ASME Section III has been the most important Code for the design and construction of nuclear components for over 30 years in Korea. During that time, some difficulties have been recognized in compliance with the Code due to the differences in industrial practices and regulatory system between Korea and the U.S. In case of NCA (General Requirements for Division 1 and 2), the administrative and procedural requirements have been applied as modified to suit domestic industry practices. For technical aspects, supplemental requirements have been added to ASME Code in order to satisfy regulatory guides. Preheating and PWHT requirements of ASME Section III are slightly different from those of ASME B 31.1. The differences are discussed in this presentation. With the issuance of MOST (Ministry of Science & Technology) notice 96-32 in 1996 regarding KEPIC (Korea Electric Power Industry Code) application, KEPIC MN has been used in selected documents instead of ASME Sec. III. Ulchin 5&6 is the first project that applied to KEPIC. The application of KEPIC - MN has been gradually expanding to the subsequent nuclear projects. For consistent use of KEPIC, some measures for foreign vendors’ application of KEPIC should be considered.