[en] In August 2004, a pipe rupture accident occurred at The Kansai Electric Power Company Mihama Unit 3. Japan Society of Mechanical Engineers (JSME) recognized that it was an urgent problem to settle the rules on Pipe Wall Thinning Management by Fluid Flow. JSME enacted 'rules on Pipe wall Thinning' that stipulates the basic requirements of pipe wall thinning management, considering from these situations. In 2006, JSME enacted the 'rules on Pipe Wall Thinning Management for PWR Power Plants' (JSME S NG1-2006, JSME rules for PWR) that satisfies the requirements of 'rules on Pipe Wall Thinning'. This JSME rules for PWR stipulates the process of inspection plan, measurement, evaluation and maintenance. This paper focuses on the technical grounds that specify the management systems, pipe components and initial FAC rate. (author)