JP2005283530A - Stress corrosion cracking suppression method - Google Patents

Stress corrosion cracking suppression method Download PDF

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JP2005283530A
JP2005283530A JP2004101804A JP2004101804A JP2005283530A JP 2005283530 A JP2005283530 A JP 2005283530A JP 2004101804 A JP2004101804 A JP 2004101804A JP 2004101804 A JP2004101804 A JP 2004101804A JP 2005283530 A JP2005283530 A JP 2005283530A
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water
hydrogen
hydrazine
stress corrosion
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JP4366227B2 (en
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Yoichi Wada
陽一 和田
Kazunari Ishida
一成 石田
Masahiko Tachibana
正彦 橘
Motohiro Aizawa
元浩 会沢
Naoshi Usui
直志 碓井
Masahito Nakamura
雅人 中村
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Hitachi 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

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Abstract

<P>PROBLEM TO BE SOLVED: To suppress stress corrosion cracking by lowering corrosion potential of reactor structure material. <P>SOLUTION: Oxide existing on the surface of structure and piping of a BWR contacting reactor water is removed. Then, hydrazine is added to reactor water together with hydrogen in an operation cycle of a boiling water reactor. As hydrazine is added to the reactor water in addition to hydrogen, oxygen and hydrogen peroxide generated in the reactor are made to react with hydrazine to be water and nitrogen so that the concentration of oxygen and hydrogen peroxide in reactor water is efficiently reduced. Since oxide is removed, the effect of hydrazine to directly lower the corrosion potential of materials can be duplicated. As the results, the corrosion potential of the reactor structure materials sufficiently lowers and stress corrosion cracking can be suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、応力腐食割れ抑制方法に係り、特に、原子力発電プラントの原子炉構造材料の応力腐食割れを抑制するのに好適な応力腐食割れ抑制方法に関する。   The present invention relates to a stress corrosion cracking suppression method, and more particularly, to a stress corrosion cracking suppression method suitable for suppressing stress corrosion cracking of a nuclear reactor plant structural material.

原子炉構造材料（ステンレス鋼及びニッケル基合金等）における応力腐食割れ（以下、ＳＣＣという）の発生は、材料等の改善により原子炉の実用化初期に比べて、はるかに抑制されており、今日、原子炉の安全性および信頼性は格段に向上している。しかしながら、今以上に、ＳＣＣの発生及び進展を抑制して原子炉をより安心できるものにするため、絶えず技術革新が行われている。   Occurrence of stress corrosion cracking (hereinafter referred to as SCC) in nuclear reactor structural materials (stainless steel, nickel-base alloys, etc.) has been greatly suppressed compared to the early stage of practical use of reactors due to improvements in materials. The safety and reliability of nuclear reactors are greatly improved. However, more than ever, technological innovations are constantly being made in order to suppress the occurrence and progress of SCC and make the reactor more secure.

例えば、沸騰水型原子炉(Boiling Water Reactor, ＢＷＲ) においてプラント稼働率向上の観点から、炉内構造物や圧力境界を構成する構造材料３０４ステンレス鋼，３１６Ｌステンレス鋼，ニッケル基合金等）のＳＣＣを抑制することは、今もなお重要な課題となっている。ＳＣＣは、材料，応力，環境の３因子が重畳したときに起こると考えられている。従って、３因子の内、少なくとも１因子を緩和することによりＳＣＣを抑制することが行われている。   For example, in the boiling water reactor (BWR), from the viewpoint of improving the plant operating rate, the SCC of the structural material 304 stainless steel, 316L stainless steel, nickel base alloy, etc. constituting the reactor internal structure and pressure boundary) Suppression is still an important issue. SCC is considered to occur when three factors of material, stress, and environment overlap. Therefore, SCC is suppressed by relaxing at least one of the three factors.

原子力発電プラント運転中、炉心の強いガンマ線及び中性子線により、原子炉冷却水が放射線分解する。その結果、炉内構造物や圧力境界を構成する構造材料は、放射線分解生成物である酸素及び過酸化水素が数百ppb 程度存在する。高温（本発明では１００℃以上を高温とし、定格出力運転時の炉心出口温度は２８８℃）の原子炉冷却水に曝されることとなる。図２に、ＳＣＣにおけるき裂進展速度(以下「Crack Growth Rate, ＣＧＲ」という) と腐食電位(Electrochemical corrosion potential, ＥＣＰ) の関係を表す。図２から、ＥＣＰが低下するとＣＧＲが減少することがわかる。図３に、酸素及び過酸化水素の濃度と高温水中における３０４型ステンレス鋼（以下「Type 304 stainless steel,
３０４ＳＳ」という）のＥＣＰとの関係を測定した結果を示す。酸素も過酸化水素も濃度の減少に伴いＥＣＰが小さくなる。従って、原子炉冷却水に曝された構造材料のＳＣＣを緩和するためにはＥＣＰを低減すること、つまり、原子炉水中に存在する酸素及び過酸化水素の濃度を低減することが有効である。 During operation of the nuclear power plant, the reactor cooling water undergoes radiolysis due to the strong core gamma rays and neutron rays. As a result, the internal structure of the furnace and the structural material constituting the pressure boundary have several hundred ppb of oxygen and hydrogen peroxide, which are radiolysis products. The reactor is exposed to high-temperature reactor cooling water (in the present invention, a temperature of 100 ° C. or higher is set to a high temperature, and the core outlet temperature at the rated power operation is 288 ° C.). FIG. 2 shows the relationship between crack growth rate (hereinafter referred to as “Crack Growth Rate, CGR”) and corrosion potential (Electrochemical corrosion potential, ECP) in SCC. FIG. 2 shows that CGR decreases as ECP decreases. FIG. 3 shows the concentration of oxygen and hydrogen peroxide and type 304 stainless steel (hereinafter “Type 304 stainless steel,
304SS ") and the measurement result of the relationship with the ECP. As the concentration of both oxygen and hydrogen peroxide decreases, the ECP decreases. Therefore, it is effective to reduce the ECP, that is, to reduce the concentration of oxygen and hydrogen peroxide present in the reactor water in order to reduce the SCC of the structural material exposed to the reactor cooling water.

この課題に対する従来技術の一つとして、炉水に水素を添加する技術（以下「水素注入」という）がある。水素注入は、ＢＷＲでは給水系に水素を加圧注入することで給水に水素を溶存させ、この水素を含む給水を原子炉内に導くことにより行われる。ここで、水素注入に伴う再結合反応について説明する。原子炉内の炉水に水素が添加されると、原子炉内の炉心を取囲むダウンカマ部で、水素が酸素及び過酸化水素と再結合する。この再結合反応は、放射線照射の作用により生成するＯＨ等の反応性に富むラジカル種が、触媒のように作用することにより速やかに進行する。この再結合反応により、炉水中での酸素及び過酸化水素の濃度は低下する。酸素及び過酸化水素の濃度が低下することにより、原子炉構造材の腐食電位（ＥＣＰ）も低下する。水素注入は、注入した水素と水の放射線分解によって生じた酸素及び過酸化水素とを反応させて水に戻すことにより、炉水中の酸素及び過酸化水素の濃度を低減する技術である。しかしながら、高濃度の水素注入を行うと水分子を構成する酸素が中性子と核反応することで生じる高エネルギーのγ線を放出する放射性窒素１６（Ｎ−１６）が蒸気中に移行しやすくなり、このＮ−１６がタービン建屋の線量率を上昇させる副作用がある。   One conventional technique for this problem is a technique for adding hydrogen to reactor water (hereinafter referred to as “hydrogen injection”). In the BWR, hydrogen is injected by pressurizing and injecting hydrogen into the water supply system to dissolve the hydrogen in the water supply and introducing the water supply containing this hydrogen into the nuclear reactor. Here, the recombination reaction accompanying hydrogen injection will be described. When hydrogen is added to the reactor water in the nuclear reactor, the hydrogen is recombined with oxygen and hydrogen peroxide in the downcomer portion surrounding the core in the nuclear reactor. This recombination reaction proceeds promptly when radical species rich in reactivity, such as OH, generated by the action of radiation irradiation act like a catalyst. By this recombination reaction, the concentration of oxygen and hydrogen peroxide in the reactor water decreases. As the concentration of oxygen and hydrogen peroxide decreases, the corrosion potential (ECP) of the reactor structural material also decreases. Hydrogen injection is a technique for reducing the concentration of oxygen and hydrogen peroxide in the reactor water by reacting the injected hydrogen with oxygen and hydrogen peroxide generated by radiolysis of water and returning them to water. However, when high-concentration hydrogen injection is performed, radioactive nitrogen 16 (N-16) that emits high-energy γ-rays generated by the nuclear reaction of oxygen that constitutes water molecules with neutrons easily moves into the vapor, This N-16 has the side effect of increasing the dose rate of the turbine building.

したがって、Ｎ−１６による副作用を生じない水素濃度範囲で腐食電位を低減することが望まれている。そこで、水素注入効果の向上に関する従来技術として、特許文献１〜特許文献５などの貴金属の水素の反応に対する触媒性を利用して腐食電位を下げるものがある。また、水素注入そのもの行わずに腐食電位を下げる従来技術として、特許文献６に記されるような、炉内に存在するチェレンコフ光を利用して光触媒を用いた防食技術がある。   Therefore, it is desired to reduce the corrosion potential in a hydrogen concentration range that does not cause side effects due to N-16. Therefore, as a conventional technique related to the improvement of the hydrogen injection effect, there is a technique that lowers the corrosion potential by utilizing the catalytic property for hydrogen reaction of noble metals such as Patent Documents 1 to 5. Further, as a conventional technique for reducing the corrosion potential without performing hydrogen injection itself, there is an anticorrosion technique using a photocatalyst using Cherenkov light existing in a furnace as described in Patent Document 6.

