Research summary on the characterization of fuel debris

JAEA, as a member of IRID, had started experimental and analytical studies on characterization of fuel debris. In this study, thermodynamic equilibrium calculations were carried out and typical debris phases were predicted. Experimental studies were also carried out using simulated fuel debris, and verify the expected fuel debris properties on typical conditions of Fukushima Daiichi Nuclear Power Station (1F). The 1F accident differs from the past severe accidents such as Three Mile Island unit-2 (TMI-2) and Chernobyl nuclear power plants. Therefore, specific factors in the 1F accident should be considered; BWR fuel assembly, control rod, core configuration and accident sequence. Further specific factors are high zirconium and iron contents, B₄C, sea water effects and molten core concrete interaction (MCCI). After the defueling, interim storage will be considered, but the treatment scenario has not defined. In this paper, research summary on the characterization of fuel debris and current research results will be described. (author)