%0 Journal Article %T Variational characterizations of the effective multiplication factor of a nuclear reactor core %A Bertrand Lods %J Mathematics %D 2008 %I arXiv %X We derive some new inf-sup and sup-inf formulae for the so-called effective multiplication factor arising in the study of reactor analysis. We treat in a same formalism the transport equation and the energy-dependent diffusion equation. %U http://arxiv.org/abs/0805.3120v1