A three-dimensional space-time model has been established for pressurized water reactor rod ejection analyses. Core neutronics is modeled with the two-group neutron diffusion equation and formulated in a coarse-mesh finite difference form. The time-dependent solution is obtained using a two-step alternating direction semi-implicit method. Nuclear data are processed from the CASMO cross-section library. Fuel temperature is calculated using finite differenced radial heat conduction equations. Core thermal hydraulics is described using the COBRA code. Dynamic reactivity is also provided to better access transient behaviors. The model is evaluated using typical rod ejection events initiated from hot full power at beginning and end of cycle conditions. Hypothetic rod configurations are designed to compare off-center-rod ejection, center-rod ejection, and quarter-core symmetric four-rod ejection under the condition of equal ejected rod worth. Results indicate that the peak fuel enthalpy increment is comparable for off-center and center-rod ejection; the core gross power and local power peaking tend to compensate for each other. This observation suggests that a single-rod ejection initiated from a given power may be characterized by the ejected rod worth if the increment of the peak enthalpy is the major interest in such events. Distributing the single ejected rod worth into four rods, however, enhances the transient core power but reduces the local power peaking even more due to spatial interactions between the ejected rods; consequently, this leads to a smaller increment of the peak fuel enthalpy.