JP2012117921A - Multistage-type foreign matter filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multistage-type foreign matter filter that can reduce pressure loss by a foreign matter filter as much as possible.SOLUTION: A multistage-type foreign matter filter 8 comprises: a first filter 81 formed by stacking a plurality of undulated plates 88 in such a manner that a flow passage with a predetermined inclined angle is formed; and a second filter 82 disposed on the downstream side of the first filter 81 and formed by stacking a plurality of undulated plates 88 in such a manner that a flow passage with an inclined angle that is different from the inclined angle of the first filter 81. In the multistage-type foreign matter filter 8, a plurality of flow-passage holes are provided in the undulated plates of the first filter 81.

Description

  The present invention relates to a multistage foreign matter filter that is attached to a lower tie plate of a nuclear fuel assembly and captures foreign matter (debris) flowing into a reactor core.

  In a boiling water reactor (BWR), a liquid coolant flows from the bottom of the core, passes through a fuel assembly loaded on the core, and flows out from the top of the assembly as a water / steam mixture. The fuel assembly is placed on a fuel support fitting that is vertically supported on the control rod guide tube.

  The structure of a normal fuel assembly used in a boiling water reactor will be described with reference to FIG. FIG. 8 (a) is a longitudinal sectional view of a 9 × 9 type fuel assembly 1, and shows an upper tie plate 5 and a lower tie plate 6, a plurality of fuel rods 3 and water rods held at both ends by these tie plates. 4. It has a structure in which a rectangular tube-shaped channel box 2 is covered with a fuel bundle composed of a plurality of fuel spacers 7 that maintain a gap between fuel rods. The lower tie plate 6 is generally composed of an inlet nozzle 61 into which a coolant flows and an upper grid 62 into which a lower end of a fuel rod is inserted and supported, and these are integrally cast.

  A seat surface is provided at an upper edge portion of a fuel support fitting (not shown) that supports the fuel assembly 1, and the outer peripheral surface of the lower tie plate 6 is in close contact with the seat surface. The coolant that has risen outside the control rod guide pipe flows into the support fitting from the inlet orifice at the bottom of the fuel support fitting, passes through the flow path inside the support fitting, and is in close contact with the upper edge portion of the lower tie plate 6. Into the lower tie plate 6 from the inlet nozzle 61. Inside the lower tie plate 6, it passes through a diffuser portion 63 whose flow area increases vertically upward, passes through flow hole (not shown) of the upper grid 62, and flows around each fuel rod.

  By the way, in the nuclear reactor, foreign substances such as peeled metal oxides and metal pieces mixed during regular inspection work are accumulated with time. Such foreign objects may block the reactor coolant circulation system as the years of use of the reactor plant increase, impairing healthy operating conditions. In particular, it is known that foreign matter that has entered the fuel assembly along with the flow of coolant is trapped by the fuel spacer, causing fretting damage to the fuel rod cladding tube. Various types of foreign matter filters are used.

  The basic function of the foreign matter filter is to filter and capture foreign matter through a mesh-like or narrowed passage hole. However, although such a filter can capture foreign matter larger than the mesh, it cannot be expected to have a filtering effect on elongated wire-like foreign matters (wire brush wires, spiral facets, etc.) that are the main cause of fretting damage. . If the filter is made fine enough to capture the wire-like foreign matter, the flow resistance of the coolant is extremely increased or the limit of the minimum dimension that can be produced as a casting is exceeded.

  In recent years, movements to eliminate fuel damage due to fretting as much as possible have become remarkable both in Japan and overseas, and various means have been proposed. As one of them, by sloping the flow path from the inlet to the outlet of the foreign matter filter by curving the passage inside the foreign matter filter so that even wire-like foreign matter can be captured, There is known a means for capturing the water at the curved portion of the flow path (Patent Document 1).

  In addition, a method has been proposed in which a linear foreign matter is captured by a multistage foreign matter filter composed of an upstream flat plate assembly and a downstream flat plate assembly whose flow paths are inclined in different directions with respect to the coolant flow direction ( Patent Documents 2 and 3).

  In particular, as shown in FIGS. 9A and 9B, the multistage foreign matter filter 8 disclosed in Patent Document 3 includes a plurality of corrugated plates 88 having peaks and valleys that are alternately formed, and the peaks and valleys of each other. Are arranged and arranged to form a straight flow path having an angle with respect to the vertically upward coolant flow direction. With respect to such a filter (first filter) 81, a linear foreign substance is captured by installing a second filter 82 having a different channel inclination direction on the downstream side. This multi-stage foreign matter filter 8 is installed at the end of the diffuser portion where the flow area is fully expanded inside the lower tie plate, so that the pressure loss does not increase more than necessary, and is linear with a structure in which corrugated plates 88 are laminated. It satisfies the trapping performance and manufacturability for foreign matter at the same time.

