[en] In the plants for reprocessing spent nuclear fuel containing fission products, due to the facts that the facilities are in high radiations fields, and the surfaces of equipments are contaminated with radioactive substances, the troubles of process equipments are directly connected to the remarkable drop of the rate of operation of the facilities. Therefore, the development of various remote maintenance techniques has been carried out so far, but this time, Hitachi Ltd. got a chance to take part in the repair of spent fuel dissolving tanks in the Tokai Reprocessing Plant of Power Reactor and Nuclear Fuel Development Corp. and the development of several kinds of remote checkup equipment related to the repair work. Especially in the repair of the dissolving tanks, a radiation-withstanding checkup and repair apparatus which has high remote operability taking the conditions of radioactive environment and the restriction of the repaired objects in consideration was required, and a dissolving tank repairing robot composed of six kinds has been developed. The key points of the development were the selective use of high radiation-withstanding parts and materials, small size structure and the realization of full remote operability. The full remote maintenance apparatus of this kind is unique in the world, and applicable to wide fields. (Kako, I.)