JP4094275B2 - Method for forming photocatalytic film of nuclear reactor structural material - Google Patents

Description

【００５２】
【表２】

【００５３】
原子炉の構造材料表面に光触媒被膜を形成する方法としては、塗布や噴霧などによって機械的に行う方法と、原子炉の炉水中に光触媒を注入して化学的に皮膜形成させる方法とがある。機械的に行う方法では、必要な部位に塗布あるいは噴霧することから、プラントに影響を与えずに行うことが可能である。
【００５４】
しかし、広範囲に行う場合や手や機械が届きにくい所に適応する場合には、炉水中に光触媒を注入する方法をとれば一度に接液部全てに皮膜形成させることが可能である。このため、既設プラントに対して原子炉全体に光触媒の皮膜形成する方法としては注入方法を、溶接部など限られた部位に適応するのは機械的な皮膜形成方法をとるのが最も適当である。
【００５５】
本発明では、酸化チタン、分散剤、バインダーなどから混入する不純物の除去、分散剤あるいはバインダーを最適化させることにある。まず、酸化チタン、分散剤、バインダーなどから混入する不純物の除去については、一般産業で市販されている光触媒用酸化チタン溶液中の塩素（Ｃｌ^-）、硫酸（ＳＯ₄ ^2-）濃度が１〜10％あるものの、酸化チタンの製法上鉱物からチタンを抽出する塩化チタン法または硫酸チタン法において使用する薬剤の不純物制御を行う。
【００５６】
その後、水酸化チタンなどの水和物に変化させる際、使用する水を極力不純物のない純水を使用する。その後、酸化チタンに酸化させる場合にも環境雰囲気の制御を行った結果、酸化チタン溶液中の塩素、硫酸濃度を１ppm程度まで低減できる。
【００５７】
次に、分散剤の最適化については、前述したように一般的には酸化チタンに対して１％程度が最適とされているが、使用目的に応じて分散剤を制御する必要がある。これは、長い期間酸化チタンの凝集を防ぐ場合には上述した量が必要かと考えるが、保存期間および使用期間を限定した場合にはこのような多量の分散剤は必要ない。
【００５８】
そこで、酸化チタンに対する分散剤の割合と酸化チタンの分散状態を実験したところ、一ヶ月以上酸化チタンの凝集を防ぐ場合には、酸化チタンに対して分散剤の割合は１％程度必要であるが、２週間程度酸化チタンの凝集を防ぐ目的であれば、分散剤は酸化チタンに対して0.4％存在すればよいことが認められた。
【００５９】
また、酸化チタンの密着性を増加させるバインダーの最適化については、一般産業用で製作されている酸化チタンゾル中のバインダーは酸化チタンに対して20％程度は混入しているが、この濃度も使用目的に応じて制御されるべきである。
【００６０】
このため、酸化チタンに対するバインダー割合を変化させ皮膜を形成し、原子炉温度および圧力条件で皮膜強度の実験を行ったところ、バインダーの種類により多少の違いがあるものの、一般産業で使用されるバインダー量に対して1/200から1/20000まで原子炉温度および圧力条件で皮膜が剥離するような傾向がないことが認められた。
【００６１】
原子炉構造材料に塗布，噴霧するまたは原子炉水中に注入して光触媒皮膜を形成させる際、以下に示す手段をトータルで制御することにより均一な光触媒皮膜を原子炉水質に悪影響なく形成することができる。
【００６２】
原子炉構造材料へ形成する酸化チタン皮膜の厚みに対する粒界応力腐食割れ防止を抑制するための材料の電位を求め、光触媒性能が十分に発揮される酸化チタン皮膜の厚みを制御する。
【００６３】
酸化チタン皮膜を形成させる際の酸化チタン自身の粒径に対する腐食電位を求め、光触媒性能が十分に発揮される酸化チタンの粒径を制御する。酸化チタン皮膜を形成する際の酸化チタン濃度に対する腐食電位を求め、光触媒性能が十分に発揮される酸化チタン濃度を制御する。
【００６４】
酸化チタン皮膜を形成する際の酸化チタンの凝集を抑制する分散剤の割合に対する腐食電位を求め、また、酸化チタンと分散剤の割合に対する原子炉水導電率の影響から、光触媒性能が十分に発揮され、かつ材料健全性の観点から設定されている水質基準以下に保つことを目的として酸化チタンの凝集を防ぐ分散剤を制御する。
【００６５】
酸化チタン皮膜を形成する際の皮膜形成を促進するためのバインダーの割合に対する腐食電位を求め、また、酸化チタンとバインダーの割合およびバインダーに使用される安定化剤などを加味した原子炉水導電率の影響から、光触媒性能が十分に発揮され、かつ材料健全性の観点から設定されている水質基準以下に保つことを目的としてバインダーを制御する。
【００６６】
酸化チタン皮膜を形成する際、酸化チタン自身、酸化チタンの凝集を抑制する分散剤、皮膜形成を促進するためのバインダーおよびバインダーの安定化剤などにおいては、これら全てが材料健全性の観点から設定されている水質基準に影響を及ぼすため、これら不純物混入濃度を制御する。
【００６７】
原子炉の材料健全性の観点で定められている水質基準は，上記の通り概ね導電率10μS/cm、塩素、硫酸濃度をそれぞれ100ppb以下にする必要がある。ただし、運転期間中である場合はさらに厳しい水質基準が推奨されており、その値は導電率１μS/cm、塩素、硫酸濃度をそれぞれ５ppb以下である。
【００６８】
原子炉内に常時酸化チタンを注入しようとすると、この基準をクリアする必要があり、酸化チタンの濃度や分散剤やバインダーの濃度，不純物濃度を低減する必要がある。それに対して、短い期間であれば、導電率10μS/cm、塩素，硫酸濃度をそれぞれ100ppb以下の基準にあわせて注入することが可能である。
【００６９】
これらの基準が現在適用されているのは起動時，中間停止時，停止時であり、これらの期間に注入すればこの基準が適用されることになる。また、これらの期間でなくとも、合計の期間が規定の時間以下であれば注入することも可能である。
【００７０】
注入する場合には、上記の条件を満たすように注入濃度や運転モードを制御する必要がある。ほとんどの原子炉には導電率計やpH計が装備されており、またイオンクロマトグラフィー等の水質測定器によって各種イオンの炉水中濃度が測定できる。これらの他に酸化チタン濃度を測定できる装置などを追設して、注入中の水質をモニターし、その値を注入システムや原子炉運転システムにフィードバックして制御する。
【００７１】
本実施の形態によれば、光が照射されると防食効果を有する光触媒の皮膜厚み、粒径、濃度、分散剤、バインダー、不純物を制御することで、原子炉の水質基準に対応した高性能光触媒層を原子炉構造材料表面において均一な皮膜を形成させ、運転中の腐食を低減することが可能となる。
【００７２】
つぎに図１から図13により本発明に係る原子炉構造材料の光触媒形成方法の具体的な実施例を説明する。
（実施例１）
実施例１は光触媒を原子炉構造材料に塗布，噴霧、または原子炉水中に注入して構造材料に皮膜を形成させ、形成した皮膜の厚みにより腐食電位がどのように影響するかを調べた実験例である。図１から明らかなように、酸化チタン皮膜の厚みが0.1μｍ〜10μｍの範囲では、粒界応力腐食割れ防止を抑制するための材料の電位−230mV以下を十分満足していることがわかる。
【００７３】
また、0.3μｍ〜２μｍの範囲では、材料の電位−300mVに維持されている。ただし、酸化チタン皮膜の厚みが２μｍ以上になると、酸化チタンにおいて光触媒反応で励起した電子と正孔が再結合を起こす反応により、粒界応力腐食割れ防止を抑制するための材料の電位は徐々に上昇している。
【００７４】
また、酸化チタン皮膜の厚みが0.1μｍを下回ると粒界応力腐食割れ防止を抑制するための材料の電位−230mVを満足できなくなる。従って、原子炉構造材料に酸化チタン皮膜の厚みを0.1μｍ〜10μｍにおいて光触媒性能を満足するが、好ましくは0.3μｍ〜２μｍに制御することが肝要となる。
【００７５】
（実施例２）
図２により本発明の実施例２を説明する。実施例２は原子炉構造材料への酸化チタン皮膜を形成する際、酸化チタン自身の粒径により腐食電位がどのように影響するのかを調べた実験例である。図２は酸化チタンの皮膜の厚みを0.3μｍにした場合であるが、酸化チタン粒径が50ｎｍ以下では、粒界応力腐食割れ防止を抑制するための材料の電位−230mV以下を十分満足していることがわかる。
【００７６】
ただし、酸化チタン粒径が30ｎｍ以上になると、酸化チタンにおいて光触媒反応で励起した電子と正孔が再結合を起こす反応により、粒界応力腐食割れ防止を抑制するための材料の電位は徐々に上昇している。
【００７７】
また、酸化チタン皮膜の厚みを減少させた場合には、単位体積当たりの比表面積が粒径と反比例する如く減少し、粒界応力腐食割れ防止を抑制するための材料の電位−230mV以下を満足しなくなる。従って、原子炉構造材料に酸化チタン皮膜を施す際の酸化チタン粒径は50ｎｍ以下において光触媒性能を満足するが、好ましくは５ｎｍ〜30ｎｍ に制御することが肝要となる。
【００７８】
（実施例３）
図３により本発明の実施例３を説明する。実施例３は原子炉構造材料への酸化チタン皮膜を形成する際、電位の移動を速やかに進行させるための光触媒助剤としてある白金ないしはロジウムの濃度により腐食電位がどのように影響するのかを調べた実験例である。図３に示すように、酸化チタン皮膜の厚みを0.3μｍとした場合、酸化チタンに対する白金の割合が0.05〜３％の範囲においては、粒界応力腐食割れ防止を抑制するための材料の電位が、酸化チタンのみの電位−300mVより向上していることがわかる。
【００７９】
また、酸化チタンに対する白金の割合が0.1％程度であると、材料の電位−330mVと非常に向上している。ただし、光触媒助剤の割合が３％以上になると酸化チタンへ照射される紫外線量の減少により光触媒反応が減少し、粒界応力腐食割れ防止を抑制するための材料の電位は徐々に上昇し、酸化チタンのみの電位−300mVを下回る。
【００８０】
また、光触媒助剤の割合が0.05％以下になると光触媒助剤としての効果が薄れ、粒界応力腐食割れ防止を抑制するための材料の電位は酸化チタンのみの−300mVを満足できなくなる。従って、原子炉構造材料に酸化チタン皮膜を形成する場合の皮膜中に白金ないしはロジウムが0.05〜３％の範囲において光触媒の助剤としての性能を満足するが、好ましくは0.1％程度に制御することが肝要となる。
【００８１】
（実施例４）