Japanese Patent No. 3065119 JP 2001-141866 A JP 2006-189434 A

  When designing a fuel assembly for replacement of an existing core, it is necessary to make the pressure loss characteristic equal to that of an existing fuel assembly in order to maintain the flow rate of the entire core and the flow distribution with mixed fuel. For this reason, the current fuel assembly must be designed so that the pressure loss is within the same or allowable range as the fuel assembly without the foreign matter filter, even if the fuel assembly has the foreign matter filter.

However, even if a multistage foreign matter filter with good pressure loss characteristics is used, the pressure loss is not zero. The pressure loss of the entire fuel assembly must be maintained almost constant. Therefore, from the viewpoint of fuel design, it is important to minimize the pressure loss of the foreign matter filter itself.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a multistage foreign matter filter capable of minimizing the pressure loss due to the foreign matter filter.

  In order to solve the above problem, a multistage foreign matter filter according to the present invention includes a first filter formed by laminating a plurality of corrugated plates so as to form a flow path having a predetermined inclination angle, and the first filter. In the multi-stage foreign matter filter provided with the second filter, which is disposed on the downstream side of the first filter and is formed by laminating a plurality of corrugated plates so as to form a flow path having an inclination angle different from that of the first filter, A plurality of flow path holes are provided in the corrugated plate of the first filter.

  The multi-stage foreign matter filter according to the present invention includes a first filter formed by laminating a plurality of corrugated plates so as to form a flow path having a predetermined inclination angle, and a downstream side of the first filter. In the multistage foreign matter filter provided with the second filter, which is disposed and formed by laminating a plurality of corrugated plates so as to form a flow path having an inclination angle different from that of the first filter, A plurality of flow path holes are alternately provided in the corrugated plate and the corrugated plate of the second filter.

  According to the present invention, it is possible to flatten the flow velocity distribution of the coolant passing through the filter and reduce the pressure loss of the filter without impairing the foreign matter capturing performance. Moreover, the design change regarding the pressure loss characteristic when the multistage foreign matter filter is backfitted to the replacement fuel is facilitated.

(A) is a block diagram of the multistage type | mold foreign material filter which concerns on 1st Embodiment, (b) is a block diagram of a 1st filter, (c) is a whole block diagram of a lower tie plate. The block diagram of the multistage type foreign material filter which concerns on the modification of 1st Embodiment. The block diagram of the multistage type foreign material filter which concerns on the modification of 2nd Embodiment. The block diagram of the multistage type foreign material filter which concerns on the modification of 3rd Embodiment. The block diagram of the multistage type foreign material filter which concerns on the modification of 4th Embodiment. (A) is a top view of the multistage type | mold foreign material filter of this invention, (b) is a side view. (A) is a top view of the multistage type foreign material filter concerning a 5th embodiment, and (b) is a side view. (A) is a longitudinal cross-sectional view of a conventional fuel assembly, and (b) is an AA cross-sectional view. (A) is a block diagram of the lower tie plate which equipped with the conventional multistage filter, (b) is a block diagram of a multistage filter.

Hereinafter, embodiments of a foreign matter filter according to the present invention will be described with reference to the drawings.
Here, parts common to or similar to each other, or parts common to or similar to the prior art are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
A multistage foreign matter filter according to a first embodiment of the present invention will be described with reference to FIGS.
(Constitution)
The multistage foreign matter filter 8 according to the first embodiment includes an upstream first filter 81 and a downstream second filter 82 formed of a plurality of corrugated plates, and includes a grid in the lower tie plate 6. It is mounted upstream of the part 62. In addition, a gap region 85 in which the coolant can freely communicate is provided in an intermediate zone between the first filter and the second filter.

  The first and second filters are formed of a laminated body in which a plurality of corrugated plates 88 molded so as to alternately have ridges and valleys, and the ridges and valleys are combined with each other, and the first and second filters The straight channels having different predetermined tilt angles with respect to the vertically upward coolant flow direction are formed.

  Each corrugated plate of the first filter 81 is provided with a plurality of oval channel holes 83 as shown in FIG. In the example of FIG. 1B, two flow path holes 83 are provided on both sides of each peak portion of the corrugated plate 88 in the flow direction. In addition, a plurality of notch portions 84 each having a substantially trapezoidal shape are provided at the upstream end portion of each corrugated plate 88 of the first filter 81.

   The shape, installation location, size, and number of the channel holes 88 can be arbitrarily set as long as there is no problem in the manufacturability and mechanical strength of the filter. For example, as shown in FIG. 2, the shape of the flow path hole 83 may be a large quadrangular shape made up of parallelograms. Thereby, simplification of the manufacturing process of a filter can be achieved.

