such that they are inclined downward from the main flow direction of the coolant "a" and prevent that Mixing waste particles into the coolant "a". Further, the other groups by the introduction of waste particles preventing plates 187 b with predetermined intervals at the other inner surface portion of the lower end plate 5, the circuit plate the first-mentioned inner surface portion of the lower From 5 opposite, mounted with predetermined gaps or distances such that they are inclined downward with respect to the main flow direction of the coolant "a" and prevent the waste particles from mixing into the coolant "a".

The one group of the discharge of waste particles preventing plates 187 a and the other group of the discharge of waste particles preventing plates 187 b are designed such that they are alternately arranged in a zigzag manner along the main flow path of the coolant "a". With this construction, even if waste particles should mix in the coolant "a" and flow into the lower end plate 5 , the coolant "a" rises up in a meandering manner, which is due to the alternately arranged plates 187 a and 187 which prevent the mixing in of waste particles b is reached. Furthermore, since the waste particles have a higher density than the coolant "a", the waste particles cannot change direction rapidly due to the inertia force, and thus flow into the lower end plate toward its inner or side surface. As a result, the waste particles are caught in the zig-zag or chevron-shaped corner areas formed by the inner surface portions of the lower end plate 5 and those of the waste particle preventing plates 187 a and 187 b. In a case where long and slim waste particles such as metallic wires are present, they cannot pass through the gaps between the plates 187 a and 187 b and are consequently prevented from flowing into the fuel element, so that the fuel element coatings or Fuel rod casings are kept intact and normal.

Referring to FIG. 52, a thirty-eighth Ausführungsbei hereinafter game of the present invention will be described in more detail. Fig. 52 is a schematic enlarged sectional view, in which the lower end plate extensive portion of the fuel element is illustrated according to the present embodiment. In this embodiment, in the same manner as in the thirty-seventh embodiment, a plurality of waste particles preventing the mixing-in are alternately arranged in the plates 187 a and 187 b which are inclined from the main flow direction of the coolant "a". Specifically, the tip-side or front ends 189 of the interference of waste particles verhin-reducing plates 187 a and 187 b arranged such that they are bent upward in this embodiment. With this structure, the effect of guiding the waste particles, which are subject to a large inertia force, to the inner surface side of the lower end plate 5 is enhanced. Accordingly, even if waste particles are present in the coolant "a" and are introduced into the lower end plate 5 , the waste particles can be blocked by the plates 187 a and 187 b preventing the entry of the waste particles, so that these waste particles do not enter the fuel assembly can. As a result, it is possible to maintain an intact and normal condition of the fuel rods.

Referring to FIG. 53, a neununddreißigstes Ausführungsbei hereinafter game of the present invention will be described in more detail. Fig. 53 shows a schematic, enlarged sectional view in which the lower end plate extensive portion of the fuel element is illustrated according to the present embodiment. In this embodiment, in the lower end plate 5 the entry of waste particles preventing plates 197 , each of which is substantially V-shaped, are arranged at predetermined intervals. Both ends of the respective waste particle-preventing plates 197 are in contact with and are connected to the inner surface of the lower end plate 5 , respectively. At different positions of the plates 197 , which are not aligned with each other, opening portions 199 are formed so that the cooling medium "a" which passes through these opening portions 199 is caused to move upward in a meandering shape. With this structure, the coolant "a" flows along the waste particle-preventing plates 197 toward the inner surface of the lower end plate 5 and passes through the opening portions 199 in the plates 197 toward the fuel rods 2 . Therefore, the number of waste particle intrusion plates 197 can be increased in comparison with a case in which these waste particle intrusion plates are arranged in such a manner that they alternately overlap on the right and left sides. As a result, the number of meandering courses of the coolant "a" and the number of waste particle capturing positions are increased, so that the waste capturing effect can be improved.