図４により本発明の実施例４を説明する。実施例４は原子炉構造材料へ酸化チタン皮膜を形成する際の酸化チタン濃度により腐食電位がどのように影響するのかを調べた実験例である。酸化チタンを対象材料に塗布・噴霧する方法においては、図４に示すように酸化チタン濃度が10％以下の範囲では、粒界応力腐食割れ防止を抑制するための材料の電位−230mV以下を十分満足していることがわかる。
【００８２】
ただし、同図に示すごとく酸化チタン濃度が５％を超えると、塗布，噴霧による皮膜形成が悪くなり、均一な皮膜の欠如あるいは密着性の欠如による脱離などが生じ、このような状態の皮膜における粒界応力腐食割れ防止を抑制するための材料の電位は徐々に上昇し、酸化チタン濃度が10％を超えると−230mV以下を満足しなくなる。
【００８３】
従って、原子炉構造材料に酸化チタン皮膜を塗布，噴霧により施す際の酸化チタン濃度は、10％以下において光触媒性能を満足するが、好ましくは５％以下に制御することが肝要となる。
【００８４】
（実施例５）
図５により本発明の実施例５を説明する。原子炉中に酸化チタンを注入することによって原子炉構造材へ被膜を形成させる方法を用いる場合、原子炉の定常運転時に長時間注入するか、起動時／停止時などのトランジェントに短期間注入するか、あるいは両方の組み合わせを行うことができる。
【００８５】
定常運転時での注入では炉水の温度は280〜288℃であり、約10000時間の注入時間となる。トランジェント時には温度は100〜288℃まで任意に選べ、注入時間は最大48時間と考えられる。
【００８６】
定常運転注入時の酸化チタン濃度は表１に示された水質基準によって制限を受ける。現在市販されている酸化チタン溶液の塩素や硫酸イオン不純物は少ないもので酸化チタンに対して、1/100程度である。このため、炉水中酸化チタンの濃度は最大500ppbである。
【００８７】
導電率に影響を与えるものは分散剤であり、分散するためには注入液に対して0.4％が必要である。炉水１μS/cmは分散剤濃度では80ppbに相当する。酸化チタンの注入液中の濃度は注入ポンプの健全性から５ %程度であることを考えると、炉水中の酸化チタン濃度は１ppmが限度となる。
【００８８】
これらは注入時の酸化チタンと不純物の割合であり、実機では酸化チタンは構造材や燃料集合体に付着し、酸化チタンと不純物ともに浄化系によって除去される。このため、連続注入を行った場合には炉水中の酸化チタンの制限値は上記よりも低くなると考えられる。
【００８９】
トランジェント注入時には、不純物イオンの基準が20倍に導電率は10倍になるため、それぞれ酸化チタンの基準への影響は10ppmとなる。図５はステンレス鋼を285℃および150℃に保持した酸化チタンの溶液中に24時間浸漬した場合の、光照射時の腐食電位の酸化チタン濃度依存性を示したものである。285℃では10ppmで0.69μｍ、150℃では0.21μｍの酸化チタンの膜が形成される。
【００９０】
図５に示すように24時間の浸漬の条件下では、太線で示した285℃の線の粒界応力腐食割れが発生しなくなるのは，炉水中で1.5ppmの濃度であり、150℃では５ppmの濃度が必要となっている。このように炉水温度，注入時間によって炉水中の酸化チタンの濃度を制御することによって、最適な被膜を形成することが可能である。
【００９１】
（実施例６）
図６および図７により本発明の実施例６を説明する。実施例６は原子炉構造材料へ酸化チタン皮膜を形成する際の酸化チタンの凝集を抑制する分散剤による腐食電位の影響、または混入する分散剤の量による原子炉健全性の観点から設定されている水質基準にどのように影響するのかを調べた実験例である。
【００９２】
図６に示すように、酸化チタンに対する分散剤の割合が0.4％以上の範囲では、粒界応力腐食割れ防止を抑制するための材料の電位−230mV以下を十分満足していることがわかる。
【００９３】
酸化チタンに対する分散剤の割合を0.4％以下にした場合には、皮膜形成前に凝集して均一な皮膜形成を困難にし、粒界応力腐食割れ防止を抑制するための材料の電位が上昇し、酸化チタンに対する分散剤の割合が0.3％を下回ると材料の電位−230mV以下を満足しなくなる。
【００９４】
ただし、分散剤としてアンモニアおよびカルボン酸を１％添加した試験片により材料の応力腐食割れを確認したところ、長期間において試験片材料の応力腐食割れは観察されない。このため、分散剤としてアンモニアないしはカルボン酸を酸化チタンに対して１％程度添加する場合においては応力腐食割れを起こすことがないことを確認している。
【００９５】
また、図７に示す如く分散剤にアンモニアを使用した場合には、酸化チタンに対する分散剤の割合を増加させると原子炉水の導電率も増加し、酸化チタンに対する分散剤の割合が0.34％を超えると原子炉水質基準の導電率１μS/cmを上回ってしまう。
【００９６】
従って、原子炉構造材料に酸化チタン皮膜を施す際の酸化チタンに対する分散剤の割合は、粒界応力腐食割れ防止を抑制するための材料の電位から酸化チタンに対して0.4％以上必要となるが、原子炉水質基準の導電率１μS/cmを担保することを考慮すると、酸化チタンに対する分散剤の割合は0.34％以下に制御する必要が生じる。
【００９７】
ただし、原子炉水質基準値としての導電率１μS/cmは、この値を超えると直ちに原子炉が停止される訳ではなく、基準値を超えられる期間として14日／12ヶ月を持たせており、分散剤などによる導電率上昇があった場合でも、以下に示すクリンナップ系で不純物除去が短時間で可能であれば問題ない。
【００９８】
すなわち、原子炉一次系においては、不純物除去の観点から、陽イオン、陰イオン成分を除去するためのクリンナップ系を設置しており、上記分散剤成分に対しての除去性能は1/10程度以上の性能を有しているため、酸化チタンに対する分散剤の割合が0.34％を超えてもクリンナップ系により短時間で浄化されるため炉水導電率は１μS/cmを担保することが可能である。
【００９９】
また、上述したように、分散剤としてアンモニアないしはカルボン酸を酸化チタンに対して１％程度添加する場合においては、応力腐食割れを起こすことがないことを確認している。従って、酸化チタンに対する分散剤の割合はクリンナップ浄化効率を換算すれば3.4％程度が混入可能であるが、材料の応力腐食割れを起こさない分散剤の濃度として、１％以下に制御することが肝要となる。
【０１００】
ただし、上記分散剤濃度については原子炉構造材5000ｍ²全てについて皮膜を形成させるのに必要な濃度を求めた結果であり、材料の応力腐食が生じやすい溶接部などを限定した皮膜形成を行う場合には、皮膜形成面積が減少するため使用する酸化チタン量なども減少できることから、原子炉水質基準および管理目標を考慮した分散剤濃度は増加することが可能となる。
上記において酸化チタンに対する分散剤の割合を原子炉水に換算する場合には表３を用いる。
【０１０１】
【表３】

【０１０２】
（実施例７）
図８により本発明の実施例７を説明する。原子炉構造材料へ酸化チタン皮膜を形成する際の皮膜形成を促進するためのバインダーによる腐食電位の影響、混入するバインダーの量による原子炉水水質基準への影響を調べた実験例である。
【０１０３】
図８に示すように、酸化チタンに対するバインダーの割合が0.01％以上の範囲では、粒界応力腐食割れ防止を抑制するための材料の電位−230mV以下を十分満足していることがわかる。ただし、酸化チタンに対するバインダーの割合を0.01％以下にした場合には、皮膜を形成するための密着性が乏しくなり、均一な皮膜形成を困難にし、粒界応力腐食割れ防止を抑制するための材料の電位−230mV以下を満足しなくなる。
【０１０４】
また、酸化チタン皮膜形成を促進するバインダーは、無機シリカ、ポリオルガノシロキサン等を使用しているが、どちらも酸化シリカをベースにしており、酸化シリカについてはイオンとして炉水中に溶け出さないため導電率を上昇させることはないが、表１に示したように酸化シリカの管理目標値は炉水中において１ppm以下にする必要がある。このため、酸化チタンに対する酸化シリカの割合は2.5％以下に制御することが必要となる。
【０１０５】
従って、酸化チタンに対するバインダーの割合は管理目標値から換算すれば2.5％以下が混入可能であるが、粒界応力腐食割れ防止を抑制するための材料の電位からバインダーの濃度として、0.02％程度かそれ以上に制御することが肝要となる。
【０１０６】
ただし、上記バインダー濃度については原子炉構造材5000ｍ²全てについて皮膜を形成させるのに必要な濃度を求めた結果であり、材料の応力腐食が生じやすい溶接部などを限定した皮膜形成を行う場合には、皮膜形成面積が減少するため使用する酸化チタン量なども減少できることから、原子炉水質基準および管理目標を考慮したバインダー濃度は増加することが可能となる。
上記において酸化チタンに対するバインダーの割合を原子炉水に換算する場合には表３を用いる。
【０１０７】
（実施例８）
図９により本発明の実施例８を説明する。原子炉中に酸化チタンを注入することによって原子炉構造材料へ被膜を形成させる方法を用いる場合、酸化チタンの付着性をよくするバインダーを加えることによって、より少ない酸化チタンの濃度で皮膜が形成する。
【０１０８】
図９で示したように、285℃で24時間，１ppmの酸化チタンにステンレス鋼をばく露するとバインダーの濃度が増加するに従って酸化チタンの付着量が増加し、腐食電位が低下する。より酸化チタン濃度を増加した場合には、バインダーは少なくすることが可能であり、また反対にバインダー濃度を増加させると酸化チタン濃度を減少させることが可能である。
【０１０９】
このように、炉水中の酸化チタン濃度とバインダーの濃度を制御することによって最適な皮膜を形成することが可能である。酸化ケイ素（ＳｉＯ₂）の目標値は定常運転時では表１にあるように１ppmである。このため、注入時にはバインダーの濃度は１ppm以下でなるべく高く制御することによって、効率よく酸化チタンを付着することができる。
【０１１０】
（実施例９）
図10により本発明の実施例９を説明する。実施例９は原子炉構造材料へ酸化チタン皮膜を形成する際、酸化チタン自身、酸化チタンの凝集を抑制する分散剤、皮膜形成を促進するためのバインダーによる不純物混入は原子炉水水質への影響を調べた実験例である。
【０１１１】
原子炉水の導電率１μS/cm以下を担保することは前述したが、導電率と同様に塩素、硫酸濃度を制御する。図10から明かなように、酸化チタンに対する塩素、硫酸濃度割合が0.022％を超えると原子炉水質管理目標値の５ppbを上回ることが認められる。
【０１１２】
