JP2014066582A - Nuclear fuel assembly for pressurized water reactor and lower nozzle used therein - Google Patents

Nuclear fuel assembly for pressurized water reactor and lower nozzle used therein Download PDF

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JP2014066582A
JP2014066582A JP2012211231A JP2012211231A JP2014066582A JP 2014066582 A JP2014066582 A JP 2014066582A JP 2012211231 A JP2012211231 A JP 2012211231A JP 2012211231 A JP2012211231 A JP 2012211231A JP 2014066582 A JP2014066582 A JP 2014066582A
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lower nozzle
water flow
water
fuel assembly
flow hole
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Shunpei Kakigi
俊平 柿木
Yukihiko Mizumoto
裕己彦 水本
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Nuclear Fuel Industries Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

PROBLEM TO BE SOLVED: To provide a lower nozzle capable of rendering uniform a flow of cooling water which flows in through water flow holes and collides with fuel rods, and to provide further a fuel assembly for a pressurized water reactor capable of restraining the generation of fretting wear.SOLUTION: There is provided a lower nozzle disposed in a nuclear fuel assembly for a pressurized water reactor in order to make cooling water flow in toward fuel rods through water flow openings provided on a lower core plate of the pressurized water reactor. In the lower nozzle, a number of water flow holes are provided on a plate part, and a size of the water flow holes on the lower nozzle which are positioned on a place directly located downstream of the cooling water through the water flow openings of the lower core plate is smaller than a size of the water flow holes on the lower nozzle which are not positioned on the place. Also, there is provided the fuel assembly for the pressurized water reactor in which the lower nozzle is used.

Description

本発明は、加圧水型原子炉用原子燃料集合体およびそれに用いられる下部ノズルに関する。   The present invention relates to a nuclear fuel assembly for a pressurized water reactor and a lower nozzle used therefor.

加圧水型原子炉（ＰＷＲ）に用いられる原子燃料集合体（以下、単に「燃料集合体」ともいう）は、図６に示すように、多数の燃料棒２１を並列し、かつシンブル管２２等を混入して複数の支持格子２３で支持させた燃料棒束部と、これらを上下から固定する上部ノズルＮ’と下部ノズルＮとで構成されている（例えば、特許文献１、特許文献２）。   As shown in FIG. 6, a nuclear fuel assembly (hereinafter also simply referred to as “fuel assembly”) used in a pressurized water reactor (PWR) has a large number of fuel rods 21 arranged in parallel and a thimble tube 22 or the like. A fuel rod bundle portion mixed and supported by a plurality of support grids 23, and an upper nozzle N ′ and a lower nozzle N that fix these from above and below are configured (for example, Patent Document 1 and Patent Document 2).

下部ノズルＮは、図７に示すように、燃料集合体の骨格となるシンブル管２２（図６参照）を固定する複数のシンブルスクリュー穴Ｓと、多数の流水孔１１とが設けられた四角形のプレート部１と、プレート部１のコーナー部より垂下し、下部炉心板Ｂとの間に所定の間隔を設けてプレート部１を支持する４本の脚部２とから構成されている。   As shown in FIG. 7, the lower nozzle N has a rectangular shape in which a plurality of thimble screw holes S for fixing a thimble tube 22 (see FIG. 6) serving as a skeleton of the fuel assembly and a plurality of water flow holes 11 are provided. The plate portion 1 is composed of four leg portions 2 that support the plate portion 1 with a predetermined interval between the plate portion 1 and a lower core plate B that hangs down from the corner portion of the plate portion 1.

そして、下部炉心板Ｂには、図８の透視図に示すように、１つの燃料集合体に対して４つの流水孔Ｈが設けられている。   And as shown in the perspective view of FIG. 8, the lower core plate B is provided with the four water flow holes H with respect to one fuel assembly.

このような燃料集合体を備えたＰＷＲにおいて、冷却材（冷却水）は下部炉心板Ｂの流水孔Ｈからプレート部１の流水孔１１を経由して燃料集合体内に流入し、燃料棒２１および支持格子２３の間を通って、上部ノズルＮ’に至る。上部ノズルＮ’に至った冷却水は、その後、再び下部炉心板Ｂに送られて、冷却水が循環する。   In the PWR having such a fuel assembly, the coolant (cooling water) flows from the flow hole H of the lower core plate B into the fuel assembly via the flow hole 11 of the plate portion 1, and the fuel rod 21 and It passes between the support grids 23 and reaches the upper nozzle N ′. Then, the cooling water that has reached the upper nozzle N ′ is sent again to the lower core plate B, and the cooling water circulates.

