Method of repairing and prolonging lifetime of nuclear power plant

After the shutdown of a reactor, components are removed as far as the position just above the spent fuel pool of the reactor building. That is, walls and roofs which are higher than the operation floor in the upper portion of the building are cut and removed, to open the upper portion of the container. Then, old internal equipments are exchanged with new internal equipments through the opening formed in the upper portion of the container for repair. Subsequently, the structures of the building upper portion are reconstructed to such a shape as having a reduced weight and capable of self-sustaining with a sufficient strength. With such a constitution, since the intact building portions corresponding to about 95% can be reutilized, the cost upon dismantling and reconstruction can be saved, thereby enabling to utilize construction resources effectively. (I.N.)