特許第２８１８９４３号公報Japanese Patent No. 2818943 特開平１０−３１９１８１号公報JP-A-10-319181 ＷＯ９９／１７３０２号公報WO99 / 17302 特開平７−１９８８９３号公報Japanese Unexamined Patent Publication No. 7-198893 特開平７−２０９４８７号公報JP-A-7-209487 特開２００１−４７８９号公報Japanese Patent Laid-Open No. 2001-4789

しかし、従来技術のように、材料表面に触媒を付着させることにより腐食電位を低減する方法では、炉内の材料表面に付着した触媒の量，分布を適切に評価することが必要であり、炉内での付着量を掻き取りすることが、米国プラントで実施されている。これは、できるだけ炉内で広く調べる必要があり、時間やコストがかかる。   However, in the method of reducing the corrosion potential by attaching a catalyst to the material surface as in the prior art, it is necessary to appropriately evaluate the amount and distribution of the catalyst attached to the material surface in the furnace. Scrape off the amount of deposits in the plant is being implemented in US plants. This needs to be investigated as widely as possible in the furnace, which is time consuming and expensive.

そこで、発明者らは、水素注入に加えてヒドラジンなどの強い還元力を持った窒素化合物（以下、還元性窒素化合物とよぶ）を注入し、炉内で発生した酸素及び過酸化水素と還元性窒素化合物を反応させて水と窒素にすることによって、炉水の酸素および過酸化水素濃度を効率的に低減し、腐食電位を下げる技術について検討した。以下にその検討結果を説明する。   In view of this, the inventors injected a nitrogen compound having a strong reducing power such as hydrazine (hereinafter referred to as a reducing nitrogen compound) in addition to hydrogen injection, and reduced oxygen and hydrogen peroxide generated in the furnace. We studied a technique to reduce the corrosion potential by efficiently reducing the oxygen and hydrogen peroxide concentrations in the reactor water by reacting nitrogen compounds into water and nitrogen. The examination results are described below.

まず、ヒドラジン注入について、検討した。図４は、水素注入を０.４ppm実施したときに、還元性窒素化合物としてヒドラジンを同時に注入したときの原子炉底部の腐食電位を解析した結果である。ヒドラジンがないときには、このプラントの腐食電位は＋１００
ｍＶvsＳＨＥを超えており、ＳＣＣにとって、厳しい条件となっている。しかし、ヒドラジンを給水系に０.８ppm程度の濃度で添加すると、炉底部の腐食電位は−１００ｍＶvs
ＳＨＥにまで低下し、さらに注入量を増やすと、−４００ｍＶvsＳＨＥ以上に低下する。したがって、水素注入とヒドラジンの添加を組み合わせることにより、ステンレスやニッケル基合金の炉内機器や配管のＳＣＣからＢＷＲを守ることができると期待される。 First, hydrazine injection was examined. FIG. 4 shows the result of analyzing the corrosion potential at the bottom of the reactor when hydrazine is simultaneously injected as a reducing nitrogen compound when hydrogen injection is performed at 0.4 ppm. In the absence of hydrazine, the corrosion potential of this plant is +100
It exceeds mV vs SHE, which is a severe condition for SCC. However, when hydrazine is added to the feed water system at a concentration of about 0.8 ppm, the corrosion potential at the bottom of the furnace is -100 mVvs.
When it decreases to SHE and further increases the injection amount, it decreases to -400 mV vs SHE or higher. Therefore, it is expected that BWR can be protected from SCC of in-furnace equipment and piping of stainless steel and nickel-base alloy by combining hydrogen injection and hydrazine addition.

ところで、このようにＢＷＲの炉水に水素と共にヒドラジンのような還元性の窒素化合物を添加して、炉水中の酸化剤（酸素あるいは過酸化水素）を除去することで腐食電位を低下し、ＳＣＣを防止する場合、還元性窒素化合物が炉水に存在する酸素や過酸化水素を消費する反応と競争的に、アンモニアの生成反応が生じる。これは、図５に示すように、酸素や過酸化水素などの酸化剤に対して、モル量で表したときに過剰となったヒドラジンが放射線により分解されて、アンモニアが生成する。したがって、ヒドラジンをできるだけ少なく炉水に添加することが、アンモニアの生成を抑制するために好ましい。また、純度の高いヒドラジンは価格も高いことから、使用量をできるだけ減らすことが、運転コストを低く押さえる上で好ましい。   By the way, by adding a reducing nitrogen compound such as hydrazine together with hydrogen to the BWR reactor water in this way, the oxidant (oxygen or hydrogen peroxide) in the reactor water is removed, thereby reducing the corrosion potential. In this case, ammonia is produced in a competitive manner with the reaction in which the reducing nitrogen compound consumes oxygen and hydrogen peroxide present in the reactor water. This is because, as shown in FIG. 5, hydrazine, which is excessive when expressed in terms of molar amount with respect to an oxidizing agent such as oxygen or hydrogen peroxide, is decomposed by radiation to produce ammonia. Therefore, it is preferable to add as little hydrazine as possible to the reactor water in order to suppress the production of ammonia. Moreover, since hydrazine having high purity is expensive, it is preferable to reduce the amount used as much as possible in order to keep the operating cost low.

ところで、ヒドラジンは、炉水中の酸素や過酸化水素とＢＷＲの炉内で、見かけ上、
（化１）,（化２）のように反応する。 By the way, hydrazine apparently appears in the furnace of oxygen, hydrogen peroxide and BWR in the reactor water.
It reacts like (Chemical formula 1) and (Chemical formula 2).

Ｎ2Ｈ4＋Ｏ2＝Ｎ2＋２Ｈ2Ｏ …（化１）
Ｎ2Ｈ4＋２Ｈ2Ｏ＝Ｎ2＋４Ｈ2Ｏ …（化２）
したがって、ヒドラジンを添加することによって、（化３），（化４）に示す水素と酸素および過酸化水素の反応が進行するのと合わせて、酸素と過酸化水素が消費される。そ
２Ｈ2＋Ｏ2＝２Ｈ2Ｏ …（化３）
Ｈ2＋Ｈ2Ｏ2＝２Ｈ2 …（化４）
の結果、図３に示すように、酸素や過酸化水素の濃度が低下し、腐食電位が低下する。これによって、図２で示す腐食電位とＳＣＣのき裂進展速度の関係からＳＣＣが抑制できる。 N 2 H 4 + O 2 = N 2 + 2H 2 O (Chemical Formula 1)
N 2 H 4 + 2H 2 O = N 2 + 4H 2 O (Chemical Formula 2)
Therefore, by adding hydrazine, oxygen and hydrogen peroxide are consumed together with the progress of the reaction of hydrogen, oxygen and hydrogen peroxide shown in (Chemical Formula 3) and (Chemical Formula 4). 2H 2 + O 2 = 2H 2 O (Chemical Formula 3)
H 2 + H 2 O 2 = 2H 2 (Chemical formula 4)
As a result, as shown in FIG. 3, the concentration of oxygen or hydrogen peroxide decreases, and the corrosion potential decreases. Thereby, SCC can be suppressed from the relationship between the corrosion potential shown in FIG. 2 and the crack growth rate of SCC.

さらに、ヒドラジンは材料表面で、（化５）の反応によって自身は酸化され、電子を放
Ｎ2Ｈ4＝Ｎ2＋４Ｈ+＋４ｅ- …（化５）
出する（反応相手があれば、その相手を還元する。）したがって、材料表面で酸素あるいは過酸化水素が電子を受け取る（反応相手があれば、その相手を酸化する）次の（化６），（化７）の反応、および、（化８）の金属材料の酸化溶出反応と混成電位を形成するこ
Ｏ2＋４Ｈ+＋４ｅ-＝２Ｈ2Ｏ …（化６）
Ｈ2Ｏ2＋２Ｈ+＋２ｅ-＝２Ｈ2Ｏ …（化７）
とによって、材料の腐食電位は低減することになる。ここで、Ｍは金属を表し、ｎは反応
Ｍ＝Ｍn+＋ｎｅ- …（化８）
に関与する電子の数である。酸素の場合で、ヒドラジンの電位低減効果を図６に示した。酸素を５０，３００、および１０００ppb の一定にしたときにヒドラジンの添加量を増やすと、ステンレスの腐食電位が低下することが実際に生じることがわかる。このとき、ステンレスの表面は酸化皮膜を形成していない状態で測定した。 Furthermore, hydrazine is oxidized on the surface of the material by the reaction of (Chemical Formula 5) and releases electrons. N 2 H 4 = N 2 + 4H + + 4e − (Chemical Formula 5)
Therefore, if there is a reaction partner, that partner is reduced. Therefore, oxygen or hydrogen peroxide receives electrons on the surface of the material (if there is a reaction partner, it oxidizes that partner). Forming a hybrid potential with the reaction of (Chemical Formula 7) and the oxidation elution reaction of the metal material of (Chemical Formula 8) O 2 + 4H + + 4e − = 2H 2 O (Chemical Formula 6)
H 2 O 2 + 2H + + 2e − = 2H 2 O (Chemical Formula 7)
This reduces the corrosion potential of the material. Here, M represents a metal, and n represents a reaction M = M n + + ne − (Chemical Formula 8)
Is the number of electrons involved. In the case of oxygen, the potential reduction effect of hydrazine is shown in FIG. It can be seen that when the amount of hydrazine is increased when the oxygen is kept constant at 50, 300, and 1000 ppb, the corrosion potential of stainless steel actually decreases. At this time, the surface of the stainless steel was measured in a state where no oxide film was formed.

ところで、ヒドラジンは、また、ステンレスやニッケル基合金等の材料表面に酸化物があると以下に示す（化９）〜（化１２）の反応をして消費されることが知られている。   By the way, it is known that hydrazine is consumed by the following reactions (Chemical 9) to (Chemical 12) when there is an oxide on the surface of a material such as stainless steel or nickel base alloy.