特開平８−１３６６８１号公報Japanese Patent Laid-Open No. 8-136681 特開２００１−４７７１号公報JP 2001-4771 A

しかしながら、従来のＰＷＲに用いられる燃料集合体においては、一般的に、プレート部１にほぼ均一に分布するように多数の流水孔１１が設けられていたため、流水孔１１から流入する冷却水に均一な流れを形成させることができなかった。   However, in the fuel assembly used in the conventional PWR, since a large number of water flow holes 11 are generally provided so as to be distributed almost uniformly in the plate portion 1, the cooling water flowing in from the water flow holes 11 is uniform. A smooth flow could not be formed.

具体的には、図９に示すように、流水孔１１の上流側にある下部炉心板Ｂの流水孔Ｈから直下流となる箇所では流速が高く、それ以外の箇所では流速が低くなるため、冷却水の不均一な流れを形成していた。   Specifically, as shown in FIG. 9, the flow velocity is high at a location immediately downstream from the flow holes H of the lower core plate B on the upstream side of the flow holes 11, and the flow velocity is low at other locations, A non-uniform flow of cooling water was formed.

このように不均一な流れで流入した冷却水は、そのまま、殆ど均一化されることなく燃料棒２１に衝突して、燃料棒２１に異常な水力振動を発生させる。   Thus, the cooling water that flows in in a non-uniform flow collides with the fuel rods 21 without being made almost uniform as it is, and generates abnormal hydraulic vibrations in the fuel rods 21.

この結果、支持格子２３と燃料棒２１との間に摩擦が生じて、いわゆるフレッティング摩耗を引き起こしていた。このフレッティング摩耗が進行して燃料棒２１を貫通すると、本来、燃料棒内に閉じこめられているべき核分裂生成物等の漏洩を招き、所謂「燃料もれ」が発生する恐れがある。   As a result, friction is generated between the support grid 23 and the fuel rods 21 to cause so-called fretting wear. If this fretting wear progresses and penetrates the fuel rod 21, the leakage of fission products or the like that should be confined in the fuel rod originally may be caused, and so-called "fuel leakage" may occur.

このため、流水孔から流入して燃料棒に衝突する冷却水の流れを均一化して、フレッティング摩耗の発生を抑制することができる燃料集合体が求められていた。   For this reason, there has been a demand for a fuel assembly that can uniformize the flow of cooling water that flows in from the water flow holes and collides with the fuel rods, thereby suppressing the occurrence of fretting wear.

本発明者は、鋭意検討の結果、以下に示す発明により、上記課題が解決できることを見出し、本発明を完成させるに至った。以下、各請求項について説明する。   As a result of intensive studies, the present inventor has found that the above problems can be solved by the invention shown below, and has completed the present invention. Each claim will be described below.

請求項１に記載の発明は、
加圧水型原子炉の下部炉心板に設けられた流水孔を経由して燃料棒へ向けて冷却水を流入させるために、加圧水型原子炉用原子燃料集合体に設けられた下部ノズルであって、
プレート部に多数の流水孔が設けられており、
前記下部炉心板の流水孔からの冷却水が直下流となる箇所に位置する前記下部ノズルの流水孔の大きさが、前記箇所に位置しない前記下部ノズルの流水孔の大きさに比べて小さいことを特徴とする下部ノズルである。 The invention described in claim 1
A lower nozzle provided in a nuclear fuel assembly for a pressurized water reactor to allow cooling water to flow toward a fuel rod via a flow hole provided in a lower core plate of the pressurized water reactor,
A number of water holes are provided in the plate part,
The size of the flow hole of the lower nozzle located at a location where cooling water from the flow hole of the lower core plate is directly downstream is smaller than the size of the flow hole of the lower nozzle not located at the location. It is a lower nozzle characterized by these.

請求項１に記載の発明においては、下部ノズルのプレート部に設けられる流水孔について、下部炉心板の流水孔からの冷却水が直下流となる箇所に位置する流水孔の大きさを、下部炉心板の流水孔からの冷却水が直下流となる箇所に位置しない流水孔の大きさに比べて小さくしている。このため、下部炉心板から流入した冷却水が下部ノズルの流水孔を通過する際、下部炉心板の流水孔の直下流では下部ノズルの流水孔の圧力損失係数を高くして、局所的に圧損を高めることができ、下部炉心板の流水孔の直下流の流速を減速させることができる。   In the first aspect of the present invention, the size of the water flow hole located in the location where the cooling water from the water flow hole of the lower core plate is directly downstream of the water flow hole provided in the plate portion of the lower nozzle is set to the lower core. The cooling water from the water flow hole of the plate is made smaller than the size of the water flow hole that is not located at a location directly downstream. For this reason, when the cooling water flowing in from the lower core plate passes through the flow holes of the lower nozzle, the pressure loss coefficient of the flow holes of the lower nozzle is increased immediately downstream of the flow holes of the lower core plate, and the pressure loss is locally reduced. And the flow velocity immediately downstream of the flow holes of the lower core plate can be reduced.

