Considerations on eigenvectors associated with the multigroup diffusion equation; case of the singular fission operator; biorthogonality relations; eigenvector degeneracy; generalized eigenvectors and their orthogonality relations; implicit flux reconstruction method; power series expansion; expansion in auxiliary functions; explicit methods; expansion in system eigenfunctions (alpha and lambda modes); expansion in pseudoharmonics with example cases in one and two spatial dimensions.

Credits: 3.0 (three)