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- 저자 : Daniele Tomatis (검색결과 2 건)
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Analysis of alpha modes in multigroup diffusion
Richard Sanchez,Daniele Tomatis,IGOR ZMIJAREVIC,주한규 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.6
The alpha eigenvalue problem in multigroup neutron diffusion is studied with particular attention to thetheoretical analysis of the model. Contrary to previous literature results, the existence of eigenvalue andeigenflux clustering is investigated here without the simplification of a unique fissile isotope or a singleemission spectrum. A discussion about the negative decay constants of the neutron precursors concentrationsas potential eigenvalues is provided. An in-hour equation is derived by a perturbationapproach recurring to the steady state adjoint and direct eigenvalue problems of the effective multiplicationfactor and is used to suggest proper detection criteria of flux clustering. In spite of the priorwork, the in-hour equation results give a necessary and sufficient condition for the existence of theeigenvalue-eigenvector pair. A simplified asymptotic analysis is used to predict bands of accumulation ofeigenvalues close to the negative decay constants of the precursors concentrations. The resolution of theproblem in one-dimensional heterogeneous problems shows numerical evidence of the predictedclustering occurrences and also confirms previous theoretical analysis and numerical results.
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Comprehensive investigation of the Ronen method in slab geometry
Roy Gross,Johan Cufe,Daniele Tomatis,Erez Gilad 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.2
A comprehensive investigation of the Ronen method is performed in homogeneous and heterogeneous slab problems from the Sood benchmark, considering isotropic and linearly-anisotropic problems. Three finite differences implementations are exercised and compared. The results are compared to reference solutions using one and two energy groups. The validation is performed for the criticality eigenvalue and the fundamental neutron flux distribution. The results demonstrate the significantly improved accuracy achievable by the Ronen method using a broad set of problems. For standard convergence tolerances, the maximal deviation in criticality eigenvalue is less than ten pcm, and the maximal deviation in the spatial distribution of the flux is less than 2%, always located near sharp interfaces or vacuum boundaries
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