Ｎ2Ｈ4＋６Ｆｅ2Ｏ3＝Ｎ2＋２Ｈ2Ｏ＋４Ｆｅ3Ｏ4 …（化９）
Ｎ2Ｈ4＋２Ｆｅ2Ｏ3＝Ｎ2＋２Ｈ2Ｏ＋４ＦｅＯ …（化１０）
Ｎ2Ｈ4＋２ＦｅＯ＝２Ｆｅ＋Ｎ2＋２Ｈ2Ｏ …（化１１）
Ｎ2Ｈ4＋４Ｆｅ(ＯＨ)3＝４Ｆｅ(ＯＨ)2＋Ｎ2＋４Ｈ2Ｏ …（化１２） N 2 H 4 + 6Fe 2 O 3 = N 2 + 2H 2 O + 4Fe 3 O 4 (Chemical Formula 9)
N 2 H 4 + 2Fe 2 O 3 = N 2 + 2H 2 O + 4FeO (Chemical Formula 10)
N 2 H 4 + 2FeO = 2Fe + N 2 + 2H 2 O (Chemical Formula 11)
N 2 H 4 + 4Fe (OH) 3 = 4Fe (OH) 2 + N 2 + 4H 2 O (Chemical Formula 12)

これらのヒドラジンによって還元の進んだ酸化物は、炉水に酸素や過酸化水素などの酸化剤少量でも存在しているときには、（化１３），（化１４）の反応により、ふたたび酸
Ｏ2＋４Ｆｅ(ＯＨ)2＋２Ｈ2Ｏ＝４Ｆｅ(ＯＨ)3 …（化１３）
Ｏ2＋４Ｆｅ3Ｏ4＝６Ｆｅ2Ｏ3 …（化１４）
化数の高い状態にもどる。したがって、酸化物が炉内の構造物や配管表面に付着していると、炉水に添加したヒドラジンが直接材料表面に及ぼす（化５）の還元作用は有効に活用できないことになる。したがって、炉水での（化１）及び（化２）の反応のみを利用してＳＣＣを抑制することになる。特に、鉄クラッドと呼ばれる、鉄の酸化物を主成分とした不溶性の０.４５μｍ 以下の粒径を持つ、給水から持込まれた鉄に起因する物質が材料表面に付着した場合は、ステンレスやニッケル基合金の高温水中の腐食によって生成した酸化物に比較して、量が多くや表面積が大きいために、その作用を十分考慮する必要がある。そこで、先述したように、ヒドラジンをできるだけ少なく使用して効率的に腐食電位を低下させたいことから、発明者らはヒドラジンが直接材料表面に及ぼす（化５）の還元作用を有効に活用できる方法が必要であることを発見した。 When these oxides that have been reduced by hydrazine are present in the reactor water even in a small amount of an oxidant such as oxygen or hydrogen peroxide, the reaction of (Chemical 13) and (Chemical 14) causes the acid O 2 + 4Fe again. (OH) 2 + 2H 2 O = 4Fe (OH) 3 (Chemical Formula 13)
O 2 + 4Fe 3 O 4 = 6Fe 2 O 3 (Chemical Formula 14)
Return to a state with a high chemical number. Therefore, if the oxide adheres to the structure in the furnace or the pipe surface, the reducing action of (hydration 5) directly applied to the material surface by the hydrazine added to the furnace water cannot be effectively utilized. Therefore, SCC is suppressed by utilizing only the reactions of (Chemical Formula 1) and (Chemical Formula 2) in the reactor water. In particular, if a substance called iron clad, which is mainly composed of iron oxide and has an insoluble particle size of 0.45 μm or less, caused by iron brought in from the water supply adheres to the surface of the material, stainless steel or nickel Compared to oxides produced by corrosion of the base alloy in high-temperature water, the amount is large and the surface area is large. Therefore, as described above, since it is desired to efficiently reduce the corrosion potential by using as little hydrazine as possible, the inventors are able to effectively utilize the reducing action of (Chemical Formula 5) that hydrazine directly affects the material surface. I found it necessary.

本発明の目的は、原子炉構造材料の腐食電位を低下させて応力腐食割れを抑制できる応力腐食割れ抑制方法を提供することにある。   An object of the present invention is to provide a stress corrosion cracking suppressing method capable of suppressing stress corrosion cracking by reducing the corrosion potential of a nuclear reactor structural material.

上記した目的を達成する本発明の特徴は、沸騰水型原子炉において、一つの運転サイクル中に、還元性窒素化合物の中から選ばれた少なくとも一つ以上の窒素化合物が、水素が炉水に添加されている間に、炉水に添加される期間を有する。水素および窒素化合物を炉水に添加する前に、ＢＷＲの炉水と接する構造物あるいは配管の表面に存在する酸化物を取り除いておく。すなわち、本発明は、還元性窒素化合物及び水素を炉水に添加するBWRにおいて、炉水と接する構造物あるいは配管の表面に存在する酸化物（酸化皮膜）が取り除かれている状態で、窒素化合物を炉水に添加するため、窒素化合物が効率的に腐食電位を低下させることができる。   The feature of the present invention that achieves the above-described object is that, in a boiling water reactor, at least one nitrogen compound selected from reducing nitrogen compounds is converted into hydrogen in the reactor water during one operation cycle. While being added, it has a period of addition to the reactor water. Prior to adding hydrogen and nitrogen compounds to the reactor water, the oxides present on the surface of the structure or piping in contact with the reactor water of the BWR are removed. That is, the present invention relates to a BWR in which a reducing nitrogen compound and hydrogen are added to the reactor water, in a state where oxides (oxide film) existing on the surface of the structure or piping in contact with the reactor water are removed. Is added to the reactor water, the nitrogen compound can efficiently lower the corrosion potential.

還元性窒素化合物及び水素を炉水に添加するＢＷＲにおいて、炉水と接する構造物あるいは配管の表面に存在する酸化物（酸化皮膜）が取り除かれていることによって、具体的には、（化９）〜（化１２）の反応を抑制して、（化５）の反応を効果的に進行させる。これによって、（化５）〜（化８）の反応によって決まる材料の腐食電位の低下効率が増大し、応力腐食割れが抑制される。特に、水素を併用することは、還元性窒素化合物の使用量を減らせるコスト上の利点だけでなく、図５に示した還元性窒素化合物の分解生成物の量を減らせることにつながる。また、水素を添加することにより、還元性窒素化合物の分解生成物を、アンモニアのみに制御することができる。窒素化合物からは、硝酸のような窒素酸化物の形態と、アンモニアのような還元形の化合物とが主として生成するが、放射線の存在下で水素が存在すると、大部分をアンモニアにすることができる。アンモニアは、炉心で蒸気に移行するので炉水濃度は大きく上昇しない利点もある。   In the BWR in which a reducing nitrogen compound and hydrogen are added to the reactor water, the oxide (oxide film) existing on the surface of the structure or piping in contact with the reactor water is removed. The reaction of (Chemical Formula 5) is effectively advanced by suppressing the reactions of (Chemical Formula 12) to (Chemical Formula 12). As a result, the efficiency of lowering the corrosion potential of the material determined by the reactions of (Chemical Formula 5) to (Chemical Formula 8) increases, and stress corrosion cracking is suppressed. In particular, the combined use of hydrogen leads not only to the cost advantage of reducing the amount of reducing nitrogen compound used, but also to the amount of decomposition products of the reducing nitrogen compound shown in FIG. Further, by adding hydrogen, the decomposition product of the reducing nitrogen compound can be controlled only to ammonia. Nitrogen compounds are mainly produced in the form of nitrogen oxides such as nitric acid and reduced compounds such as ammonia. However, when hydrogen is present in the presence of radiation, most of it can be converted to ammonia. . Ammonia moves to steam in the reactor core, so there is an advantage that the reactor water concentration does not increase greatly.

ところで、残留熱除去系の放射能付着を抑制することを目的とする特開２００２−
２３６１９１号公報は、残留熱除去系を化学除染した後にヒドラジンを注入し、酸素を消費することによって腐食を抑制する、プラント運転中の炭素鋼の保管についての記載が開示されている。また、キャビテーションを利用することの記載も見られる。この従来技術は、本発明と以下の点で異なっている。 By the way, Japanese Patent Application Laid-Open No. 2002-2000, which aims at suppressing radioactivity adhesion in a residual heat removal system.
Japanese Patent No. 236191 discloses a description of storage of carbon steel during plant operation in which hydrazine is injected after chemical decontamination of the residual heat removal system and oxygen is consumed to suppress corrosion. There is also a description of using cavitation. This prior art differs from the present invention in the following points.

