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Results of numerical analysis of stress intensity factors K I for semielliptical surface cracks in the WWER-1000 reactor pressure vessel by emergency cooling simulation with known engineering procedures, the equivalent spatial integration and direct methods are presented. Engineering procedures employ the results of numerical solution of axially symmetric boundary value problems of thermoelasticity based on the mixed mesh-projection scheme of the finite element method implemented in the RELAX software. The three-dimensional K I computations were performed with the SPACE software.Keywords: finite element method, mixed mesh-projection scheme, stress intensity factor, equivalent spatial integration method, direct method, semielliptical crack, reactor pressure vessel.One of the conditions of reliable service of nuclear power plant equipment is the reactor pressure vessel (RPV) integrity both in normal operation and in an emergency. Under RPV operation conditions caused by an emergency, in particular by thermal shock, the basic strength criterion for the RPV material is assumed to be its ability to resist brittle fracture. Stress intensity factor calculations are an appropriate basis for this.The present study cites the results of comparing calculated K I values for a longitudinal semielliptical surface crack in the WWER-1000 RPV obtained by engineering and numerical procedures. Among the first ones are the procedures employing approximate formulas [1, 2] and dimensionless K I values calculated by the method of weight functions [3,4], among the second ones are the procedures making use of the equivalent spatial integration method [5] and the direct method [6] based on solving the boundary value problem of thermoelasticity with the mixed mesh-projection scheme of the finite element method (FEM) [7], which provides a higher accuracy of determining thermostress and strain fields as compared to the classical finite element displacement method.The stress intensity factor by engineering procedures [1-4] is determined from the relationwhere σ is the calculated stress and Y is the dimensionless function for different points of the crack front allowing for crack dimensions and the RPV wall thickness. The stressed state on the crack surface ( Fig. 1) is expressed in terms of stresses (Eq. 1), which are proposed to calculate along the crack with different approximating functions from stress-strain state calculation results for the integral structure. 1380039-2316/07/3902-0138

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