PWR-depressurization and its hydraulic analogy

Kurzfassung

The aim of this work is to provide an experimental verification of codes to be used for numerical simulation of the depressurization process in a pressurized water reactor (PWR) in case of a hypothetical blowdown accident. Here, the downcomer of a PWR is approximately treated as a two-dimensional plane region (unwrapped). The flow is simulated experimentally using the hydraulic analogy of free surface waves in a shallow water bed and compared to numerical simulations for the analogous flow of an ideal gas with an isentropic coefficient equal to two. The differences between the results of both models are less than 10%. Also reported are results of a similar study for a one-dimensional case (depressurization in a pipe). The depressurization process can be subdivided into three phases: (1) Fluid still at rest, smooth depressurization wave, pressure drops, (2) Fluid accelerates, pressure recovers near the outlet (in 2-dim. case), (3) Quasi-steady flow, oscillations (in 2-dim. case). It is suggested that the results serve as a bench-mark for blow-down accident analysis codes.