Space-time diffusion equations for three-dimensional control rod withdrawal reactor accident

Space-time diffusion equations for three-dimensional control rod withdrawal reactor accident with SOR (Successive Over Relactation) has been done. This objective of this research is to observe behavior of reactor during control rod withdrawal accident. The rod withdrawal is simulated by linierly decreasing the thermal absorption cross-section over three time zones. When absorption cross-section decreasing linearly, neutron flux increase exponentioally. When absorption cross-section is constant, neutron flux increase slowly linier.