Current conservation factors for consistent one-dimensional neutronics modeling

A one-dimensional neutronics formulation is established within the framework of the nonlinear analytic nodal method such that it can result in consistent one-dimensional models that produce the same axial information as their corresponding reference three-dimensional models. Consistency is achieved by conserving axial interface currents as well as the planar reaction rates of the three-dimensional case. For current conservation, flux discontinuity is introduced in the solution of the two-node problem. The degree of discontinuity, named the current conservation factor, is determined such that the surface averaged axial current of the reference three-dimensional case be retrieved from the two-node calculation involving the radially collapsed group constants and the discontinuity factor. The current conservation factors are derived from the analytic nodal method and various core configurations are analyzed to show that the errors in K-eff and power distributions can be reduced by a order of magnitude by the use of the current conservation factor with no significant computational overhead. (author)