そこで、前述の如く、酸化チタンの製法上鉱物からチタンを抽出する塩化チタン法あるいは硫酸チタン法において使用する薬剤の不純物制御、その後の水酸化チタンなどの水和物に変化させる際、使用する水を極力不純物のない純水を使用する。
【０１１３】
さらに酸化チタンに酸化させる場合にも環境雰囲気の制御を行うことで、酸化チタン溶液中の塩素、硫酸濃度を酸化チタンに対して0.002％程度まで低減できる。従って、原子炉構造材料に酸化チタン皮膜を施す際の酸化チタン溶液中の塩素、硫酸濃度は酸化チタンに対して0.02％以下に制御することが肝要となる。
【０１１４】
ただし、上記塩素、硫酸濃度については原子炉構造材5000ｍ²全てについて皮膜を形成させるのに必要な濃度を求めた結果であり、材料の応力腐食が生じやすい溶接部などを限定した皮膜形成を行う場合には、皮膜形成面積が減少するため使用する酸化チタン量なども減少できることから、原子炉水質基準および管理目標を考慮した塩素、硫酸濃度は増加することが可能となる。
上記において酸化チタンに対する不純物濃度を原子炉水に換算する場合には表３を用いる。
【０１１５】
（実施例10）
図11と図12により本発明の実施例10を説明する。
原子炉１中に酸化チタンを注入することによって原子炉構造材料に酸化チタン皮膜を形成させる場合，酸化チタンは注入点２ａ，２ｂ，２ｃの中のどれか、あるいは全てから注入され、原子炉１、給水ライン16およびPLR（原子炉再循環系）ライン３，CUW（原子炉冷却材浄化系）ライン５の接液している材料表面に付着する。
【０１１６】
また、注入された酸化チタンおよび分散剤，バインダー，それらに含まれる不純物はほとんどがCUWライン５に設置されている浄化系７のろ過脱塩器によって炉水中から除去される。このため、それらの濃度は材料表面への付着と注入と浄化のバランスによって決定すると考えられ、濃度制御には、注入ポンプ12とCUWポンプ６の流量を制御することによって可能となる。
【０１１７】
ほとんどの原子炉は健全性確認のために導電率やpHおよび不純物イオン濃度を測定できる水質の測定システム11を持っている。この通常の測定システム11に酸化チタンの濃度を測定できるシステムを加えて、そのデータを注入制御システム14と原子炉の運転システムにフィードバックをかける。
【０１１８】
導電率と不純物濃度の制限値よりも低い値、例えば90％の値を目標値として設定する。酸化チタン濃度と不純物濃度が目標値を超えた場合には、注入ポンプ12の流量を低下させ、CUWポンプ６の流量を増加させる。酸化チタン濃度のみが目標値を超えた場合には、注入ポンプ12の流量のみを低下させる。
【０１１９】
酸化チタン濃度が低いにもかかわらず増加傾向になく、不純物濃度が目標値よりも小さい場合には注入ポンプ６の流量を増加させ、目標値よりも高い場合には注入ポンプ12、CUWポンプ６ともに流量を増加させる。このような操作を行うことによって、原子炉の健全性を損なわずに酸化チタンの皮膜を形成することが可能である。
【０１２０】
注入開始時のＴｉＯ₂濃度と電導度の時間変化の例を図12に示す。注入を開始するとＴｉＯ₂濃度と電導度はともに増加する。ＴｉＯ₂濃度は注入した量と構造材料や燃料棒表面に付着する分と浄化系によって除去される分とで差し引きしながら増加する。
【０１２１】
これに対し、不純物量を代表すると考えられる電導度は注入した量と浄化系に除去される分とでやはり濃度が増加する。ＴｉＯ₂が目標濃度に達すると注入ポンプの流量を減少させて、目標濃度になるように注入する。電導度が制限濃度の例えば90％に達するとCUWポンプの流量を増加させ、浄化力を向上させる。
【０１２２】
すると電導度も低下し、かつＴｉＯ₂濃度も低下する。電導度が低下し，例えば85％を下回った時点で注入ポンプの流量を増加してＴｉＯ₂濃度を増加させる。このようにしてＴｉＯ₂濃度，電導度を監視しながら注入ポンプ，CUWポンプを制御することによって、水質規制を逸脱せずに注入が行うことができる。
【０１２３】
（実施例11）
図13および図14により本発明の実施例11を説明する。
図13においては図11と同一部分には同一符号を付している。原子炉１中に酸化チタンを注入することによって原子炉構造材料へ皮膜を形成させる方法を用いる場合、酸化チタンは注入点２の中のどれかあるいはすべてから注入され、原子炉１およびPLRライン３，CUWライン５の接液している材料表面に付着する。
【０１２４】
材料表面への付着は原子炉水の温度と酸化チタンの濃度およびバインダー濃度に依存する。これらの濃度の制御は注入ポンプ12の流量を増加することによって増加し、逆にCUWポンプ６の流量を増加することによって減少する。炉水の温度は原子炉定常時にはほぼ変化がないが、起動時／停止時のトランジェント時には変化し、制御することが可能である。
【０１２５】
例えば、停止時には、残留熱除去系の流量を上げること、あるいは主蒸気系の隔離弁を開けることによって温度を下げることが可能である。酸化チタンの付着量を最適化するためにサンプリングした原子炉水中に試験片18を浸漬し，適宜付着量を付着量測定システム17によって測定する。この付着量のデータを注入制御システム14および原子炉運転システムにフィードバックをかける。
【０１２６】
試験片18の付着量がそれまでの付着時間を考慮した目標値よりも下回っている場合には、注入ポンプ12の流量を増加し、水質が制限値に近い場合には温度を上昇させる。目標値よりも上回っている場合には注入ポンプ12の流量を低下し、CUWポンプ６の流量を上げる。注入ポンプ12の流量を制御し、原子炉材料表面に最適な酸化チタンの皮膜を形成することが可能である。
【０１２７】
注入開始時のＴｉＯ₂濃度とＴｉＯ₂皮膜厚さの時間変化の例を図14に示す。24時間で目標厚さまで注入する場合の例である。注入を開始してからは２時間おきに付着試験片を取り出して分析するものとする。注入開始時には濃度の暫定目標値の1/3で注入を行う。
【０１２８】
２時間後の付着厚さが目標の２％だったとすると，36倍（濃度で1/3，時間で1/12）しても目標に達しないことから、暫定値でも過剰な付着は起こらないと判断して，暫定値の濃度で注入を開始する。その後、さらに２時間後に付着試験片を取り出して付着厚さを分析する。２時間の間の付着厚さ増加量が目標の８％だったとすると、残り時間では付着厚さに達しないために暫定値の120％で注入を行う。
【０１２９】
その後、２時間おきに付着量を測定し、付着厚さが目標の90％に達したところで注入を暫定値の1/3にして微調整を行う。このように、付着試験片において付着厚さを監視しながら付着させることによって、付着厚さを目標値に制御することが可能となる。
【０１３０】
【発明の効果】
本発明によれば、光が照射されると防食効果を有する光触媒の皮膜厚み，粒径，濃度，分散剤，バインダー，不純物を制御することにより、原子炉冷却水水質基準に対応した高性能光触媒層を原子炉構造材料の表面に均一な皮膜を形成させ、原子炉運転中の腐食を低減することができる。
【図面の簡単な説明】
【図１】本発明の実施例１を説明するための、酸化チタン皮膜厚みと材料の電位との関係を示す特性図。
【図２】本発明の実施例２を説明するための、酸化チタン粒径と材料の電位との関係を示す特性図。
【図３】本発明の実施例３を説明するための、酸化チタンに白金を加えた割合に対する材料の電位との関係を示す特性図。
【図４】本発明の実施例４を説明するための、酸化チタン濃度と材料の電位との関係を示す特性図。
【図５】本発明の実施例５を説明するための、炉水中濃度と材料の電位との関係を示す特性図。
【図６】本発明の実施例６を説明するための、酸化チタンに分散剤を加えた割合に対する材料の電位との関係を示す特性図。
【図７】図６と同じく、酸化チタンに分散剤を加えた割合に対する炉水導電率との関係を示す特性図。
【図８】本発明の実施例７を説明するための、酸化チタンにバインダーを加えた割合に対する材料の電位との関係を示す特性図。
【図９】本発明の実施例８を説明するための、炉水中濃度と材料の電位との関係を示す特性図。
【図１０】本発明の実施例９を説明するための、酸化チタンに不純物を加えた割合に対する炉水の塩素，硫酸濃度との関係を示す特性図。
【図１１】本発明の実施例10を説明するための、原子炉とその周囲の配管系統図。
【図１２】図11において、注入開始時のＴｉＯ₂濃度と電導度の時間変化を示す特性図。
【図１３】本発明の実施例11を説明するための、原子炉とその周囲の配管系統図。
【図１４】図13において、注入開始時のＴｉＯ₂濃度と皮膜厚さの時間変化を示す特性図。
【符号の説明】
１…原子炉、２（２ａ，２ｂ，２ｃ）…注入点、３，４…PLRライン、５，６…CUWライン、７…浄化系、８，９…RHRライン、10…サンプリングライン、10ａ，10ｂ…サンプリング点、11…測定システム、12…注入ポンプ、13…注入ライン、14…注入制御システム、15…信号ライン、16…給水ライン、17…付着量測定システム、18…付着試験片。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a photocatalytic film for a nuclear reactor structure material, in which a photocatalytic film is formed on the surface of the nuclear reactor structural material in order to suppress corrosion of a primary reactor material of a nuclear power plant.
[0002]
[Prior art]
In a boiling water nuclear power plant (BWR), oxygen, hydrogen peroxide, and the like generated by radiolysis of water in a radiation field are present in reactor water. It is known that stainless steel and nickel-based metals, which are nuclear reactor structural materials, cause stress corrosion cracking in the presence of oxygen and hydrogen peroxide in a high temperature environment such as a nuclear reactor.
