Core analysis at Paks NPP with a new generation of VERONA

In 2002 the Hungarian Paks NPP started a large-scale reconstruction project to upgrade its core monitoring system called VVER On-Line Analysis (VERONA). The main reason for the reconstruction decision was the planned reactor thermal power increase from 1375 MW to 1485 MW (108%), in order to achieve 500 MW electric power output. Considering safety margins and operation limits the basic approach was to keep all previously valid limits at 108%, as well. However, increased core power and a new type of fuel required a more accurate and more frequent core analysis; therefore modernization of the VERONA system was necessary and unavoidable. At this moment Unit 3 and Unit 4 are served by the new system. The reconstruction project is planned to be fully completed in 2008, when all Paks units will have a modernized core analysis system, providing state-of-the art services and operator support.The paper first presents a brief overview of the reconstruction process, and then main design principles and functions of the new VERONA system are outlined. Details of the new system architecture, hardware devices and software tools are also given, and then elements of the new human–machine interface are described and illustrated. A special emphasis is devoted to the new core analysis software with a detailed description of the validation methods and results. The process of reaching 108% power at Unit 4 is discussed; core behavior is illustrated by real data taken during the power increase procedure. Finally experience related to the development and operation of the new system is discussed briefly.