Evolutionary design features of the new nuclear plants with pressure-tube reactors of the RBMK type

The upgrading strategy for the RBMK plants of the first generation, developed in 1989, is being successfully implemented at operating nuclear units. At the same time, new -evolutionary - design features are being introduced at Kursk 5 which is under construction now. The paper describes in particular the new graphite stack at Kursk 5. The graphite stack was modified to change the reactivity effects, ensure graphite integrity in off-normal conditions and extend graphite life in the reactor. The paper includes the results of numerous experiments and calculations performed to demonstrate the new features of the stack. The authors describe the new confining systems and the reactor control and protection system. Safety aspects are discussed in the context of plant compliance to current regulatory requirements, including environmental impact assessment. Further evolution of pressure-tube designs is discussed based on three modifications of MKER-type reactors- MKER-800, MKER-1000 and MKER-1500. The discussion covers potential reactor operation with natural circulation of coolant, provision of full containment, significant simplification of a multi-loop circulation circuit, new emergency and long-term cooling systems. The cost effectiveness of the MKER plants is discussed briefly. The paper gives the layout of the main buildings of the MKER plants, and contains tables with technical and performance data of the plants. (authors)