Analysis of mechanical HCDA consequences in the coolant loops for demonstration of primary containment integrity in SNR 300

The demonstration of the accomodation of the mechanical consequences of a hypothetic core disruptive accident (HCDA) within the primary system is an essential objective in the safety assessment for SNR-300. For this purpose a mathematical model has been developed, in which the pressure pulse propagation in fluid-filled piping systems is calculated. This model takes into account the compressibility of the fluid as well as the elastic-plastic deformation of the pipe walls. It is the special aim of this work to estimate the attenuation of pressure peaks by elastic-plastic response of the pipe walls and to calculate the remaining strains. The basic system of partial differential equations includes the conservation laws for mass and momentum and the equations of state for the fluid and the pipe wall material. Additionally, the equation of motion for the pipe wall is provided, which considers the inertia of structure response after the pressure loading. The stress is described in a one-dimensional way. Axial stresses and strains are neglected. The numerical solution of the differential equations is carried out by an explicit extended Lax-Wendroff difference-scheme with the help of an intermediate step. The accuracy of the implemented calculation models is examined using the results of experiments. First of all, pressure wave experiments are taken, where the rising pressure pulse is so chosen, that the response of the pipe wall material lies exclusively within the elastic region of the diagram. These investigations have been carried out by INTERATOM. The comparison between measured and calculated values shows an excellent agreement of experiment and calculation