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Oral presentation

Fundamental experiment on the U-Zr-Gd-O molten corium solidification behavior

Sudo, Ayako; Poznyak, I.*; Nagae, Yuji; Nakagiri, Toshio; Kurata, Masaki

no journal, , 

no abstracts in English

Oral presentation

Revisiting the TMI-2 core melt specimens to verify the simulated corium for Fukushima Daiichi NPS

Takano, Masahide; Onozawa, Atsushi; Suzuki, Miho; Obata, Hiroki

no journal, , 

For the decommissioning of damaged cores of Fukushima Daiichi NPS, the retrieval operation of solidified core melt (corium) and its safe management are essential tasks. To understand characteristics of corium specific to the 1F cores, we have prepared and analyzed various types of simulated corium specimens in laboratory scale. To verify the effect of cooling condition found on the simulated corium, we revisit the actual corium specimens collected from the TMI-2 accident core, which have been stored at the Reactor Fuel Examination Facility (RFEF) in JAEA Tokai since 1991. Comparing the phases and microstructure, rapid-cooled specimens have dense microstructure and consist of single phase of cubic structure. On the other hand, the slow-cooled specimens consist of U-rich cubic and Zr-rich tetragonal phases distributed minutely. From these observations we have confirmed the similar dependence of microstructure and mechanical property on the cooling condition.

Oral presentation

Phases and morphology in U-Zr-Gd-Fe-Ca-O systems as main component of oxide corium

Takano, Masahide; Onozawa, Atsushi

no journal, , 

(U,Zr)O$$_{2}$$ solid solution is considered as the main component of oxide corium generated in the core-meltdown accident at Fukushima Daiichi NPS. The actual oxide corium is expected to contain some minor solutes such as lanthanides from burnable poison (Gd) and fission products, Fe from stainless steel, and Ca from see water and concrete. In this paper, influences of these minor elements on the phases, morphology, and oxidation behavior of (U,Zr)O$$_{2}$$ is investigated. As results of sample characterization, (1) the Fe inclusion tends to form a complicated microstructure of U-rich and Zr-rich phases tangled in $$mu$$m-scale; (2) the influence of Ca inclusion is the stabilization of Zr-rich tetragonal phase into cubic phase when the O/M ratio is within hypostoichiometric range; (3) the impact of lanthanide inclusion is that the cubic (U,Zr)O$$_{2+x}$$ domain expands to lower temperatures region where UO$$_{2}$$ and (U,Zr)O$$_{2}$$ is oxidized to U$$_{3}$$O$$_{8-z}$$ and orthorhombic U(V)-Zr-O.

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