この結果、下部ノズルのプレートの下流側において、冷却水の均一な流速分布が実現されて、燃料棒に異常な水力振動を発生させることが充分に抑制され、フレッティング摩耗によるトラブルの発生を抑制することができる。   As a result, a uniform flow rate distribution of the cooling water is realized on the downstream side of the lower nozzle plate, and abnormal hydrodynamic vibrations are sufficiently suppressed in the fuel rods, thereby preventing problems caused by fretting wear. can do.

請求項２に記載の発明は、
請求項１に記載の下部ノズルが用いられていることを特徴とする加圧水型原子炉用原子燃料集合体である。 The invention described in claim 2
A nuclear fuel assembly for a pressurized water reactor, wherein the lower nozzle according to claim 1 is used.

請求項２に記載の発明においては、異常な水力振動の発生が充分に抑制されるため、燃料漏れ等、支持格子燃料棒間のフレッティング摩耗によるトラブルの発生が低減されたＰＷＲ用原子燃料集合体を提供することができる。   In the invention according to claim 2, since the occurrence of abnormal hydraulic vibration is sufficiently suppressed, the occurrence of trouble due to fretting wear between the support grid fuel rods, such as fuel leakage, is reduced. The body can be provided.

本発明によれば、流水孔から流入して燃料棒に衝突する冷却水の流れを均一化できる下部ノズルを提供することができると共に、フレッティング摩耗の発生を抑制できる加圧水型原子炉用燃料集合体を提供することができる。   ADVANTAGE OF THE INVENTION According to this invention, while providing the lower nozzle which can equalize the flow of the cooling water which flows in from a water flow hole and collides with a fuel rod, while being able to suppress generation | occurrence | production of fretting wear, the fuel assembly for pressurized water reactors The body can be provided.

本発明の下部ノズルの流水孔の配置の一例を示す平面図である。It is a top view which shows an example of arrangement | positioning of the water flow hole of the lower nozzle of this invention. 従来の一般的な下部ノズルの流水孔の配置を示す平面図である。It is a top view which shows arrangement | positioning of the flow hole of the conventional common lower nozzle. 本発明の一実施の形態の下部ノズルを通過する前後の冷却水の流速を説明する断面図である。It is sectional drawing explaining the flow velocity of the cooling water before and behind passing the lower nozzle of one embodiment of this invention. 本発明の下部ノズルの流水孔の配置の他の例を示す平面図である。It is a top view which shows the other example of arrangement | positioning of the water flow hole of the lower nozzle of this invention. 本発明の下部ノズルの流水孔の配置のさらに他の例を示す平面図である。It is a top view which shows the further another example of arrangement | positioning of the water flow hole of the lower nozzle of this invention. 燃料集合体の構成を模式的に示す正面図である。It is a front view which shows typically the structure of a fuel assembly. 従来の一般的な下部ノズルの斜視図である。It is a perspective view of the conventional common lower nozzle. 下部ノズルと下部炉心板の流水孔との位置関係を示す透視図である。It is a perspective view which shows the positional relationship of a lower nozzle and the flow hole of a lower core plate. 従来の下部ノズルを通過する前後の冷却水の流速を説明する断面図である。It is sectional drawing explaining the flow rate of the cooling water before and behind passing through the conventional lower nozzle.

以下、本発明を実施の形態により説明する。   Hereinafter, the present invention will be described with reference to embodiments.

本実施の形態の下部ノズルは、基本的には従来の下部ノズルと同じ構造を有している。即ち、図７に示すように、四角形のプレート部１とプレ−ト部１のコーナー部から垂下する複数の脚部２を備えている。   The lower nozzle of the present embodiment has basically the same structure as a conventional lower nozzle. That is, as shown in FIG. 7, a rectangular plate portion 1 and a plurality of leg portions 2 depending from the corner portion of the plate portion 1 are provided.

