REQUALIFICATION OF THE STEAM SUPPLY SYSTEMS OFUNITS 3 AND 4 OF THE KOZLODUY NPP

摘要

In order to achieve significant advance in operational safety level, the project characteristics, thernpossibility of safety systems upgrading and operational conditions of Units 1 to 4 of the KozloduyrnNPP were an object of very serious and in-depth analysis in the years 1990-2000. This systematicrnevaluation was initiated under the broad international concern resulted from the conclusions of IAEArnmissions held during 1990-1991 to assess the safety of the units. As a result of the efforts of the plantrnstaff and many international experts the operational conditions, design safety and plant managementrnwere dramatically improved which resulted in bringing the plant to a new safety level. This reviewrnalso developed such that the design safety features of Units 3 and 4 are significantly different fromrnthose units of the so-called V-230 group. The principle difference and advantages of Units 3 and 4rndesign were clarified and confirmed. A review process of the changed status of Units 3 and 4 safetyrnwas conducted in 1999-2000 with the help of IAEA experts and the experts of RISKAUDIT andrnWENRA. The process led to the conclusion that the significance of advantages of the safety levelrnneed to be encapsulated within a new safety case and the corresponding set of steps was combined asrna “Project for upgrading the Nuclear Steam Supply System of Units 3 and 4 of Kozloduy NPP tornmodel WWER-440/B-209M”. The completion of the activities under this project is expected in 2002rnfollowing the major implementation phase during 2001/2002 units'outages.