Furthermore, the positions of the opening portions 199 differ in the respective plates preventing the ingress of waste particles, so that the coolant "a" is caused to flow in a meandering manner. Even if the waste particles are introduced into the coolant "a" and have flowed into the lower end plate 5 , these waste particles, which have a high density, cannot follow the meandering movement of the coolant "a" and separate from them, so that they flow toward the inner surface side of the lower end plate 5 . As a result, the waste particles are captured in the chevron-shaped areas which are formed by the inner side surface and the plates 197 preventing the penetration of waste particles. Furthermore, since the ingress of waste particles preventing plates 197 are substantially V-shaped, the number of plates 197 which overlap one another, ie the number of meandering movements or kinking courses of the coolant "a", and increase the number of positions capturing waste particles. Therefore, it is possible to block the waste particles through the plates 197 so that the waste particles cannot enter the fuel assembly. This makes it possible to maintain the intact and normal condition of the fuel rods.

A fortieth embodiment of the present invention will be described below with reference to FIGS. 54A, 54B and 54C. FIG. 54A shows a ver größerte perspective view of a fin-shaped (or auxiliary rib-like) shape according to the fortieth embodiment of the present invention. In FIGS. 54B and 54C are shown partial sectional views which are cut along the illustrated in Fig. 54A lines XXXXXIVB-XXXXXIVB or XXXXXIVC-XXXXXIVC.

In this embodiment, narrow grooves (ribs) 200 are formed on the surfaces of the lower end plate, the cylindrical body, the guide body guiding the dropping of waste particles, the hook-shaped catch plates, the spiral plate unit, etc. along the coolant flow, these narrow grooves 200 are in contact with the coolant flow and are provided in the fuel assemblies according to the exemplary embodiments explained above. It is possible to use as the ribs 200 U-shaped ribs (auxiliary ribs) as shown in Fig. 54B, V-shaped ribs as shown in Fig. 54C, or other similar shaped ribs.

Regarding the height "h" and the distance "d" of each of the ribs 200, there is a situation where the height "h" and the distance or pitch "d" are the same as the thickness δ1 of the viscous Bottom layer (viscosity bottom layer) of a turbulent flow, best suited to avoid the frictional losses of the coolant on the wall surfaces of those elements of the fuel assemblies that are in contact with the coolant flow. In this case, the thickness δ1 of the viscous bottom layer is known to be the optimal width of the rib grooves. This means that the optimal width δ1 of the rib grooves can be expressed by the following equation:

δ1 = h (rib height) = d (pitch).

This optimal width 81 of the rib grooves is determined as a function of the flow speed and the viscosity coefficient of the coolant and is given by the equation given below:

δ1 = 123 × (D / 2) / (uD / ν) ^7/8 ).

Here "u" denotes the flow velocity of the turbulent flow, "D" denotes the inside diameter of the cylinder or the equivalent hydraulic one Diameter of the lower end plate, and "ν" stands for the viscosity coefficient.

By arranging the vertical grooves (fins) 200 having the optimal fin width δ1 obtained according to the above equation, the friction loss of the coolant flowing into the lower end plate is reduced, so that the pressure loss in the lower end plate is reduced.

