Study on Coupled Neutronic and Thermodynamic Instabilities in a Double Rectangular Channel Natural Circulation System under Rolling Motion

The ocean condition thermal-hydraulic analysis code RELAP5/MC is coupled with a 3D neutron transport code TDOT-T by Parallel Virtual Machine（PVM） and coupled neutronic and thermodynamic instabilities in a double parallel channel natural circulation system under rolling motion have been studied.Results indicate that the system has two oscillation modes: the in-phase oscillation caused by rolling motion and the out-of-phase oscillation caused by DWO.The neutronic feedback stabilizes the system in type 1 DWO region and suppresses the in-phase oscillation in two-phase region,but has little effect on the type 2 DWO and the in-phase oscillation in single-phase region.The calculated results have been analyzed based on the nonlinear theory and it is found that the nonlinear of system is enhanced with nuclear feedback.As the result of the system flow oscillation caused by the rolling motion superimposes with the DWO,and this extremely complicated phenomenon includes the synchronization and chaotic phenomena in the coupling of nonlinear oscillators.