特開２００２−２３６１９１号公報では、残留熱除去系の化学除染の後、炭素鋼の保管水に全面腐食抑制剤としてヒドラジンを添加する。この場合ヒドラジンの注入は、図７に示す原子炉の停止運転時の残留熱除去系起動以降、あるいは運転モードを停止モードに切り替えて以降の原子炉停止時に行われる化学除染の後に実施される。保管水とは、原子炉の運転中に停止している残留熱除去系の配管内に満たされた水である。したがって、炭素鋼は静止している保管水に接している。保管水は通常のＢＷＲの運転では残留熱除去系の起動投入前にフラッシングされ、放射性廃棄物処理系に排出されるので炉水に運転中に入ることはない。また、水素の併用と、腐食電位の制御についての記載はない。一方、本願は、残留熱除去系を対象としていない。この系は炭素鋼からなり、ＢＷＲ条件では局部腐食であるＳＣＣの懸念が非常に少ない。また、ヒドラジンと水素は、図７に示す一つの運転サイクル（起動モードへの切り替えから、停止モードへの切り替えまで）のほとんど大部分の期間を占める、起動運転，定格運転、あるいは停止運転中において、ＳＣＣが問題となる１００℃以上の水に連続的に炉水に添加される。材料は炭素鋼ではなく、炉内の構造物と再循環系の配管を構成するステンレスとニッケル基合金を対象としている。ＳＣＣを抑制するには腐食電位−１００ｍＶvsＳＨＥ以下にする必要がある。したがって、運転時期，目的とする効果，部位，材料が異なっている。特開２００２−２３６１９１号公報では、残留熱除去系のキャビテーションで除染したあとに酸化皮膜を形成するが、本発明は酸化皮膜を形成する行為をしない。したがって、特開２００２−２３６１９１号公報は本発明とは目的も作用も異なっている。そのため、特開２００２−２３６１９１号公報は本発明とは全く異なる発明である。   In Japanese Patent Laid-Open No. 2002-236191, hydrazine is added as a general corrosion inhibitor to the storage water of carbon steel after chemical decontamination of the residual heat removal system. In this case, the injection of hydrazine is performed after starting the residual heat removal system during the reactor shutdown operation shown in FIG. 7 or after chemical decontamination performed when the reactor is shut down after switching the operation mode to the shutdown mode. . The stored water is the water filled in the residual heat removal system piping that is stopped during the operation of the nuclear reactor. Thus, the carbon steel is in contact with stationary storage water. In the normal BWR operation, the stored water is flushed before starting up the residual heat removal system and discharged to the radioactive waste treatment system, so that it does not enter the reactor water during operation. Moreover, there is no description about combined use of hydrogen and control of corrosion potential. On the other hand, the present application is not intended for a residual heat removal system. This system is made of carbon steel, and there is very little concern about SCC, which is local corrosion, under BWR conditions. In addition, hydrazine and hydrogen occupy most of the period of one operation cycle (from switching to the start mode to switching to the stop mode) shown in FIG. 7, during start-up operation, rated operation, or stop operation. , SCC is added to the reactor water continuously to water at 100 ° C. or higher, which is a problem. The material is not carbon steel, but stainless steel and nickel-base alloys that constitute the furnace structure and the recirculation piping. In order to suppress SCC, it is necessary to make the corrosion potential -100 mV vs SHE or lower. Therefore, the operation time, target effect, part, and material are different. In Japanese Patent Laid-Open No. 2002-236191, an oxide film is formed after decontamination by cavitation of a residual heat removal system, but the present invention does not act to form an oxide film. Therefore, Japanese Patent Application Laid-Open No. 2002-236191 differs from the present invention in both purpose and function. Therefore, Japanese Patent Application Laid-Open No. 2002-236191 is completely different from the present invention.

本発明の好ましい例について以下に説明する。   Preferred examples of the present invention will be described below.

好ましくは、前述の構造物または配管の腐食電位が−１００ｍＶ（水素電極基準）以下となるように水素および還元性窒素化合物の炉水濃度を決定することが望ましい。これによって、図２に示すようにステンレスではき裂進展速度が、水素もヒドラジンも添加しない場合に対して１／１０以下となって、応力腐食割れが抑制される。   Preferably, it is desirable to determine the reactor water concentration of hydrogen and a reductive nitrogen compound so that the corrosion potential of the aforementioned structure or piping is -100 mV (hydrogen electrode standard) or less. As a result, as shown in FIG. 2, the crack growth rate of stainless steel is 1/10 or less of that in the case where neither hydrogen nor hydrazine is added, and stress corrosion cracking is suppressed.

好ましくは、前述の構造物あるいは配管の表面に存在する酸化物は少なくとも溶接部を含むように取り除かれることである。応力腐食割れは、溶接部の近傍で発生する。これは粒界でのクロム欠乏による耐食性の低下であったり、溶接の歪みにより硬化が生じたりすることによる。したがって、溶接線を含む表面の腐食電位を下げることで、応力腐食割れが抑制される。   Preferably, the oxide existing on the surface of the structure or the pipe is removed so as to include at least a weld. Stress corrosion cracking occurs in the vicinity of the weld. This is due to a decrease in corrosion resistance due to chromium deficiency at the grain boundaries, or hardening due to welding distortion. Therefore, stress corrosion cracking is suppressed by lowering the corrosion potential of the surface including the weld line.

好ましくは、前述の還元性窒素化合物を、ヒドラジン類，ヒドラゾン類，ヒドラジド類、およびヒドロキシルアミン類から選ばれた少なくとも一つ以上の化合物とすることである。これらの化合物は還元性が高く、酸素や過酸化水素との反応性に富むために、応力腐食割れが抑制できる。   Preferably, the above-mentioned reducing nitrogen compound is at least one compound selected from hydrazines, hydrazones, hydrazides, and hydroxylamines. Since these compounds are highly reducible and rich in reactivity with oxygen and hydrogen peroxide, stress corrosion cracking can be suppressed.

好ましくは、前述の構造物および配管をステンレスまたはニッケル基合金製とすることが望ましい。ＢＷＲの配管および構造材料は、３００系のステンレスか、ニッケル基合金で構成されている。発明者らは、ステンレスとインコネルの腐食電位が酸素や過酸化水素に対してほとんど同じ電位を示すこと、またそれがヒドラジンの濃度に対しても、ほぼ同じ変化を示すことから、同じように管理をして良いとの知見を得た。これによって、個々の材料の違いを考慮せずに、腐食電位の管理で応力腐食割れが抑制される。   Preferably, the aforementioned structure and piping are made of stainless steel or a nickel-based alloy. BWR piping and structural materials are made of 300 series stainless steel or nickel-base alloy. The inventors have managed in the same way because the corrosion potential of stainless steel and Inconel shows almost the same potential with respect to oxygen and hydrogen peroxide, and it shows almost the same change with respect to the concentration of hydrazine. I learned that I could do it. As a result, stress corrosion cracking can be suppressed by managing the corrosion potential without considering the difference between the individual materials.

好ましくは、酸化物を取り除く方法を、レーザー光，放電，炉水の噴流によるキャビテーション，超音波，砥石または樹脂たわしによる研磨・研削，ショット、またはサンドブラスト等の物理的方法、あるいは、化学除染と呼ばれる酸化物の酸化や還元を伴う、酸やアルカリによる溶解等の化学的方法とするとよい。これによって、効果的に酸化物が除去され、応力腐食割れが抑制される。レーザーや、キャビテーションなどの物理的方法を用いた除染技術は、それぞれ特開平１１−１８３６９３号公報、あるいは特開２００２−
１１６２９５号公報に記載されている。化学除染は、材料表面の酸化皮膜を、シュウ酸などの有機酸を還元剤として使用して鉄酸化物を還元溶解し、クロム酸化物を過マンガン酸イオンで酸化溶解することで、除去する技術である。特開２０００−１０５２９５号公報に記載されている。オゾンを用いた技術も特開２００３−９８２９４号公報に開示されている。 Preferably, the method for removing the oxide is a physical method such as laser light, electric discharge, cavitation by jets of reactor water, ultrasonic waves, grinding / grinding with a grindstone or a resin scrub, shot or sandblasting, or chemical decontamination. It is preferable to use a chemical method such as dissolution with an acid or alkali that involves oxidation or reduction of an oxide. This effectively removes the oxide and suppresses stress corrosion cracking. A decontamination technique using a physical method such as laser or cavitation is disclosed in Japanese Patent Application Laid-Open Nos. 11-183893 and 2002-2002, respectively.
No. 116295. Chemical decontamination removes the oxide film on the material surface by reducing and dissolving iron oxide using an organic acid such as oxalic acid as a reducing agent, and oxidizing and dissolving chromium oxide with permanganate ions. Technology. It is described in JP-A-2000-105295. A technique using ozone is also disclosed in Japanese Patent Laid-Open No. 2003-98294.

好ましくは、前述の酸化物を取り除く工程を、原子炉の停止時に設定することである。上記した物理的な方法では、炉内にアクセスすることが必要であり、原子炉を停止し、圧力容器の蓋を開ける必要がある。また、化学的方法では、炉水温度を１００℃以下に下げる必要があるため、原子炉の停止モード以降の作業が適している。この時期に酸化被膜を除去することで、効果的に応力腐食割れが抑制される。   Preferably, the step of removing the oxide is set when the reactor is shut down. The physical methods described above require access to the reactor, shut down the reactor, and open the pressure vessel lid. In addition, in the chemical method, it is necessary to lower the reactor water temperature to 100 ° C. or lower, and therefore work after the reactor shutdown mode is suitable. By removing the oxide film at this time, stress corrosion cracking is effectively suppressed.

好ましくは、前述の酸化物を取り除く工程を原子炉の運転サイクルの一時期とするとよい。また、このとき少なくともヒドラジンまたは水素のいずれか一方の添加量を腐食電位が−５００〜−４００ｍＶ（水素電極基準）になるように制御して、酸化物の溶解を促進するものである。第七の発明では、原子炉の停止時に実施したが、この発明ではヒドラジンあるいは水素の還元作用を用いて、原子炉運転中に酸化皮膜を還元して表面から溶かし出すことを行う。これによって、原子炉を止めずに、酸化皮膜が除去可能となり、応力腐食割れが抑制される。   Preferably, the step of removing the oxide is a period of a reactor operation cycle. At this time, at least one of hydrazine and hydrogen is controlled so that the corrosion potential is -500 to -400 mV (hydrogen electrode standard) to promote dissolution of the oxide. In the seventh aspect of the invention, this was performed when the reactor was shut down. In this invention, however, the reduction action of hydrazine or hydrogen is used to reduce the oxide film during the operation of the reactor and dissolve it from the surface. As a result, the oxide film can be removed without stopping the nuclear reactor, and stress corrosion cracking is suppressed.