  Moreover, the shape of the notch 84 is not limited to a trapezoidal shape, and other shapes such as a semicircular shape, an elliptical shape, and a square shape can be adopted. Moreover, the installation location of the notch part 84 can be provided in arbitrary places, such as the peak part of a corrugated plate, and the top part of a trough.

(Function)
Although the flow velocity distribution of the coolant flowing in from the inlet nozzle 61 of the lower tie plate 6 is unevenly distributed due to the influence of the inlet orifice of the fuel support fitting located upstream and the shape of the flow path in the support fitting, FIG. ) Has a flow velocity peak substantially in the center of the flow path, spreads in the diffuser portion 63 and flows into the multistage foreign matter filter 8. Thus, since the coolant flow rate flowing into the foreign matter filter 8 is not uniform, the pressure loss of the foreign matter filter is governed by the pressure drop in the region where the flow rate is fast.

  In the multistage foreign matter filter 8 of the first embodiment, since the plurality of flow path holes 83 are provided in the corrugated plate 88 of the first filter 81, as shown by 9 in FIG. The coolant in the high speed region that has flowed into the filter can flow out to the adjacent flow path. Thereby, since it acts in the direction in which the flow velocity distribution of the coolant is flattened inside the first filter, the pressure loss in the high flow velocity region is reduced.

  In addition, the multistage foreign matter filter 8 has a gap region 85 in which a coolant can freely communicate with the intermediate zone between the first filter 81 and the second filter 82, so that the second filter 82 on the downstream side of this has a gap region 85. Even if the flow path hole 83 is provided, the flattening effect of the flow velocity distribution cannot be expected. Also, if the second filter is provided with a flow path hole, the second filter may be disposed at a position that can be seen straight from the flow path hole of the first filter, and in that case, there is a possibility that a linear foreign matter will pass through. Arise. For the above reason, in the first embodiment, the second filter is not provided with a channel hole.

  Further, the flow path area in the first filter is reduced by the cross-sectional integral of the filter structure material as compared with the flow path area immediately before the filter. Due to this steep reduction in the step flow area at the inlet face of the first filter, the flow direction pressure also drops sharply, thereby impacting the inlet face of the first filter. Therefore, by providing the notch 84 on the upstream side of the corrugated plate of the first filter, by avoiding a sudden increase in the cross-sectional area of the filter structure material in the first filter entrance surface, Mitigates the impact caused by a sudden decrease in flow area.

(effect)
According to the first embodiment, the plurality of flow passage holes are provided in the upstream filter of the multistage foreign matter filter, so that the foreign matter is surely removed and the flow rate distribution of the coolant flowing through the multistage foreign matter filter. Can be flattened. In addition, by providing the cutout portion in the upstream filter, it is possible to mitigate the impact caused by the rapid decrease in the channel area.

[Second Embodiment]
A multistage foreign matter filter according to a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, as shown in FIG. 3, the size of the flow path hole 83 of the corrugated plate 88 of the first filter 81 is increased at the center of the plate and stepwise toward the periphery. Or, it is characterized by being made smaller gradually.

  As shown in the flow velocity distribution in FIG. 1 (c), the coolant flow velocity near the center of the filter is the fastest. In the second embodiment, the above configuration makes it possible to The resistance of the directional flow can be reduced, and the effect of flattening the flow velocity distribution can be further enhanced.

[Third Embodiment]
A foreign matter filter according to a third embodiment of the present invention will be described with reference to FIG.
In the third embodiment, as shown in FIG. 4, the corrugated plate 88 of the first filter 81 is provided with every other passage hole 83a with respect to the peak portion, and the wave of the second filter 82 is provided. Similarly, the mold plate 88 is provided with every other passage hole 83b so as to be alternated with the passage hole 83a of the first filter. Furthermore, a notch 84b is also provided at the downstream end of the second filter.

  With these configurations, the flow velocity distribution of the coolant can be further flattened without affecting the foreign matter capturing performance. In addition, the multistage foreign matter filter 8 is turned upside down so that it can be used even if the first filter and the second filter are interchanged, so that the mounting property to the lower tie plate is increased and the service life can be extended. .

[Fourth Embodiment]
A foreign matter filter according to a fourth embodiment of the present invention will be described with reference to FIG.
In the fourth embodiment, as shown in FIG. 5, the flow path of the first filter formed by the corrugated plate 88 is predetermined on both sides of the central portion in the downstream direction, each toward the outer peripheral portion. It is characterized by being inclined at an angle of. Similarly, the flow path of the second filter is also inclined at both sides of the central portion so that each of them is directed toward the central portion in the downstream direction.

