To determine reactor pressure vessel (RPV) residual lifetime as well as its brittle failure probability at pressurized thermal shock (PTS) conditions the original “indirect” solution method for the nonstationary temperature problem in axisymmetric formulation with the method of further stress calculation is developed. Both methods are based on transfer matrix approach and use exact analytical expressions for the thick-walled cylinders.

The automatic timestep determination method is implemented, which provides maximum calculation speed, but without the loss of the critical timepoints of scenarios under consideration. Also the accuracy of the model is improved by separate temperature calculations for “cold” plume and “hot” rest of the reactor, according to IEAE recommendations. At that axial strain of the “hot” part is used to load “cold” one.

The comparison of the methods with well-known theoretical results as well as with numerical tests demonstrates very high accuracy. It is proved by the methods of shell theory that possible difference with full 3D model of cylinder can’t be essential. Obtained fields of the temperature and stresses can be used for further estimation of the allowable value of the ductile-to-brittle transition temperature.

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