JP3692289B2

JP3692289B2 - Method for cleaning steam generator inside nuclear power plant

Info

Publication number: JP3692289B2
Application number: JP2000317921A
Authority: JP
Inventors: 和豊村田; 隆司上野; 博幸藤原; 高久服部
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2000-10-18
Filing date: 2000-10-18
Publication date: 2005-09-07
Anticipated expiration: 2020-10-18
Also published as: JP2002131468A

Description

【０００１】
【発明の属する技術分野】
本発明は大型のシェルチューブ型熱交換器の内部を洗浄する方法に関し、特に原子力プラントの蒸気発生器の内部を洗浄する方法に関する。
【０００２】
【従来の技術】
現在発電用として広く使用されている加圧水型原子炉は、一般に２乃至４基の蒸気発生器を使用している。この蒸気発生器は細部では構造が異なるが、シェルチューブ型熱交換器を蒸気発生器として使用したものである。即ち、多数の伝熱管の内部に高温の一次流体即ち原子炉冷却材を流し、伝熱管の外側の胴側空間に二次流体即ち給水を流し、この給水を蒸発せしめて主蒸気とする。而して、胴側空間（以下２次側空間という。）においては、給水が蒸発を繰り返すのでその中に含まれていた不純物が伝熱管の外表面及び２次側空間部機器表面にスケールとして付着する。このようなスケールは腐食などを促進するから伝熱管等の健全性維持などに好ましくなく、定期的或いは必要に応じてスケール除去の洗浄が行われる。
【０００３】
以上のような事情から、従来行われている蒸気発生器内部洗浄方法の一例を、図４を参照して説明する。図において、蒸気発生器１０の構造は概念的に示されているが、竪型の胴１１の下側は厚い管板１３に一体的に接続され、又図示しない汽水分離器などを収容する上方拡大部１１ａは、主蒸気弁１５を備えた主蒸気管に連絡している。管板１３の下側は鏡板１７によって囲まれ、その中に水室１９、２１が隔壁２３によって分けられて形成されている。そして、１本のみ概念的に示された逆Ｕ字形の伝熱管２５が胴１１の中に設けられ、その両端は管板１３の穴に挿入されてそれぞれ水室１９、２１に開口している。伝熱管２５は薄肉の細管であって、非常に狭い間隔で配置されて伝熱管束を形成しているが、その外面に鉄酸化物スケール２７が付着する。また胴１１内側表面、管板１３表面等２次側機器表面にも鉄酸化物スケールが付着する。洗浄はこの鉄酸化物スケール２７を除去しようとするものである。尚、通常運転時には、原子炉冷却材が水室２１、伝熱管２５及び水室１９を順次流れ、二次側の給水を加熱する。
【０００４】
このような構造の蒸気発生器内部を洗浄するには、図４（ａ）に示すように、胴１１の内部に化学洗浄液２９を入れ、被洗浄部を浸漬する。そして、主蒸気弁１５を閉じ、内部の温度を１７０℃、圧力を１０ataとする。化学洗浄液２７をこの温度に維持するには、伝熱管２５内を流れる一次流体の熱を使用しても良い。この状態では、化学洗浄液２９中の温度差により自然対流が生じ、化学洗浄液２９は流動する。そして、主蒸気弁１５を全開して図４（ｂ）に示すようにする。即ち、主蒸気弁１５の全開により、内部の圧力は大気圧となるから、化学洗浄液２９内の随所で沸騰が生じ、気泡は上昇し、化学洗浄液２９は激しく流動乃至撹拌される。このような沸騰作用により、鉄酸化物スケール２７の溶解作用が促進され、洗浄が促進される。このような洗浄は、化学洗浄液２９による鉄酸化物スケール２７の溶解反応が基になっており、その進行は溶解物の拡散により規制されているから、前述の沸騰撹拌により大きく促進される。
【０００５】
【発明が解決しようとする課題】
以上説明したように、従来の蒸気発生器内部洗浄方法においては、洗浄作業の進行を大きく規制する洗浄液撹拌を減圧沸騰に依存していたため、洗浄作業時間が長くなるという問題があった。これは又、蒸気発生器が、狭い遮蔽区画室の内部に設けられていて、通常の撹拌促進装置を使用しがたいという事情も影響している。更には、前述のように、蒸気発生器が複数設けられているため、一基毎に行う洗浄方法では長時間の洗浄作業が余儀なくされていた。
従って、本発明の目的は、原子力プラントにある複数の蒸気発生器の内部を短時間で効率よく洗浄する方法を提供することである。
【０００６】
【課題を解決するための手段】