[0003]
As a countermeasure against this, hydrogen injection technology that reduces oxygen and hydrogen peroxide in reactor water by injecting hydrogen from the feedwater has been used in several nuclear power plants in Japan and overseas. The effect of reducing oxygen and hydrogen peroxide appears in the corrosion potential of the material, and the corrosion potential decreases. The occurrence of stress corrosion cracks and the progress of cracks depend on this corrosion potential. The lower the potential, the more the cracks are generated and the cracks are suppressed.
[0004]
Hydrogen injection is carried out against such a background, but a harmful effect is an increase in the dose rate of the turbine system. This is because N-16 produced by the nuclear reaction reacts with hydrogen to become volatile ammonia and easily shifts to the vapor system. Also, in hydrogen injection, various facilities such as recombination by injecting oxygen into off-gas excess hydrogen generated by the injected hydrogen are required.
[0005]
In order to reduce this harmful effect as much as possible and reduce the corrosion potential of structural materials, in recent years, a method has been proposed in which a noble metal is added to the reactor water, the noble metal is attached to the structural material, and the corrosion potential is lowered by a small amount of hydrogen injection. ing. This is because noble metals such as platinum use the property of selectively capturing the reversible reaction of hydrogen with a low potential. By attaching the noble metal to the structural material, the corrosion potential is reduced with a small amount of hydrogen injection. .
[0006]
However, it has been found that when this method is carried out in an actual plant, it also deposits on the zirconium oxide film of the fuel, which increases the oxidation and hydrogenation of the fuel material. In addition, there are problems such as an increase in dose rate due to an increase in the shift to N-16 turbine systems. The influence on the soundness of the fuel material due to the deterioration of the water quality due to the use of the noble metal agent containing impurities at a high concentration is also a problem.
[0007]
Because of these effects, that is, conventional noble metal injection technology has a negative effect on water quality conservation, radioactivity transfer reduction and high fuel burnup, the amount of precious metal injection is reduced and the use of expensive noble metal Development of substances that reduce the amount or replace noble metals is important.
[0008]
Recently, the use of a photocatalytic reaction has attracted attention as a method for reducing the corrosion potential. It has been found that when a photocatalyst is placed on the surface of a material and irradiated with light having a wavelength in the vicinity of ultraviolet light, the corrosion potential is reduced by the action of electrons activated by a photoexcitation reaction. This reaction proceeds efficiently due to the presence of noble metal in the vicinity of the photocatalyst, and the corrosion potential is lowered.
[0009]
By utilizing this reaction, it is possible to attach a photocatalyst or high-function photocatalyst that has been preliminarily attached to the surface of the structural material, and to reduce the corrosion potential during operation using the light of Cherenkov light generated in the reactor core. .
[0010]
As a method for inhibiting corrosion of a water-cooled nuclear reactor primary system material, the present inventors have proposed conventional hydrogen injection, a method of attaching noble metal colloidal particles to a material surface and performing hydrogen injection, and ZrO.₂A photocatalytic method, which is a method for forming an insulating film such as the above on the surface of a material, was filed as Japanese Patent Application Laid-Open No. 2001-4789 and published.
[0011]
[Problems to be solved by the invention]
When photocatalyst is applied to or sprayed on the reactor structural material or injected into the reactor water to form a photocatalyst film on the reactor structural material, how the corrosion potential is affected by the thickness of the formed film It becomes.
[0012]
The present invention was made in order to solve the above problems, and is set from the viewpoint of reactor soundness while securing the photocatalyst as a method of forming a photocatalyst film so that a sufficient effect can be expected for the photocatalyst in the nuclear reactor. It is an object of the present invention to provide a method for forming a photocatalytic film on a nuclear reactor structure material, which can control the concentration of impurities that satisfy the water quality standard and can form the photocatalytic film uniformly on the surface of the nuclear reactor structure material.
[0013]
[Means for Solving the Problems]
  In the invention according to claim 1, the component constituting the photocatalyst is added to the nuclear reactor structural material.In the reactor waterIn the method of injecting and forming the photocatalyst film on the nuclear reactor structural material, the particle size of the photocatalyst to be injected, the ratio of the dispersant, binder and impurities contained in the photocatalyst agent are defined,The photocatalyst is TiO ₂ And this TiO ₂ The film thickness of 0.1 From μm Ten When injecting a photocatalyst-containing solution into the reactor water controlled to μm and continuously injecting during steady operation of the reactor 500ppb When injecting at the time of starting and stopping transients: 10ppm The dispersant that controls the concentration of the photocatalyst and suppresses aggregation of the photocatalyst is composed of ammonia or carboxylic acid, and the concentration of the dispersant relative to the photocatalyst is 0.34 % Or less (however, not including 0), a binder for promoting film formation of the photocatalyst with respect to the photocatalyst 2.5 From% 0.01 ToIt is characterized by controlling.
[0014]
  The invention according to claim 2 is a method in which a component constituting a photocatalyst is applied to a nuclear reactor structural material and injected by a spraying method to form a film of the photocatalyst on the nuclear reactor structural material. The ratio of the dispersant, binder and impurities contained in the photocatalyst agent; ₂ And this TiO ₂ The film thickness of 0.1 From μm Ten When the spray solution is applied and sprayed by the spray method, Ten % Or less (however, not including 0), the dispersing agent for controlling the concentration of the photocatalyst to suppress aggregation of the photocatalyst is composed of ammonia or carboxylic acid, and the concentration of the dispersing agent is set to the photocatalyst. 0.34 % Or less (however, not including 0), a binder for promoting film formation of the photocatalyst with respect to the photocatalyst 2.5 From% 0.01 % To control.
[0015]
  According to the first or second aspect of the present invention, the reactor water set from the viewpoint of reactor health, that is, the reactor structural material surface without affecting the water quality standard and the control target value of the reactor cooling water. A high-performance photocatalyst film having photoexcitation characteristics in which an electric current flows by irradiation with light or radiation existing in a nuclear reactor can be formed uniformly..
[0016]
The invention according to claim 2 is the method according to claim 1, wherein the photocatalyst is TiO.₂(Titanium oxide) and this TiO₂The film thickness is controlled from 0.1 μm to 10 μm.
[0017]
  Also,TiO as photocatalyst ₂ By selecting the film thickness from 0.1 μm to 10 μm, it is possible to sufficiently satisfy the potential of −230 mV or less of the material for suppressing the intergranular stress corrosion cracking prevention. If the film thickness is less than 0.1 μm, the material potential of −230 mV for suppressing the prevention of intergranular stress corrosion cracking cannot be satisfied. On the other hand, if the film thickness exceeds 10 μm, the material potential cannot be satisfied as well. Absent. Preferably, the thickness is controlled from 0.3 μm to 2 μm.
  In the invention of claim 2, TiO as a photocatalyst is used. ₂ Concentration Ten The reason for limiting to less than Ten %, The potential of the material to suppress the intergranular stress corrosion cracking prevention- 230 No more than mV. Note that a stable potential can be obtained by controlling to 5% or less.
  Further, in the invention of claim 1, TiO as a photocatalyst is contained in the reactor water. ₂ When injecting the components that constitute the 500ppb Below, during transients at startup and shutdown 10ppm Control to: TiO during steady operation injection ₂ Concentration 500ppb The reason for limiting to the following is as follows.
  Commercially available TiO, limited by water quality standards ₂ Chlorine and sulfate ion impurities in the solution are TiO ₂ Against 1/100 Degree. For this reason, TiO into the reactor water ₂ The concentration of 500ppb It is.
  500ppb Exceeds TiO ₂ The effect of film formation cannot be expected. on the other hand, 10ppm The reason for the control is as follows. 20 Doubled, conductivity is Ten Doubling each, TiO ₂ The impact on standards 10ppm It is based on becoming. TiO ₂ Concentration of 10ppm If it exceeds 1, it becomes difficult to form an optimum film.
  In the invention of claim 1 or 2, the photocatalytic TiO ₂ The concentration of the dispersing agent when ammonia or carboxylic acid is used as the dispersing agent to suppress the aggregation of TiO 2 ₂ Against 0.34 The reason why it is limited to less than or equal to% can be maintained in a good state without causing stress corrosion cracking, considering the cleanup effect of the ion exchange resin for removing impurities in the primary reactor system, 0.34 If it exceeds 50%, the effect of maintaining a good state cannot be expected. Preferably, it is controlled to 1% or less.
  In addition, TiO of photocatalyst ₂ TiO as a binder to promote film formation ₂ Against 2.5 From% 0.01 The reason to control to 0.01 If it is less than%, the adhesion for forming the film becomes poor, it is difficult to form a uniform film, and the potential of the material for suppressing the prevention of intergranular stress corrosion cracking − 230 No more than mV. on the other hand, 2.5 If it exceeds 50%, the electrical conductivity increases and the potential of the material for suppressing prevention of intergranular stress corrosion cracking is not satisfied. Preferably, 0.02 Control over%.
[0018]
The invention according to claim 3 is characterized in that, in claim 1 or 2, the particle size of the photocatalyst is controlled to 20 nm or less (excluding 0).
In the invention of claim 3, TiO as a photocatalyst₂The reason why the particle size is limited to 50 nm or less is not preferable because if the particle size exceeds 50 nm, the potential of the material for suppressing the prevention of intergranular stress corrosion cracking is −230 mV or less. It should be noted that when the thickness is preferably selected from 5 nm to 30 nm, a result satisfying the photocatalytic performance can be obtained.
[0019]
  Invention according to claim 4BeforeAt least one photocatalyst assistant of Pt, Rh, Ru or Pd is adhered to the surface of the photocatalyst by 0.05% to 3%.
[0020]
According to invention of Claim 4, TiO as a photocatalyst₂Although 0.05% to 3% of photocatalyst assistant such as Pt or Rh is adhered to the surface of the metal, the effect as a photocatalyst assistant is less than 0.05%, and if it exceeds 3%, the amount of ultraviolet rays irradiated to titanium oxide is reduced. As a result, the photocatalytic reaction is reduced and the effect of suppressing intergranular stress corrosion cracking is diminished, which cannot be expected.
[0030]
  Claim5Inventions related toSaidThe binder is controlled to 1 ppm or less.
  Claim5In the invention of, BaThe reason why the inner is controlled to 1 ppm or less in the reactor water is that the TiO as the binder concentration increases.₂This is based on the fact that the adhesion amount increases, but the corrosion potential decreases. TiO in reactor water₂An optimal film can be efficiently formed by controlling the concentration and the binder concentration. However, if the concentration exceeds 1 ppm, the potential of the material increases, which is not preferable.
