Detection of Damped Flow Oscillations in a CANDU 6 SOPHT Simulation using Noise Perturbations

Abstract

Quantifying the actual margins of stability and the effectiveness of outlet header interconnects are beneficial in CANDU reactors, both at the design stage and after implementation. This paper describes how a thermohydraulics code SOPHT (Simulation Of pHWR Heat Transport) has been successfully used as a CANDU reactor noise model (CRNM) to study the effectiveness of the interconnect. By introducing a small flow noise perturbation (2% peak-to-peak) in the SOPHT simulation, the damped flow oscillation with discharge boiling at 100% full power can be detected. For the first time, the damping ratio of the stabilized discharging mode can be estimated numerically, with the interconnect in place. We anticipate that the method of detecting the damped oscillation and estimating the damping ratio will be valuable for the design and evaluation of the new CANDU reactors.