Analysis of Novo-Voronezh NPP unit 3 radiation lifetime of the WWER-440 reactor pressure vessel given samplings Original Research Article

The analysis of the residual radiation lifetime of the Novo-Voronezh NPP Unit 3 reactor pressure vessel which had spherical samplings after annealing was performed for the spectrum of the ‘worst’ modes of the emergency situation category. For the residual radiation lifetime estimation within the given study, two approaches to determine stress intensity factors, KI have been used simultaneously. The first approach included a direct numeric modelling of postulated cracks in the cut-out zone with the use of the 3D finite element method. The second approach included K1 calculation using 3D weight functions calculated with the use of the boundary element method. For KI, calculation flaws have been postulated as surface longitudinal semielliptical flaws located in the deepest point of a cut-out. The results of KI calculations obtained using different methods were practically the same. The allowable critical brittleness temperature was determined as 175°C that permitted the extension of the radiation lifetime by up to 6 years after annealing.