[en] While the development of the future Korean nuclear reactor system design will be solely pursued by KAERI, new technologies from foreign vendors will also be continuously monitored and adapted through joint R and D program and/or system design participation. Starting from Joint System Design with CE for Yen 3 and 4 in 1986, KAERI has been putting extensive efforts on the technical self reliance for NSLS system design through the Korean Standardization Project, technology transfer and system design support. Today, KAERI find itself as sole responsible NSLS system designer for UCH 3 and 4, which are the first ever units to be designed and constructed with Korean technology. Even though the Yen 3 and 4 design has already adapted several improved design features relative to CE System 80, KAERI has been further investigating 16 advanced design features (ADCs) and has selected those which are more feasible for the Korean situation through the Phase II and III of Korean Standardization Program. In UCH 3 and 4, in order to cope with the tight project schedule, only 10 ADCs have been adapted among them. However, KAERI will continue to develop not only those remaining 5 ADCs from Kp but also other ADCs developed by ABB.-CE so that they can be incorporated into future Korean PWRs, including Yen 5 and 6. In addition to this evolutionary plant development, the revolutionary (passive) reactor project has been initiated and actively pursued from this year. Since this project has just begun, there is a need to further define what should be done. However, its first goal will be focused on the feasibility study of the development of 600 MW or larger passive reactors and the 'PASSIVIZATION' of the current Korean Standardized Plant.