しかし、本実施の形態の下部ノズルの場合、プレート部１に設けられた多数の流水孔の大きさが均一でない点が従来の下部ノズルの場合と相違する。図１に本実施の形態の下部ノズルの流水孔の配置の一例を示す。また、比較のため、図２に従来の一般的な下部ノズルの流水孔の配置を示す。図１、図２は共に平面図であり、図１、図２において、Ｎは下部ノズル、１はプレート部であり、１１は下部ノズルの流水孔である。また、下部炉心板との平面視における位置関係を表すため、下部炉心板の流水孔Ｈを破線で併記した。なお、図が煩雑になるのを避けるため、脚部およびシンブルスクリュー穴の記載を省略してある。   However, the lower nozzle according to the present embodiment is different from the conventional lower nozzle in that the size of the many water holes provided in the plate portion 1 is not uniform. FIG. 1 shows an example of the arrangement of the flow holes of the lower nozzle of the present embodiment. For comparison, FIG. 2 shows the arrangement of water flow holes in a conventional general lower nozzle. 1 and 2 are plan views. In FIGS. 1 and 2, N is a lower nozzle, 1 is a plate portion, and 11 is a flow hole of the lower nozzle. Moreover, in order to express the positional relationship in plan view with the lower core plate, the flow holes H of the lower core plate are also shown with broken lines. In addition, in order to avoid a figure becoming complicated, description of a leg part and a thimble screw hole is abbreviate | omitted.

図２に示すように、従来の下部ノズルＮではいずれの流水孔１１の大きさも均一である。このため、前記のように冷却水の流速は流水孔Ｈの直下流で高く、それ以外では流速が低くなる。そして、この冷却水の流速の不均一さは、下部ノズルＮの流水孔１１を通過した後も殆ど均一化されない。このため不均一な流速を有する冷却水が燃料棒に衝突して、燃料棒に異常な水力振動が発生していた。   As shown in FIG. 2, in the conventional lower nozzle N, the size of any flowing water hole 11 is uniform. For this reason, as described above, the flow rate of the cooling water is high immediately downstream of the water flow hole H, and the flow rate is low otherwise. The non-uniformity in the flow rate of the cooling water is hardly uniform even after passing through the water flow holes 11 of the lower nozzle N. For this reason, the cooling water having a non-uniform flow velocity collided with the fuel rod, and abnormal hydraulic vibration occurred in the fuel rod.

一方、図１に示すように、本実施の形態の下部ノズルＮでは流水孔Ｈの直下流に位置する流水孔１１の大きさが、流水孔Ｈの直下流に位置しない流水孔１１の大きさに比べて小さくなるように形成されている。このように流水孔Ｈの直下流に位置する流水孔１１の大きさを流水孔Ｈの直下流に位置しない流水孔１１の大きさに比べて小さく構成することにより、図３に示すように冷却水が流水孔１１を通過した後には、前記のように流水孔Ｈの直下流の流速が減速され、プレート部１の下流側では流速が均一化される。なお、図３は本実施の形態の下部ノズルＮにおいてプレート部１を通過する前後の冷却水の流速を説明する断面図であり、矢印は冷却水の速度ベクトルを示している。   On the other hand, as shown in FIG. 1, in the lower nozzle N of the present embodiment, the size of the water flow hole 11 located immediately downstream of the water flow hole H is the size of the water flow hole 11 not located immediately downstream of the water flow hole H. It is formed to be smaller than As shown in FIG. 3, the size of the water flow hole 11 located immediately downstream of the water flow hole H is made smaller than the size of the water flow hole 11 not located immediately downstream of the water flow hole H. After the water passes through the water flow hole 11, the flow velocity immediately downstream of the water flow hole H is decelerated as described above, and the flow velocity is made uniform on the downstream side of the plate portion 1. FIG. 3 is a cross-sectional view illustrating the flow rate of the cooling water before and after passing through the plate portion 1 in the lower nozzle N of the present embodiment, and the arrows indicate the cooling water velocity vectors.

即ち、下部炉心板Ｂの流水孔Ｈの直下流に位置する下部ノズルＮの流水孔１１の圧力損失係数を高くして、局所的に冷却水を流れにくくすることにより、下部ノズルＮのプレート１の下流で均一な冷却水の流速分布を実現させることができる。そして、このような均一な流速を有する冷却水が燃料棒に衝突するため、燃料棒の異常な水力振動の発生が抑制される。   That is, by increasing the pressure loss coefficient of the water flow hole 11 of the lower nozzle N located immediately downstream of the water flow hole H of the lower core plate B and making it difficult for the cooling water to flow locally, the plate 1 of the lower nozzle N It is possible to realize a uniform flow rate distribution of the cooling water downstream. And since the cooling water which has such a uniform flow velocity collides with a fuel rod, generation | occurrence | production of the abnormal hydraulic vibration of a fuel rod is suppressed.

