A code-based Kartini reactor simulator was improved as a facility for the human resource development of a nuclear reactor. The simulator simulates the plant dynamics regarding a change of a control rod position. Reactor operation parameter calculations of the reactor power, coolant flow, and fuel temperatures adopt a one-channel method with assumptions of homogeneous radial power distribution and a cosine function of the axial power distribution. Point reactor kinetics, radial conduction heat transfer, and mass and energy conservation are the calculation code's governing equations. Reactivity feedback due to the coolant density and fuel temperature changes are considered. Reactor pressure is fixed at 1 atm due to an open pool-type research reactor. A graphical user interface was developed to operate the simulator. The operation results of the simulator show that the power calculation agrees well with the experimental data. An accident of excess reactivity due to a control ejection is assumed to happen, causing a positive reactivity insertion of 1.11$. However, the safety criterion of the cladding temperature is satisfied due to the negative reactivity feedback. Besides, early application of 3D virtual reality was carried out to provide an immersive interaction between the users and the virtual Kartini reactor plant. The further development of integrating both the virtual reality and the simulator in the recent Kartini reactor-based internet reactor laboratory is interesting to provide a facility with features of remote as well as immersive education and training.