High accurate three-dimensional neutron noise simulator based on GFEM with unstructured hexahedral elements

다국어 초록 (Multilingual Abstract)

The purpose of the present study is to develop the 3D static and noise simulator based on Galerkin FiniteElement Method (GFEM) using the unstructured hexahedral elements. The 3D, 2G neutron diffusion andnoise equations are discretized using the unstructured hexahedral by considering the linear approximationof the shape function in each element. The validation of the static calculation is performed viacomparison between calculated results and reported data for the VVER-1000 benchmark problem. Asensitivity analysis of the calculation to the element type (unstructured hexahedral or tetrahedron elements)is done. Finally, the neutron noise calculation is performed for the neutron noise source of typeof variable strength using the Green function technique.
It is shown that the error reduction in the static calculation is considerable when the unstructuredtetrahedron elements are replaced with the hexahedral ones. Since the neutron flux distribution andneutron multiplication factor are appeared in the neutron noise equation, the more accurate calculationof these parameters leads to obtaining the neutron noise distribution with high accuracy. The investigationof the changes of the neutron noise distribution in axial direction of the reactor core shows thatthe 3D neutron noise analysis is required instead of 2D.

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