Multi-group unified nodal method with two-group coarse-mesh finite difference formulation

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Han, Tae Young; Joo, Han Gyu; Lee, Hyun Chul; Kim, Chang Hyo
Issue Date
Ann. Nucl. Eng. 35, 1975
Unified Nodal MethodMultigroupCMFD
The one-node kernels of the unified nodal method (UNM) which were originally developed for two-group
(2G) problems are extended to solve multi-group (MG) problems within the framework of the 2G coarsemesh
finite difference (CMFD) formulation. The analytic nodal method (ANM) kernel of UNM is reformulated
for the MG application by adopting the Padé approximation to avoid the similarity transform
required to diagonalize the G G buckling matrix. In addition, a one-node semi-analytic nodal method
(SANM) kernel which is considered adequate for multi-group calculations is also integrated into the
UNM formulation by expressing it in the form consistent with the other UNM kernels. As an efficient global
solution framework, the 2G CMFD formulation with dynamic group condensation and prolongation is
established and the performance of the various MG kernels is examined using various static and transient
benchmark problems. It turns out that the SANM kernel is the best one for MG problems not only because
it retains accuracy comparable to MGANM with a shorter computing time but also because its accuracy or
its convergence does not depend on the eigenvalue range of the buckling matrix of the system. The 2G
CMFD formulation with MG one-node UNM kernels turns out to be very effective in that it conveniently
accelerates the MG source 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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