Some CEA research activities in support of Fukushima Daiichi fuel debris retrieval

• For more than 10 years, CEA has been contributing to the R&D for Fukushima Daiichi decommissioning. • Fabrication and analysis of fuel debris simulants and prototypes. • Study of fuel debris cutting and related aerosol safety and of fuel debris leaching. • Very large amount of data has already been collected and provided to Japanese stakeholders. • Still many issues that require R&D to support the future large-scale fuel debris retrieval. Fuel debris retrieval is one of the important challenges in view of Fukushima Daiichi decommissioning. Indeed, hundreds of tons of fuel debris will have to be cut and collected in the 3 units that have been subject to core meltdown in March 2011. A large R&D effort has been supported by the Japanese stakeholders in support of this retrieval. In this context, CEA has used its severe accident and decommissioning research expertise to launch research activities in support of fuel debris retrieval. A first series of works aims to acquire knowledge about these fuel debris: experiments have been carried out to simulate Molten Core Concrete Interaction or to fabricate fuel debris simulants or depleted uranium-containing prototypes. These samples have been thoroughly analyzed and their properties have been determined. A second line of research deals with fuel debris cutting. CEA has successfully applied and improved its laser cutting technology to fuel debris. Mechanical cutting has also been studied. One of the important safety issues related to debris cutting is the generation of radioactive aerosols and particles. Dedicated research programs have been carried out to characterize these releases and study mitigation techniques.