PWR Control Rod Ejection Analysis with the Method Of Characteristic Code DeCART

During the past several years, a comprehensive high fidelity reactor core modeling capability has been developed called the Numerical Nuclear Reactor (NNR) (Weber,2003) for detailed analysis of Light Water Reactors. The NNR achieves high fidelity with a whole-core neutron transport solution and ultra-fine-mesh computational fluid dynamics/heat transfer solution. Previous applications of the NNR have been to the steady-state analysis of both pressurized and boiling water reactors. Recently there has been interest in taking advantage of the NNR to improve the fidelity for PWR transient analysis. The work described in this paper is a preliminary demonstration of the ability of the whole core neutron transport code, DeCART, to provide a detailed intra-pin-power distribution during a control rod ejection accident. The current state of the art in analysis of this event relies upon the assembly averaged power from a whole core nodal neutronics simulator and some type of pin power reconstruction within the fuel assembly. Both methodologies are briefly presented and applied to model a super-prompt reactivity insertion accident. The difference in the results of both approaches are discussed and the benefit of the DeCART methodology is described. (authors)