前述の課題を解決するため、本発明による原子力プラントの蒸気発生器内部洗浄方法は、少なくとも２基の蒸気発生器の胴側空間の底部を移送配管により互いに連通させ、一方の蒸気発生器の胴側空間に洗浄液を所定量供給し、しかる後、この洗浄液に不活性ガス圧を作用させて、前記移送配管を介して他方の蒸気発生器に前記洗浄液を移送し、所定時間後に、同様にして、前記洗浄液を前記他方の蒸気発生器から前記一方の蒸気発生器に逆移送し、複数の蒸気発生器に交互に給排するものである。洗浄液の駆動源としては、蒸気発生器の主蒸気弁を介する加圧不活性ガスの圧力を使用しても、これに移送配管に設けた移送ポンプを併用しても良い。又、本発明の別の態様によれば、原子力プラントの蒸気発生器内部洗浄方法は、少なくとも２基の蒸気発生器の胴側空間において、上部同士を上部連結管により連通させ、下部同士をＵ字管によりそれぞれ連通させ、このＵ字管の一方の脚部に窒素ガスを注入すると共に他方の脚部に洗浄液を注入して、Ｕ字管と上部連結管を介して複数の蒸気発生器間に洗浄液の循環流を形成させ、その後、一方の脚部に洗浄液を注入すると共に他方の脚部に窒素ガスを注入するように切り替え、流れ方向の逆転した循環流を形成させることを特徴とするものである。このようにして、循環する洗浄液が、その流れ方向を逆転させながら、伝熱管の外面の鉄酸化物スケールとの溶解反応部に順次流れ込むと、溶解物の拡散が促進され、溶解反応乃至洗浄が促進される。好適な実施形態によれば、循環流の流れ方向は適宜逆転され、又、伝熱管内に原子炉冷却材を流して加熱蒸発により拡散を更に促進させることができる。
【０００７】
【発明の実施の形態】
以下添付の図面を参照して本発明の実施形態を説明する。尚、従来技術に関する図面を含め、全図にわたり同一部分には同一の符号を付し、発明の迅速且つ正確な理解の一助とする。
先ず、図１に示すように２基の蒸気発生器１０のブローダウン配管３１を移送配管３３で繋ぐ。ブローダウン配管３１は、蒸気発生器１０の管板１３近傍に開口して元々設けられているもので、本来の目的は胴１１の内部の給水を排出するものである。移送配管３３には移送ポンプ３５が設けられているが、その取り付けスペースが原子力プラント内に確保できないときは、移送ポンプ３５を取り付けなくても良い。移送配管３３で繋がれた２基の蒸気発生器１０は同一構造であるが、以下の洗浄操作の説明では、これらを峻別するためそれぞれ符号を１０ａ、１０ｂとする。先ず、蒸気発生器１０ａに洗浄液２９を所定水位まで入れる。次いで主蒸気弁１５を経由して加圧窒素ガスを供給すると共に移送ポンプ３５を作動する。これにより、洗浄液２９は、蒸気発生器１０ａのブローダウン配管３１、移送配管３３及び蒸気発生器１０ｂのブローダウン配管３１を通り蒸気発生器１０ｂの中に移される。このとき、蒸気発生器１０ｂの主蒸気弁１５は開放されており、蒸気発生器１０ｂ内の空気は主蒸気弁１５を通って大気中に押し出される。所定時間後、同様な操作により、蒸気発生器１０ｂ内の洗浄液を移送ポンプ３５３を通って蒸気発生器１０ａ内へ逆移送する。この移送操作と逆移送操作を適宜繰り返す。
【０００８】
上述の洗浄液の移送操作により、洗浄液２９が押し出される蒸気発生器１０ａ内では、伝熱管２５の外面に沿って洗浄液が下向きに流れ、一方洗浄液が流入する蒸気発生器１０ｂ内では、洗浄液の液面が上昇するに際し伝熱管２５の外面の鉄酸化物スケール２７に洗浄液２９が次々と衝突、接触する。このような洗浄液の流動及び鉄酸化物スケールとの接触作用により、鉄酸化物スケール２７の溶解は促進され、洗浄が効果的に行われる。更に、洗浄作業は、少なくとも２基の蒸気発生器について同時に行うので、この面からも洗浄時間が短縮されると共に必要洗浄液量は１基分の容量となるので、材料の削減となると共に後から行う洗浄液処理作業も半減し、廃液処理コストも削減される。
【０００９】
撹拌による洗浄作用の効果を実証すべく、次のような比較試験を行った。被洗浄物は鉄酸化物として代表的なマグネタイト（Ｆｅ₃Ｏ₄）を使用し、洗浄液はマロン酸７％、アスコルビン酸３％を含む液を用いた。試験温度は６０℃である。その結果を図２に示す。図２のグラフにおいて、曲線Ｉが撹拌した場合の溶出鉄イオンの経時変化、曲線IIが撹拌をしない場合の溶出鉄イオンの経時変化を示している。ここではマグネタイトを洗浄液中に静止したケースと、定期的にステーラー撹拌による水位上下振動を積極的に実施撹拌したケース、の２ケースの結果を示した。図２のグラフから判るように、マグネタイト１０ｇを溶解せしめるのに要した時間は、撹拌をした場合は約５時間程度であるのに対し、撹拌しない場合では、２５時間経過した後でも撹拌をした場合の溶解は得られない。
【００１０】
