Transport Mechanism of Thermohydraulic Instability in Natural Circulation Boiling Water Reactors during Startup

Numerical Investigation of Startup Instabilities in Parallel-Channel Natural Circulation Boiling Systems

“…It can be inferred that the flow in both the channels is in-phase, until it reaches the peak of the first pulse and from there on develops a phase difference. Earlier, the persistence of out-of-phase oscillations even under equal power condition between channels was reported through experimental studies by Subki et al [5] and Chen et al [15]. Similar observation is reported by Jain et al [16] in their experiments conducted in a natural circulation parallel-channel model; they also characterized such oscillations as mixed mode oscillation.…”

“…Very few investigations have been done to study the low-pressure transients that could occur in a parallel channel natural circulation boiling system. An experimental study using a double-channel natural circulation loop was carried out, and the transport mechanism of various types of instability under startup conditions was discussed [5]. In-phase and out-of-phase flow oscillations were reported.…”

Validations of Thermohydraulic Models for Geysering in a Natural Circulation Loop Using an Impedance Needle Probe

“…Janssens-Maenhout et al experimentally investigated the effect of riser width and initial static height on geysering frequency. Subki et al observed geysering phenomenon in a double-channel boiling SWNC loop and confirmed that the startup at low pressures and low heat fluxes results in geysering instability of high frequencies and flashing-induced instability. Zhang et al investigated the geysering of cryogenic propellant and recommended a method for suppressing its severity.…”