[0031]
  Claim6The invention according toThe aboveThe photocatalyst, the dispersant, and the binder are harmful impurities such as Cl in the reactor water during reactor operation.^-Or SO_Four ^2-Is controlled to be equal to or less than 0.05 ppb and to be equal to or less than a reference value during normal operation of the reactor.
[0032]
  Claim6In the present invention, the photocatalytic TiO₂, TiO, a dispersant that suppresses aggregation of TiO₂Binder and impurity concentration for promoting film formation of Cl, which is a typical harmful impurity in reactor water during reactor operation^-Or SO_Four ^2-The reason why the control is made to be 0.05ppb or less and below the standard during normal operation of the reactor is to solve the problem affecting the water quality of the reactor water. That is, TiO₂If the chlorine / sulfuric acid ratio exceeds 0.022%, the water quality management target value for reactor water will exceed the target value of 5 ppb. Therefore, TiO as the nuclear reactor structural material₂TiO when coating₂The concentration of chlorine and sulfuric acid in the solution₂However, the above problem can be solved by controlling how 0.5ppb.
[0033]
  Claim7The invention according to,originalControl is performed such that the conductivity of the reactor water during operation of the sub-reactor is 0.1 μS / cm, which is the reference value during normal operation of the reactor.
[0034]
  Claim7According to the present invention, the structural material of the reactor is TiO 2 without deteriorating the soundness of the reactor.₂Can be formed. The reason for controlling the electrical conductivity in the reactor water during reactor operation to be 0.1 μS / cm, which is the standard for normal reactor operation, is that the reactor structural material is TiO 2.₂By not exceeding the water quality standards for the formation of the film.
[0035]
  Claim8The invention according to,originalThe photocatalyst is allowed to adhere during start-up, intermediate stop, and final stop during which the water quality of the sub-reactor is excluded from the standard set for normal operation.
[0036]
  Claim8According to this invention, it is possible to inject in a short period of time in conformity with the criteria of conductivity 10 μS / cm, chlorine and sulfuric acid concentrations of 100 ppb or less. That is, if the water quality of the reactor is injected during a start-up period, an intermediate stop period, a stop-time period, etc., which is excluded from the standard set for normal operation, the standard will be applied. Moreover, it can also inject | pour, if the total period is below regulation time. In the case of injection, the injection concentration and operation mode are controlled. The water quality during injection is monitored and the value is controlled.
[0037]
  Claim9The invention according toIn forming the photocatalytic film during the start-up, intermediate stop, and final stop periods when the water quality of the reactor is excluded from the standard established for normal operation,Reactor water during operation of the reactorHarmfulImpurity Cl^- as well asSO_Four ^2-Concentration ofRespectivelyIt is characterized in that it is controlled to 5 ppb or less and the conductivity to 1 μS / cm or less.
[0038]
  Reactor water quality standards established from the viewpoint of reactor material integrity are generally 1 μS / cm conductivity and chlorine and sulfuric acid concentrations of 100 ppb or less, but 1 μS / cm conductivity, chlorine, The sulfuric acid concentration is 5 ppb or less. Claim9According to this invention, it can inject | pour according to this.
[0039]
  Claim10The invention according to,originalFeatures a measurement system that measures the concentration, conductivity, and pH of the photocatalyst and impurities in the sub-reactor water, and feeds back the measurement system data to the control system for the injection system, temperature, flow rate, flow path, and purification system flow rate And
[0040]
  Claim10According to the invention of TiO, without impairing the integrity of the reactor₂Can be formed on the reactor structural material. TiO₂By controlling the injection pump and the reactor coolant purification system pump while monitoring the concentration and conductivity, TiO without departing from water quality regulations₂Can be injected into the reactor.
[0041]
  Claim11The invention according to,originalThe amount of the photocatalyst attached to the structural material immersed in the sub-reactor water is fed back to a control system having an injection system, temperature, flow rate, and flow path.
[0042]
  Claim11According to the invention, the TiO of the test piece₂TiO optimal for the reactor structural material by controlling the flow rate of the injection pump while taking into account the amount and time of deposition₂A film can be formed. In addition, TiO adhering to the test piece₂TiO as the reactor structural material while monitoring the adhesion thickness₂By depositing, the deposition thickness can be controlled to a target value.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
The water quality standard value set from the viewpoint of reactor health is determined under various operating conditions, but the conductivity is generally 1 μS / cm, and the standard value for chlorine, sulfuric acid, and silica oxide concentrations and Management target values are set as shown in Table 1.
[0044]
On the other hand, as a method for producing titanium oxide, when extracting titanium from minerals, there are mainly a titanium chloride method using hydrochloric acid and a titanium sulfate method using sulfuric acid. From these, hydrates such as titanium hydroxide can be obtained. After that, titanium oxide is obtained. Titanium oxide sol manufactured for general industry is not restricted to chlorine, sulfuric acid, etc., and is mixed in the order of several percent in the solution. It is generally chlorine and sulfuric acid is mixed as an impurity. Currently.
[0045]
Therefore, an increase in the amount of titanium oxide film causes an increase in the amount of chlorine and sulfuric acid, and exceeding the reactor water quality standard value causes a reactor shutdown. Similarly, in order to stabilize titanium oxide chemically and mechanically on the surface of the material, it is necessary to use titanium oxide which is difficult to dissolve in water as small particles and suspended. For this reason, it is necessary to stably disperse in a liquid before use.
[0046]
About 2% to 10% of the dispersant in the titanium oxide sol manufactured for general industry is mixed, and the agent involved in the dispersion also increases the conductivity, which is the standard for reactor water quality, depending on the type and concentration. These chemicals include ammonia, carboxylic acid, etc., and in order to ensure a conductivity of 1 μS / cm, there is a possibility of raising the standard conductivity and shutting down the reactor unless the reactor water concentration is controlled below 80 ppb. is there.
[0047]
Furthermore, it is necessary to use a binder for the purpose of improving the adhesion of the titanium oxide film. About 20% of the binder in the titanium oxide sol manufactured for general industry is mixed with the titanium oxide. Like the dispersant, the binder type and concentration, and the agent that stabilizes the binder in the solution, Increasing conductivity, which is the standard for reactor water quality.
[0048]
Examples of these agents include inorganic silica oxide and polyorganosiloxane as binders. Silica oxide does not dissolve in the reactor water as ions, so its conductivity is not increased, but ethanol is used to stabilize the binder, and its concentration can reach as much as 40%.
[0049]
When these alcohols are decomposed and dissolved as carbonate ions in the reactor water, the reactor water concentration must be controlled below 1000 ppb in order to ensure a conductivity of 1 μS / cm. It may be a factor to stop.
[0050]
The reference values (reactor structure material area and reactor water volume are plant design parameters) and management target values set from the viewpoint of the material soundness of the reactor shown above are shown in Table 1 and are commercially available photocatalysts. Table 2 shows the properties of titanium oxide which is one of the above.
[0051]
[Table 1]

[0052]
[Table 2]

[0053]
As a method for forming a photocatalytic film on the surface of the structural material of the nuclear reactor, there are a method of mechanically performing by coating or spraying, and a method of chemically forming a film by injecting a photocatalyst into the reactor water of the nuclear reactor. The mechanically performed method can be performed without affecting the plant because it is applied or sprayed to a necessary site.
[0054]
However, when it is performed over a wide range or adapted to places where it is difficult to reach by hand or machine, it is possible to form a film on all wetted parts at once by adopting a method of injecting a photocatalyst into the reactor water. For this reason, it is most appropriate to adopt an injection method as a method for forming a photocatalyst film on the entire reactor for an existing plant, and a mechanical film formation method to be applied to limited parts such as welds. .
[0055]
In the present invention, it is to remove impurities mixed from titanium oxide, a dispersant, a binder, etc., and to optimize the dispersant or the binder. First, for removal of impurities mixed in from titanium oxide, a dispersant, a binder, etc., chlorine (Cl in a titanium oxide solution for photocatalyst commercially available in general industry is used.^-), Sulfuric acid (SO_Four ^2-) Although the concentration is 1 to 10%, chemical impurities used in the titanium chloride method or titanium sulfate method for extracting titanium from minerals in the manufacturing process of titanium oxide are controlled.
[0056]
Thereafter, when changing to a hydrate such as titanium hydroxide, pure water free from impurities is used as much as possible. After that, when the titanium oxide is oxidized, the environmental atmosphere is controlled. As a result, the chlorine and sulfuric acid concentrations in the titanium oxide solution can be reduced to about 1 ppm.
[0057]
Next, with respect to optimization of the dispersant, as described above, generally about 1% is optimum with respect to titanium oxide, but it is necessary to control the dispersant according to the purpose of use. This is considered to be necessary for the above-mentioned amount when preventing aggregation of titanium oxide for a long period of time, but such a large amount of dispersant is not necessary when the storage period and use period are limited.
[0058]
Therefore, when the ratio of the dispersant to the titanium oxide and the dispersion state of the titanium oxide were tested, the proportion of the dispersant relative to the titanium oxide needs to be about 1% in order to prevent aggregation of the titanium oxide for one month or longer. For the purpose of preventing aggregation of titanium oxide for about 2 weeks, it was confirmed that the dispersant should be present at 0.4% with respect to titanium oxide.
[0059]
As for the optimization of the binder that increases the adhesion of titanium oxide, about 20% of the binder in the titanium oxide sol produced for general industrial use is mixed with titanium oxide, but this concentration is also used. It should be controlled according to the purpose.
[0060]
For this reason, a film was formed by changing the binder ratio with respect to titanium oxide, and an experiment was conducted on the film strength under reactor temperature and pressure conditions. It was found that there was no tendency for the coating to peel at reactor temperature and pressure conditions from 1/200 to 1/20000 of the quantity.
[0061]
When a photocatalytic film is formed by coating, spraying or injecting into reactor structural materials to form a photocatalytic film, a uniform photocatalytic film can be formed without adversely affecting the reactor water quality by controlling the following means in total. it can.
[0062]
The potential of the material for suppressing the prevention of intergranular stress corrosion cracking with respect to the thickness of the titanium oxide film formed on the nuclear reactor structural material is obtained, and the thickness of the titanium oxide film that sufficiently exhibits the photocatalytic performance is controlled.
[0063]
The corrosion potential with respect to the particle size of the titanium oxide itself when the titanium oxide film is formed is obtained, and the particle size of the titanium oxide that sufficiently exhibits the photocatalytic performance is controlled. The corrosion potential with respect to the titanium oxide concentration when forming the titanium oxide film is obtained, and the titanium oxide concentration at which the photocatalytic performance is sufficiently exhibited is controlled.