次に図３を参照して別の実施形態を説明する。先ず、図示するように２基の蒸気発生器１０（これらも同一構造であるが作用の説明に便なるように符号１０ａ、１０ｂを付けて区別する。）の胴１１の上部を上部連結管４１により連通させる。具体的にはその部分にあるマンホールの蓋と同形のフランジを上部連結管４１の両端に取り付けることにより、上部連結管４１の取着は容易に行われる。次に蒸気発生器１０ａ、１０ｂの下部にあるブローダウン配管３１をＵ字管４３により連結する。Ｕ字管４３の下方脚部には、対応する位置にジョイント４３ａ、４３ｂを備え、これらは後述するように窒素ガス注入ライン４５、洗浄液注入ライン４７に着脱自在に連結可能である。自明のことであるが、上部連結管４１及びＵ字管４３の取付は、洗浄の準備作業であるので同時並行的に行っても、先後入れ替えて行っても良い。
【００１１】
前述のように準備が完了したら、窒素ガス供給ライン４５をジョイント４３ａに、洗浄液注入ライン４７をジョイント４３ｂに接続して、窒素ガスと洗浄液とをＵ字管４３にそれぞれ注入する。このようにすると、窒素ガスはそのまま上向きに流れ、蒸気発生器１０ａに流入するが、洗浄液もこの流れに導かれて蒸気発生器１０ａに流れ込む。この際、蒸気発生器１０ａの主蒸気弁１５は開放されていて、窒素ガスは大気中に逃れるから、窒素ガス流は好適に維持される。洗浄液の水位が、上部連結管４１の位置に達すれば、蒸気発生器１０ａ、１０ｂ、上部連結管４１及びＵ字管４３を通る時計回りの洗浄液循環流が生じる。この洗浄液循環流を所定時間続け、その後窒素ガス供給ライン４５と洗浄液注入ライン４７の接続関係を入れ替え、窒素ガス注入と洗浄液注入とを行う。そうすると、洗浄液循環流の向きは反時計方向に切り替わる。このような、洗浄液の循環流により、伝熱管２５の外面の鉄酸化物スケール２７と洗浄液との溶解反応は、反応部の溶液が迅速に入れ替わるので、促進される。
【００１２】
選択的な操作ではあるが、前述の洗浄液循環流の維持に合わせ、伝熱管２５の中に相対的には高温の原子炉冷却材を流す。このようにすると、洗浄液は加熱されて昇温し、蒸気を発生する。このような蒸気発生を効果的に行うため、窒素ガス流入側の蒸気発生器１０の主蒸気弁１５を開閉する。このようにして、加圧減圧が繰り返され、沸騰乃至蒸気発生が繰り返され、撹拌される。窒素ガスが流入しない側の蒸気発生器１０の主蒸気弁１５は閉じておく。このようにして、伝熱管２５の外面の鉄酸化物スケールの外面には、循環流及び蒸気発生による洗浄液循環流の流動が生じ、溶解反応乃至洗浄が促進される。
【００１３】
【発明の効果】
以上説明したように、本発明によれば、少なくとも２基の蒸気発生器を連通し、蒸気発生器のみの洗浄に必要な量の洗浄液を往復移送させ又は流れの向きを替えて循環させて洗浄液を流動させつつ洗浄を行うので、流動により撹拌が促進され、効率よく短時間で多くの蒸気発生器を洗浄することができる。なお、洗浄液を２基の蒸気発生器間で往復移送する場合には、使用洗浄液の量は１基分でよいので、廃液も少なく、廃液処理コストも大幅に削減することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態を示す系統図である。
【図２】前記実施形態の作用効果を説明するための試験結果を示すグラフである。
【図３】本発明の別の実施の形態を示す系統図である。
【図４】従来技術を説明するための系統図である。
【符号の説明】
１０、１０ａ、１０ｂ蒸気発生器
１１胴
１３管板
１５主蒸気弁
１７鏡板
１９、２１水室
２３隔壁
２５伝熱管
２７鉄酸化物スケール
２９洗浄液
３１ブローダウン配管
３３移送配管
３５移送ポンプ
４１上部連結管
４３Ｕ字管
４５窒素ガス供給ライン
４７洗浄液注入ライン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cleaning the inside of a large shell tube heat exchanger, and more particularly to a method for cleaning the inside of a steam generator in a nuclear power plant.
[0002]
[Prior art]
The pressurized water reactor currently widely used for power generation generally uses 2 to 4 steam generators. Although this steam generator has a different structure in detail, a shell tube type heat exchanger is used as the steam generator. That is, a high-temperature primary fluid, that is, a reactor coolant, is caused to flow inside a large number of heat transfer tubes, and a secondary fluid, that