[en] Following the Fukushima Daiichi Nuclear Power Station accident associated with the Great East Japan Earthquake, Hitachi Group has been developing the necessary equipment for decontamination work and environmental maintenance on the premises of the power plant, as well as for various investigations toward fuel debris retrieval. This paper introduces the following devices together with their application experiments: (1) 'ASTACO-SoRa'; dual-arm heavy machine robot for conducting heavy work as a work robot, (2) 'muscle robot'; flexible structure arm with resistance to high radiation environment, (3) 'PMORPH'; shape-changing robot as a research robot for investigating inside the reactor containment vessel, (4) 'Gengo ROV' and 'Tri-Diver'; robot for monitoring a torus room as underwater environment, and (5) boat with a diving function for surveying the underwater portion inside the reactor containment vessel. This paper also introduces next-generation robot technology that Hitachi plan to use in the future, with a focus on the operation support technology for robots with high radiation environment compatibility as well as the drones for surveying and monitoring. (A.O.)