Two-level coarse mesh finite difference formulation with multigroup source expansion nodal kernels

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Yoon, Joo Il; Joo, Han Gyu
Issue Date
Atomic Energy Society of Japan = 日本原子力学会
J. Nucl. Sci. Technol., 45, 668 (2008)
Souce ExpansionNodal MethodCMFDSANMMultigroupTwo-node Kernel
As an effort to establish a fast, yet accurate multigroup nodal solution method that is crucial in repeated
static and transient calculations for advanced reactors, the source expansion form of the semi-analytic
nodal method (SANM) is introduced within the framework of the coarse mesh finite difference (CMFD)
formulation. The source expansion is to expand the analytic form of the source appearing in the groupwise
neutron diffusion equation with a set of orthogonal polynomials in order to obtain a group decoupled analytic
solution. Both one- and two-node formulations are examined to determine the best nodal kernel. For
the acceleration, a two-level CMFD scheme is established employing a multigroup and two-group CMFD.
In addition, an alternative two-node direct SANM formulation with a quartic polynomial is examined to
assess the direct vs. iterative resolution of the group coupling. The performance of the CMFD formulation
with three different multigroup SANM nodal kernels is examined for a wide variety of multigroup benchmark
problems including several MOX-loaded LWR cores and large FBR cores. It is demonstrated that
superior accuracy is achievable with all the SANM kernels while the iterative two-node SANM kernel
outperforms the others in the multigroup calculations employing more than two groups, and the two-level
CMFD formulation is quite efficient in the acceleration of the outer iteration.
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Energy Systems Engineering (에너지시스템공학부)Nuclear Engineering (원자핵공학전공)Journal Papers (저널논문_원자핵공학과)
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