is, feed water, is caused to flow to the trunk side space outside the heat transfer tubes, and this feed water is evaporated to become main steam. Thus, in the trunk side space (hereinafter referred to as the secondary side space), the water supply repeatedly evaporates, so the impurities contained therein are scaled on the outer surface of the heat transfer tube and the surface of the secondary side space part device. Adhere to. Since such a scale promotes corrosion and the like, it is not preferable for maintaining the soundness of the heat transfer tube and the like, and cleaning for removing the scale is performed periodically or as necessary.
[0003]
From the above situation , an example of a conventional steam generator internal cleaning method will be described with reference to FIG . In the figure, the structure of the steam generator 10 is conceptually shown, but the lower side of the saddle-shaped body 11 is integrally connected to a thick tube plate 13 and accommodates a brackish water separator (not shown). The enlarged portion 11 a communicates with a main steam pipe provided with a main steam valve 15. The lower side of the tube plate 13 is surrounded by the end plate 17, and the water chambers 19 and 21 are formed therein by being separated by a partition wall 23. An inverted U-shaped heat transfer tube 25, conceptually shown only one, is provided in the barrel 11, and both ends thereof are inserted into holes in the tube plate 13 and open to the water chambers 19 and 21, respectively. . The heat transfer tube 25 is a thin thin tube and is arranged at a very narrow interval to form a heat transfer tube bundle, and an iron oxide scale 27 adheres to the outer surface thereof. Further, iron oxide scales are also attached to the secondary equipment surface such as the inner surface of the body 11 and the surface of the tube sheet 13. Washing is intended to remove the iron oxide scale 27. During normal operation, the reactor coolant sequentially flows through the water chamber 21, the heat transfer tube 25, and the water chamber 19 to heat the secondary side water supply.