好ましくは、前述の水素の注入が給水系または炉浄化系を用いて行われ、前記還元性の窒素化合物の注入が給水系，炉浄化系，再循環系，制御棒駆動水系の中から選ばれた少なくとも一つ以上の箇所から行われることが望ましい。水素は系統圧力の関係から復水昇圧ポンプの吸い込み側から注入するのが効率的である。また、原子炉の起動運転や停止運転時には、給水系が動いていないので、常時運転可能な炉浄化系を用いることが望ましい。ヒドラジンなどの還元性窒素化合物は、運転中に炉水に添加することができる系統として、給水系，炉浄化系，再循環系，制御棒駆動水系の中から選ばれた少なくとも一つ以上の箇所が好ましい。これによって、環境が緩和され応力腐食割れが抑制される。   Preferably, the aforementioned hydrogen injection is performed using a feed water system or a furnace purification system, and the reducing nitrogen compound injection is selected from a feed water system, a furnace purification system, a recirculation system, and a control rod drive water system. It is desirable to be performed from at least one location. It is efficient to inject hydrogen from the suction side of the condensate booster pump because of the system pressure. Moreover, since the water supply system is not moving during the start-up operation and stop operation of the reactor, it is desirable to use a reactor purification system that can be operated at all times. Reducing nitrogen compounds such as hydrazine are systems that can be added to the reactor water during operation. At least one or more locations selected from the water supply system, the furnace purification system, the recirculation system, and the control rod drive water system Is preferred. This relaxes the environment and suppresses stress corrosion cracking.

本発明によれば、水素注入に加えて、ヒドラジンなどの強い還元力を持った還元性窒素化合物を炉水に注入し、炉内で発生した酸素及び過酸化水素を還元性窒素化合物とを反応させて水と窒素にすることによって、炉水の酸素および過酸化水素濃度が効率的に低減し、腐食電位が低下する。さらに、酸化物の除去と組み合わせることにより、窒素化合物が直接材料の腐食電位を下げる効果を重畳させることができ、効果的に還元性窒素化合物を利用することができる。その結果、炉水の酸素，過酸化水素あるいは窒素化合物濃度を管理するという簡単な管理の下で、原子炉構造材料の腐食電位が十分に低下して、応力腐食割れを抑制することができる。   According to the present invention, in addition to hydrogen injection, a reducing nitrogen compound having a strong reducing power such as hydrazine is injected into the reactor water, and oxygen and hydrogen peroxide generated in the furnace are reacted with the reducing nitrogen compound. By making it into water and nitrogen, the oxygen and hydrogen peroxide concentrations in the reactor water are efficiently reduced and the corrosion potential is lowered. Furthermore, by combining with the removal of oxide, the effect of the nitrogen compound directly lowering the corrosion potential of the material can be superimposed, and the reducing nitrogen compound can be effectively used. As a result, the corrosion potential of the reactor structural material is sufficiently lowered under the simple control of controlling the oxygen, hydrogen peroxide or nitrogen compound concentration in the reactor water, and stress corrosion cracking can be suppressed.

以下に好適な実施例を説明する。   A preferred embodiment will be described below.

（実施例１）
ＢＷＲに本発明を適用するときの、水素とヒドラジンの注入に関わるシステム構成の例を、図１を使って説明する。 (Example 1)
An example of a system configuration related to hydrogen and hydrazine injection when the present invention is applied to a BWR will be described with reference to FIG.

ＢＷＲは復水ろ過脱塩器１０３で高純度にした水を、復水ポンプ１２３ｂで給水ヒータ１０５ａに送り加熱し、さらに給水ポンプ１０４で昇圧した後、給水ヒータ１０５ｂで約２２０℃まで昇温して原子炉圧力容器１０１に供給する。   BWR feeds high purity water in the condensate filtration demineralizer 103 to the feed water heater 105a by the condensate pump 123b, heats it, and further boosts the water by the feed water pump 104, and then raises the temperature to about 220 ° C. by the feed water heater 105b. To the reactor pressure vessel 101.

原子炉圧力容器１０１に供給された水（給水）は、給水スパージャ１２５を通して炉水に混合される。原子炉圧力容器１０１を流れ降りた炉水は、原子炉冷却水再循環系配管
１１６ａ，１１６ｂに入り、原子炉冷却水再循環ポンプ１０７ａ，１０７ｂによって駆動され、ジェットポンプ１１５ａ，１１５ｂの作動流体となって、炉水を巻き込みながら、原子炉圧力容器１０１の下部に流れ込む。 Water (feed water) supplied to the reactor pressure vessel 101 is mixed with the reactor water through the feed water sparger 125. Reactor water flowing down the reactor pressure vessel 101 enters the reactor coolant recirculation piping 116a and 116b, is driven by the reactor coolant recirculation pumps 107a and 107b, and the working fluid of the jet pumps 115a and 115b. Thus, the reactor water flows into the lower part of the reactor pressure vessel 101 while entraining the reactor water.

さらに、炉水は炉心１２８に入り、核燃料によって加熱され、蒸気を生成する。蒸気は主蒸気配管１１４を通った後、タービン１０２を駆動する。タービン１０２の回転によってエネルギーを失った蒸気は復水器１１３によって凝縮され、復水となる。このとき、一部の非凝縮性の成分はオフガス系１２１で処理される。復水は復水ポンプ１２３ａで復水ろ過脱塩器１０３に送水され、再びタービン１０２を駆動するための蒸気を作るために使用される。   Furthermore, the reactor water enters the core 128 and is heated by the nuclear fuel to produce steam. The steam drives the turbine 102 after passing through the main steam pipe 114. The steam that has lost its energy due to the rotation of the turbine 102 is condensed by the condenser 113 and becomes condensate. At this time, some non-condensable components are processed in the off-gas system 121. The condensate is sent to the condensate filtration / demineralizer 103 by the condensate pump 123a, and is used to make steam for driving the turbine 102 again.

ＢＷＲを運転中の炉水は、原子炉冷却水浄化系ポンプ１０９によって、原子炉冷却水浄化系配管１１０に設置された原子炉冷却水ろ過脱塩器１１２に送水され、浄化される。このとき、原子炉冷却水ろ過脱塩器１１２には、樹脂が用いられているため、炉水は原子炉冷却水浄化系熱交換器１１１ａ，１１１ｂによって温度を下げる。浄化された炉水は給水系配管１０６に送られ、原子炉圧力容器１０１内に戻される。   Reactor water during operation of the BWR is sent to the reactor cooling water filtration / demineralizer 112 installed in the reactor cooling water purification system piping 110 by the reactor cooling water purification system pump 109 and purified. At this time, since the resin is used for the reactor cooling water filtration demineralizer 112, the temperature of the reactor water is lowered by the reactor cooling water purification system heat exchangers 111a and 111b. The purified reactor water is sent to the water supply system pipe 106 and returned to the reactor pressure vessel 101.

給水系配管１０６を流れる給水の水質は水質モニター１０７ａで測定される。原子炉圧力容器下部の炉水の水質はボトムドレン配管１０８を通してサンプリングされ、水質モニター１０７ｃで測定される。また、原子炉冷却水浄化系配管１１０の水質は水質モニター１０７ｂで測定される。これらの水質モニター１０７ａ，１０７ｂ，１０７ｃは溶存酸素計，溶存水素系，導電率計，ｐＨ計から構成される。これらの水質モニター１０７ａ，
１０７ｂ，１０７ｃ点でサンプリングされた炉水のアンモニア濃度を測定して、ヒドラジンの注入量について制御をかけることもできる。また、これらの点で、ヒドラジンの濃度を手分析あるいはヒドラジン濃度センサを使って測定してもよい。 The quality of the feed water flowing through the feed water system pipe 106 is measured by a water quality monitor 107a. The water quality of the reactor water under the reactor pressure vessel is sampled through the bottom drain pipe 108 and measured by the water quality monitor 107c. Further, the water quality of the reactor cooling water purification system piping 110 is measured by the water quality monitor 107b. These water quality monitors 107a, 107b, and 107c are composed of a dissolved oxygen meter, a dissolved hydrogen system, a conductivity meter, and a pH meter. These water quality monitors 107a,
It is also possible to control the injection amount of hydrazine by measuring the ammonia concentration of the reactor water sampled at points 107b and 107c. In these respects, the concentration of hydrazine may be measured manually or using a hydrazine concentration sensor.

酸素注入は、酸素注入装置１２６を復水ポンプ１２３ｂより上流の圧力の低いところに接続して実施する。３０〜５０ppb の給水濃度で運転する。   The oxygen injection is performed by connecting the oxygen injection device 126 to a place where the pressure is low upstream from the condensate pump 123b. It operates with a water supply concentration of 30-50ppb.

水素注入は、通常、水素注入装置１１９を復水ポンプ１２３ｂより上流の圧力の低いところに接続して実施すると比較的低圧で系統を構成できるメリットがある。通常、水素の注入量は、給水流量に追従させて水素流量調節弁１２０の開度を制御する。これにより、給水への水素流量を一定に保つことができる。水素注入時の給水の水素濃度は水質モニター１０７ａ、炉水の水質は水質モニター１０７ｂ，１０７ｃで監視する。加えて、ボトムドレン配管１０８に腐食電位センサ１２４ａを設置することで、腐食電位が目標まで低下することを確認できる。腐食電位センサ１２４ａは、原子炉冷却水再循環系配管１１６ａ，１１６ｂにフランジなどを用いて設置してもよいし、炉心１２８や原子炉圧力容器101の下部に中性子計装管を利用して設置してもよい。本実施例では、主蒸気系の線量率が増加し始める直前の０.４ppmでの注入量に設定する。主蒸気系線量率は、主蒸気配管線量率モニター１１８で監視する。   In general, hydrogen injection has a merit that a system can be configured at a relatively low pressure when the hydrogen injection device 119 is connected to a place where the pressure upstream of the condensate pump 123b is low. Usually, the amount of hydrogen injected follows the feed water flow rate to control the opening of the hydrogen flow rate adjustment valve 120. Thereby, the hydrogen flow rate to the feed water can be kept constant. The hydrogen concentration of the feed water at the time of hydrogen injection is monitored by the water quality monitor 107a, and the water quality of the reactor water is monitored by the water quality monitors 107b and 107c. In addition, by installing the corrosion potential sensor 124a in the bottom drain pipe 108, it can be confirmed that the corrosion potential decreases to the target. The corrosion potential sensor 124a may be installed on the reactor coolant recirculation piping 116a, 116b using a flange or the like, or installed on the lower part of the core 128 or the reactor pressure vessel 101 using a neutron instrumentation tube. May be. In this embodiment, the injection amount is set to 0.4 ppm just before the dose rate of the main steam system starts to increase. The main steam system dose rate is monitored by a main steam pipe dose rate monitor 118.

