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DOE OSTI · 23042648

Improved Variable-Transformation Algorithm for the Hexagonal Variational Nodal Method

Li, Yunzhao·Li, Zhipeng·Wu, Hongchun·Cao, Liangzhi
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Abstract

Hexagonal Variational Nodal Method (VNM) has been widely employed in fast reactor core calculation codes. It provides the weak form solution of the second order transport equation. It employs a direct three-dimensional expansion instead of the transverse integration technique, with the singular term caused by transverse integration over the hexagonal nodal avoided. However, as the increasing Pn expansion order in angle, the number of moments increases dramatically, which significantly increases the requirements in both memory and computational time. As a consequence, Yang proposed the Variable-Transformation Algorithm. It firstly used the reverse Cuthill-McKee (RCMK) reordering method to transform the response matrices into block-diagonal. Then, for the unreducible matrices, orthogonal transformation was applied, after which the matrices were sparse enough to be reduced by using the RCMK reordering once more. In this summary, based on a newly developed hexagonal VNM code NECP-VioletHex, the Variable Transformation Algorithm was investigated and improved by adopting more constraints to the basis functions to further take advantage of the symmetric properties of the hexagonal-z nodes. (authors)

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS97 MATHEMATICS AND COMPUTINGALGORITHMSFAST REACTORSMATRICESORTHOGONAL TRANSFORMATIONSREACTOR CORESSYMMETRYTHREE-DIMENSIONAL CALCULATIONSTRANSPORT THEORYVARIATIONAL METHODS

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Li, Yunzhao, Li, Zhipeng, Wu, Hongchun, Cao, Liangzhi. 2016-07-01. Improved Variable-Transformation Algorithm for the Hexagonal Variational Nodal Method. https://www.osti.gov/biblio/23042648

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