  As described above, the coolant flow in the lower tie plate becomes a flow that spreads in the diffuser portion, but in the fourth embodiment, the direction of the coolant passage in the first filter is changed from the center portion of the lower tie plate. By setting the direction toward the outer peripheral portion, the degree of obstructing the flow direction of the coolant is reduced, so that the pressure loss due to the change in the flow direction of the coolant can be reduced.

[Fifth Embodiment]
A multistage foreign matter filter according to a fifth embodiment of the present invention will be described with reference to FIGS.
The multistage foreign matter filter 8 shown in FIGS. 6A and 6B is laminated so that the longitudinal direction of the corrugated plate is parallel to a pair of opposite sides of the filter. Therefore, the inflow direction to the first filter 81 and the outflow direction from the second filter 82 are constant over the entire inflow surface and outflow surface to the multistage foreign matter filter 8.

  On the other hand, due to the symmetry of the flow path shape in the fuel support bracket, the flow velocity distribution of the coolant is substantially symmetrical with respect to the diagonal line including the inflow direction of the inlet orifice (not shown). Further, the coolant flow that flows into the lower tie plate 6 from the inlet nozzle 61 becomes a flow that spreads in the diffuser portion.

  In the fifth embodiment, in consideration of such a flow velocity distribution of the coolant, as shown in FIGS. 7A and 7B, the corrugated plates are laminated so as to be parallel to the diagonal direction, and the filter is formed. Configure. Furthermore, the inclination angle of the flow path of the first filter 81 and the inclination angle of the flow path of the second filter 82 are configured as shown in FIG.

Thereby, the flow direction of the coolant flowing into the multistage foreign matter filter 8 can be smoothly introduced into the multistage foreign matter filter 8 without changing the flow direction as much as possible, and the flow loss due to the change of the flow direction can be reduced.
In the fifth embodiment, the same effect can be obtained for a multistage foreign matter filter in which the first filter 81 is not provided with a flow hole.

  As described above, the application example of the multistage foreign matter filter of the present invention to the fuel assembly for boiling water reactor has been described, but the same effect can be expected when applied to the fuel assembly for pressurized water reactor. Note what you can do.

  Moreover, said embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, combinations, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Fuel assembly, 2 ... Channel box, 3 ... Fuel rod, 4 ... Water rod, 5 ... Upper tie plate, 6 ... Lower tie plate, 61 ... Inlet nozzle, 62 ... Upper grid part, 63 ... Diffuser part, 7 DESCRIPTION OF SYMBOLS ... Fuel spacer, 8 ... Multistage type | mold foreign material filter, 81 ... 1st filter, 82 ... 2nd filter, 83 ... Channel hole, 84 ... Notch part, 85 ... Gap area | region, 88 ... Corrugated plate.

Claims (8)

A first filter formed by laminating a plurality of corrugated plates so as to form a flow path having a predetermined inclination angle, and an inclination angle different from that of the first filter disposed on the downstream side of the first filter In a multistage foreign matter filter provided with a second filter formed by laminating a plurality of corrugated plates so as to form a flow path having
A multistage foreign matter filter, wherein a plurality of flow path holes are provided in the corrugated plate of the first filter.   2. The multistage foreign matter filter according to claim 1, wherein at least one flow path hole is provided in the flow direction of the corrugated plate of the first filter.   3. The multistage foreign matter filter according to claim 1 or 2, wherein the size of the flow path hole is gradually or gradually reduced from the central portion toward the peripheral portion.   The flow path of the first filter is inclined toward the outer peripheral portion on the downstream side on both sides of the central portion, and the flow path of the second filter is directed on the both sides of the central portion toward the central portion on the downstream side. The multistage foreign matter filter according to any one of claims 1 to 3, wherein the multistage foreign matter filter is inclined.   5. The multistage foreign matter filter according to claim 4, wherein the corrugated plate of the first filter and the corrugated plate of the second filter are arranged in parallel to one of the diagonal lines of the foreign matter filter.   The multistage foreign matter filter according to any one of claims 1 to 5, wherein a plurality of notches are provided at an upstream end of the corrugated plate of the first filter. A first filter formed by laminating a plurality of corrugated plates so as to form a flow path having a predetermined inclination angle, and an inclination angle different from that of the first filter disposed on the downstream side of the first filter In a multistage foreign matter filter provided with a second filter formed by laminating a plurality of corrugated plates so as to form a flow path having
A multistage foreign matter filter, wherein a plurality of flow path holes are alternately provided in the corrugated plate of the first filter and the corrugated plate of the second filter.   8. The multistage system according to claim 7, wherein a plurality of notches are provided at an upstream end of the corrugated plate of the first filter and a downstream end of the corrugated plate of the second filter. Foreign matter filter.

Images