[0064]
The corrosion potential for the proportion of the dispersant that suppresses the aggregation of titanium oxide when forming the titanium oxide film is obtained, and the photocatalytic performance is fully demonstrated from the influence of the reactor water conductivity on the proportion of titanium oxide and the dispersant. In addition, a dispersant that prevents aggregation of titanium oxide is controlled for the purpose of keeping it below the water quality standard set from the viewpoint of material soundness.
[0065]
Reactor water conductivity considering the corrosion potential with respect to the ratio of the binder to promote film formation when forming the titanium oxide film, and taking into account the ratio of titanium oxide and binder and the stabilizer used in the binder Therefore, the binder is controlled for the purpose of maintaining the photocatalyst performance sufficiently and maintaining the water quality standard or less set from the viewpoint of material soundness.
[0066]
When forming a titanium oxide film, titanium oxide itself, a dispersant that suppresses aggregation of titanium oxide, a binder to promote film formation, and a stabilizer for the binder are all set from the viewpoint of material soundness. In order to influence the water quality standards, the concentration of these impurities is controlled.
[0067]
As described above, the water quality standards established from the viewpoint of material integrity of the nuclear reactor need to have a conductivity of 10 μS / cm and chlorine and sulfuric acid concentrations of 100 ppb or less, respectively. However, more stringent water quality standards are recommended during the operation period, with values of conductivity 1 μS / cm and chlorine and sulfuric acid concentrations of 5 ppb or less, respectively.
[0068]
In order to always inject titanium oxide into the nuclear reactor, it is necessary to satisfy this standard, and it is necessary to reduce the concentration of titanium oxide, the concentration of dispersant and binder, and the concentration of impurities. On the other hand, in a short period, it is possible to inject in accordance with the criteria of conductivity 10 μS / cm, chlorine and sulfuric acid concentrations of 100 ppb or less.
[0069]
These standards are currently applied at the time of start-up, intermediate stop, and stop, and if injected during these periods, this standard will be applied. Moreover, even if it is not these periods, it is also possible to inject as long as the total period is not more than a specified time.
[0070]
In the case of injection, it is necessary to control the injection concentration and the operation mode so as to satisfy the above conditions. Most nuclear reactors are equipped with conductivity meters and pH meters, and the concentration of various ions in the reactor water can be measured by a water quality measuring device such as ion chromatography. In addition to these, a device capable of measuring the titanium oxide concentration is added to monitor the water quality during injection, and the value is fed back to the injection system and the reactor operation system for control.
[0071]
According to this embodiment, by controlling the film thickness, particle size, concentration, dispersant, binder, and impurities of the photocatalyst that has an anticorrosive effect when irradiated with light, the high performance corresponding to the water quality standard of the reactor It is possible to form a uniform film on the surface of the reactor structural material on the photocatalyst layer and reduce corrosion during operation.
[0072]
Next, a specific embodiment of the method for forming a photocatalyst for a nuclear reactor structure material according to the present invention will be described with reference to FIGS.
Example 1
Example 1 is an experiment in which a photocatalyst is applied to a nuclear reactor structural material, sprayed, or injected into the nuclear reactor water to form a film on the structural material, and the corrosion potential is affected by the thickness of the formed film. It is an example. As apparent from FIG. 1, it can be seen that when the thickness of the titanium oxide film is in the range of 0.1 μm to 10 μm, the potential of the material for suppressing the prevention of intergranular stress corrosion cracking is −230 mV or less.
[0073]
In the range of 0.3 μm to 2 μm, the potential of the material is maintained at −300 mV. However, when the thickness of the titanium oxide film is 2 μm or more, the potential of the material for suppressing the prevention of intergranular stress corrosion cracking is gradually increased due to the reaction that recombines electrons and holes excited by photocatalytic reaction in titanium oxide. It is rising.
[0074]
On the other hand, if the thickness of the titanium oxide film is less than 0.1 μm, the potential of −230 mV of the material for suppressing the prevention of intergranular stress corrosion cracking cannot be satisfied. Therefore, although the photocatalytic performance is satisfied when the thickness of the titanium oxide film on the nuclear reactor structural material is 0.1 μm to 10 μm, it is important to control the thickness to 0.3 μm to 2 μm.
[0075]
(Example 2)
A second embodiment of the present invention will be described with reference to FIG. Example 2 is an experimental example in which the corrosion potential is affected by the particle size of titanium oxide itself when a titanium oxide film is formed on the nuclear reactor structural material. FIG. 2 shows a case where the thickness of the titanium oxide film is 0.3 μm. When the titanium oxide particle size is 50 nm or less, the potential of the material for suppressing the intergranular stress corrosion cracking is sufficiently below −230 mV. I understand that.
[0076]
However, when the titanium oxide particle size becomes 30 nm or more, the potential of the material to prevent the intergranular stress corrosion cracking gradually increases due to the reaction that recombines electrons and holes excited by photocatalytic reaction in titanium oxide. is doing.
[0077]
In addition, when the thickness of the titanium oxide film is decreased, the specific surface area per unit volume decreases so as to be inversely proportional to the particle size, and the potential of the material to suppress the intergranular stress corrosion cracking is −230 mV or less. No longer. Therefore, the titanium oxide particle size when the titanium oxide film is applied to the nuclear reactor structural material satisfies the photocatalytic performance at 50 nm or less, but it is important to control it to 5 nm to 30 nm.
[0078]
(Example 3)
Embodiment 3 of the present invention will be described with reference to FIG. Example 3 investigates how the corrosion potential is affected by the concentration of platinum or rhodium as a photocatalyst aid to rapidly move the potential when forming a titanium oxide film on the reactor structural material This is an experimental example. As shown in FIG. 3, when the thickness of the titanium oxide film is 0.3 μm, the potential of the material for suppressing the prevention of intergranular stress corrosion cracking is within the range of 0.05 to 3% of platinum with respect to titanium oxide. It can be seen that the potential of only titanium oxide is improved from −300 mV.
[0079]
Further, when the ratio of platinum to titanium oxide is about 0.1%, the potential of the material is greatly improved to -330 mV. However, when the ratio of the photocatalyst auxiliary is 3% or more, the photocatalytic reaction is reduced due to the decrease in the amount of ultraviolet rays irradiated to the titanium oxide, and the potential of the material for suppressing the prevention of intergranular stress corrosion cracking gradually increases. The potential of titanium oxide alone is below -300mV.
[0080]
When the ratio of the photocatalyst aid is 0.05% or less, the effect as a photocatalyst aid is reduced, and the potential of the material for suppressing the prevention of intergranular stress corrosion cracking cannot satisfy −300 mV of titanium oxide alone. Accordingly, when a titanium oxide film is formed on the reactor structural material, platinum or rhodium satisfies the performance as a photocatalyst auxiliary in the range of 0.05 to 3%, but preferably controlled to about 0.1%. Is essential.
[0081]
Example 4
Embodiment 4 of the present invention will be described with reference to FIG. Example 4 is an experimental example in which the corrosion potential is affected by the concentration of titanium oxide when a titanium oxide film is formed on the nuclear reactor structural material. In the method of applying / spraying titanium oxide to the target material, as shown in FIG. 4, the potential of the material −230 mV or less is sufficient to prevent the intergranular stress corrosion cracking when the titanium oxide concentration is 10% or less. You can see that you are satisfied.
[0082]
However, when the titanium oxide concentration exceeds 5% as shown in the figure, the film formation by coating and spraying deteriorates, and the film is in such a state due to lack of uniform film or lack of adhesion. The potential of the material for suppressing the prevention of intergranular stress corrosion cracking gradually increases, and when the titanium oxide concentration exceeds 10%, −230 mV or less is not satisfied.
[0083]
Accordingly, the titanium oxide concentration when the titanium oxide film is applied to the nuclear reactor structural material by spraying satisfies the photocatalytic performance at 10% or less, but it is important to control it to 5% or less.
[0084]
(Example 5)
Embodiment 5 of the present invention will be described with reference to FIG. When using a method of forming a coating on the reactor structural material by injecting titanium oxide into the nuclear reactor, it is injected for a long time during steady operation of the nuclear reactor, or for a short time during transients such as startup / shutdown Or a combination of both.
[0085]
In the injection in the steady operation, the temperature of the reactor water is 280 to 288 ° C, and the injection time is about 10,000 hours. During the transient, the temperature can be arbitrarily selected from 100 to 288 ° C, and the injection time is considered to be 48 hours at the maximum.
[0086]
The titanium oxide concentration at the time of steady operation injection is limited by the water quality standards shown in Table 1. The titanium oxide solution currently on the market has few impurities such as chlorine and sulfate ions, which is about 1/100 of that of titanium oxide. For this reason, the maximum concentration of titanium oxide in the reactor water is 500 ppb.
[0087]
What affects the electrical conductivity is a dispersant, and in order to disperse, 0.4% of the injected solution is required. 1 μS / cm of reactor water corresponds to 80 ppb at the dispersant concentration. Considering that the concentration of titanium oxide in the injection liquid is about 5% from the soundness of the injection pump, the titanium oxide concentration in the reactor water is limited to 1 ppm.
[0088]
These are the ratios of titanium oxide and impurities at the time of injection. In the actual machine, titanium oxide adheres to the structural material and the fuel assembly, and both the titanium oxide and impurities are removed by the purification system. For this reason, when continuous injection is performed, the limit value of titanium oxide in the reactor water is considered to be lower than the above.
[0089]
At the time of transient injection, since the impurity ion standard is 20 times and the conductivity is 10 times, the influence on the titanium oxide standard is 10 ppm. FIG. 5 shows the dependence of the corrosion potential upon light irradiation on the titanium oxide concentration when stainless steel is immersed in a solution of titanium oxide maintained at 285 ° C. and 150 ° C. for 24 hours. A titanium oxide film of 0.69 μm is formed at 10 ppm at 285 ° C. and 0.21 μm at 150 ° C.
[0090]
As shown in FIG. 5, under the condition of immersion for 24 hours, the intergranular stress corrosion cracking of the 285 ° C. line indicated by the thick line does not occur at a concentration of 1.5 ppm in the reactor water, and 5 ppm at 150 ° C. The concentration of is required. Thus, an optimal film can be formed by controlling the concentration of titanium oxide in the reactor water according to the reactor water temperature and the injection time.