従って、本実施の形態の下部ノズルＮを用いることにより、燃料棒の異常な水力振動の発生を抑制することができ、燃料漏れ等、支持格子燃料棒間フレッティング摩耗によるトラブルの発生が低減される。   Therefore, by using the lower nozzle N of the present embodiment, it is possible to suppress the occurrence of abnormal hydraulic vibration of the fuel rods, and to reduce the occurrence of troubles due to fretting wear between the support grid fuel rods such as fuel leakage. The

なお、本実施の形態においては、図１に示すように、流水孔１１の形状として円形の場合を示したが、本発明においては、流水孔１１の形状は円形に限定されず、他の形状であってもよい。例えば図４に示すように流水孔１１の形状が四角形あるいは図５に示すように流水孔１１の形状が扇形である等、如何なる形状であっても流水孔が円形の場合と同等の効果を奏する。   In addition, in this Embodiment, as shown in FIG. 1, although the case where the shape of the water flow hole 11 was circular was shown, in this invention, the shape of the water flow hole 11 is not limited to a circle, Other shapes It may be. For example, the shape of the water flow hole 11 is square as shown in FIG. 4 or the shape of the water flow hole 11 is fan-shaped as shown in FIG. .

そして、上記のような下部ノズルＮを用いることにより、燃料漏れ等の支持格子燃料棒間フレッティング摩耗によるトラブルの発生が低減された燃料集合体を提供することができる。   By using the lower nozzle N as described above, it is possible to provide a fuel assembly in which occurrence of troubles due to fretting wear between support grid fuel rods such as fuel leakage is reduced.

以上、本発明を実施の形態に基づいて説明したが、本発明は上記の実施の形態に限定されるものではない。本発明と同一および均等の範囲内において、上記の実施の形態に対して種々の変更を加えることができる。   While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiments within the same and equivalent scope as the present invention.

１ プレート部
２ 脚部
１１ 下部ノズルの流水孔
２１ 燃料棒
２２ シンブル管
２３ 支持格子
Ｂ 下部炉心板
Ｈ 下部炉心板の流水孔
Ｎ 下部ノズル
Ｎ’ 上部ノズル
Ｓ シンブルスクリュー穴 DESCRIPTION OF SYMBOLS 1 Plate part 2 Leg part 11 Flowing hole 21 of lower nozzle Fuel rod 22 Thimble tube 23 Support grid B Lower core plate H Flowing hole N of lower core plate Lower nozzle N 'Upper nozzle S Thimble screw hole

Claims (2)

加圧水型原子炉の下部炉心板に設けられた流水孔を経由して燃料棒へ向けて冷却水を流入させるために、加圧水型原子炉用原子燃料集合体に設けられた下部ノズルであって、
プレート部に多数の流水孔が設けられており、
前記下部炉心板の流水孔からの冷却水が直下流となる箇所に位置する前記下部ノズルの流水孔の大きさが、前記箇所に位置しない前記下部ノズルの流水孔の大きさに比べて小さいことを特徴とする下部ノズル。 A lower nozzle provided in a nuclear fuel assembly for a pressurized water reactor to allow cooling water to flow toward a fuel rod via a flow hole provided in a lower core plate of the pressurized water reactor,
A number of water holes are provided in the plate part,
The size of the flow hole of the lower nozzle located at a location where cooling water from the flow hole of the lower core plate is directly downstream is smaller than the size of the flow hole of the lower nozzle not located at the location. Lower nozzle characterized by 請求項１に記載の下部ノズルが用いられていることを特徴とする加圧水型原子炉用原子燃料集合体。   A nuclear fuel assembly for a pressurized water reactor, wherein the lower nozzle according to claim 1 is used.
JP2012211231A 2012-09-25 2012-09-25 Nuclear fuel assembly for pressurized water reactor and lower nozzle used therein Pending JP2014066582A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112185600A (en) * 2020-09-30 2021-01-05 中国核动力研究设计院 Nuclear reactor lower cavity stepped flow distribution device and distribution structure

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112185600A (en) * 2020-09-30 2021-01-05 中国核动力研究设计院 Nuclear reactor lower cavity stepped flow distribution device and distribution structure
CN112185600B (en) * 2020-09-30 2022-02-01 中国核动力研究设计院 Nuclear reactor lower cavity stepped flow distribution device and distribution structure

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