本実施例では、還元性窒素化合物として、ヒドラジンを選び、ヒドラジン注入装置122を原子炉冷却水浄化系熱交換器１１１ａと給水系配管１０６の間の原子炉冷却水浄化系配管１１０に接続する例を示した。原子炉冷却水浄化系を使用すると、この系統は、原子炉の運転サイクルおよび停止時のいずれにおいても作動できるので、給水系の作動していない、原子炉起動時や停止操作時にも還元性窒素化合物を炉水に注入することができる。したがって、起動時や停止操作時にはこの系統から水素の注入を給水系の水素注入装置の補助として実施してもよい。   In this embodiment, hydrazine is selected as the reducing nitrogen compound, and the hydrazine injector 122 is connected to the reactor cooling water purification system pipe 110 between the reactor cooling water purification system heat exchanger 111a and the feed water system pipe 106. showed that. When the reactor cooling water purification system is used, this system can be operated both during the reactor operation cycle and when it is shut down, so reducing nitrogen can be used even during reactor start-up and shutdown operations when the feedwater system is not operating. The compound can be injected into the reactor water. Therefore, hydrogen may be injected from this system at the time of start-up or stop operation as an auxiliary to the hydrogen injection device of the feed water system.

例えば、このとき原子炉冷却水浄化系の流量が１２０ｔ／ｈであったとする。ヒドラジンを一水和物の６０％溶液を１０Ｌ／ｈ程度で注入すると、原子炉冷却水浄化系でのヒドラジン濃度は４０ppm、給水系では０.７ppmとなる。   For example, it is assumed that the flow rate of the reactor coolant purification system is 120 t / h at this time. When a 60% solution of hydrazine is injected at about 10 L / h, the hydrazine concentration in the reactor cooling water purification system is 40 ppm, and 0.7 ppm in the water supply system.

図１１はヒドラジン注入装置１２２の実施例である。ヒドラジンの薬液は薬液タンク
２０５ａに貯蔵される。薬液タンク内の残量が少なくなったとき、あらかじめ準備してあった薬液タンク２０５ｂに切り替える。切り替えはバルブ２０４ａを閉じて、バルブ204bを開くことで行う。薬液は注入流量を流量計２０３でモニターしながら、注入ポンプ202によって、原子炉冷却水浄化系配管１１０に注入される。注入ポンプ２０２と原子炉冷却水浄化系配管１１０の間には、逆止弁２０１ａ，２０１ｂを二重に設置して、さらにバルブ２００を設けて、万が一にも注入装置の不具合による炉水の漏洩を防止する。薬液タンク２０５ａ，２０５ｂは気密構造とし、薬液タンク内部から外部への高濃度のヒドラジンや過酸化水素が気化漏洩しないように設計されている。内部が負圧になったときには外部から大気が入るように弁２０６ａ，２０６ｂを設置する。 FIG. 11 shows an embodiment of the hydrazine injection device 122. The chemical liquid of hydrazine is stored in the chemical tank 205a. When the remaining amount in the chemical solution tank is reduced, the chemical solution tank 205b prepared in advance is switched. Switching is performed by closing the valve 204a and opening the valve 204b. The chemical solution is injected into the reactor cooling water purification system piping 110 by the injection pump 202 while monitoring the injection flow rate with the flow meter 203. Between the injection pump 202 and the reactor cooling water purification system piping 110, check valves 201a and 201b are double installed and a valve 200 is provided. To prevent. The chemical tanks 205a and 205b have an airtight structure and are designed to prevent vaporization and leakage of high-concentration hydrazine and hydrogen peroxide from the inside of the chemical tank to the outside. Valves 206a and 206b are installed so that air enters from the outside when the inside becomes negative pressure.

続いて、酸化皮膜を除去する工程について説明する。図９に示すように、一つの運転サイクルにおいて、起動モードにより起動運転を始めた原子炉は、定格出力に到達する。ここまでを起動運転時と呼ぶ。その後、大部分の期間を定格出力で運転する。この期間を定格運転時と呼ぶ。定格出力で運転していた原子炉を停止するには、停止操作に切り替え、炉水の循環流量を下げ、また制御棒を挿入して出力を下げる。発電機を解列し、温度と圧力を降下する。１５０℃以下で残留熱除去系を作動し、１００℃以下に炉水温度を下げ、停止モードに切り替える。ここまでを停止運転時と呼び、以降を原子炉の停止時と呼ぶ。   Then, the process of removing an oxide film is demonstrated. As shown in FIG. 9, in one operation cycle, the nuclear reactor that has started the startup operation in the startup mode reaches the rated output. This is called the start-up operation. Then, operate at rated power for most of the period. This period is called rated operation. To shut down the reactor that was operating at the rated power, switch to the shutdown operation, lower the circulation flow rate of the reactor water, and insert a control rod to lower the output. Disconnect the generator and drop the temperature and pressure. The residual heat removal system is operated at 150 ° C. or lower, and the reactor water temperature is lowered to 100 ° C. or lower to switch to the stop mode. The process up to this point is called a stop operation, and the rest is called a reactor stop.

本願の酸化皮膜の除去は、水素および還元性窒素化合物の注入を開始する一つの運転サイクルの起動モード切り替えに先立つ原子炉の停止時に実施する。つまり、図９においては前運転サイクルに続く原子炉の停止時に酸化皮膜を除去し、続く運転サイクルにおいて水素と還元性窒素化合物の注入を実施する。   The removal of the oxide film of the present application is performed when the reactor is shut down prior to switching the start-up mode of one operation cycle in which the injection of hydrogen and a reducing nitrogen compound is started. That is, in FIG. 9, the oxide film is removed when the reactor is stopped following the previous operation cycle, and hydrogen and a reducing nitrogen compound are injected in the subsequent operation cycle.

原子炉の停止時に、格納容器が開放され、続いて原子炉圧力容器が開放される。これで、炉内へのアクセスが可能となるので、炉水の噴流によるキャビテーションを利用して、材料表面の酸化物を取り除く。あるいは、砥石やエメリー紙，樹脂製の研磨具などにより表面を研磨し、酸化皮膜を除いてもよい。酸化皮膜除去の終了後、他の作業を実施した後、原子炉圧力容器、ついで格納容器を復旧し、起動に備える。   When the reactor is shut down, the containment vessel is opened, followed by the reactor pressure vessel. This makes it possible to access the inside of the furnace, so that the oxide on the surface of the material is removed using cavitation caused by the jet of the reactor water. Alternatively, the oxide film may be removed by polishing the surface with a grindstone, emery paper, a resin polishing tool, or the like. After completing the removal of the oxide film, perform other operations, then restore the reactor pressure vessel and then the containment vessel to prepare for startup.

原子炉を起動モードに切り替え、原子炉の起動運転を実施する。原子炉が定格に到達したら、給水系配管１０６から水素注入装置１１９を用いて水素の注入を開始する。これは、給水系配管１０６が作動し始めれば、定格出力到達以前に注入を開始してもよい。水素の注入に続いて、ヒドラジン（還元性窒素化合物の一例）注入装置１１２を用いてヒドラジンを原子炉冷却水浄化系配管１１０に注入する。   Switch the reactor to start-up mode and carry out start-up operation of the reactor. When the reactor reaches the rating, hydrogen injection is started from the feed water system pipe 106 using the hydrogen injection device 119. If the feed water system pipe 106 starts to operate, the injection may be started before the rated output is reached. Following the injection of hydrogen, hydrazine is injected into the reactor cooling water purification system piping 110 using a hydrazine (an example of a reducing nitrogen compound) injection device 112.

このように、あらかじめ原子炉の起動に先立ち、酸化皮膜が除去されているので、効果的にヒドラジンの注入により腐食電位を低減し、アンモニアの生成を抑制できる。   Thus, since the oxide film has been removed prior to the start-up of the reactor, the corrosion potential can be effectively reduced by injecting hydrazine, and the generation of ammonia can be suppressed.

（実施例２）
ＢＷＲに本発明を適用した別の実施例を図１０を使って説明する。ＢＷＲのシステム，ヒドラジンと水素の注入、および酸化皮膜の除去は実施例１と同じである。 (Example 2)
Another embodiment in which the present invention is applied to a BWR will be described with reference to FIG. The BWR system, hydrazine and hydrogen injection, and oxide film removal are the same as in Example 1.

本実施例では、本実施例でも、ヒドラジン注入装置１２２を原子炉冷却水浄化系熱交換器１１１ａと水質モニター１１７が設置される給水サンプリング配管の給水系配管１０６との接続点と、給水スパージャ１２５との間の給水系配管１０６に接続する例を示した。この例では、給水系が作動しているときしか、還元性窒素化合物と水素を供給できないので、定格運転時にのみ水素と還元性窒素化合物の注入を実施する場合に適している。細く，長く、かつ高温の配管系統をヒドラジンが流れる時間が短く、ヒドラジンと配管の反応を抑制することができる利点がある。   In this embodiment, also in this embodiment, the hydrazine injection device 122 is connected to the connection point between the reactor cooling water purification system heat exchanger 111a and the water supply pipe 106 of the water supply sampling pipe where the water quality monitor 117 is installed, and the water supply sparger 125. The example which connects with the water supply system piping 106 between is shown. In this example, since the reducing nitrogen compound and hydrogen can be supplied only when the water supply system is operating, this is suitable for the case where the injection of hydrogen and the reducing nitrogen compound is performed only during rated operation. There is an advantage that the reaction time of hydrazine and piping can be suppressed because the time for hydrazine to flow through a thin, long and high-temperature piping system is short.