Claims (47)

1. fuel assembly, which is arranged in a reactor core section of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ) an upper end plate, which holds the upper ends of the fuel rods ( 2 ), a lower end plate ( 5 ), the lower ends of the Fuel rods ( 3 ) holds, a plurality of spacers ( 8 ) which are arranged at intervals between the two end plates and serve to maintain the distances between mutually adjacent fuel rods ( 2 ), and a channel box ( 1 ) in which the fuel rods ( 3 ) are housed, wherein coolant (a) which flows into the fuel assembly from the underside of the lower end plate ( 5 ) flows upward to the fuel rods in the fuel assembly, characterized by
a swirler ( 22 ) disposed in the lower portion of the lower end plate ( 5 ) in the axial direction of the fuel assembly and a central hub ( 23 ) and a plurality of blades ( 24 ) arranged around the central hub ( 23 ) and by which an upward vortex flow is impressed on the coolant flowing upwards towards the fuel rods ( 2 ),
a cylindrical body ( 21 ) which is arranged in the vertical direction in the lower end plate ( 5 ) and has an upper-side and a lower-side end section, each of which is open, the cylindrical body ( 21 ) extending upwards to a predetermined, extends on the downstream side of the swirling device ( 22 ) and the waste particle-containing coolant (a) flows upward while making a vortex-shaped movement along the inner peripheral surface of the cylindrical body ( 21 ), and
a waste collecting portion ( 25 ) which is formed between the outer surface of the lower side of the cylindrical body and the inner surface of the lower end plate ( 5 ) and is used for collecting waste particles from the top end portion of the cylindrical body ( 21 ) after flow out and sink down. 2. Fuel assembly according to claim 1, characterized in that the cylindrical body ( 21 ) is arranged coaxially to and along the axial direction of the fuel assembly, that the central hub ( 23 ) is arranged coaxially along the axial direction, and that each of the blades ( 24 ) equally spaced around the central hub ( 23 ) and connected to the inner surface of the lower portion of the cylindrical body ( 21 ). 3. Fuel assembly according to claim 1 or 2, characterized in that each of the leaves ( 24 ) has a substantially spirally twisted shape. 4. Fuel element according to one of the preceding claims, characterized in that the cylindrical body ( 21 ) is formed with a mesh shape. 5. Fuel assembly according to one of the preceding claims, characterized in that an upper portion of the cylindrical body ( 41 ) has indentations such that sawtooth-shaped portions ( 41 a) are formed, the upward and along the inner peripheral surface of the cylindrical body ( 41 ) vortex-moving waste particles are collected through the indented portions of the upper portion of the cylindrical body ( 41 ). 6. Fuel assembly according to one of the preceding claims, characterized by an annular, waste particle catching hook element ( 46 ) which is arranged coaxially to the upper portion of the inner peripheral wall of the cylindrical body ( 21 ) and from the inner peripheral wall of the cylindrical body ( 21 ) protrudes downward and serves to prevent upward movement of the waste particles present in the coolant (a). 7. Fuel assembly according to claim 3, characterized in that the cylin drical body ( 51 ) has a lower cylindrical portion ( 51 a) which is connected to the intermingling device ( 22 ), a tapering portion ( 51 b) which of the upper end portion of the lower cylindrical portion ( 51 a) is coaxial and tapered upward, and includes a small diameter pointing portion ( 51 c) which is coaxial cylindrical starting from the upper end portion of the tapered portion ( 51 b) , wherein the diameter of the small diameter portion ( 51 c) is smaller than the diameter of the lower cylindrical portion ( 51 a). 8. Fuel assembly according to one of claims 1 to 6, characterized in that the cylindrical body ( 21 ) has a plurality of cylinders ( 21 , 57 ) which are arranged adjacent to and vertically in the lower end plate ( 5 ), and in that one the adjacent cylinder is located above the other adjacent cylinder and has a diameter which is smaller than the diameter of the other adjacent cylinder, so that an annular gap ( 58 ) is formed between the adjacent cylinders. 9. Fuel element according to one of claims 1 to 6, characterized in that above the cylindrical body ( 21 ), a second cylindrical body ( 59 ) is arranged at a predetermined vertical distance, that the second cylindrical body ( 59 ) has the same diameter as that Has the former cylindrical body ( 21 ) and that the second cylindrical body ( 59 ) is held on the inner surface of the lower end plate ( 5 ) by means of a mounting wall ( 60 ). 