A development of the HEXNEM nodal expansion method

In this paper a development of the HEXNEM nodal expansion methods is presented, together with a program implementation and results from comparisons with benchmark problem solutions. The new development consists in the introduction of tangentially weighted exponential basis functions and continuity and boundary conditions for the tangential moments of the partial current in a way similar to that employed in some methods of the AFEN family. This is aimed at a better accounting for the flux variation along the radial node faces which for the large WWER-1000 assemblies can be a significant source of error. The test problem results presented in the paper indicate that an improved accuracy for WWER-1000 is achieved as compared with the HEXNEM2 method.

► A further development of the HEXNEM family of nodal expansion methods is presented.
► Continuity and boundary conditions on the partial current moments are introduced.
► Two-group diffusion benchmark problems for WWER reactors are solved.
► The solution accuracy is found to be improved over the existing HEXNEM2 method.