（実施例３）
ＢＷＲに本発明を適用した別の実施例を図１１を使って説明する。ＢＷＲのシステム，ヒドラジンと水素の注入、および酸化皮膜の除去は実施例１と同じである。本実施例では、ヒドラジン注入装置１２２を制御棒駆動装置冷却水系１３０に接続する。制御棒駆動装置冷却水系１３０には、復水器１１３で凝縮した蒸気を復水ろ過脱塩器１０３を通し、浄化したあと、復水貯蔵タンク１２９を経た水が供給されている。制御棒駆動装置冷却水系１３０も、原子炉冷却水浄化系と同様に、原子炉の起動および停止操作時にも水が流れているので、一つの運転サイクルの広い時期にわたり還元性窒素化合物を添加することができる。 (Example 3)
Another embodiment in which the present invention is applied to a BWR will be described with reference to FIG. The BWR system, hydrazine and hydrogen injection, and oxide film removal are the same as in Example 1. In this embodiment, the hydrazine injection device 122 is connected to the control rod drive device cooling water system 130. The control rod drive unit cooling water system 130 is supplied with water passing through the condensate storage tank 129 after purifying the steam condensed in the condenser 113 through the condensate filtration demineralizer 103. In the control rod drive system cooling water system 130, as in the reactor cooling water purification system, water flows even during the start-up and shut-down operations of the reactor, so the reducing nitrogen compound is added over a wide period of one operation cycle. be able to.

（実施例４）
ＢＷＲに本発明を適用した別の実施例を図１２を使って説明する。ＢＷＲのシステム，ヒドラジンと水素の注入、および酸化皮膜の除去は実施例１と同じである。本実施例では、ヒドラジン注入装置１２２を原子炉冷却水再循環系配管サンプリングライン１３１に接続する。原子炉冷却水再循環系配管サンプリングライン１３１を用いることで炉内に直接ヒドラジンを注入することができる利点があり、特に原子炉の下部の構造物に対して効果が大きい。その反面で、炉の上部に位置する構造物への効果が余り期待できないことと、原子炉冷却水再循環系配管１１６ａ，１１６ｂの２系統にヒドラジン注入装置１２２をそれぞれ接続しないと、炉内における腐食環境緩和効果にムラが生じる場合がある。 Example 4
Another embodiment in which the present invention is applied to a BWR will be described with reference to FIG. The BWR system, hydrazine and hydrogen injection, and oxide film removal are the same as in Example 1. In this embodiment, the hydrazine injector 122 is connected to the reactor coolant recirculation system piping sampling line 131. The use of the reactor cooling water recirculation system piping sampling line 131 has the advantage that hydrazine can be directly injected into the reactor, and is particularly effective for the structure under the reactor. On the other hand, if the effect on the structure located in the upper part of the reactor cannot be expected much, and if the hydrazine injector 122 is not connected to the two systems of the reactor coolant recirculation pipes 116a and 116b, Unevenness may occur in the effect of mitigating the corrosive environment.

（実施例５）
酸化皮膜を除去する工程について、別の実施例を説明する。実施例１と原子炉の停止時までは同じである。図１３に示すように、停止時に、格納容器の開放につづき、原子炉圧力容器１０１が開放される。ここで、炉心１２８から燃料を取り出し、再び圧力容器の蓋を閉める。次に酸化や還元を伴う化学除染を実施し、炉内および原子炉冷却水再循環系配管１１６ａ，１１６ｂの酸化皮膜を取り除く。終了後、原子炉圧力容器１０１を開放し、他の作業を実施した後、原子炉圧力容器、ついで格納容器を復旧し、起動に備える。原子炉冷却水再循環系配管１１６ａ，１１６ｂの配管のみを酸化皮膜除去する場合、圧力容器が開放された後、原子炉冷却水再循環系配管１１６ａ，１１６ｂの配管と原子炉圧力容器１０１との間を閉止する。その後、酸化や還元を伴う化学除染を原子炉冷却水再循環系配管１１６ａ,１１６ｂの配管にのみ実施し、原子炉冷却水再循環系配管１１６ａ,１１６ｂの酸化皮膜を取り除く。終了後、閉止部を開き、圧力容器、ついで格納容器を復旧し、起動に備える。起動後、水素と還元性窒素化合物を注入する。 (Example 5)
Another embodiment of the process of removing the oxide film will be described. This is the same as in Example 1 until the reactor is shut down. As shown in FIG. 13, at the time of stoppage, the reactor pressure vessel 101 is opened following the opening of the containment vessel. Here, the fuel is taken out from the core 128, and the pressure vessel lid is closed again. Next, chemical decontamination accompanied with oxidation and reduction is performed to remove oxide films in the reactor and on the reactor coolant recirculation pipes 116a and 116b. After the completion, the reactor pressure vessel 101 is opened and other operations are performed, and then the reactor pressure vessel and then the containment vessel are restored to prepare for startup. In the case of removing the oxide film from only the reactor coolant recirculation piping 116 a and 116 b, after the pressure vessel is opened, the reactor coolant recirculation piping 116 a and 116 b are connected to the reactor pressure vessel 101. Close the gap. Thereafter, chemical decontamination involving oxidation and reduction is performed only on the piping of the reactor cooling water recirculation piping 116a, 116b, and the oxide film on the reactor cooling water recirculation piping 116a, 116b is removed. After completion, the closure is opened and the pressure vessel and then the containment vessel are restored to prepare for startup. After startup, hydrogen and reducing nitrogen compound are injected.

（実施例６）
酸化皮膜を除去する工程について、別の実施例を説明する。本実施例では、図１４に示すように、一つの運転サイクルで、定格運転時に化学的に酸化皮膜を除去する。原子炉の出力が定格に到達した後、水素とヒドラジンを炉水に添加する。主蒸気配管線量率モニター１１８のモニター値がプラントごとに定まった線量率の上限を超えないように監視しながら、ヒドラジンの注入量を増加する。ヒドラジンの添加により、腐食電位を−５００から−４００ｍＶvsＳＨＥまで低下すると、酸化皮膜が還元されて、炉水に金属が溶出し始めるので、一時的な一定の期間この電位を保持することにより酸化皮膜を薄くすることができる。その後、注入量を腐食電位のモニターにより必要最小限まで減らして定常的な水素とヒドラジンの添加を行う。 (Example 6)
Another embodiment of the process of removing the oxide film will be described. In this embodiment, as shown in FIG. 14, the oxide film is chemically removed during rated operation in one operation cycle. After the reactor power reaches the rating, hydrogen and hydrazine are added to the reactor water. The amount of hydrazine injected is increased while monitoring so that the monitor value of the main steam pipe dose rate monitor 118 does not exceed the upper limit of the dose rate determined for each plant. When the corrosion potential is lowered from -500 to -400 mV vs SHE by adding hydrazine, the oxide film is reduced and the metal begins to elute into the reactor water. Can be thinned. Thereafter, the injection amount is reduced to the minimum necessary by monitoring the corrosion potential, and hydrogen and hydrazine are constantly added.

本発明の好適な一実施例である実施例１の応力腐食割れ抑制方法を適用する、水素及びヒドラジンの各注入装置を備えた沸騰水型原子力発電プラントの構成図である。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a boiling water nuclear power plant equipped with hydrogen and hydrazine injection devices to which a stress corrosion cracking suppressing method according to a first embodiment which is a preferred embodiment of the present invention is applied. ２８８℃高温水中での３０４型ステンレス鋼の腐食電位と、き裂進展速度の関係を示す特性図である。It is a characteristic view which shows the relationship between the corrosion potential of 304 type | mold stainless steel in 288 degreeC high temperature water, and a crack growth rate. ２８０℃高温水中に過酸化水素を添加した場合の３０４型ステンレス鋼の腐食電位の過酸化水素添加濃度依存性を示す特性図である。It is a characteristic figure which shows the hydrogen peroxide addition density | concentration dependence of the corrosion potential of 304 type stainless steel at the time of adding hydrogen peroxide in 280 degreeC high temperature water. 水素注入及びヒドラジン注入を併用したときにおける給水ヒドラジン濃度と原子炉の炉底部ＥＣＰとの関係を示す特性図である。It is a characteristic view which shows the relationship between the feed water hydrazine density | concentration when using hydrogen injection and hydrazine injection together, and the reactor bottom part ECP of a nuclear reactor. ガンマ線照射時のヒドラジン濃度と生成アンモニア濃度の関係を示す特性図である。It is a characteristic view which shows the relationship between the hydrazine density | concentration at the time of gamma ray irradiation, and a production | generation ammonia density | concentration. いくつかの酸素濃度でのヒドラジン濃度の増加に伴うステンレスの腐食電位の低減効果を示す特性図である。It is a characteristic view which shows the reduction effect of the corrosion potential of stainless steel accompanying the increase in the hydrazine density | concentration in several oxygen concentrations. ＢＷＲの一つの運転サイクル、及び原子炉停止時の説明図である。It is explanatory drawing at the time of one operation cycle of BWR and a nuclear reactor stop. 図１に示すヒドラジン注入装置の実施例の構成図である。It is a block diagram of the Example of the hydrazine injection apparatus shown in FIG. 酸化皮膜の除去工程を示す説明図である。It is explanatory drawing which shows the removal process of an oxide film. 本発明の他の実施例である実施例２の応力腐食割れ抑制方法を適用する、水素及びヒドラジンの各注入装置を備えた沸騰水型原子力発電プラントの他の構成図である。It is another block diagram of the boiling water nuclear power plant provided with each injection device of hydrogen and hydrazine to which the stress corrosion cracking suppression method of embodiment 2 which is another embodiment of the present invention is applied. 本発明の他の実施例である実施例３の応力腐食割れ抑制方法を適用する、水素及びヒドラジンの各注入装置を備えた沸騰水型原子力発電プラントの他の構成図である。It is another block diagram of the boiling water nuclear power plant provided with each injection device of hydrogen and hydrazine to which the stress corrosion cracking suppression method of embodiment 3 which is another embodiment of the present invention is applied. 本発明の他の実施例である実施例４の応力腐食割れ抑制方法を適用する、水素及びヒドラジンの各注入装置を備えた沸騰水型原子力発電プラントの他の構成図である。It is another block diagram of the boiling water nuclear power plant provided with each injection | pouring apparatus of hydrogen and hydrazine to which the stress corrosion cracking suppression method of Example 4 which is another Example of this invention is applied. 本発明の他の実施例である実施例５の応力腐食割れ抑制方法を適用する、水素及びヒドラジンの各注入装置を備えた沸騰水型原子力発電プラントの他の構成図である。It is another block diagram of the boiling water nuclear power plant provided with each injection device of hydrogen and hydrazine to which the stress corrosion cracking suppression method of embodiment 5 which is another embodiment of the present invention is applied. 本発明の他の実施例である実施例６の応力腐食割れ抑制方法を適用する、水素及びヒドラジンの各注入装置を備えた沸騰水型原子力発電プラントの他の構成図である。It is another block diagram of the boiling water nuclear power plant provided with each injection device of hydrogen and hydrazine to which the stress corrosion cracking suppression method of embodiment 6 which is another embodiment of the present invention is applied.