10. Fuel assembly according to one of claims 1 to 6, characterized in that the cylindrical body ( 61 ) has a lower cylindrical portion ( 61 a) having a constant diameter and a plurality of hole-like windows ( 71 ) on a peripheral wall of the lower cylindrical portion are formed at a height which correspond to the bottom of the waste collecting portion ( 25 ), and has an upper cylindrical or conical portion ( 61 b) which extends coaxially from the lower cylindrical portion and is conical so that the Diameter of the upper portion ( 61 b) gradually increases toward the downstream side, that a projection ( 72 ) is arranged above the cylindrical body ( 61 ), which from the inner surface of the lower end plate ( 5 ) in the open upper end portion of the upper portion ( 61 b) protrudes, the projection being a cylindrical, koa has xial shape and is curved such that it covers the space above the peripheral edge of the upper end portion of the upper portion ( 61 b). 11. Fuel element according to claim 9 or 10, characterized in that on the window-like holes ( 71 ) in the lower cylindrical portion ( 61 a) each waste particle intercepting networks ( 73 ) are provided. 12. Fuel element according to one of claims 1 to 3, characterized in that the cylindrical body ( 81 ) has a lower cylindrical portion ( 81 a), to which the swirling device ( 24 ) is attached, and an upper cylindrical portion ( 80 b) , The coaxial to the lower cylindrical portion ( 81 a) and has a plurality of slots which are formed on a peripheral wall portion of the upper cylindrical portion ( 81 b), which is arranged near its upper end portion, spirally or obliquely. 13. The fuel assembly according to claim 12, characterized in that each of the slots has a spiral or oblique orientation which coincides with the swirling direction of the coolant (a) swirled by the swirling device ( 22 ). 14. Fuel element according to one of claims 1 to 3, characterized in that the cylindrical body ( 81 A) has a lower cylindrical section ( 81 a), on which the swirling device ( 22 ) is attached, and an upper cylindrical section ( 81 b1) has, which extends coaxially to the lower cylindrical portion ( 81 a) and has a plurality of round holes ( 85 ) which are formed on that peripheral wall portion of the upper cylindrical portion which is arranged in the vicinity of the upper end portion of the upper portion . 15. Fuel assembly according to one of claims 1 to 3, characterized in that an outer cylindrical body ( 96 ) is mounted concentrically to the cylindrical body ( 81 a) with a fixed radial gap to this in the lower end plate ( 5 ) and an upper End portion which extends to the upper end portion of the cylindrical body and is fixedly connected thereto, and has a lower end portion which is fixedly attached to the inner surface of the lower end plate ( 5 ) that between the cylindrical body ( 81 a) and the outer cylindrical body ( 96 ) existing gap is blocked that the cylindrical body ( 81 a) has a plurality of slots ( 84 ) which are spirally or obliquely formed on an upper circumferential wall portion of the cylindrical body ( 81 a), wherein the waste particles that emerge through the slots ( 84 ) to the outside, in the between the cylindrical body he ( 81 a) and the outer cylindrical body ( 96 ) formed space can be collected. 16. The fuel assembly according to claim 15, characterized by waste particles a catching plates ( 97 ) which are respectively arranged at inlet portions of the slots ( 84 ) formed in the cylindrical body ( 81 ) and which protrude in a direction opposite to the vortex-shaped flow of the Coolant is. 17. The fuel assembly according to claim 15, characterized in that instead of the slots ( 84 ) formed in the upper peripheral wall section of the cylindrical body ( 81 ), round holes ( 85 ) are formed therein. 18. Fuel element according to claim 17, characterized in that the diameter of the holes formed in the cylindrical body ( 85 A) are different depending on whether the round holes ( 85 A) on the upstream side of the cylindrical body or on the downstream side of the same are arranged. 19. Fuel element according to one of claims 15 to 18, characterized in that the upper end region of the outer cylindrical body ( 96 ), which extends in the direction of the upper end region of the cylindrical body ( 81 ) and is fixedly connected thereto, in Form a mesh-like or lattice-like structure is formed. 20. Fuel assembly according to one of claims 15 to 18, characterized in that the lower end region of the outer cylindrical body ( 96 B) is arranged spaced from the lower end plate ( 5 ), so that a coolant flow path ( 99 ) is formed, which Connects inside of the outer cylindrical body ( 96 B) with its outer region. 