報告書番号

U97019

タイトル（和文）

浸漬試験によるセメント材料の長期変成挙動に関する検討

タイトル（英文）

CHANGE OF LONG-TERM CHEMICAL PROPERTIES OF CEMENT MATERIALS DUE TO LEACHING

概要 （図表や脚注は「報告書全文」に掲載しております）

セメント材料を人工バリア材に使用した場合の放射性廃棄物処分の安全性評価のため，セメントの化学的性質の長期変成挙動解明及び評価モデル確立が必要である。本研究ではまず変成挙動に関し既往の報告を調査し課題点の抽出を行うと同時に，溶解反応を促進する液固比の増大，鉱物の生成に寄与する反応性イオンの添加，鉱物の熱変成を起こす温度上昇など，変成を促進する因子とその効果について，浸漬法による予備変成試験を行い，長期変成挙動を評価する試験方法としての適用性を検討した。その結果単一の方法での変成の促進では実環境の変成を十分に記述出来ないことが確認され，セメント長期変成挙動評価のためには，実条件における各反応の競合を考慮し，各条件を組み合わせて試験を立案する必要があることが分かった。

概要 （英文）

CEMENT MATERIALS, WHICH ARE USED AS AN ENGINEERED BARRIER FOR DISPOSAL OF RADIOACTIVE WASTE, ARE EXPECTED TO RETARDTHE RELEASE OF RADIONUCLIDES BOTH AS PHYSICAL AND CHEMICAL BARRIERS. IN DISPOSAL OF TRU-WASTE (WASTE CONTAINING LONG-LIFE RADIONUCLIDES), THELONG-TERM CHEMICAL PROPERTIES LIKE THE SORPTION PROPERTY OF CEMENT MATERIALS ARE A KEY ISSUE BECAUSE CEMENT ALTERATION OCCURS IN THE REPOSITORY. THE LONG-TERM CHARACTERISTICS OF CEMENT ALTERATION WERE STUDIED BY SURVEYING PREVIOUS REPORTS, AND PRELIMINARY LEACHING TESTS OF CEMENT MATERIALS WERE USED TO CLARIFY PROBLEMS IN ACCELERATED AGING TESTS. THE RESULTS ARE AS FOLLOWS: (I) DISSOLUTION: DISSOLUTION CAN BE ACCELERATED BY LEACHING SOLUTION REPLACEMENT OR AT A LARGE LIQUID/SOLID RATIO. BUT THE CHANGE IN THE SOLID PHASE IS PECULIAR TO EACH TEST CONDITION. IT ISIMPORTANT UNDERSTAND THE SOLID PHASE GENERATED IN REAL REPOSITORY CONDITIONS. (II) EFFECT OF AGGRESSIVE IONS: MINERAL PHASE FORMATION AND COMPOSITION CHANGE DUE TO AGGRESSIVE IONS WERE OBSERVED IN A RELATIVELY SHORT PERIOD. THESE REACTIONS COULD NOT BE RELATED DIRECTLY TO THOSE IN REAL REPOSITORY CONDITIONS. (III) EFFECT OF HEATING: THE COMPOSITION ANDSTRUCTURE OF THE CEMENT MINERAL PHASE DIFFER AT EACH TEMPERATURE CONDITION. EACH METHOD COULD ACCELERATE ALTERATION OF CEMENT MATERIALS, BUT ANY DOMINANT REACTION COULD MASK OTHER IMPORTANT REACTIONS. IT IS IMPORTANT TO SET THE EXPERIMENTAL CONDITIONS, CONSIDERING THAT THE LONG-TERMPROPERTIES OF CEMENT MATERIALS, SUCH AS DISSOLUTION, HYDRATION, FORMATION OF MINERAL PHASE ETC., THAT MIGHT OCCUR SIMULTANEOUSLY IN REAL REPOSITORY CONDITIONS.

報告者

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