[0004]
In order to clean the inside of the steam generator having such a structure, as shown in FIG. 4A, a chemical cleaning liquid 29 is put into the body 11 and the portion to be cleaned is immersed. Then, the main steam valve 15 is closed, the internal temperature is set to 170 ° C., and the pressure is set to 10 ata. In order to maintain the chemical cleaning liquid 27 at this temperature, the heat of the primary fluid flowing in the heat transfer tube 25 may be used. In this state, natural convection occurs due to a temperature difference in the chemical cleaning liquid 29, and the chemical cleaning liquid 29 flows. Then, the main steam valve 15 is fully opened as shown in FIG. That is, when the main steam valve 15 is fully opened, the internal pressure becomes atmospheric pressure, so that boiling occurs everywhere in the chemical cleaning liquid 29, the bubbles rise, and the chemical cleaning liquid 29 is vigorously fluidized or stirred. Such boiling action promotes the dissolving action of the iron oxide scale 27 and promotes cleaning. Such cleaning is based on the dissolution reaction of the iron oxide scale 27 by the chemical cleaning solution 29, and the progress thereof is regulated by the diffusion of the dissolved matter, so that it is greatly promoted by the above-described boiling stirring.
[0005]
[Problems to be solved by the invention]
As described above, the conventional steam generator internal cleaning method has a problem that the cleaning operation time becomes longer because the cleaning liquid stirring that largely restricts the progress of the cleaning operation relies on the boiling under reduced pressure. This also has the effect that the steam generator is provided inside a narrow, shielded compartment and it is difficult to use a normal stirring accelerator. Further, as described above, since a plurality of steam generators are provided, the cleaning method performed for each unit necessitates a long-time cleaning operation.
Accordingly, an object of the present invention is to provide a method for efficiently cleaning the inside of a plurality of steam generators in a nuclear power plant in a short time.
[0006]
[Means for Solving the Problems]
To solve the problems described above, the steam generator inside the cleaning method of the nuclear power plant that by the present invention, the bottom portion of the body-side space of the steam generator of the at least two groups is communicated with each other by transfer pipe, one steam generator A predetermined amount of the cleaning liquid is supplied to the body side space of the cylinder, and then the cleaning liquid is transferred to the other steam generator via the transfer pipe by applying an inert gas pressure to the cleaning liquid. a manner, the cleaning liquid to the reverse transfer to one of the steam generator from said the other of the steam generator, is to supply and discharge alternately into a plurality of steam generators. As a driving source for the cleaning liquid, the pressure of pressurized inert gas via the main steam valve of the steam generator may be used, or a transfer pump provided in the transfer pipe may be used in combination. Further, according to another aspect of the present invention, in the steam generator internal cleaning method of a nuclear power plant , the upper parts are communicated with each other by the upper connecting pipe in the trunk side space of at least two steam generators, and the lower parts are connected to each other by U communicated respectively by shaped tube, by injecting the cleaning liquid to the other leg while injecting nitrogen gas into one leg of the U-shaped tube, through the U-tube and the upper connecting pipe between a plurality of steam generators to form a circulating flow of the cleaning liquid, then switched to inject nitrogen gas into the other leg portion with injecting a cleaning liquid to the one leg, characterized in that to form a reverse circulation flow in the flow direction Is . In this way, cleaning liquid circulates, while reversing the direction of flow, and successively flow into non-dissolution reaction of the iron oxide scale on the outer surface of the heat transfer tube, the diffusion of the melt is accelerated dissolution reaction or washing Is promoted. According to a preferred embodiment, the flow direction of the circulating flow is reversed as appropriate, also be Ru further promote diffusion by thermal evaporation by passing the reactor coolant in the heat transfer tube.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same part over all drawings including drawing regarding a prior art, and it helps a quick and accurate understanding of invention.
