Assessment of the capability of the trace code to model the propagation of linear acoustic pressure waves in one-dimensional flows

A variety of nuclear systems transients can lead to rapid and large local pressure changes that propagate along the hydraulic system at the speed of sound, both in single phase and in two-phase fluids. Because of the relevance for safety issues, nuclear system codes like TRACE need to be assessed with respect to their capabilities to predict pressure wave behavior. Therefore, we have analyzed the propagation of pressure waves in a one-dimensional configuration, a pipe filled with liquid water. The pressure waves are harmonically driven by one-sided pressure boundary conditions, which lead to standing pressure waves. The agreement of the TRACE results with the analytical solution is, in general, very good to good with respect to the pressure maxima and a small difference is only observed in the wave speed. At the resonance frequencies, the code is tested to the extreme and shows that enforcing small time step sizes is crucial for the quality of the performance of the code. Non-linear effects are observed in the code results for the large amplitudes encountered at the closest neighborhood of the resonances, where the analytical linear standing wave solution diverges and the linear approximation fails. Also for these non-linear standing waves TRACE yields qualitatively physically correct behavior as the pressure amplitudes are limited and a plateau is reached. It is intended to extend the analysis presented in this paper with the cases of one-dimensional traveling pressure pulses and two-dimensional standing waves, for which also analytical solutions are available.