符号の説明Explanation of symbols

１０１…原子炉圧力容器、１０２…タービン、１０３…復水ろ過脱塩器、１０４…給水ポンプ、１０６…給水系配管、１０８…ボトムドレン配管、１１０…原子炉冷却水浄化系配管、１１３…復水器、１１４…主蒸気配管、１１６ａ，１１６ｂ…原子炉冷却水再循環系配管、１１７ａ，１１７ｂ，１１７ｃ…水質モニター、１１８…主蒸気配管線量率モニター、１１９…水素注入装置、１２０…水素流量調節弁、１２２…ヒドラジン注入装置、１２４ａ，１２４ｂ…腐食電位センサ、１２５…給水スパージャ、１２６…酸素注入装置、１２８…炉心、１３０…制御棒駆動装置冷却水系、１３１…原子炉冷却水再循環系配管サンプリングライン、２０２…注入ポンプ、２０３ａ，２０３ｂ…流量計、２０５ａ，
２０５ｂ…薬液タンク。

DESCRIPTION OF SYMBOLS 101 ... Reactor pressure vessel, 102 ... Turbine, 103 ... Condensate filtration demineralizer, 104 ... Feed water pump, 106 ... Feed water system piping, 108 ... Bottom drain piping, 110 ... Reactor cooling water purification system piping, 113 ... Recovery Water vessel, 114 ... main steam piping, 116a, 116b ... reactor cooling water recirculation piping, 117a, 117b, 117c ... water quality monitor, 118 ... main steam piping dose rate monitor, 119 ... hydrogen injection device, 120 ... hydrogen flow rate Control valve, 122 ... Hydrazine injection device, 124a, 124b ... Corrosion potential sensor, 125 ... Feed water sparger, 126 ... Oxygen injection device, 128 ... Core, 130 ... Control rod drive device cooling water system, 131 ... Reactor cooling water recirculation system Pipe sampling line, 202 ... infusion pump, 203a, 203b ... flow meter, 205a,
205b ... Chemical tank.

Claims (9)

窒素酸化物が炉水と接する沸騰水型原子炉の構造物あるいは配管の表面に存在する酸化物を取り除き、前記沸騰水型原子炉における一つの運転サイクル中に、前記構造物あるいは前記配管の表面から前記酸化物が取り除かれた状態で、還元性窒素化合物の中から選ばれた少なくとも一つ以上の窒素化合物を、水素が炉水に添加されている間に、前記炉水に添加することを特徴とする応力腐食割れ抑制方法。   Oxide present on the surface of the boiling water reactor structure or piping where nitrogen oxides contact the reactor water is removed, and the surface of the structure or piping is removed during one operation cycle in the boiling water reactor. Adding at least one nitrogen compound selected from reducing nitrogen compounds to the reactor water while hydrogen is being added to the reactor water with the oxide removed from the reactor water. A method for suppressing stress corrosion cracking. 前記構造物または配管の腐食電位が−１００ｍＶ（水素電極基準）以下となるように前記水素および前記還元性窒素化合物の炉水濃度を決定する請求項１記載の応力腐食割れ抑制方法。   The stress corrosion cracking suppression method according to claim 1, wherein the reactor water concentration of the hydrogen and the reducing nitrogen compound is determined so that the corrosion potential of the structure or piping is −100 mV (hydrogen electrode standard) or less. 前記構造物あるいは配管の表面に存在する酸化物は少なくとも溶接部を含むように取り除かれる請求項１または請求項２に記載の応力腐食割れ抑制方法。   The stress corrosion cracking suppression method according to claim 1 or 2, wherein the oxide existing on the surface of the structure or pipe is removed so as to include at least a weld. 前記還元性窒素化合物は、ヒドラジン類，ヒドラゾン類，ヒドラジド類、およびヒドロキシルアミン類から選ばれた少なくとも一つ以上の化合物である請求項１ないし請求項３のいずれか１項に記載の応力腐食割れ抑制方法。   The stress corrosion cracking according to any one of claims 1 to 3, wherein the reducing nitrogen compound is at least one compound selected from hydrazines, hydrazones, hydrazides, and hydroxylamines. Suppression method. 前記構造物および配管はステンレスまたはニッケル基合金によって構成されている請求項１ないし請求項４のいずれか１項に記載の応力腐食割れ抑制方法。   The stress corrosion cracking suppression method according to any one of claims 1 to 4, wherein the structure and the pipe are made of stainless steel or a nickel-based alloy. 酸化物を取り除く方法は、レーザー光，放電，炉水の噴流によるキャビテーション，超音波，砥石または樹脂たわしによる研磨・研削，ショット、またはサンドブラスト等の物理的方法、あるいは、化学除染と呼ばれる酸化物の酸化や還元を伴う、酸やアルカリによる溶解等の化学的方法である請求項１ないし請求項５のいずれか１項に記載の応力腐食割れ抑制方法。   Oxide removal methods include physical methods such as laser light, electric discharge, cavitation caused by jets of reactor water, ultrasonic waves, grinding / grinding using a grindstone or resin scrub, shots, or sandblasting, or oxides called chemical decontamination. 6. The method for suppressing stress corrosion cracking according to any one of claims 1 to 5, wherein the method is a chemical method such as dissolution with an acid or an alkali accompanied by oxidation or reduction. 前記酸化物を取り除く工程が、原子炉の停止時である請求項１ないし請求項６のいずれか１項に記載の応力腐食割れ抑制方法。   The method for suppressing stress corrosion cracking according to any one of claims 1 to 6, wherein the step of removing the oxide is when the nuclear reactor is stopped. 前記酸化物を取り除く工程が原子炉の運転サイクルの一時期であって、少なくともヒドラジンまたは水素のいずれか一方の添加量を一時的に腐食電位が−５００〜−４００ｍＶ（水素電極基準）になるように制御して酸化物の溶解を促進し、その後あらかじめ設定された水素および還元性窒素化合物の濃度で注入を実施する請求項１ないし請求項５のいずれか１項に記載の応力腐食割れ抑制方法。   The step of removing the oxide is a period of the operation cycle of the reactor, and at least the addition amount of either hydrazine or hydrogen is temporarily set to a corrosion potential of −500 to −400 mV (hydrogen electrode standard). The stress corrosion cracking suppression method according to any one of claims 1 to 5, wherein the dissolution is controlled to promote dissolution of the oxide, and thereafter, injection is performed at a predetermined concentration of hydrogen and a reducing nitrogen compound. 前記水素の注入が給水系または原子炉冷却水浄化系を用いて行われ、前記還元性の窒素化合物の注入が給水系，炉浄化系，再循環系，制御棒駆動水系の中から選ばれた少なくとも一つ以上の箇所から行われる請求項１ないし請求項８のいずれか１項に記載の応力腐食割れ抑制方法。
The hydrogen injection is performed using a feed water system or a reactor cooling water purification system, and the reducing nitrogen compound injection is selected from a feed water system, a reactor purification system, a recirculation system, and a control rod drive water system. The stress corrosion cracking suppression method according to any one of claims 1 to 8, wherein the method is performed from at least one location.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008070207A (en) * 2006-09-13 2008-03-27 Hitachi-Ge Nuclear Energy Ltd Stress corrosion crack mitigation method of reactor structure material, and boiling water type nuclear power plant
WO2010104062A1 (en) * 2009-03-10 2010-09-16 株式会社東芝 Method and system for controlling water quality in power generation plant

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008070207A (en) * 2006-09-13 2008-03-27 Hitachi-Ge Nuclear Energy Ltd Stress corrosion crack mitigation method of reactor structure material, and boiling water type nuclear power plant
JP4668152B2 (en) * 2006-09-13 2011-04-13 日立Ｇｅニュークリア・エナジー株式会社 Stress corrosion cracking mitigation method for nuclear reactor structural materials and boiling water nuclear power plant
WO2010104062A1 (en) * 2009-03-10 2010-09-16 株式会社東芝 Method and system for controlling water quality in power generation plant
US9758880B2 (en) 2009-03-10 2017-09-12 Kabushiki Kaisha Toshiba Method and system for controlling water chemistry in power generation plant

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