21. The fuel assembly according to one of claims 1 to 3, characterized by a guide body ( 100 ) provided for the falling waste particles, which has a substantially crown-like shape and is open in its central portion such that the guide body ( 100 ) is arranged such that it surrounds the inner and outer peripheral portion of the edge of the upper end portion of the cylindrical body ( 21 ), and thus converts the upward flow of the coolant flowing upward along the inner peripheral edge of the cylindrical body ( 21 ) into a flow that flows downward on the outer peripheral surface side of the cylindrical body ( 21 ). 22. A fuel assembly according to claim 21, characterized in that the Füh approximately body (100) consists of a flat ring portion (100 a), which is arranged above the edge of the upper end portion of the cylindrical body (21), and an inner and an outer cylindrical drooping Section ( 100 b, 100 c), which from the inner and outer peripheral edge of the ring portion ( 100 a) down so that they are substantially parallel to the inner and outer peripheral surface of the edge of the upper end portion of the cylindrical body, and that a plurality of waste particles capturing plates (101) is present, which have substantially zungenförmi ge shape and are arranged in the downward flow path of the coolant flowing through the gap between the inner peripheral surface of the outer cylindrical suspending portion (100 c), and the outer peripheral surface of the upper end portion of the cylindrical body ( 21 ) is defined. 23. A fuel assembly according to claim 22, characterized in that the waste particles trapping plates (101) (C 100) are mounted projectingly on the inner peripheral surface of the outer cylindrical drooping portion, and that the plates are (101) inclined upwards, so that their altitude gradually and gradually increases towards their front ends. 24. The fuel assembly according to claim 22, characterized in that each of the waste particle capturing plates ( 101 B) has a body portion which is substantially horizontal, with a front end portion of the body portion bent upward such that each of the plates ( 101 B) is substantially ausgebil det in the form of an L. 25. The fuel assembly according to claim 22, characterized in that each of the waste particles capturing plates ( 101 C) is bent such that the plates are provided with a semi-circular arc shape, the arcuate inner surfaces of the plates ( 101 C) each to the Guide body ( 100 ) are directed. 26. The fuel assembly of claim 22, characterized in that a plurality of waste particle capturing ribs ( 102 ) are disposed around the cylindrical body ( 21 ), the waste particle capturing ribs ( 102 ) overall being generally frog-shaped and each of the ribs ( 102 ) is each provided with an essentially needle-like shape. 27. The fuel assembly of claim 22, characterized in that a plurality of annular, irregular portions ( 103 ) are provided which extend along the inner peripheral surface of the cylindrical body and are seen vertically in succession on the inner peripheral surface of the cylindrical body. 28. The fuel assembly according to claim 27, characterized in that the irregular portions ( 103 ) have concave grooves ( 103 a) which are arranged at regular intervals along the vertical direction, and in that each of the concave grooves has an inner peripheral edge portion with an inner width and has an outer peripheral edge portion with an outer width, wherein the inner width of the respective inner peripheral edge portions is smaller than the outer width of the outer peripheral edge portions. 29. Fuel element according to claim 21, characterized in that the Füh approximately body ( 100 A) has an outer diameter which is set such that it is smaller than the inner diameter of an inner coolant inlet hole of the lower end plate ( 5 ), through which the coolant into the flows in lower end plate ( 5 ). 30. fuel assembly, which is arranged in a reactor core portion of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ), an upper end plate that holds the upper ends of the fuel rods ( 2 ), a lower end plate ( 5 ) that the lower Ends of the fuel rods ( 2 ) holds, a plurality of spacers ( 8 ), which are arranged at intervals between the two end plates and serve to maintain the distances between adjacent fuel rods ( 2 ), and a channel box ( 1 ) in which the fuel rods ( 2 ) are housed, and a coolant (a) flowing into the fuel assembly from the lower end portion of the lower end plate ( 5 ) is adapted to move upward toward the fuel rod side in the fuel assembly , marked by
