Treated water of The Tokai Reprocessing Plant used for cooling water and fire fighting water, is supplied by the steel pipes. These pipes are laid down under the ground or in the trench. Treated water had leaked, because the part of the underground pipe flange corrosion. The cause of this breakage was presumed that the pipe flange has been loaded the stress continuously. The stress generated depend of that the underground pipes sank with the ground subsidence by influence of the 2011 earthquake of the Pacific coast of Tohoku. The repair of the breakage flange and the pipes was adopted to use clamp (flexibility joint) for pipe connection as one of the countermeasures for tremble of the earthquake. This report shows the technical evaluation for the clamp performance on the practical use.