Abstract: The paper introduces a three-dimensional nodal and subchannel analysis code package for the core transient in PWPs-SNENM/RTSP, including the model of neutronics and thermohydraulics used in the package. The preliminary results of applying this code package to the analysis of Steam-Line Break accident for Qinshan NPP are given and also evaluated briefly.

Key words: core transient analysis, 3D nodal method, subchannel model, steam-line break