[en] The objective of the work is to assess various issues in nuclear safety regulation in consideration of circumstantial changes. Emphasis is given to the safety of operating NPPs. It is concluded that the Periodic Safety Review (PSR) should be implemented in Korea as soon as possible, in harmonization with the regulation for life extension of NPPs. The IAEA guidelines, including 10 year intervals and 11 safety factors, should be used as the basic guidelines. The approach to improve regulatory effectiveness is also reviewed and a transition to 'knowledge-based regulation' is suggested