The core instability analysis under ocean condition for offshore floating nuclear power plant with neutron coupling based on multi-point model

For offshore floating nuclear power system the ocean conditions, such as rolling, must be considered for safe design. The neutron kinetics decides the power distribution and variation. Both of them will change the characteristics of the core instability. In this paper the ocean condition model and multi-point reactor model are added into the parallel channel system thermal-hydraulic model. A reactor core with 121 assemblies based on QinshanII nuclear power plant is selected as research object. The inherent instability of the system is studied firstly as the basis of comparison. Then the instability boundaries under motion condition and neutron feedback are obtained separately. The joint influence of motion and neutron feedback is studied. The results indicate that ocean condition has very limited effect for such system with so many parallel channels. Neutron feedback in different inlet subcooling regions have different influence tendency. The combined effect is very powerful and should be paid more attention. At last part the spectral analysis method is used to discuss the influence of the coupling calculation method.