Lambda-modes calculated by the Nodal Green’s Function Method / Bestimmung der Lambda-Moden mit Hilfe der nodalen Green-Funktions- Methode

Abstract

Lambda(λ)-modes are very useful for many reactor physics analysis applications. Since modern nodal methods are known to be fast and efficient, it is suggested here - for reasons of accuracy and saving computation time - to calculate the λ-modes by such modern nodal techniques instead of using finite difference methods. Because there is a lack of a precedent, we demonstrate here the computation and usage of λ-modes of nodal equations by selecting the power iteration procedure with a simplified orthogonalization technique to calculate the λ-modes by the Nodal Green's Function Method (NGFM). The concept of nodal adjoint equation is introduced and the NGFM adjoint equation has been solved for the first time. At last, the physical meaning and usage of lamda-modes of nodal equations is discussed. Numerical results have demonstrated the success of this calculation procedure as well as its excellence performance, that is accuracy, time-saving and consistency with results obtained by analytical and finite difference methods.