抄録
At the moment, Ukraine and other countries are implementing a program to extend the nuclear power plants operation over the design period, which is economically advantageous, as the level of capital expenditure required for this is significantly lower than for the new power units building. Particular attention is paid to assessing the technical condition and extending the reactor vessel operation (thermal shock assessment), as the vessel is the most expensive and complicated element of the power unit in terms of manufacturing and replacement. For this assessment, in particular, for the thermal-hydraulic analysis, special methodologies are used in the world. Analysis of the main existing methodologies of thermal-hydraulic analysis used in Ukraine and the world has shown that the practice of performing thermal-hydraulic analysis in Ukraine is ahead of theoretical knowledge, international experience and early national experience, and therefore requires optimization and improvement. In the present work, the most relevant results of thermohydraulic, probabilistic and strength evaluations performed for SUNPP-3 were analyzed. In addition, the obtained results were compared with other results obtained for other power units recently. These estimates were performed with the purpose of the Ukrainian NPPs lifetime extension using existing methodology that can be improved with current experience. Reason of all estimate types analysis is that the power unit extension is a complex task: thermal-hydraulic analysis of scenarios with a high probability realization is performed, and strength analysis allows estimating scenarios quantitatively and to conclude that the scenarios are representative in relation to a thermal shock or not. This can to allow reasonable to reduce the number of scenarios that require a quantitative assessment. Particular attention is paid to SUNPP Unit 3, which is now at the stage of life extension. Methodology can be improved and after this can be used to lifetime extension of Ukrainian NPPs vessel reactors, for which the relevant work has not yet begun, as well as in the case of the repeated extension. In addition, the results of the work and the Ukrainian experience can be taken into account in the next edition of the IAEA guideline or practice.