a swirler ( 22 ) disposed in the lower portion of the lower end plate ( 5 ) along the axis direction of the fuel assembly and including a central hub ( 23 ) and a plurality of blades ( 24 ) surrounding the central hub ( 23 ) are arranged and serve to apply an upward vortex-shaped flow to the coolant migrating upwards towards the fuel rods ( 2 ), and
a plurality of waste particle trapping plates ( 114 ) arranged above the swirler ( 112 ) in the lower end plate ( 5 ) and each of which protrudes in a direction against the vortex-shaped caused by the swirler ( 112 ) Flow is directed, which, viewed in cross section, have essentially the shape of an L. 31. Fuel element according to claim 30, characterized in that the plates ( 114 A) which capture the waste particles are each formed with a lattice-like structure. 32. Fuel assembly according to one of the preceding claims, characterized in that each of the leaves ( 24 ) has a substantially arcuate shape and a spirally twisted shape, which is directed towards the underside of the lower end plate ( 5 ), and that the middle hub ( 23 ) extends upwards from the central position of the blades ( 24 ), the Verwirbelungsein device serving as a mounting guide for mounting the fuel assembly on the boiling water reactor. 33. Fuel element according to one of the preceding claims, characterized records that the central hub of the swirler towards its downstream side is extended. 34. fuel assembly, which is arranged in a reactor core section of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ), an upper end plate ( 5 ) which holds the upper ends of the fuel rods ( 2 ), a lower end plate ( 5 ), the holds the lower ends of the fuel rods ( 2 ), a plurality of spacers ( 8 ), which are arranged at intervals between the two end plates and serve to maintain the intervals between adjacent fuel rods ( 2 ), and a channel box ( 1 ), in which the fuel rods ( 2 ) are housed, wherein coolant (a) flowing into the fuel assembly from a lower end portion of the lower end plate ( 5 ) is provided to move toward the side of the fuel rods ( 2 ) in the fuel assembly to move upwards, characterized by a cylindrical element ( 128 ) which in the lower portion of the lower end plate ( 5 ) along the axi alen direction of the fuel assembly is provided and has a plurality of spiral flow paths ( 129 ), each of the spiral flow paths ( 129 ) on the upper end surface and the lower end surface of the cylindrical member ( 128 ) is open, so that mutually independent spiral flow paths are formed each of the spiral flow paths ( 129 ) has concave grooves ( 130 ) formed at predetermined positions of the flow paths to which the centrifugal force caused by the coolant flowing in the spiral flow paths acts, the concave grooves run perpendicular to the flow direction of the coolant flowing in the spiral flow paths. 35. fuel assembly, which is mounted in a reactor core portion of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods, an upper end plate which holds the upper ends of the fuel rods ( 2 ), a lower end plate ( 5 ) which holds the lower ends of the fuel rods ( 2 ) holds, a plurality of spacers ( 8 ) which are arranged at intervals between the two end plates and are used to maintain the distances between adjacent fuel rods, and a channel box ( 1 ) in which the fuel rods ( 2 ) are housed are, wherein a coolant (a) which flows from the lower end portion of the lower end plate ( 5 ) into the fuel assembly is guided such that it moves up to the side of the fuel rods ( 2 ) in the fuel assembly, characterized by
a plurality of vertically elongated flow restriction plates ( 143 ) extending upward in the lower end plate ( 5 ) from a lower central portion and bent along the circumferential direction with respect to the axial direction of the fuel assembly,
a flow path blocking plate ( 144 ) which is provided at the upper end positions of the flow restricting plates ( 143 ) such that the upward moving coolant (a) impinges on the flow path blocking plate ( 144 ) so that the coolant is distributing downward toward the inner peripheral side surface of the lower end plate ( 5 ), and
a waste trapping section including a plurality of grooves ( 147 ) extending along the vertical direction and provided on the inner peripheral surface of the lower end plate ( 5 ). 36. Fuel assembly according to claim 35, characterized by a mouth opening ( 141 ) which is provided in a coolant inlet hole at the lower end portion of the lower end plate ( 5 ) and is provided for throttling the coolant flowing through the inlet hole into the lower end plate ( 5 ) . 37. fuel assembly, which is arranged in a reactor core section of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ), an upper end plate which holds the upper ends of the fuel rods ( 2 ), a lower end plate ( 5 ) which the lower Holds ends of the fuel rods, a plurality of spacers ( 8 ), which are arranged at intervals between the two end plates and serve to maintain the distances between adjacent fuel rods ( 2 ), and a channel box ( 1 ) in which the fuel rods ( 2 ) are housed, wherein a coolant that flows from the lower end portion of the lower end plate ( 5 ) into the fuel element is designed to move upward toward the side of the fuel rods ( 2 ) in the fuel element by
