報告書番号

L15006

タイトル（和文）

シビアアクシデント後の破損・溶融燃料の安定性に関する研究 -TMI-2溶融デブリ試料と使用済燃料試料からの核種浸出傾向の把握-

タイトル（英文）

Examination of stability of molten and dameged materials from TMI-2 and irradiated fuel sample

概要 （図表や脚注は「報告書全文」に掲載しております）

概要 （英文）

In the severe accident of nuclear power plants, brine water or boric-acid solution are possibly used for the emergent cooling of the reactor. This leads to the situation that the fuels which might be damaged or molten are kept in the cooling water containing brine components or boric acid over a long duration after the accident. The influence of these solutes on the corrosion behavior of the fuel has not been investigated enough. Although some knowledge has been obtained from the evaluation of TMI-2 accident data or other corrosion tests which simulate long term storage condition of the spent fuels, their application is limited because their conditions are different in cooling water constituents or the fuel characteristics. The aim of this research is to reveal the leaching behavior of actinides and fission products (FPs) taking into consideration the influences of damaged fuel and the different solutes. In the leaching tests with TMI-2 molten debris, samples taken from the molten fuel core region of TMI-2 reactor and ones from the metallic crust region were immersed in pure water or boric-acid water. The cumulative moles of U, Pu, Np, Ag, Zr, Mo, Tc, Cs, Ce which leached out from the debris sample were measured. It was revealed that the leached amounts of Ag, Pu, Ce, Mo and Tc are different depending on the characteristics of the debris samples. On the other hand, other measured elements showed similar behavior for both types of samples and solutions, which implies that the addition of boric acid to the cooling water has no significant influence on the leaching behavior. It was also confirmed that the amount of U leached from the unit mass of molten debris sample is similar to that of normal irradiated fuel sample. The leaching tests with sliced irradiated fuel sample with a brine water were also carried out and leaching velocity of the actinides and main FPs were evaluated. The FIAP (Fraction of Inventory in Aqueous Phase) was evaluated for most of the elements. Based on FIAP values, the characteristics of leaching behavior of each elements were explained and compared with existing data to show a consistency.

報告者

キーワード