Comparisons of the finite-element-with-discontiguous-support method to continuous-energy Monte Carlo for pin-cell problems (summary) Conference Paper uri icon

abstract

  • The standard multigroup (MG) method for energy discretization of the transport equation can be sensitive to approximations in the weighting spectrum chosen for cross-section averaging. As a result, MG often inaccurately treats important phenomena such as self-shielding variations across a material. From a finite-element viewpoint, MG uses a single fixed basis function (the pre-selected spectrum) within each group, with no mechanism to adapt to local solution behavior. In this work, we introduce the Finite-Element-with-Discontiguous-Support (FEDS) method, whose only approximation with respect to energy is that the angular flux is a linear combination of unknowns multiplied by basis functions. A basis function is non-zero only in the discontiguous set of energy intervals associated with its energy element. Discontiguous energy elements are generalizations of bands and are determined by minimizing a norm of the difference between snapshot spectra and their averages over the energy elements. We begin by presenting the theory of the FEDS method. We then compare to continuous-energy Monte Carlo for one-dimensional slab and two-dimensional pin-cell problem. We find FEDS to be accurate and efficient at producing quantities of interest such as reaction rates and eigenvalues. Results show that FEDS converges at a rate that is approximately first-order in the number of energy elements and that FEDS is less sensitive to weighting spectrum than standard MG.

published proceedings

  • Physics of Reactors 2016, PHYSOR 2016: Unifying Theory and Experiments in the 21st Century

author list (cited authors)

  • Till, A. T., Harm, M., Lou, J., Morel, J. E., & Adams, M. L.

complete list of authors

  • Till, AT||HarmÅ¡, M||Lou, J||Morel, JE||Adams, ML

publication date

  • January 2016