Confinement strength and integrity, nuclear power plant V-1 Bohunice Slovakia

Within the framework of the extension of the safety standards of the Bohuni ce V-1 nuclear power plant, the integrity and load bearing capacity of the confinement under accident conditions was demonstrated. For this purpose, s pecifications were developed for the design basis loads and stresses and lo ad and stress combinations, and the criteria and methods employed were defi ned and developed, respectively. In addition to loads and stresses arising out of the plant design and from thermal origins, also those loads and stresses were considered which are sp ecified for the design basis accident (DBA) and for events exceeding that d esign basis by the regulatory authority, UJD SR, ranging from a double-ende d break of the pressurizer pipe with an equivalent leak diameter of 200 mm to the double-ended break of a main coolant system pipe of 500 mm diameter. As far as materials properties are concerned, long-term phenomena, such as creeping and shrinkage, as well as the influence of potential cracks in th e concrete of the confinement were taken into account. On the whole, the sa fety analysis was based on European standards, and the safety factors follo wed the recommendations by the International Atomic Energy Agency (IAEA). Because of the geometric complexity of the confinement, a three-dimensional finite-element model was employed in the analysis. The result of this safety analysis indicates, for the sections of the Bohun ice V-1 nuclear power plant under investigation, absolute agreement of the level of safety also with international requirements, both for design basis accidents and for events exceeding the design basis.