a waste particle removing plate ( 158 ) which is provided with a plurality of holes ( 157 ) therethrough, is mounted in the lower end plate ( 5 ) and is inclined with respect to the vertical direction of main flow of the coolant (a), and one Prevents passage of the waste particles contained in the coolant (a), and
a waste collecting section ( 161 ) formed between the inner surface of an upper end portion of the plate ( 157 ) and the inner peripheral surface of the lower end plate ( 5 ) and for collecting the waste particles falling from the inner surface of the upper end portion of the plate ( 158 ) . 38. Fuel assembly according to claim 37, characterized in that the plate ( 158 ) is provided with a shape such that it gradually extends from a central position of the lower end plate ( 5 ) in the direction of the circumferential region thereof rising upwards. 39. fuel assembly, which is mounted in a reactor core portion of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ), an upper end plate that holds the upper ends of the fuel rods ( 2 ), a lower end plate ( 5 ), the lower Ends of the fuel rods ( 2 ) holds, a plurality of spacers ( 8 ) which are arranged at intervals between the two end plates and serve to maintain the distances between adjacent fuel rods ( 3 ), and comprises a channel box ( 1 ) in which the plurality of fuel rods ( 2 ) is accommodated, the coolant flowing into the fuel assembly from the lower end portion of the lower end plate ( 5 ) being designed or guided such that it is directed towards the side of the fuel rods ( 2 ) moved up in the fuel assembly, characterized by
a network portion ( 169 ) attached to an upper end portion of the lower end plate ( 5 ) for holding the fuel rods ( 2 ) and having a lower surface, a plurality of holes ( 157 ) being formed in the lower surface therethrough and the lower surface has a shape such that, starting from a central position of the lower surface, it gradually rises toward the peripheral area, thereby preventing the waste particles contained in the coolant (a) from passing through, and
a waste collecting portion ( 161 A) which is formed between an inner surface of the upper end portion of the lower surface of the network portion and the inner peripheral surface of the lower end plate ( 5 ) and serves to collect the waste particles falling from the upper end portion of the lower surface of the network portion . 40. Fuel element according to claim 39, characterized in that the waste collecting section ( 161 B) has essentially the shape of a sheet or blade-shaped profile. 41. fuel assembly, which is formed in a reactor core portion of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ), an upper end plate that holds the upper end of the fuel rods ( 2 ), a lower end plate ( 5 ) on their is provided with a network section ( 9 ) which holds the lower end plugs of the lower ends of the fuel rods, a plurality of spacers ( 8 ) which are arranged at intervals between the two end plates and for maintaining the distances between adjacent fuel rods ( 2 ), and has a channel box ( 1 ) in which the fuel rods ( 2 ) are accommodated, a coolant (a) flowing into the fuel assembly from the lower end side of the lower end plate ( 5 ) being designed or guided in this way that it moves up towards the side of the fuel rods ( 2 ) in the fuel assembly, characterized by
means for defining flow holes ( 174 ) in the network section through which the coolant (a) flowing into the lower end plate ( 5 ) passes in the form of an upwardly flowing stream, and
Coolant flow paths having outlet portions and each formed in the lower end plug, each of the coolant flow paths being curved so that the upward moving coolant passing through the coolant flow paths is deflected to the side, the outlet portions of the coolant flow paths each being in one Space above the flow holes of the network section are open. 42. fuel assembly, which is mounted in a reactor core portion of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ), an upper end plate which holds the upper ends of the fuel rods ( 2 ), a lower end plate, the lower end of which at its upper end Carries end plugs of the lower ends of the fuel rods ( 2 ), a plurality of spacers ( 8 ) which are arranged at intervals between the two end plates and serve to maintain the intervals between adjacent fuel rods ( 2 ), and comprises a channel box ( 1 ), in which the plurality of fuel rods ( 2 ) are accommodated, wherein coolant (a) that flows into the fuel assembly from an underside end region of the lower end plate ( 5 ) is designed or guided such that it is directed upward to the side of the fuel rods ( 2 ) the fuel assembly moves, characterized by