[0091]
(Example 6)
A sixth embodiment of the present invention will be described with reference to FIGS. Example 6 is set from the viewpoint of the influence of the corrosion potential due to the dispersant that suppresses the aggregation of titanium oxide when the titanium oxide film is formed on the nuclear reactor structural material, or from the viewpoint of the integrity of the reactor due to the amount of the mixed dispersant. This is an example of how the water quality standards are affected.
[0092]
As shown in FIG. 6, it can be seen that when the ratio of the dispersant to titanium oxide is in the range of 0.4% or more, the potential of the material for suppressing the prevention of intergranular stress corrosion cracking is −230 mV or less.
[0093]
When the ratio of the dispersant to titanium oxide is 0.4% or less, it aggregates before film formation and makes uniform film formation difficult, and the potential of the material to prevent intergranular stress corrosion cracking increases, If the ratio of the dispersant to titanium oxide is less than 0.3%, the material potential does not satisfy −230 mV or less.
[0094]
However, when stress corrosion cracking of the material was confirmed with a test piece to which 1% of ammonia and carboxylic acid was added as a dispersant, no stress corrosion cracking of the test piece material was observed over a long period of time. For this reason, when adding about 1% of ammonia or carboxylic acid as a dispersant to titanium oxide, it has been confirmed that stress corrosion cracking does not occur.
[0095]
In addition, when ammonia is used as the dispersant as shown in FIG. 7, increasing the ratio of the dispersant to titanium oxide increases the conductivity of the reactor water, and the ratio of the dispersant to titanium oxide is 0.34%. If exceeded, it will exceed the reactor water quality standard of 1μS / cm.
[0096]
Therefore, the ratio of the dispersant to the titanium oxide when the titanium oxide film is applied to the nuclear reactor structural material is required to be 0.4% or more with respect to the titanium oxide from the potential of the material for suppressing the intergranular stress corrosion cracking prevention. In consideration of ensuring the electrical conductivity of 1 μS / cm based on the reactor water quality standard, the ratio of the dispersant to titanium oxide needs to be controlled to 0.34% or less.
[0097]
However, the electrical conductivity of 1μS / cm as the reactor water quality standard value does not mean that the reactor will be shut down immediately if this value is exceeded, but it has a period of 14 days / 12 months that can exceed the standard value. Even if there is an increase in conductivity due to a dispersant or the like, there is no problem if impurities can be removed in a short time by the following cleanup system.
[0098]
That is, in the reactor primary system, from the viewpoint of removing impurities, a cleanup system for removing cation and anion components is installed, and the removal performance for the above dispersant components is about 1/10 or more. Therefore, even if the ratio of the dispersant to titanium oxide exceeds 0.34%, it is purified in a short time by the cleanup system, so that the reactor water conductivity can be secured to 1 μS / cm.
[0099]
In addition, as described above, it has been confirmed that stress corrosion cracking does not occur when ammonia or carboxylic acid is added as a dispersant at about 1% with respect to titanium oxide. Therefore, the ratio of the dispersant to the titanium oxide can be mixed with about 3.4% if the cleanup purification efficiency is converted. However, it is important to control the concentration of the dispersant not to cause stress corrosion cracking of the material to 1% or less. It becomes.
[0100]
However, the above dispersant concentration is about 5000m of reactor structural material²This is the result of obtaining the concentration required to form a film for all, and when forming a film that limits the welded part where stress corrosion of the material is likely to occur, titanium oxide is used because the film formation area decreases. Since the amount and the like can be reduced, the concentration of the dispersant can be increased in consideration of the reactor water quality standard and the management target.
In the above, Table 3 is used when the ratio of the dispersant to the titanium oxide is converted into the reactor water.
[0101]
[Table 3]

[0102]
(Example 7)
Embodiment 7 of the present invention will be described with reference to FIG. This is an experimental example in which the influence of the corrosion potential by the binder for promoting the film formation when forming the titanium oxide film on the reactor structural material, and the influence on the water quality standard of the reactor by the amount of the mixed binder are examined.
[0103]
As shown in FIG. 8, it can be seen that when the ratio of the binder to titanium oxide is 0.01% or more, the potential of the material for suppressing the prevention of intergranular stress corrosion cracking is −230 mV or less. However, when the ratio of the binder to titanium oxide is 0.01% or less, the adhesion for forming the film becomes poor, making it difficult to form a uniform film, and a material for suppressing the prevention of intergranular stress corrosion cracking. The potential of −230 mV or less is not satisfied.
[0104]
In addition, the binder that promotes the formation of titanium oxide film uses inorganic silica, polyorganosiloxane, etc., but both are based on silica oxide, and silica oxide does not dissolve in the reactor water as ions. Although the rate is not increased, as shown in Table 1, the management target value of silica oxide needs to be 1 ppm or less in the reactor water. For this reason, it is necessary to control the ratio of silica oxide to titanium oxide to 2.5% or less.
[0105]
Therefore, if the ratio of binder to titanium oxide is converted from the management target value, 2.5% or less can be mixed, but the binder concentration is about 0.02% from the potential of the material to prevent intergranular stress corrosion cracking prevention. It is important to control more than that.
[0106]
However, regarding the binder concentration above, reactor structural material 5000m²This is the result of obtaining the concentration required to form a film for all, and when forming a film that limits the welded part where stress corrosion of the material is likely to occur, titanium oxide is used because the film formation area decreases. Since the amount and the like can be reduced, the binder concentration can be increased in consideration of the reactor water quality standard and the management target.
In the above, Table 3 is used when the ratio of the binder to the titanium oxide is converted into the reactor water.
[0107]
(Example 8)
Embodiment 8 of the present invention will be described with reference to FIG. When using a method of forming a film on the nuclear reactor structural material by injecting titanium oxide into the nuclear reactor, a film is formed at a lower titanium oxide concentration by adding a binder that improves the adhesion of titanium oxide. .
[0108]
As shown in FIG. 9, when stainless steel is exposed to 1 ppm of titanium oxide at 285 ° C. for 24 hours, the amount of titanium oxide attached increases and the corrosion potential decreases as the binder concentration increases. When the titanium oxide concentration is further increased, the amount of the binder can be decreased. Conversely, when the binder concentration is increased, the titanium oxide concentration can be decreased.
[0109]
As described above, it is possible to form an optimum film by controlling the titanium oxide concentration and the binder concentration in the reactor water. Silicon oxide (SiO₂) Is 1 ppm as shown in Table 1 during steady operation. For this reason, at the time of injection, the concentration of the binder is controlled to be as high as 1 ppm or less, so that titanium oxide can be efficiently attached.
[0110]
Example 9
A ninth embodiment of the present invention will be described with reference to FIG. In Example 9, when a titanium oxide film is formed on a nuclear reactor structure material, titanium oxide itself, a dispersant that suppresses aggregation of titanium oxide, and contamination by binders to promote film formation affect the water quality of the reactor water. This is an experimental example.
[0111]
As described above, the reactor water conductivity of 1 μS / cm or less is secured, but the chlorine and sulfuric acid concentrations are controlled in the same manner as the conductivity. As is clear from FIG. 10, when the chlorine and sulfuric acid concentration ratio with respect to titanium oxide exceeds 0.022%, it is recognized that it exceeds the reactor water quality management target value of 5 ppb.
[0112]
Therefore, as described above, the water used when the titanium oxide method for extracting titanium from minerals in the titanium oxide method or the impurity control of the chemical agent used in the titanium sulfate method is changed to a hydrate such as titanium hydroxide. Use pure water with as little impurities as possible.
[0113]
Furthermore, when the titanium oxide is oxidized, the concentration of chlorine and sulfuric acid in the titanium oxide solution can be reduced to about 0.002% with respect to titanium oxide by controlling the environmental atmosphere. Therefore, it is important to control the chlorine and sulfuric acid concentrations in the titanium oxide solution when the titanium oxide film is applied to the reactor structural material to 0.02% or less with respect to titanium oxide.
[0114]
However, for the above chlorine and sulfuric acid concentrations, the reactor structural material is 5000 m.²This is the result of obtaining the concentration required to form a film for all, and when forming a film that limits the welded part where stress corrosion of the material is likely to occur, titanium oxide is used because the film formation area decreases. Since the amount and the like can also be reduced, the chlorine and sulfuric acid concentrations can be increased in consideration of the reactor water quality standards and management objectives.
In the above, Table 3 is used when the impurity concentration with respect to titanium oxide is converted into reactor water.
[0115]
(Example 10)
A tenth embodiment of the present invention will be described with reference to FIGS.
When a titanium oxide film is formed on the reactor structural material by injecting titanium oxide into the nuclear reactor 1, the titanium oxide is injected from any or all of the injection points 2a, 2b, 2c. Adhering to the surface of the material in contact with the water supply line 16 and the PLR (reactor recirculation system) line 3 and the CUW (reactor coolant purification system) line 5.
[0116]
Moreover, most of the injected titanium oxide, dispersant, binder, and impurities contained therein are removed from the reactor water by the filtration desalter of the purification system 7 installed in the CUW line 5. For this reason, it is considered that these concentrations are determined by the balance between adhesion to the material surface, injection and purification, and the concentration can be controlled by controlling the flow rates of the injection pump 12 and the CUW pump 6.
[0117]
Most nuclear reactors have a water quality measurement system 11 that can measure conductivity, pH and impurity ion concentration for soundness confirmation. A system capable of measuring the concentration of titanium oxide is added to the normal measurement system 11, and the data is fed back to the injection control system 14 and the reactor operation system.
[0118]
A value lower than the limit values of conductivity and impurity concentration, for example, 90% is set as a target value. When the titanium oxide concentration and the impurity concentration exceed the target values, the flow rate of the injection pump 12 is decreased and the flow rate of the CUW pump 6 is increased. When only the titanium oxide concentration exceeds the target value, only the flow rate of the infusion pump 12 is decreased.
[0119]
In spite of the low titanium oxide concentration, there is no tendency to increase, and when the impurity concentration is lower than the target value, the flow rate of the injection pump 6 is increased. When the impurity concentration is higher than the target value, both the injection pump 12 and the CUW pump 6 are increased. Increase the flow rate. By performing such an operation, it is possible to form a titanium oxide film without impairing the soundness of the nuclear reactor.
[0120]
TiO at the start of injection₂An example of changes in concentration and conductivity over time is shown in FIG. When injection starts, TiO₂Both concentration and conductivity increase. TiO₂The concentration increases while subtracting the amount injected, the amount adhering to the surface of the structural material or fuel rod, and the amount removed by the purification system.
