Numerical simulation of fluid–structure interaction dynamics under seismic loadings between main and safety vessels in a sodium fast reactor

A safety vessel is incorporated in the sodium cooled fast reactors surrounding the main vessel to contain the sodium, in case of a leak in the main vessel. This paper presents the determination of dynamic pressures on the main vessel as well as safety vessel generated due to fluid–structure interaction effects under seismic excitations. Axisymmetric reactor geometry is investigated with 2D ‘Fourier harmonic’ analysis, as well as corresponding 3D geometry developed by 180° rotation. Results show that 2D approach provides satisfactory results for the global parameters such as displacements, reaction forces and dynamic pressures. Subsequently, 3D analysis is performed to determine critical buckling load and interaction between horizontal and vertical vibration modes. These apart, the application of these numerical analyses for the 500 MWe Prototype Fast Breeder Reactor (PFBR) demonstrates the structural integrity of safety vessel under the seismic loadings during main vessel leaked condition and quantifies the design basis loads for the inner wall of the reactor vault.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Dominant coupled natural frequencies of main vessel and safety vessel due to fluid structural interactions lie in 9–16 Hz. ► Associated modal masses are ∼80% and ∼50% in horizontal–vertical directions. ► Relative displacements between main vessel and safety vessel ∼3 mm and 1.2 mm in horizontal and vertical directions. ► Peak dynamic pressures on safety vessel are 25 kPa and 16 kPa during horizontal vertical excitations. ► Reaction forces on the concrete reactor vault support for safety vessel are ±365 (shear force), ±2500 tm (bending moment) and ±1400 (axial force).