報告書番号

T95057

タイトル（和文）

アルカリ水溶液中のインコネル６９０合金の耐ＩＧＡ／ＳＣＣ長期健全性の評価

タイトル（英文）

EVALUATION OF LONG-TERM INTEGRITY AGAINST IGA/SCC OF INCONEL ALLOY 690TT IN HIGH-TEMPERATURE ALKALINE SOLUTION

概要 （図表や脚注は「報告書全文」に掲載しております）

アルカリ加速腐食試験条件下で初期の伝熱管材料に用いられてるインコネル６００ＭＡ合金，熱処理を改善した中期の伝熱管材料６００ＴＴ合金，および熱処理と化学組織の双方を改良した新規６９０ＴＴ合金の耐粒界腐食／応力腐食割れ（ＩＧＡ／ＳＣＣ）発生試験を行い，以下の知見を得た。１．６００ＭＡおよびＴＴ合金とも高温ミルアニール材料の方が，低温ミルアニール材料よりも耐ＩＧＡ／ＳＣＣ性は優れていた。また，６００ＴＴ合金のＩＧＡ／ＳＣＣき裂進展速度は，６００ＭＡ合金の数分の一であった。２．新伝熱管材料６９０ＴＴ合金の長期耐ＩＧＡ／ＳＣＣ性，および伝熱管の支持構造の改善による不純物の低減効果を考慮した場合の６００ＴＴ合金の長期耐ＩＧＡ／ＳＣＣ性は，初期伝熱管６００ＭＡ合金の１０倍以上であり，十分であると評価された。

概要 （英文）

AS MENTIONED IN A PREVIOUS REPORT,A METHOD FOR PREDICTING IGA/SCC IN STEAM GENERATOR TUBES WAS DEVELOPED BY COMBINING IGA/SCC DEGRADATION RATE DATA FROM PLANTS AND LABORATORY TEST DATA. THE LONG-TERM INTEGRITY AGAINST IGA/SCC OF INCONEL MILL-ANNEALED ALLOY (600MA),THERMALLY-TREATED ALLOY 600(600TT) AND 690TT WERE EVALUATED USING THIS PREDICTIVE METHOD. IGA/SCC TESTS FOR 600MA,600TT AND 690TT WERECONDUCTED IN ALKALINE SOLUTIONS AT 320DEGREE USING THE C-RING TEST METHOD. THE TEST TIME AND CUMULATIVE FRACTION FAILED WERE PLOTTED ON WEIBULL PAPER. THE PARAMETERS OF THE WEIBULL DISTRIBUTION (SLOPE,AND SCALE PARAMETER) WERE DETERMINED. STATISTICAL ANALYSIS SHOWED THAT THE TUBE DEGRADATION RATE OF 600TT WAS SEVERAL TIMES SLOWER THAN THAT OF 600MA. INADDITION TAKING INTO ACCOUNT THE REDUCED EFFECT OF IMPURITY CONCENTRATION BY IMPROVEMENT OF SUPPORT PLATE STRUCTURE,THE DEGRATION RATE OF 600TT ALLOY WAS ABOUT 10 TIMES SLOWER THAN THAT OF 600MA ALLOY. THE IGA/SCC PROPAGATION RATE WAS IN THE ORDER: 600TT(H)<600TT(L)<600MA(H)<600MA(L) STATISTICAL ANALYSIS ALSO SHOWED THAT THE TUBE DEGRADATION RATE OF 690TT WAS MORE THAN 10TIMES SLOWER THAN THAT OF 600MA.

報告者

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