[0121]
On the other hand, the conductivity, which is considered to represent the impurity amount, also increases in concentration depending on the amount injected and the amount removed by the purification system. TiO₂When the target concentration is reached, the flow rate of the injection pump is decreased to inject the target concentration. When the electrical conductivity reaches 90% of the limit concentration, for example, the flow rate of the CUW pump is increased and the purification power is improved.
[0122]
As a result, the conductivity decreases and TiO₂Concentration also decreases. When the conductivity decreases, for example, below 85%, the flow rate of the infusion pump is increased and TiO₂Increase concentration. In this way TiO₂By controlling the infusion pump and CUW pump while monitoring the concentration and conductivity, the infusion can be performed without departing from the water quality regulations.
[0123]
(Example 11)
Embodiment 11 of the present invention will be described with reference to FIG. 13 and FIG.
In FIG. 13, the same parts as those in FIG. 11 are denoted by the same reference numerals. When using a method of forming a film on the reactor structural material by injecting titanium oxide into the reactor 1, the titanium oxide is injected from any or all of the injection points 2, and the reactor 1 and the PLR line 3. , CUW line 5 adheres to the surface of the wetted material.
[0124]
Adhesion to the material surface depends on reactor water temperature, titanium oxide concentration and binder concentration. The control of these concentrations increases by increasing the flow rate of the infusion pump 12 and conversely decreases by increasing the flow rate of the CUW pump 6. The temperature of the reactor water hardly changes when the reactor is stationary, but it changes and can be controlled during transients at startup / shutdown.
[0125]
For example, at the time of stopping, the temperature can be lowered by increasing the flow rate of the residual heat removal system or by opening the main steam system isolation valve. In order to optimize the adhesion amount of titanium oxide, the test piece 18 is immersed in the sampled reactor water, and the adhesion amount is measured by the adhesion amount measurement system 17 as appropriate. This deposition amount data is fed back to the injection control system 14 and the reactor operation system.
[0126]
When the adhesion amount of the test piece 18 is lower than the target value considering the previous adhesion time, the flow rate of the injection pump 12 is increased, and when the water quality is close to the limit value, the temperature is increased. When it exceeds the target value, the flow rate of the infusion pump 12 is decreased and the flow rate of the CUW pump 6 is increased. By controlling the flow rate of the injection pump 12, it is possible to form an optimum titanium oxide film on the surface of the reactor material.
[0127]
TiO at the start of injection₂Concentration and TiO₂An example of the change over time in film thickness is shown in FIG. This is an example of injecting to the target thickness in 24 hours. The adhesion test piece is taken out and analyzed every 2 hours after the injection is started. At the beginning of injection, injection is performed at 1/3 of the provisional target value of concentration.
[0128]
If the adhesion thickness after 2 hours is 2% of the target, the target will not be reached even if it is 36 times (1/3 in concentration, 1/12 in time). The injection is started at the provisional concentration. Then, after another 2 hours, the adhesion test piece is taken out and the adhesion thickness is analyzed. If the amount of increase in adhesion thickness during 2 hours is 8% of the target, since the adhesion thickness is not reached in the remaining time, injection is performed at 120% of the provisional value.
[0129]
Thereafter, the amount of adhesion is measured every 2 hours, and when the adhesion thickness reaches 90% of the target, the injection is finely adjusted to 1/3 of the provisional value. As described above, the adhesion thickness can be controlled to the target value by attaching the adhesion test piece while monitoring the adhesion thickness.
[0130]
【The invention's effect】
According to the present invention, by controlling the film thickness, particle size, concentration, dispersant, binder, and impurities of a photocatalyst that has an anticorrosive effect when irradiated with light, a high-performance photocatalyst that meets the reactor cooling water quality standard The layer can form a uniform film on the surface of the reactor structural material to reduce corrosion during reactor operation.
[Brief description of the drawings]
FIG. 1 is a characteristic diagram showing the relationship between the thickness of a titanium oxide film and the potential of a material for explaining Example 1 of the present invention.
FIG. 2 is a characteristic diagram showing the relationship between the titanium oxide particle size and the potential of the material for explaining Example 2 of the present invention.
FIG. 3 is a characteristic diagram showing a relationship between a potential of a material and a ratio of platinum added to titanium oxide for explaining Example 3 of the present invention.
FIG. 4 is a characteristic diagram showing a relationship between a titanium oxide concentration and a material potential for explaining Example 4 of the present invention.
FIG. 5 is a characteristic diagram showing the relationship between the concentration in the reactor water and the potential of the material for explaining Example 5 of the present invention.
FIG. 6 is a characteristic diagram showing the relationship between the potential of a material and the ratio of a titanium oxide added with a dispersant for explaining Example 6 of the present invention.
FIG. 7 is a characteristic diagram showing the relationship between the reactor water conductivity and the proportion of titanium oxide added with a dispersant, as in FIG. 6;
FIG. 8 is a characteristic diagram showing the relationship between the potential of a material and the ratio of titanium oxide to which a binder is added, for explaining Example 7 of the present invention.
FIG. 9 is a characteristic diagram showing the relationship between the concentration in the reactor water and the potential of the material for explaining Example 8 of the present invention.
FIG. 10 is a characteristic diagram showing the relationship between the concentration of chlorine and sulfuric acid in reactor water with respect to the ratio of impurities added to titanium oxide, for explaining Example 9 of the present invention.
FIG. 11 is a piping system diagram of a nuclear reactor and its surroundings for explaining Example 10 of the present invention.
FIG. 12 shows TiO at the start of implantation in FIG.₂The characteristic view which shows the time change of a density | concentration and electrical conductivity.
FIG. 13 is a piping system diagram of a nuclear reactor and its surroundings for explaining Example 11 of the present invention.
FIG. 14 shows TiO at the start of implantation in FIG.₂The characteristic view which shows the time change of a density | concentration and film thickness.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 (2a, 2b, 2c) ... Injection point, 3, 4 ... PLR line, 5, 6 ... CUW line, 7 ... Purification system, 8, 9 ... RHR line, 10 ... Sampling line, 10a, 10 ... Sampling point, 11 ... Measurement system, 12 ... Injection pump, 13 ... Injection line, 14 ... Injection control system, 15 ... Signal line, 16 ... Water supply line, 17 ... Adhesion amount measurement system, 18 ... Adhesion test piece.

Claims (11)

In a method of forming a film of the photocatalyst on the nuclear reactor structural material by injecting a component constituting the photocatalyst into the nuclear reactor structural material into the nuclear reactor water ,
The particle size of the photocatalyst to be injected, the ratio of the dispersant, binder and impurities contained in the photocatalyst agent are defined. The photocatalyst is TiO ₂ , and the film thickness of the TiO ₂ is controlled from 0.1 μm to 10 μm. When injecting the photocatalyst-containing solution into the reactor water, the photocatalyst is added to 500 ppb or less when continuously injecting during steady operation of the reactor, and to 10 ppm or less when injecting during transients at startup and shutdown. The dispersant that controls concentration and suppresses aggregation of the photocatalyst is made of ammonia or carboxylic acid, and the concentration of the dispersant is controlled to 0.34 % or less (excluding 0) with respect to the photocatalyst. A method for forming a photocatalytic film of a nuclear reactor structure material, wherein a binder for promoting film formation is controlled from 2.5 % to 0.01 % with respect to the photocatalyst. In the method of forming the photocatalyst film on the nuclear reactor structural material by applying a component constituting the photocatalyst to the nuclear reactor structural material and injecting it by a spraying method .
The particle size of the photocatalyst to be injected, the ratio of the dispersant, binder and impurities contained in the photocatalyst agent are defined. The photocatalyst is TiO ₂ , and the film thickness of the TiO ₂ is controlled from 0.1 μm to 10 μm. When the spray solution is applied and injected by the spray method , the concentration of the photocatalyst is controlled to 10 % or less (excluding 0), and the dispersant for suppressing the aggregation of the photocatalyst is made of ammonia or carboxylic acid, The concentration of the dispersant is controlled to 0.34 % or less (excluding 0) with respect to the photocatalyst, and the binder for promoting film formation of the photocatalyst is controlled from 2.5 % to 0.01 % with respect to the photocatalyst. A method for forming a photocatalytic film for a nuclear reactor structural material.   The method for forming a photocatalytic film for a nuclear reactor structure material according to claim 1 or 2, wherein the particle size of the photocatalyst is controlled to 20 nm or less (however, not including 0). The nuclear reactor structural material according to any one of claims 1 to 3, wherein 0.05% to 3% of at least one photocatalyst assistant of Pt, Rh, Ru, or Pd is attached to the surface of the photocatalyst. The photocatalyst film formation method of. The method for forming a photocatalytic film for a nuclear reactor structural material according to any one of claims 1 to 4, wherein the binder is controlled to 1 ppm or less. The photocatalyst, the dispersant, and the binder are controlled to a reference value or less during normal operation of the reactor by reducing Cl ⁻ or SO ₄ ²⁻ of harmful impurities to 0.05 ppb or less in reactor water during reactor operation. The method for forming a photocatalytic film of a nuclear reactor structural material according to any one of claims 1 to 5 . Reactor operation when the reactor water conductivity according to any one of claims 1 to 6 any one and controls so that 0.1 .mu.S / cm is a reference value at the reactor normal operation A method for forming a photocatalytic film of a nuclear reactor structural material. At startup the quality of nuclear reactor is excluded from the normal operation sometimes prescribed criteria during intermediate stop, claims 1 to 4 any one characterized by a period of time of the last stop to deposit the photocatalytic A method for forming a photocatalytic film of a nuclear reactor structural material according to claim 1. When the photocatalytic film is formed during startup, intermediate shutdown, and final shutdown, the water quality of the reactor is excluded from the standards established for normal operation. there Cl ^- and SO ₄ ^{2-concentrations} respectively 5ppb or less, the photocatalytic film-forming method of the nuclear reactor structural material according to claim 8, wherein the controlling the conductivity to below 1 [mu] S / cm. The concentration of the photocatalyst and impurities before Symbol reactor water conductivity, a measurement system arranged to measure the pH, the measurement system data injection system, temperature, flow rate, flow path, can be fed back to the control system of the clean-up system flow The method for forming a photocatalytic film of a nuclear reactor structural material according to any one of claims 7 to 9 . Sampling the previous SL reactor water, and immersing the sampled reactor water to the test piece, injection system adhesion amount of the photocatalyst to the test piece, temperature, flow, that is fed back to the control system having a flow path The method for forming a photocatalyst film of a nuclear reactor structure material according to claim 1 or 2 .

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