In this study, an alternative method to retrieve fuel debris and MCCI (Molten Corium Concrete Interaction) products in Fukushima Daiichi Nuclear Power Plants is proposed, where geopolymer is used for semi-stabilization of those debris. Facing the realization of this method, the fluidity and the setting time of geopolymer are regarded as one of the problems. Thus, for investigating and evaluating those properties, slump flow experiment, funnel experiment and viscosity measurement have been done. The results have showed that even under hot temperature or underwater geopolymer can perform enough workability in each process of its application. In concrete, geopolymer has transportability, spreading ability and solidification ability. The results also have revealed that its property of the viscosity is sensitive to the raw material of the products, but after some additional experiments it has been found that the setting time can be controlled by adding only a few amount of water.