First, as shown in FIG. 1, the blowdown pipes 31 of the two steam generators 10 are connected by the transfer pipe 33. The blow-down pipe 31 is originally provided in the vicinity of the tube plate 13 of the steam generator 10, and the original purpose is to discharge the water supply inside the barrel 11. The transfer pipe 33 is provided with the transfer pump 35. However, when the installation space cannot be secured in the nuclear power plant, the transfer pump 35 may not be attached. The two steam generators 10 connected by the transfer pipe 33 have the same structure, but in the following description of the cleaning operation, the reference numerals are denoted by 10a and 10b, respectively, in order to distinguish them. First, the cleaning liquid 29 is put into the steam generator 10a to a predetermined water level. Next, pressurized nitrogen gas is supplied via the main steam valve 15 and the transfer pump 35 is operated. As a result, the cleaning liquid 29 passes through the blow-down pipe 31 and the transfer pipe 33 of the steam generator 10a and the blow-down pipe 31 of the steam generator 10b and is transferred into the steam generator 10b. At this time, the main steam valve 15 of the steam generator 10b is opened, and the air in the steam generator 10b is pushed out through the main steam valve 15 into the atmosphere. After a predetermined time, the cleaning liquid in the steam generator 10b is reversely transferred into the steam generator 10a through the transfer pump 353 by the same operation. This transfer operation and reverse transfer operation are repeated as appropriate.
[0008]
In the steam generator 10a where the cleaning liquid 29 is pushed out by the above-described cleaning liquid transfer operation, the cleaning liquid flows downward along the outer surface of the heat transfer tube 25, while in the steam generator 10b into which the cleaning liquid flows, the level of the cleaning liquid As the temperature rises, the cleaning liquid 29 collides and contacts the iron oxide scale 27 on the outer surface of the heat transfer tube 25 one after another. Due to the flow of the cleaning liquid and the contact action with the iron oxide scale, dissolution of the iron oxide scale 27 is promoted, and cleaning is performed effectively. Further, since the cleaning operation is simultaneously performed on at least two steam generators, the cleaning time is reduced from this aspect and the amount of cleaning liquid required is one volume, which leads to a reduction in materials and later. The cleaning liquid processing operation to be performed is halved and the waste liquid processing cost is reduced.
[0009]
In order to demonstrate the effect of the cleaning action by stirring, the following comparative test was conducted. As the object to be cleaned, magnetite (Fe ₃ O ₄ ), which is a typical iron oxide, was used. As the cleaning liquid, a liquid containing 7% malonic acid and 3% ascorbic acid was used. The test temperature is 60 ° C. The result is shown in FIG. In the graph of FIG. 2, curve I shows the time-dependent change of the eluted iron ion when stirring, and curve II shows the time-dependent change of the eluted iron ion when not stirred. Here, the results of two cases of a case where the magnetite is stationary in the cleaning liquid and a case where the water level up-and-down vibration by periodic stirring is actively performed and stirred are shown. As can be seen from the graph of FIG. 2, the time required to dissolve 10 g of magnetite was about 5 hours when stirring was performed, but when stirring was not performed, stirring was performed even after 25 hours had elapsed. In some cases no dissolution is obtained.
[0010]
Next, another embodiment will be described with reference to FIG. First, as shown in the figure, the upper part of the upper body 11 of the body 11 of the two steam generators 10 (these are also of the same structure but are distinguished by adding reference numerals 10a and 10b for convenience of explanation). To communicate with each other. Specifically, the upper connecting pipe 41 is easily attached by attaching flanges having the same shape as the manhole cover at the both ends of the upper connecting pipe 41. Next, the blow-down piping 31 under the steam generators 10 a and 10 b is connected by a U-shaped tube 43. The lower legs of the U-shaped tube 43 are provided with joints 43a and 43b at corresponding positions, and these can be detachably connected to a nitrogen gas injection line 45 and a cleaning liquid injection line 47 as described later. Obviously, the attachment of the upper connecting pipe 41 and the U-shaped pipe 43 is a preparatory work for cleaning, and thus may be performed simultaneously or may be performed after the replacement.
