Extension of the analytic nodal diffusion solver ANDES to triangular-Z geometry and coupling with COBRA-IIIc for hexagonal core analysis

Abstract

In this paper the extensión of the multigroup nodal diffusion code ANDES, based on the Analytic Coarse Mesh Finite Difference (ACMFD) method, from Cartesian to hexagonal geometry is presented, as well as its coupling with the thermal-hydraulic (TH) code COBRA-IIIc for hexagonal core analysis.In extending the ACMFD method to hexagonal assemblies, triangular-Z nodes are used. In the radial plañe, a direct transverse integration procedure is applied along the three directions that are orthogonal to the triangle interfaces. The triangular nodalization avoids the singularities, that appear when applying transverse integration to hexagonal nodes, and allows the advantage of the mesh subdivisión capabilities implicit within that geometry. As for the thermal-hydraulics, the extensión of the coupling scheme to hexagonal geometry has been performed with the capability to model the core using either assemblywise channels (hexagonal mesh) or a higher refinement with six channels per fuel assembly (triangular mesh). Achieving this level of TH mesh refinement with COBRA-IIIc code provides a better estimation of the in-core 3D flow distribution, improving the TH core modelling.The neutronics and thermal-hydraulics coupled code, ANDES/COBRA-IIIc, previously verified in Cartesian geometry core analysis, can also be applied now to full three-dimensional VVER core problems, as well as to other thermal and fast hexagonal core designs. Verification results are provided, corresponding to the different cases of the OECD/NEA-NSC VVER-1000 Coolant Transient Benchmarks.

Monte Carlo current-based diffusion coefficients: Application to few-group constants generation in Serpent

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Boron dilution transient simulation analyses in a PWR with neutronics/thermal-hydraulics coupled codes in the NURISP project

“…In this application, the stand-alone nodal solver is employed which is capable of modelling 3D Cartesian or hexagonal-Z geometries (Lozano et al, 2010), using multigroup cross sections libraries.…”

Testing the NURESIM platform on a PWR main steam line break benchmark

“…The first step is a diagonalization of the multi-group diffusion matrix to transform the coupled multi-group diffusion equation into a set of uncoupled equations; the second step is a transverse integration procedure to transform the n-dimensional equation into n one-dimensional equations in order to find an analytic ID solution on each dimension. ANDES has been extensively validated for a number of numerical benchmarks (Lozano et al, 2010).…”