a network section, which is attached to an upper portion of the lower end plate ( 5 ) and has receiving holes for receiving the lower end plugs into which the lower end plugs of the fuel rods are respectively inserted without providing flow holes, and
Coolant flow paths that have outlet portions and are formed in the lower end plugs, respectively, the coolant flow paths being curved such that the upward moving coolant that passes through the coolant flow paths flows to the side or is deflected. 43. Fuel element according to claim 41 or 42, characterized in that the Outlet sections of the coolant flow paths in a substantially parallel shape, in substantially V-shaped, substantially L-shaped, substantially S-shaped or essentially cranked shape, seen in side view, exhibit.   44. fuel assembly, which is mounted in a reactor core portion of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ) an upper end plate which holds the upper ends of the fuel rods ( 2 ), a lower end plate ( 5 ) which the lower ends the fuel rods ( 2 ) holds, a plurality of spacers ( 8 ), which are arranged at intervals between the two end plates and serve to maintain the distances between adjacent fuel rods ( 2 ), and comprises a channel box ( 1 ) in which the A plurality of fuel rods are accommodated, wherein the coolant (a) which flows into the fuel assembly from an underside end region of the lower end plate ( 5 ) is guided such that it moves towards the side of the fuel rods ( 2 ) in the fuel assembly moved above, characterized by
a first group of the intrusion of waste particle preventing plates ( 187 a) which are attached at predetermined intervals to an inner surface portion of the lower end plate ( 5 ) such that they are inclined downward from the main vertical flow direction of the coolant and serve to waste catch particles from the coolant (a), and
a second group of the intrusion of waste particles preventing plates ( 187 b), which are mounted at predetermined intervals on another inner surface portion of the lower end plate ( 5 ) such that they are inclined downward from the main vertical flow direction of the coolant (a) and serve to prevent the ingress of waste particles into the coolant, the other inner surface portion of the lower end plate ( 5 ) facing the one inner surface portion thereof, and the first group of plates ( 187a ) and the other group of plates ( 187 b) are positioned such that they are alternately arranged along the main flow direction. 45. Fuel assembly according to claim 44, characterized in that each of the plates ( 187 a, 187 b) has upwardly bent front ends ( 189 ). 46. fuel assembly, which is mounted in a reactor core portion of a reactor pressure vessel of a boiling water reactor and a plurality of fuel rods ( 2 ), an upper end plate which holds the upper ends of the fuel rods ( 2 ), a lower end plate ( 5 ) which the lower Ends of the fuel rods ( 2 ) holds, a plurality of spacers ( 8 ) which are arranged at intervals between the two end plates and serve to maintain the distances between adjacent fuel rods ( 2 ), and comprises a channel box ( 1 ) in which the fuel rods ( 2 ) are accommodated, wherein a coolant (a) which flows into the fuel element from the lower region of the lower end plate ( 5 ) is designed or guided such that it extends upwards to the side of the fuel rods ( 2 ) moved in the fuel assembly, characterized by
intrusion-preventing plates ( 197 ) each substantially V-shaped and arranged at predetermined intervals in the lower end plate ( 5 ), the two ends of the respective plates ( 197 ) each in contact with the inner surface of the lower one End plate ( 5 ) are and are connected to this, and
means for defining opening portions ( 199 ) passing through the respective plates ( 197 ) at different positions of the plates so that the coolant passing through the opening portions ( 199 ) meanders upward. 47. The fuel assembly according to any one of the preceding claims, characterized by a rib portion ( 200 ) having a plurality of thin grooves formed side by side along the flow direction of the coolant and on at least one inner peripheral surface of the cylindrical body and / or the surfaces of the blades ( 24 ) is formed, thereby reducing the resistance of the coolant flow paths.