[0011]
When the preparation is completed as described above, the nitrogen gas supply line 45 is connected to the joint 43a, the cleaning liquid injection line 47 is connected to the joint 43b, and nitrogen gas and cleaning liquid are injected into the U-shaped tube 43, respectively. If it does in this way, nitrogen gas will flow upwards as it is, and will flow in into steam generator 10a, but cleaning fluid will also be led to this flow and will flow into steam generator 10a. At this time, the main steam valve 15 of the steam generator 10a is opened and the nitrogen gas escapes into the atmosphere, so that the nitrogen gas flow is suitably maintained. When the water level of the cleaning liquid reaches the position of the upper connecting pipe 41, a clockwise cleaning liquid circulating flow through the steam generators 10a and 10b, the upper connecting pipe 41 and the U-shaped pipe 43 is generated. This cleaning liquid circulation flow is continued for a predetermined time, and thereafter, the connection relationship between the nitrogen gas supply line 45 and the cleaning liquid injection line 47 is switched to perform nitrogen gas injection and cleaning liquid injection. Then, the direction of the cleaning liquid circulation flow is switched counterclockwise. By such a circulating flow of the cleaning liquid, the dissolution reaction between the iron oxide scale 27 on the outer surface of the heat transfer tube 25 and the cleaning liquid is promoted because the solution in the reaction section is quickly replaced.
[0012]
Although it is a selective operation, a relatively high-temperature reactor coolant is caused to flow through the heat transfer tube 25 in accordance with the maintenance of the above-described cleaning liquid circulation flow. If it does in this way, cleaning fluid will be heated and it will heat up and generate | occur | produce a vapor | steam. In order to effectively generate such steam, the main steam valve 15 of the steam generator 10 on the nitrogen gas inflow side is opened and closed. In this way, pressurization and depressurization are repeated, boiling or steam generation is repeated, and stirring is performed. The main steam valve 15 of the steam generator 10 on the side where the nitrogen gas does not flow is closed. In this way, the flow of the cleaning liquid circulation flow due to the circulation flow and the generation of steam occurs on the outer surface of the iron oxide scale on the outer surface of the heat transfer tube 25, and the dissolution reaction or cleaning is promoted.
[0013]
【The invention's effect】
As described above, according to the present invention, at least two steam generators communicate with each other, and a cleaning liquid in an amount necessary for cleaning only the steam generator is reciprocated or circulated by changing the flow direction. Since the washing is performed while flowing, stirring is promoted by the flow, and many steam generators can be washed efficiently in a short time. When the cleaning liquid is reciprocated between the two steam generators, the amount of the cleaning liquid used may be one, so that there is little waste liquid and the waste liquid processing cost can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the present invention.
FIG. 2 is a graph showing test results for explaining the operational effects of the embodiment.
FIG. 3 is a system diagram showing another embodiment of the present invention.
FIG. 4 is a system diagram for explaining the prior art.
[Explanation of symbols]
10, 10a, 10b Steam generator 11 Body 13 Tube plate 15 Main steam valve 17 End plate 19, 21 Water chamber 23 Partition 25 Heat transfer tube 27 Iron oxide scale 29 Cleaning liquid 31 Blowdown piping 33 Transfer piping 35 Transfer pump 41 Upper connecting tube 43 U-tube 45 Nitrogen gas supply line 47 Cleaning liquid injection line

Claims

Communicated with each other by a transfer pipe bottom of the body-side space of the steam generator of the at least two groups, the washing liquid a predetermined amount supplied to the shell side space of one of the steam generator, after which action the inert gas pressure in the cleaning solution by, and through the transfer pipe transferring the cleaning fluid to the other of the steam generator, after a predetermined time, in the same manner, inversely transferring the cleaning fluid from the other steam generator to one of the steam generator wherein A method for cleaning a steam generator inside a nuclear power plant.

2. The method of cleaning a steam generator inside a nuclear power plant according to claim 1 , wherein a transfer pump is provided in the transfer pipe in order to promote transfer and reverse transfer of the cleaning liquid.

In the trunk side space of at least two steam generators , the upper parts communicate with each other by an upper connecting pipe, the lower parts communicate with each other by a U-shaped pipe, and nitrogen gas is injected into one leg of the U-shaped pipe. the wash was injected into the other leg, via the U-tube and the upper connecting pipe to form a circulating flow of the cleaning liquid between the plurality of steam generator, the other leg along with then injecting washing liquid into one leg A method for cleaning the inside of a steam generator of a nuclear power plant, characterized in that a nitrogen flow is switched to be injected into a section to form a circulating flow having a reverse flow direction .