The in situ magnetohydrodynamic (MHD) concept is a new proposal to convert the power of a nuclear fusion tokamak reactor into electricity. To determine the feasibility of this concept, quasi-one-dimensional calculations of MHD generators with a mercury-cesium medium are performed. The question of whether the electron cyclotron radiation emitted by the fusion plasma can be absorbed by the medium in the MHD generator so as to be able to work with enhanced nonequilibrium ionization is studied. It is concluded that this cannot be realized in practice. To obtain reasonably compact MHD generators, the stagnation pressure at the inlet of the generator should be rather low (< 1.8 bars). Under these circumstances, however, the absorption length that is needed for the generator medium to absorb the cyclotron radiation is excessively large. It is concluded that an enthalpy extraction of 35% per generator leads to a cycle efficiency of only 16.7%. To convert 35% of the fusion power into electricity, the enthalpy extraction of each generator should be increased to ∼70%. This is not considered to be realistic in view of the enthalpy extractions obtained experimentally in seeded noble gas MHD generators at a stagnation temperature of ∼2000 K.